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The Src homology region 2 domain-containing phosphatase-1 (SHP-1) is an intracellular tyrosine phosphatase that plays a negative regulatory role in immune cell signaling. Absent or diminished SHP-1 catalytic activity results in reduced bone mass with enhanced bone resorption. Here, we sought to investigate if Shp1 overexpression leads to increased bone mass and improved mechanical properties. Male and female wildtype (WT) and SHP1-transgenic (Tg) mice at 28, 56, and 84 days of age were compared. We applied microcomputed tomography to assess femoral cortical bone geometry and trabecular architecture and 3-point mechanical bending to assess mid-diaphyseal structural and estimated material properties. Serum OPG, RANKL, P1NP, and CTX-1 concentrations were measured by enzyme-linked immunoassay. The majority of transgene effects were restricted to the 28-day-old mice. Trabecular bone volume per total volume, trabecular number, and connectivity density were greater in 28-day-old female SHP1-Tg mice when compared to WTs. SHP1-Tg female mice showed increased total and medullary areas, with no difference in cortical area and thickness. Cortical tissue mineral density was strongly genotype-dependent. Failure load, yield load, ultimate stress, and yield stress were all lower in 28-day-old SHP1-Tg females. In 28-day-old SHP1-Tg females, circulating levels of OPG and P1NP were higher and RANKL levels were lower than WT controls. Our study demonstrates a role for SHP-1 in early postnatal bone development; SHP-1 overexpression negatively impacted whole bone strength and material properties in females., (© 2023. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

This review discusses the changes in bone mass, structure, and metabolism that occur upon gender-affirming hormonal treatment (GAHT) in transgender adults and adolescents, as well as their clinical relevance. In general, available evidence shows that GAHT in transgender adults is not associated with major bone loss. In transgender adolescents, pubertal suppression with gonadotropin-releasing hormone agonist monotherapy impairs bone development, but at least partial recovery is observed after GAHT initiation. Nevertheless, a research gap remains concerning fracture risk and determinants of bone strength other than bone mineral density. Attention for bone health is warranted especially in adult as well as adolescent trans women, given the relatively high prevalence of low bone mass both before the start of treatment and after long-term GAHT in this population. Strategies to optimize bone health include monitoring of treatment compliance and ensuring adequate exposure to administered sex steroids, in addition to general bone health measures such as adequate physical activity, adequate vitamin D and calcium intake, and a healthy lifestyle. When risk factors for osteoporosis exist the threshold to perform DXA should be low, and treatment decisions should be based on the same guidelines as the general population., (© 2022. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

In this study, we aimed to (a) evaluate postnatal changes in bone development in relation to growth and (b) to determine factors associated with bone development, from birth to 24 months of corrected age. The metacarpal speed of sound (mcSOS) and metacarpal bone transmission time (mcBTT) were used to evaluate bone development in 98 preterm infants, during hospitalization and follow-up. The mcSOS and mcBTT values not only declined in the first 6 weeks of hospitalization but also during follow-up. The mcSOS reached its lowest point at 12 months (β=-34.64), while the mcBTT reached a plateau between 12 and 24 months (β=0.06). Univariable analysis showed that gender (p=0.28), time (p<0.001), and growth parameters (p<0.001) were significant negative associated factors with mcSOS, whereas with mcBTT, time (p=0.009), length (p=0.063), length standard deviation scores (SDS) (p=0.027), head circumference (p=0.005), and head circumference SDS (p=0.007) were significant positive. The multivariable model revealed that time (β= -3.364, p=<0.001), weight (β=-0.007, p<0.001) and length (β=1.163, p<0.001) for mcSOS and length (β=-0.021, p<0.001), and length SDS (β= 0.066, p<0.001) and head circumference (β=0.049, p<0.001) for mcBTT remained highly significant associated factors.Conclusion: The most important finding is that mcSOS decreased and the mcBTT reached a plateau to 24 months. In both mcSOS and mcBTT, the growth parameters were significant factors.Clinical Trial Registration: N/A What is known: • Metabolic bone disease is one of the possible long term adverse outcomes after preterm birth. • Metacarpal speed of sound (mcSOS) and metacarpal bone transmission time (mcBTT) decline in the early postnatal period. What is new: • During follow-up, mcSOS further decreased and reached its lowest point at 12 months, while the mcBTT reached a plateau up to 24 months. • Postnatal nutrition in relation to comorbidity does not meet the optimal mineralization rate of the developing preterm bone., (© 2021. The Author(s).)

Background: Inflammatory rheumatic diseases in childhood and adolescence are a special challenge in the treatment of acute trauma. The pharmaceutical treatment strategies for children and adolescents have been modified., Objective: Which special aspects must be considered in young patients suffering from rheumatism when a trauma necessitates an operative procedure?, Material and Method: A literature search was carried out to elaborate recommendations for the practice., Results: The joint-related alterations in young patients suffering from rheumatism differ with respect to the differently altered inflammatory rheumatic destruction. The extent of these inflammatory destructive alterations dictates the operative approach. Consequences arise in paying attention to the concurrent medication with respect to avoidance of events triggering an exacerbation and tissue infections. The bone strength necessitates an individualized selection of implants and sometimes influences the duration of follow-up treatment. In the early stages of the inflammatory process the approach in cases of trauma is no different to that for healthy patients but in later stages (Larsen stage III) it does differ., Conclusion: An interdisciplinary concept can help to avoid disadvantages in the treatment of the underlying disease. Due to the special dysplastic anatomy and tissue alterations, trauma in these patients is a particular challenge.

Fructose is metabolized in the cytoplasm by the enzyme ketohexokinase (KHK), and excessive consumption may affect bone health. Previous work in calcium-restricted, growing mice demonstrated that fructose disrupted intestinal calcium transport. Thus, we hypothesized that the observed effects on bone were dependent on fructose metabolism and took advantage of a KHK knockout (KO) model to assess direct effects of high plasma fructose on the long bones of growing mice. Four groups (n = 12) of 4-week-old, male, C57Bl/6 background, congenic mice with intact KHK (wild-type, WT) or global knockout of both isoforms of KHK-A/C (KHK-KO), were fed 20% glucose (control diet) or fructose for 8 weeks. Dietary fructose increased by 40-fold plasma fructose in KHK-KO compared to the other three groups (p < 0.05). Obesity (no differences in epididymal fat or body weight) or altered insulin was not observed in either genotype. The femurs of KHK-KO mice with the highest levels of plasma fructose were shorter (2%). Surprisingly, despite the long-term blockade of KHK, fructose feeding resulted in greater bone mineral density, percent volume, and number of trabeculae as measured by µCT in the distal femur of KHK-KO. Moreover, higher plasma fructose concentrations correlated with greater trabecular bone volume, greater work-to-fracture in three-point bending of the femur mid-shaft, and greater plasma sclerostin. Since the metabolism of fructose is severely inhibited in the KHK-KO condition, our data suggest mechanism(s) that alter bone growth may be related to the plasma concentration of fructose.

This study aimed to describe the association of vitamin D status at different stages of growth with bone measures in adolescence and early adulthood. There were 415 participants followed from age 8 to 16, and 201 further followed to age 25. Areal bone mineral density (BMD) at the spine, hip and total body was measured by dual-energy X-ray absorptiometry at ages 16 and 25, and tibial and radial trabecular and cortical bone microarchitecture by high resolution peripheral quantitative computerised tomography at age 25. Serum 25-hydroxyvitamin D (25OHD) concentrations were measured at ages 8, 16 and 25. Multivariable linear regression was used to analyse the association of 25OHD concentrations at three timepoints with bone measures at ages 16 and 25. The proportion of participants with vitamin D deficiency (< 50 nmol/L) was 11%, 43% and 41% at three timepoints, respectively. Serum 25OHD concentrations at age 8 were not significantly associated with any bone measures at age 16 or 25. Serum 25OHD concentrations at age 16 had a significant association with higher BMD at nearly all sites at ages 16 and 25 as well as lower radial porosity and more compact trabecular microarchitecture (higher density, increased number and reduced separation) at both the radius and tibia at age 25. Serum 25OHD concentrations at age 25 were only associated with hip BMD. Higher vitamin D concentrations in adolescence, to a lesser extent at age 25, have beneficial associations with BMD and bone microarchitecture in early adulthood. Optimising vitamin D status particularly during adolescence should be a priority.

Background: The ring apophyses of the cervical spine have a variable appearance that changes with age. The times at which they appear and fuse at each level are not fixed. In this study, we aim to detail normal ranges of appearance of these ossification centers for each age group., Materials and Methods: One hundred and eighty patients under the age of 21 attending the Royal Stoke University Hospital for cervical spine radiographs were retrospectively identified. The presence or absence of ring apophyses at each cervical level and whether these had undergone fusion was reported, as were the thickness, length, and craniocaudal and anteroposterior distance of the apophysis from the vertebral body. The angulation of the apophysis relative to the endplate was also noted., Results: The youngest patient in which apophyses were seen was aged 3, but apophyses were otherwise rarely seen before the age of 6. All apophyses were present from age 14, and the superior apophyses fused by the age of 18, although unfused inferior apophyses were still seen in the 20-year age group. It was observed that apophyses were rarely separated from the vertebral body by greater than 1 mm in craniocaudal distance (1%) or 2.5 mm in anteroposterior distance (2.6%) and the anterior apophysis was angulated towards the endplate in only 1% of cases., Conclusions: We have detailed the range of normal appearances of the ring apophyses of the developing cervical spine. Cervical spine apophyseal injury is thought to be rare, but knowledge of normative morphological features should help in this diagnosis.

An autosomal-recessive inactivating mutation R272Q in the human intestinal cell kinase (ICK) gene caused profound multiplex developmental defects in human endocrine-cerebro-osteodysplasia (ECO) syndrome. ECO patients exhibited a wide variety of skeletal abnormalities, yet the underlying mechanisms by which ICK regulates skeletal development remained largely unknown. The goal of this study was to understand the structural and mechanistic basis underlying skeletal anomalies caused by ICK dysfunction. Ick R272Q knock-in transgenic mouse model not only recapitulated major ECO skeletal defects such as short limbs and polydactyly but also revealed a deformed spine with defective intervertebral disk. Loss of ICK function markedly reduced mineralization in the spinal column, ribs, and long bones. Ick mutants showed a significant decrease in the proliferation zone of long bones and the number of type X collagen-expressing hypertrophic chondrocytes in the spinal column and the growth plate of long bones. These results implicate that ICK plays an important role in bone and cartilage development by promoting chondrocyte proliferation and maturation. Our findings provided new mechanistic insights into the skeletal phenotype of human ECO and ECO-like syndromes.

Advanced glycation end products (AGEs) accumulate in bone extracellular matrix as people age. Although previous evidence shows that the accumulation of AGEs in bone matrix may impose significant effects on bone cells, the effect of matrix AGEs on bone formation in vivo is still poorly understood. To address this issue, this study used a unique rat model with autograft implant to investigate the in vivo response of bone formation to matrix AGEs. Fluorochrome biomarkers were sequentially injected into rats to label the dynamic bone formation in the presence of elevated levels of matrix AGEs. After sacrificing animals, dynamic histomorphometry was performed to determine mineral apposition rate (MAR), mineralized surface per bone surface (MS/BS), and bone formation rate (BFR). Finally, nanoindentation tests were performed to assess mechanical properties of newly formed bone tissues. The results showed that MAR, MS/BS, and BFR were significantly reduced in the vicinity of implant cores with high concentration of matrix AGEs, suggesting that bone formation activities by osteoblasts were suppressed in the presence of elevated matrix AGEs. In addition, MAR and BFR were found to be dependent on the surrounding environment of implant cores (i.e., cortical or trabecular tissues). Moreover, MS/BS and BFR were also dependent on how far the implant cores were away from the growth plate. These observations suggest that the effect of matrix AGEs on bone formation is dependent on the biological milieu around the implants. Finally, nanoindentation test results indicated that the indentation modulus and hardness of newly formed bone tissues were not affected by the presence of elevated matrix AGEs. In summary, high concentration of matrix AGEs may slow down the bone formation process in vivo, while imposing little effects on bone mineralization.

Targeted weight-bearing activities during the pre-pubertal years can improve cortical bone mass, structure and distribution, but less is known about the influence of habitual physical activity (PA) and fitness. This study examined the effects of contrasting habitual PA and fitness levels on cortical bone density, geometry and mass distribution in pre-pubertal children. Boys (n = 241) and girls (n = 245) aged 7-9 years had a pQCT scan to measure tibial mid-shaft total, cortical and medullary area, cortical thickness, density, polar strength strain index (SSIpolar) and the mass/density distribution through the bone cortex (radial distribution divided into endo-, mid- and pericortical regions) and around the centre of mass (polar distribution). Four contrasting PA and fitness groups (inactive-unfit, inactive-fit, active-unfit, active-fit) were generated based on daily step counts (pedometer, 7-days) and fitness levels (20-m shuttle test and vertical jump) for boys and girls separately. Active-fit boys had 7.3-7.7 % greater cortical area and thickness compared to inactive-unfit boys (P < 0.05), which was largely due to a 6.4-7.8 % (P < 0.05) greater cortical mass in the posterior-lateral, medial and posterior-medial 66 % tibial regions. Cortical area was not significantly different across PA-fitness categories in girls, but active-fit girls had 6.1 % (P < 0.05) greater SSIpolar compared to inactive-fit girls, which was likely due to their 6.7 % (P < 0.05) greater total bone area. There was also a small region-specific cortical mass benefit in the posterior-medial 66 % tibia cortex in active-fit girls. Higher levels of habitual PA-fitness were associated with small regional-specific gains in 66 % tibial cortical bone mass in pre-pubertal children, particularly boys.

Purpose: This study aimed to evaluate development of the tibia after Ilizarov lengthening and deformity correction depending on whether or not the simultaneous resection of fibular anlage was performed in children with fibular aplasia type II, who did not undergo early surgery., Methods: The study analyses results of reconstructive treatment in 38 children at the age of over four years. Two groups of children are compared: bifocal tibial lengthening with the Ilizarov device (group I) and bifocal lengthening associated with resection of the fibular anlage (group II). The results were estimated at 12 months and in the long-term exceeding three years., Results: Radiological data of measurement of the anatomical lateral distal tibial angle (aLDTA) show surgical correction of deformities achieved in both groups. During the further limb growth a tendency to normalisation of the aLDTA was observed only in the group II. Quick relapse of the angular deformities of the tibial shaft in the first group occurred mainly during further growth of the limb regardless of complete correction at the time of treatment. On the other hand, there were no recurrences of diaphyseal deformities in the group II., Conclusions: In children with congenital fibular deficiency of type II at the age of four years, the bone lengthening and deformity correction should be associated with fibular anlage resection. That approach improves conditions for distal tibia development and prevents or decreases significantly the recurrence of deformities of the tibia and ankle joint in long-term follow-up.

Mineralization in higher vertebrates is restricted to bones and teeth. Pathological calcification is mostly known in vasculature but can basically affect all soft tissues. Simply put, tissue mineralization occurs through the interplay of three key determinants: extracellular matrix suitable for mineralization, extracellular levels of inorganic phosphate and calcium, and the levels of mineralization inhibitors that may be expressed systemically or locally. In this article we describe the role of a prototypic systemic inhibitor protein of mineralization, the hepatic plasma protein α2-Heremans-Schmid glycoprotein/fetuin-A. Fetuin-A mediates the formation of stable colloidal mineral-protein complexes called calciprotein particles (CPPs). Thus, fetuin-A is important in the stabilization and clearance of amorphous mineral precursor phases. Efficient clearance of CPPs and, thus, of excess mineral from circulation prevents local buildup of mineral and calcification of soft tissue. Besides calcium phosphate binding, fetuin-A also acts as a carrier for lipids, which may influence calcification, inflammation, and apoptosis. Fetuin-A-deficient (Ahsg(-/-)) mice show impaired growth of their long bones and premature growth plate closure. We posit that the absence of fetuin-A in the growth plate causes simultaneous lack of calcification inhibition and excess lipid hormone signaling, leading to premature growth plate mineralization and shortened long bones. This suggests that fetuin-A regulates endochondral ossification through mineralization inhibition and lipid (hormone) binding.

In adult articular cartilage, the extracellular matrix is maintained by a balance between the degradation and the synthesis of matrix components. Chondrocytes that sparsely reside in the matrix and rarely proliferate are the key cellular mediators for cartilage homeostasis. There are indications for the involvement of the WNT signaling pathway in maintaining articular cartilage. Various WNTs are involved in the subsequent stages of chondrocyte differentiation during development, and deregulation of WNT signaling was observed in cartilage degeneration. Even though gene expression and protein synthesis can be activated upon injury, articular cartilage has a limited ability of self-repair and efforts to regenerate articular cartilage have so far not been successful. Because WNT signaling was found to be involved in the development and maintenance of cartilage as well as in the degeneration of cartilage, interfering with this pathway might contribute to improving cartilage regeneration. However, most of the studies on elucidating the role of WNT signaling in these processes were conducted using in vitro or in vivo animal models. Discrepancies have been found in the role of WNT signaling between chondrocytes of mouse and human origin, and extrapolation of results from mouse models to the human situation remains a challenge. Elucidation of detailed WNT signaling functions will provide knowledge to improve cartilage regeneration.

The extent to which nutrient intake may influence bone structure and strength during maximal rates of skeletal growth remains uncertain. We examined the relationship of dietary intake of micronutrients and bone macroarchitectural structure in young girls. This cross-sectional analysis included baseline data from 363 fourth- and sixth-grade girls enrolled in the Jump-In study. Nutrient intake was assessed using the Harvard Youth/Adolescent Food Frequency Questionnaire. Volumetric BMD (vBMD), bone geometry, and strength were measured by peripheral quantitative computed tomography. Correlations and regression modeling assessed relations between usual nutrient intake and bone parameters. In fourth-grade girls, metaphyseal and diaphyseal area and circumferences as well as diaphyseal strength were associated with vitamin C intake (r = 0.15-0.19, p < 0.05). Zinc intake was correlated with diaphyseal vBMD (r = 0.15-0.16, p < 0.05). Using multiple linear regression to adjust for important covariates, we observed significant independent associations for vitamin C and zinc with bone parameters. For every milligram per day of vitamin C intake trabecular area increased by 11 %, cortical strength improved by 14 %, and periosteal and endosteal circumferences increased by 5 and 8.6 %, respectively. For every milligram per day of zinc intake, cortical vBMD increased by <1 %. No significant associations were observed in sixth-grade girls. Results of this study suggests that vitamin C and zinc intake are positively associated with objective measures of bone geometry, size, and strength in fourth-grade girls. This indicates that potential differences in micronutrient and bone associations at various age-associated stages of bone maturation may be indicative of competing hormonal influences.

We aimed to determine whether precocious adrenarche (PA) has a different impact on screening tests for metabolic issues and pubertal timing in boys and girls born appropriate for gestational age (AGA). Puberty and initial metabolic screening results of 47 girls and 23 boys with PA born AGA followed up from our outpatient endocrinology clinic between May 2000 and October 2009 were reviewed. Initial anthropometric measurements except for body mass index standard deviation score (SDS) being higher in boys than girls (p = 0.01), bone age (BA) SDS, homeostasis model assessment of insulin resistance, and plasma lipids were similar between sexes. Hormone levels except for significantly higher dehydroepiandrosterone sulfate levels in boys than girls (p = 0.0006) were also similar between the sexes. BA SDS and BA/chronological age were significantly advanced (p < 0.05) with respect to initial evaluation in 28 girls at onset of gonadarche unlike the case in 13 boys with PA (p > 0.05). In conclusions, PA in children born AGA does not herald any significant differences with respect to adverse metabolic screening results between sexes, and it appears to be a discrete process from onset of puberty in girls unlike boys, in whom it is likely a variant of normal puberty.

Mechanical loading is essential for bone development and prevention of age-related bone diseases. Muscular contractions during physical activity and the generated strain magnitude are primary determinants for the osteogenic response. However, the adaptation capacity of bones, especially due to different muscle contraction types, is largely unknown. In the present study we examined the effect of different running modes characterized by different muscle contraction types and loading patterns on the morphological, structural, and mechanical properties of different sites in the femur of growing rats. Thirty-six female Sprague-Dawley rats were randomly assigned to a nonactive age-matched control (AMC), a level running (LEVEL), and a 20° decline downhill running (DOWN) group (n = 12 each). Running groups were trained on a treadmill for 30 min/day, 5 days/week for 6 weeks. After death, pQCT analysis of the meta- and diaphyses, micro-CT analysis of the epiphysis, and mechanical testing of the femur were performed. The Tb.BMD in the metaphysis was significantly (P < 0.05) increased in the DOWN compared to the AMC group, whereas level running had no effect on Tb.BMD. While Young's modulus was significantly different (P < 0.05) between the DOWN and LEVEL groups, no structural alterations were found in the diaphysis between the groups. Further, subchondral trabecular bone did not show exercise-induced changes caused by the different running modes but displayed a remarkably high intraepiphyseal variability. Downhill running seems to be a potent osteogenic stimulus in the femoral metaphysis.

We present age- and gender-specific normative bone status data evaluated by quantitative ultrasound (QUS) in the calcaneus with the Lunar Achilles device and compare these estimates with bone mineral content (BMC) and bone mineral density (BMD) estimated by dual X-ray absorptiometry (DXA). Included were a sample of 518 population-based collected Swedish girls and 558 boys aged 6-19 years. QUS measurements included speed of sound (SOS), broadband ultrasound attenuation (BUA), and stiffness index (SI) in the calcaneus. DXA measurements included BMC and BMD in the femoral neck (FN), lumbar spine (L2-L4), and total body (TB). Height and weight were measured with standard equipment. Age, height, and weight were significantly associated with SOS, BUA, and SI. Compared to SOS, in both girls and boys there was a higher correlation between BUA and FN BMC (r = 0.71 and r = 0.73, respectively), FN BMD (r = 0.68 and r = 0.67, respectively), L2-L4 BMC (r = 0.70 and r = 0.64, respectively), L2-L4 BMD (r = 0.69 and r = 0.64, respectively), TB BMC (r = 0.76 and r = 0.75, respectively), and TB BMD (r = 0.74 and r = 0.74, respectively). The correlations between SOS and FN BMC (r = 0.38 and r = 0.52, respectively), FN BMD (r = 0.41 and r = 0.52, respectively), L2-L4 BMC (r = 0.31 and r = 0.40, respectively), L2-L4 BMD (r = 0.32 and r = 0.41, respectively), TB BMC (r = 0.42 and r = 0.49, respectively), and TB BMD (r = 0.48 and r = 0.54, respectively) were lower, although still significant (all P < 0.001). BUA seems to be the QUS parameter that best resembles the changes in BMC during growth.

We have previously shown that exercise during growth increases post-yield deformation in C57BL6/129 (B6;129) male tibiae at the expense of reduced pre-yield deformation and structural and tissue strength. Other research in the literature indicates that increased mineral content, cross-sectional geometry and structural strength due to exercise can be maintained or increased after exercise ends for as long as 14 weeks. It was therefore hypothesized that after our exercise protocol ended, effects of exercise on mechanical properties would persist, resulting in increased post-yield behavior and rescued strength versus age-matched control mice. Beginning at 8 weeks of age, exercise consisted of running on a treadmill (30 min/day, 12 m/min, 5 degrees incline) for 21 consecutive days. At the end of running and 2 weeks later, in the cortical bone of the tibial mid-diaphyses of B6;129 male mice, changes due to exercise and latency following exercise were assayed by mechanical tests and analyses of cross-sectional geometry. Exercise increased structural post-yield deformation compared with weight-matched control mice, without changes in bone size or shape, suggesting that exercised-induced changes in pre-existing bone quality were responsible. Over the 2-week latency period, no growth-related changes were noted in control mice, but exercise-induced changes resulted in increased tissue stiffness and strength versus mice sacrificed immediately after exercise ended. Our data indicate that periods of exercise followed by latency can alter strength, stiffness, and ductility of bone independent of changes in size or shape, suggesting that exercise may be a practical way to increase the quality of the bone extracellular matrix.

Objectives: Knowledge of bone age in achondroplasia is required for the prediction of adult height, timings of limb lengthening, and epiphysiodesis procedures. The purpose of this investigation was to determine the differences in skeletal age in achondroplasia and a control population with the Tanner-Whitehouse 3 method using the RUS score and to determine the right age for the interventional procedure for limb lengthening procedure or deformity correction in these patients., Materials and Methods: Left hand radiographs of 34 patients (age range, 5-18 years) with achondroplasia were evaluated for skeletal age using the RUS scoring system, which were compared with the left hand radiographs of 41 patients (age range, 5-18 years) without achondroplasia measuring skeletal age. The difference in chronological age and RUS bone age were evaluated statistically according to gender and age group., Results: In the achondroplasia group, chronological age were 10.5 +/- 4.3 years for males and 10.1 +/- 3.6 years for females and RUS bone age were 9.2 +/- 4.0 years for males and 8.9 +/- 3.4 years for females, which showed statistically significantly difference (males p = 0.0003 and females p < 0.0001), while in the control group, chronological age were 11.1 +/- 2.9 years for males and 10.7 +/- 3.4 years for females and RUS bone age were 11.2 +/- 3.4 years for males and 10.7 +/- 3.3 years for females, which did not show statistically significantly difference (males p = 0.54 and females p = 0.76). Our finding suggested a delay of 1.4 years for males and 1.2 years for females in the maturation of bone in achondroplasia patients. Difference between chronological age and RUS bone age was 0.9 +/- 1.1 for <10 years and 1.6 +/- 0.9 for >10 years in the study group, while 0.1 +/- 1.1 for <10 years and -0.2 +/- 0.6 for >10 years in the control group, which also showed >statistically significant difference (<10 years p = 0.04 and >10 years p < 0.0001). These differences indicate that there was a delay in the maturation of bones by 1 year in the group <10 years and 1.8 years in the group >10 years in achondroplasia patients compared to nonachondroplasia patients., Conclusion: We recommend the use of the Tanner-Whitehouse 3 method especially the radius, ulna, short bone score to measure the skeletal age and to wait for a longer time before interventional procedures in achondroplasia patients.

Studies in preterm infants show reduced speed of sound (SOS) as measured by quantitative ultrasound (QUS) during the immediate neonatal period. There is a scarcity of data on SOS changes following hospital discharge. The aim of this study was to assess SOS over the first 2 years in preterm infants. Infants were recruited from a neonatal follow-up clinic. Tibial QUS was performed using the Omnisense 7000P scanner. Thirty-nine infants born at <32 weeks' gestation had a single SOS measurement (median 3,203 m/second, range 2,609-3,495) which correlated with corrected gestational age (CGA) (r = 0.8, P < 0.005). The majority of measurements were within the manufacturer's reference range for term infants. SOS standard deviation score (SDS) in infants aged 0-6 months CGA demonstrated a negative correlation with duration of total parenteral nutrition (r = 0.7, P < 0.05) and a positive correlation with serum phosphate (r = 0.6, P < 0.05.) Two groups of infants had serial measurements: eight had measurements performed at term CGA and early infancy (early) and seven had measurements in later infancy (late). In the early group SOS SDS increased (P < 0.005), and the greatest increase in SOS over time occurred in infants with the lowest SOS at term (r = 0.9). In the late group there was no significant change over time. SOS SDS change did not show any correlation to weight SDS change. Catch-up in SOS occurs postterm in most infants by 6 months and is independent of postnatal growth. Infants with the lowest SOS at term have the fastest rate of catch-up. The opportunity for catch-up may be greatest in early infancy.

Bone formation in a variety of contexts depends on angiogenesis; however, there are few reports of the vascular response to osteogenic skeletal loading. We used the rat forelimb compression model to characterize vascular changes after fatigue loading. The right forelimbs of 72 adult rats were loaded cyclically in vivo to one of four displacement levels, to produce four discrete levels of ulnar damage. Rats were killed 3-14 days after loading, and their vasculature was perfused with silicone rubber. Transverse histological sections were cut along the ulnar diaphysis. We quantified vessel number, average vessel area, total vessel area, and bone area. On day 3, we observed a dramatic periosteal expansion near the ulnar midshaft, with significant increases in periosteal vascularity; total vessel area was increased 250-450% (P < 0.001). Vascularity remained elevated on days 7 and 14. Vessel number and average vessel area were not correlated (P = 0.09) and contributed independently to total vascular increases. Bone area was not increased on day 3 but on days 7 and 14 was increased significantly in all displacement groups (P < 0.01) due to periosteal woven bone formation. Vascular and bone changes depended on longitudinal location (P < 0.001), with peak increases 2 mm distal to the midshaft. Vascular and bone changes also depended on displacement level (P < 0.005), with greater increases at higher levels of fatigue displacement. We conclude that skeletal fatigue loading induces a rapid increase in periosteal vascularity, followed by an increase in bone area. The angiogenic-osteogenic response is spatially coordinated and scaled to the level of the mechanical stimulus.

Genetic selection for rapid body growth in broiler chickens has resulted in adverse effects on the skeletal system exemplified by a higher rate of cortical fractures in leg bones. Strontium (Sr) has been reported to have beneficial effects on bone formation and strength. We supplemented the diet of 300-day-old chicks with increasing dosages of Sr (0%, 0.12%, or 0.24%) to study the capacity of the element to improve bone quality and mechanical integrity. Treatment with Sr increased cortical bone volume and reduced bone porosity as measured by micro-computed tomography. The higher level of Sr significantly reduced bone Ca content (34.7%) relative to controls (37.2%), suggesting that Sr replaced some of the Ca in bone. Material properties determined by the three-point bending test showed that bone in the Sr-treated groups withstood greater deformation prior to fracture. Load to failure and ultimate stress were similar across groups. Our results indicate that Sr treatment in rapidly growing chickens induced positive effects on bone volume but did not improve the breaking strength of long bones.

Four-and-a-half LIM 2 (FHL2) is a member of a family of LIM domain proteins which mediate protein-protein interactions. FHL2 acts as a coactivator and binds to important regulators of bone formation such as insulin-like growth factor binding protein (IGFBP)-5, androgen receptor, and beta-catenin. We hypothesized that FHL2 is an important regulator of bone formation. We evaluated growth and skeletal parameters in FHL2 knockout (KO) and wild-type (WT) mice at 4, 8, and 12 weeks of age. At 4 weeks of age, lack of FHL2 reduced femur, tibia, and total bone mineral content (BMC) and body weight in all mice. A gender-by-treatment interaction (P

In order to discuss and illustrate the effects common to normal and abnormal enchondral bone at the physes and at all other growth plates of the developing child, the term "acrophysis" was proposed. Acrophyses include the growth plates of secondary growth centers including carpals and tarsals and apophyses, and the growth plates at the nonphyseal ends of small tubular bones. Abnormalities at acrophyseal sites are analogous to those at the physeal growth plates and their metaphyses. For example, changes relating to the zone of provisional calcification (ZPC) are often important to the demonstration of such similarities. Lead lines were an early example of the concept of analogy from abnormality due to physeal and to acrophyseal disturbance. The ZPC is a key factor in understanding patterns of rickets and its healing. Examples (including hypothyroidism, scurvy and other osteoporosis, Ollier disease, achondroplasia, and osteopetrosis, as well as the family of frostbite, Kashin-Beck disease, and rat bite fever) illustrate the acrophysis principle and in turn their manifestations are explained by that principle.

As research into bone maintenance and turnover is accelerated and expanded due to public health concerns about osteoporosis and other age-related changes and pathologies of bone, nonhuman animal models are becoming increasingly important as they allow for enhanced experimental manipulation and environmental control relative to humans. Old World Monkeys, such as the rhesus macaque, share physiological and developmental characteristics that make these primates particularly well suited to such studies. The purpose of this study was to characterize normal age and sex variation in osteon remodeling dynamics in skeletally immature and mature rhesus macaques. Femoral cross-sections from 75 Macaca mulatta were examined to evaluate the effect of age, sex, and skeletal maturity on osteon remodeling dynamics in this popular research primate. Results indicate that sex has a significant effect on osteon area (On.Ar), but generally is not an important contributor to normal variation in intracortical remodeling dynamics. Age and skeletal maturity, however, contribute significantly to variation in osteon population density (OPD), activation frequency (Ac.f), and bone formation rate (BFR), as is the case in humans. This study is the first to characterize normal age and sex variation in osteon remodeling in growing and adult rhesus macaques and its results support the use of this animal as a model for age-related changes and pathologies in the human skeleton.

In order to discuss and illustrate the common effects on normal and abnormal enchondral bone at the physes and at all other growth plates of the developing child, the term "acrophysis" is proposed. Acrophyses include the growth plates of secondary growth centers including carpals and tarsals and apophyses, and the growth plates at the non-physeal ends of small tubular bones. The last layer of development of both physes and acrophysis is the cartilaginous zone of provisional calcification (ZPC). The enchondral bone abutting the ZPC shares similar properties at physes and acrophyses, including the relatively lucent metaphyseal bands of many normal infants at several weeks of age. The bone-in-bone pattern of the normal vertebral bodies and bands of demineralization of the tarsal bones just under the ZPC are the equivalent of those bands. The growth arrest/recovery lines of metaphyses similarly have equivalent lines in growth centers and other acrophyseal sites. Nearly the same effects can also be anticipated from the relatively similar growth plate at the cartilaginous cap of benign exostoses ("paraphysis"). The companion article will explore abnormalities at acrophyseal sites, including metabolic bone disease and dysplasias.

Interaction of chondrocytes with the surrounding matrix significantly influences differentiation and growth. These processes involve cell surface proteins, particularly integrins. The aim of this study was to compare the expression of integrins (alpha1, alpha2, alpha3, alpha5, alpha6, alphav, beta1, beta3, and beta5 subunits) together with matching binding proteins in human childhood and adolescent growth plate cartilage using immunohistochemistry. Integrin beta1 was detected in all chondrocytes of the growth plate cartilage, beta3 only in osteoclasts of the opening zone, and beta5 in hypertrophic chondrocytes and osteoblasts. Integrin alpha1, alpha2, and alpha5 subunits were expressed by chondrocytes in the proliferative and hypertrophic zone as well as in osteoblasts and osteoclasts. Integrin av and alpha6 subunits were present in chondrocytes of all zones, alpha3 only in osteoclasts. Collagen type II and fibronectin were seen throughout the growth plate, collagen type X in the hypertrophic zone, collagen type I in the ossifying trabecules. Laminin was expressed by chondrocytes in the resting zone and more weakly in the proliferative zone, collagen VI was present in the pericellular and interterritorial matrix in all zones of the growth plate. These results differ from previous reports on the distribution of integrins in the fetal growth plate. However, there was no difference in integrin expression in children before and during puberty. Our results indicate that integrin expression is not influenced by endocrine factors during sexual maturation and suggest that the process of skeletal maturation is not regulated via altered integrin expression.

In vitro studies about the regenerative capacity of chondrocytes located in the growth plate of long bones revealed a potential for reparation. A measurable advance in the understanding of the physiologic processes in the bone growth plate and their modifications after defined lesions is based on the recognition of the role of the vascular architecture. Newly formed bridging arteries crossing from the metaphysis to the epiphysis through the growth plate are thought to be responsible for the cell proliferation observed after Salter-Harris I and II lesions. We aimed to examine the influence of mechanical microstimulations on the growth or inhibition of the proliferation of the chondrocytes in the tibial growth plate. We studied 22 tibial bone fractures, which were stabilized with a dynamic or a stable external fixateur. Proliferative changes in the bone tissue were examined by immunohistochemical classification using bromodeoxyuridine (BUdR), a thymidine analogue. Radiologic studies, computer tomography, and magnetic resonance imaging documented the results in comparison with histological examination. Cell proliferation in the growth plate was not stimulated in the 1st week after distraction. The histological studies revealed an initial increase in proliferation of chondrocytes, especially between the 2nd and the 4th week. This was more clearly seen with the use of the dynamic fixator. We conclude that a temporary ischemia with a reactive hyperemia takes place, which we could document by histological analysis and MRI. These results could modify the current clinical therapy of growth plate fractures.

We investigated the concept of using bioactive substrates as templates for in vitro synthesis of bone tissue for transplantation by assessing the osteogenic potential of a melt-derived bioactive glass ceramic (Bioglass 45S5) in vitro. Bioactive glass ceramic and bioinert (plastic) substrates were seeded with human primary osteoblasts and evaluated after 2, 6, and 12 days. Flow cytometric analysis of the cell cycle suggested that the bioactive glass-ceramic substrate induced osteoblast proliferation, as indicated by increased cell populations in both S (DNA synthesis) and G2/M (mitosis) phases of the cell cycle. Biochemical analysis of the osteoblast differentiation markers alkaline phosphatase (ALP) and osteocalcin indicated that the bioactive glass-ceramic substrate augmented osteoblast commitment and selection of a mature osteoblastic phenotype. Scanning electron microscopic observations of discrete bone nodules over the surface of the bioactive material, from day 6 onward, further supported this notion. A combination of fluorescence, confocal, transmission electron microscopy, and X-ray microprobe (SEM-EDAX) examinations revealed that the nodules were made of cell aggregates which produced mineralized collagenous matrix. Control substrates did not exhibit mineralized nodule formation at any point studied up to 12 days. In conclusion, this study shows that Bioglass 45S5 has the ability to stimulate the growth and osteogenic differentiation of human primary osteoblasts. These findings have potential applications for tissue engineering where this bioactive glass substrate could be used as a template for the formation of bioengineered bone tissue.

To investigate the event-related profiles of musculoskeletal development in weight-categorized athletes, we measured the cross-sectional areas (CSA) of bone and muscle in the forearm, upper arm, lower leg and thigh, using a B-mode ultrasound apparatus, in college Olympic weightlifters (OWL, n = 19) and wrestlers (WR, n = 17) and untrained men (UM, n = 24), whose body masses were within the range from 55 kg to 78 kg. Both bone and muscle CSA at all sites were significantly correlated to the two-thirds power of fat-free mass (FFM(2/3)) with correlation coefficients of 0.430-40.741 (P < 0.05) and 0.608-0.718 (P < 0.05), respectively. Moreover, there were significant correlations between bone and muscle CSA at all sites (r = 0.664-0.829, P < 0.05). Even when bone and muscle CSA were expressed relative value to FFM(2/3), both OWL and WR showed significantly greater values than UM at all sites except for the lower leg. Furthermore, the comparison of the lean (bone + muscle) CSA ratio from site to site indicated a higher distribution of lean tissues in the upper extremities in OWL and WR compared to UM. While there was no significant difference between the two athlete groups in FFM(2/3), OWL showed significantly larger values than WR in the bone CSA of the upper arm and thigh and in the muscle CSA of the lower leg and thigh. However, lean CSA ratios of the upper extremities to the lower ones were significantly higher in WR than in OWL. Thus, the present results indicated that, compared to UM, OWL and WR had a greater lean tissue CSA in limbs, especially in the upper extremities, even when the difference in FFM was normalized. Moreover, the relative distribution of lean tissues in limbs differed between the two weight-categorized athletes in spite of there being no difference in FFM, which may be attributable to their own training regimens and/or competition style.

The aim of the present study was to characterize cells involved in resorption during endochondral bone formation. We investigated whether the cells involved in cartilage breakdown at the epiphyseal/metaphyseal border, i.e., chondroclasts, share the characteristics of bone/cartilage-resorbing osteoclasts at the metaphyseal/diaphyseal border regarding ultrastructural features and functional activity. Morphometric evaluation showed that chondroclasts do not form ruffled borders and clear zones, i.e., well-known resorption characteristics, to the same extent as osteoclasts, present at the lower metaphysis. Instead, chondroclasts tend to express an undifferentiated surface adjacent to the matrix, not structurally different from the basolateral plasma membrane. Tartrate-resistant acid phosphatase (TRAP) was used as a marker for functional activity. Immunohistochemical staining by light microscopy was strong in both chondroclasts and in osteoclasts. Furthermore, in situ hybridization revealed large amounts of TRAP mRNA in chondroclasts as well as in osteoclasts. Ultrastructural immunohistochemistry suggests extensive secretion of the TRAP enzyme in the ruffled border area of both chondroclasts and osteoclasts. Intracellular accumulation was seen particularly in chondroclasts, possibly as a consequence of a relative disinclination to develop a ruffled border. Thus, semiquantitative estimation of TRAP distribution showed an inverse relationship between extracellular and intracellular TRAP in chondroclasts and osteoclasts. These results indicate that chondroclasts and osteoclasts differ, not only with respect to location but possibly also by mode of action. The observed differences may reflect the maturation sequence of these multinucleated cells when associated with different metaphyseal trabecular surfaces.

Exposure to zero gravity has been shown to cause a decrease in bone formation. This implicates osteoblasts as the gravity-sensing cell in bone. Osteoblasts also are known to produce neutral proteinases, including collagenase and tissue plasminogen activator (tPA), which are thought to be important in bone development and remodeling. The present study investigated the effects of zero gravity on development of calvariae and their expression of collagenase and tPA. After in utero exposure to zero gravity for 9 days on the NASA STS-70 space shuttle mission, the calvariae of rat pups were examined by immunohistochemistry for the presence and location of these two proteinases. The ages of the pups were from gestational day 20 (G20) to postnatal (PN) day 35. Both collagenase and tPA were found to be present at all ages examined, with the greatest amount of both proteinases present in the PN14 rats. At later ages, high amounts were maintained for tPA but collagenase decreased substantially between ages PN21 to PN35. The location of collagenase was found to be associated with bone-lining cells, osteoblasts, osteocytes, and in the matrix along cement lines. In contrast, tPA was associated with endothelial cells lining the blood vessels entering bone. The presence and developmental expression of these two proteinases appeared to be unaffected by the exposure to zero gravity. The calvarial thickness of the pups was also examined; again the exposure to zero gravity showed little to no effect on the growth of the calvariae. Notably, from G20 to PN14, calvarial thickness increased dramatically, reaching a plateau after this age. It was apparent that elevated collagenase expression correlated with rapid bone growth in the period from G20 to PN14. To conclude, collagenase and tPA are present during the development of rat calvariae. Despite being produced by the same cell in vitro, i.e., the osteoblast, they are located in distinctly different places in bone in vivo. Their presence, developmental expression, and quantity do not seem to be affected by a brief exposure to zero gravity in utero.

Little is known about the dynamics of bone formation and bone resorption in utero, particularly the normal changes that occur throughout gestation and in clinical situations that result in low bone mass at birth. The objectives of this study were to describe the effects of gestational age on markers of fetal bone turnover, and to investigate whether the reported low bone mass at birth in small-for-gestational-age (SGA) infants and infants of diabetic mothers (IDMs) was associated with biochemical markers of decreased bone formation or increased bone resorption in utero. Bone formation and resorption were assessed by measurement of carboxyterminal propeptide of type I procollagen (PICP) and cross-linked carboxyterminal telopeptide of type I collagen (ICTP), respectively, in 201 amniotic fluid samples. These markers are by-products of type I collagen formation and degradation, respectively, and have been used in the assessment of bone metabolism ex utero. Both PICP and ICTP concentrations in amniotic fluid were inversely associated with gestational age (P < 0.0001). Amniotic fluid concentrations of PICP increased exponentially in relation to infant birthweight (P = 0.008), and SGA infants had lower amniotic fluid PICP concentrations than controls (P = 0.07). The presence of diabetes in the mother was not associated with alterations in amniotic fluid PICP or ICTP concentrations. Although maturational effects on clearance of bone markers from amniotic fluid cannot be excluded, these data are consistent with a high turnover of bone matrix early in fetal life, and a reduction in bone formation when fetal growth is compromised.

Bone loss associated with estrogen depletion is well documented in cancellous bone but less well characterized in cortical bone. The effects of ovariectomy on the aged beagle skeleton were studied by histomorphometric analysis of the cortical bone in sequential rib biopsies. Biopsies were taken from each ovariectomized or sham-operated dog at the time of surgery and at 1, 4, and 8.5 months after surgery. Just prior to each postoperative biopsy, tetracycline, calcein, and xylenol orange, respectively, were administered by a fluorochrome labeling procedure (2d-10d-2d) to provide markers of bone formation. Analysis of sequential rib biopsies provided a means to follow the ovariectomy response over time and to compare each animal against its own baseline. Though ovariectomy did not influence histomorphometric indices at 1 month after surgery, a transient increase in cortical bone formation occurred thereafter, with a sixfold increase over that of sham-operated dogs at 4 months (P < 0.001) and a return to near control levels at 8.5 months. Cortical porosity increased by the fourth month after ovariectomy and remained high at 8.5 months. These data demonstrate for the first time that rib cortical bone is a responsive site for the effects of ovariectomy in aged female dogs.

Bone's biologic mechanisms adapt it to meet the needs of its mechanical usage and muscle strength. Modeling by drifts can increase bone strength and "mass," BMU-based remodeling can conserve or reduce them, and neither can do the other's work. Under increasing forces on bone, modeling increases bone strength and "mass" and remodeling maintains the extra bone. In disuse, modeling turns OFF and remodeling reduces bone strength and "mass" to cause osteopenia. Osteopenia increases bone fragility as does bone microdamage, and they can coexist. Too little bone for one's mechanical usage and muscle strength can cause spontaneous fractures and/or bone pain. The bone-loss and tissue-dynamic patterns in acute and chronic disuse strongly copy the patterns in developing and established osteopenias in known medical conditions. Such things suggest that at least three osteoporosis variants can occur: (1) in physiologic osteopenias, bone strength and "mass" would decrease to correspond to reduced muscle strength and physical activity so that spontaneous fractures and bone pain would not occur. An intrinsic bone disorder would not cause this osteopenia, and fractures would only follow injuries, usually of extremity bones. (2) In "true osteoporosis," bone strength and "mass" could not meet the needs of muscle strength and physical activities, so that spontaneous fractures and/or bone pain would occur, mainly in the spine. An intrinsic bone disorder would cause this affection. Of course, injuries could fracture extremity bones too. (3) Features of (1) and (2) could combine variably in "combination states." These proposals have implications for the diagnosis, management, and study of the osteoporoses.

In general, physical exercise appears to have favorable effects on the skeleton. However, a few recent reports have described negative effects, including reduced bone density (BMD) and high bone turnover in runners. The aim of our study was to compare endurance runners to controls with respect to BMD at different sites and ultrasound transmission through the peripheral skeleton, and to use PTH, total serum calcium, and biochemical markers of bone metabolism as a complement in evaluating the effects of endurance running on bone. Thirty runners (mean age 32 years, range 19-54 years) participated in the study. Their main form of training consisted of endurance running at moderate intensity for about 7 hours (range 2-12 hours) per week, and they had been active in their sport for about 12 years (range 1-21 years). For a comparison, 30 age- and sex-matched population based controls were investigated. BMD values, measured by dual energy X-ray absorptiometry (DXA), were higher in runners than in controls for the total body (3.6%; P = 0.03), legs (9.6%; P = 0. 001), femoral neck (10.0%; P = 0.01), trochanter (9.9%; P = 0.01), and Wards triangle (11.8%; P = 0.02), but not in the lumbar spine or in the forearm measured by single energy X-ray absorptiometry (SXA). The quantitative ultrasound measurement of the calcaneus also revealed higher values in runners than in controls for both broadband ultrasound attenuation (9.2%; P = 0.002) and speed of sound (3.1%; P = 0.0001). At all sites, BMD was related to ultrasound measurements in controls, but no such relationship was evident in runners. Concentrations of parathyroid hormone (PTH) were lower (23.2%; P = 0.02) in runners than in controls, whereas total serum calcium concentrations were slightly higher (3.0%; P = 0.003). The levels of PICP (bone formation) and ICTP (bone resorption) in serum were lower (18.0%; P = 0.03 and 22.2%; P = 0.004, respectively) in runners than in controls, but no differences were seen for osteocalcin or bone specific alkaline phosphatase (b-ALP). In conclusion, BMD at the focus of strain for running, that is, the legs, is higher in endurance runners when compared to matched controls. Low bone turnover in runners, indicated by lower levels of PTH and biochemical markers of bone metabolism, point to an influence of endurance running at the cellular level.

In this paper a general mathematical framework is developed to describe cases of fixed and moving growth surfaces. This formulation has the mathematical structure suggested by Skalak (1981), but is extended herein to include discussion of possible singularities, incompatibilities, residual stresses and moving growth surfaces. Further, the general theoretical equations necessary for the computation of the final form of a structure from the distribution of growth velocities on a growth surface are presented and applied in a number of examples. It is shown that although assuming growth is always in a direction normal to the current growth surface is generally sufficient, growth at an angle to the growth surface may represent the biological reality more fully in some respects. From a theoretical viewpoint, growth at an angle to a growth surface is necessary in some situations to avoid postulating singularities in the growth velocity field. Examples of growth on fixed and moving surfaces are developed to simulate the generation of horns, seashells, antlers, teeth and similar biological structures.

There is abundant data on cancellous bone in the aging human spine, but little relating to the growing vertebral cancellous bone in childhood an adolescence. The purpose of this study was to map vertebral cancellous bone in a growth and age series of historic skeletal samples and to make comparisons with data published on recent material. Lumbar vertebral bodies were collected from 65 skeletons (0-60 years) from a medieval Nubian population. Ethnohistoric information was collected to interpret conditions that might have influenced bone structure and metabolism. The cancellous bone was studied three dimensionally, using stereophotography and scanning electron microscopy and morphometrically by performing a semiautomatic structural analysis on digitized backscattered electron images of polymethacrylate-embedded material. The cancellous bone structure in the children consisted mainly of a densely packed, uniform network of small rodlike trabeculae. The greatest bone volume fraction with small, more platelike trabeculae was observed during adolescence. In young adults, larger platelike trabeculae were present in the central zone and smaller trabeculae in the superior and inferior zones, as described for modern skeletal material. Structural changes associated with aging were observed much sooner than in modern man. by the estimated age of approximately 50-60 years, the predominant architectural elements were slender rarified rods in both sexes. The ethnohistorical data suggest that this was essentially a black African population of physically active peasants, not likely to suffer Vitamin D insufficiency or deficient calcium intake. Thus an earlier onset of the biological age changes in cancellous bone found in modern populations was probably relevant.

Calcium deficiency is a major etiological determinant of rickets in Nigerian children and is accompanied by undermineralization of the developing bone matrix which is composed largely of type I collagen. We have assessed types I and III collagen metabolism by measuring the circulating concentrations of teh N- and C-terminal pro-peptides (intact PINP and PICP) and the C-terminal telopeptide (ICTP) of type I collagen, and the N-terminal pro-peptide (PIIINP) of type III collagen in 94 healthy Nigerian children and in 44 children aged 1-5 years with active calcium-deficiency rickets. In active rickets the mean levels of the four collagen metabolites were approximately twofold higher than in the healthy children, despite a wide variation of individual values. Mean intact PINP was 812 +/- 279 versus 403 +/- 189 microg/liter; PICP was 573 +/- 265 versus 348 +/- 299 microg/liter; PIIINP was 16.8 +/- 8.6 versus 10.8 +/- 3.6 microg/liter, and ICTP was 28.4 +/- 17.2 versus 11.9 +/- 4.1 microg/liter (all P < 0.001), in rachitic and healthy children, respectively. Healthy children younger than 3 years had higher levels of all the collagen metabolites than those between 3 and 5 years (all P < 0.05). Alkaline phosphatase was greater in rickets than in the healthy group (P < 0.001) whereas mean osteocalcin levels were slightly lower (P = 0.009). 1,25(OH)2D correlated with all the collagen propeptides, but not with ICTP in the healthy children. No such correlations were found in rickets, where there was a poor inverse correlation between 1,25(OH)2D and ICTP. These data suggest that collagen turnover is elevated in cases of calcium-deficiency rickets, where vitamin D status is adequate, possibly indicating increased turnover of undermineralized osteoid.

Adolescence is characterized by rapid skeletal development and high demands for bone minerals. Though the stimulative effect of calcitriol on intestinal calcium and phosphorus absorption is well understood, its effect on bone development is not completely clear. It may be directly involved in the facilitation of calcium economy during this critical phase of skeletal development. Therefore, we evaluated the serum concentrations of calcitriol in relation to skeletal development in a cross-sectional study of 178 healthy Caucasian females during different pubertal stages, extending from childhood to young adulthood. In addition, a subsample of 57 younger girls was followed for a 1-year period to evaluate the association among serum calcitriol, nutrition parameters (dietary calcium, phosphorus, and vitamin D), bone mass accumulation, and biochemical markers of bone turnover. The serum calcitriol concentration in a cross-sectional sample was the highest during pubertal growth spurt (sexual maturity index 3-4, age 11-13 years) (ANOVA; F = 2.4945; P = 0.0329). This correlated to the peak skeletal calcium accretion (g/year) and bone mass accumulation in total body and forearm. In a longitudinal sample, there was a positive association between annual change in TBBMC (P = 0.0255); TBBMD (P = 0.0168); proximal radius (1/3 distance from styloid process) BMC (P = 0.0096); BMD (P = 0.0541), and baseline calcitriol level in forward stepwise regression analyses. The results of the forward stepwise regression analyses with serum calcitriol as a dependent variable and different serum, urinary, and dietary parameters measured at baseline (age 11 years, n = 114) and after 1 year (age 12 years, n = 57) showed that osteocalcin was positively associated with calcitriol in both years; more so in a second year (P = 0.0514, P < 0.001, respectively). Dietary vitamin D and phosphorus showed negative association with serum calcitriol at age 11, and dietary Ca and P were selected at age 12. The results of this study show that calcitriol is a significant correlate of bone mass accumulation during pubertal growth, presumably in response to the high requirements for calcium during this critical phase of skeletal development.

Fifty-six Sprague-Dawley rats were either ovariectomized (OVX, n = 24), sham-operated (Sham, n = 24), or sacrificed (n = 8) at the beginning of the experiment to serve as a baseline group. The OVX and Sham groups were further randomly divided into control (CTRL), slow running (R10), and faster running (R18) groups. R10 and R18 groups ran for 2 x 30 min/day for 8 weeks at speeds of 10 m/min and 18 m/min, respectively. Exercise did not affect the mechanical or histomorphometric parameters of bone in the sham-operated rats. There was no effect of exercise on body weight gain in the OVX-R10 group, but in OVX-R18 it decreased the gain of body weight. In the OVX-CTRL group the maximal load and energy absorption of the femoral neck were 16.7% (P < 0.001) and 30.0% (P < 0.001) lower than in the Sham-CTRL group, respectively. In OVX animals, slow running had a positive effect on the maximal load of the femoral neck (86.5 N) when compared with OVX-CTRL rats (77.1 N, P < 0.07). 51.7% of the trabecular bone was lost in the distal femur as a result of OVX and exercise reduced this loss to 30.2% (R10) and 39.9% (R18). Ovariectomy increased the bone formation rate (BFR) and the mineral apposition rate (MAR) on the periosteum of the femoral shaft. Exercise decreased the periosteal BFR and MAR in OVX rats, but increased it at the endosteum. Osteoclast numbers in the femoral metaphysis were increased after OVX and running exercise inhibited this effect significantly. The maximal bending load of the humerus increased after OVX by 12.1% (P < 0.05). Exercise enhanced this effect, the slow running being more effective. These results suggest that bone in OVX rats is either more sensitive to exercise than in sham-operated rats or that the higher body weight with slow running induces optimal loading and strengthens the bones.

Osteopenia has been described as a complication of insulin-dependent diabetes mellitus (IDDM). We measured bone modeling indexes during the first year of IDDM. At each time point the values obtained from diabetic children have been compared with those of control subjects. We selected 27 prepubertal children with IDDM (6.35 +/- 2.16 years). We also enrolled 30 healthy prepubertal children of comparable age (5.85 +/- 3.05 years). Height, height standard deviation scores, glycated haemoglobin (HbA1C), basal c-peptide concentrations, insulin dose, serum concentrations of procollagen type I C-terminal propeptide (PICP), and collagen type I C-terminal telopeptide (ICTP) were measured at onset of IDDM and at 3, 6 and 12 months. ICTP was in the normal range at onset of IDDM and decreased during the follow-up to reach a significant difference compared to controls after 3, 6 and 12 months of insulin treatment (P < 0.04). PICP concentrations increased significantly at 3 months (P = 0.05) compared to onset. At 3 and 12 months PICP values were significantly higher than those of control children (P = 0.04). Correlations were found between PICP concentrations and HbA1C and c-peptide at onset of diabetes (r = -0.45 and r = 0.47, respectively). Bone formation at onset of IDDM is not impaired; the introduction of insulin therapy, together with the achievement of a good metabolic control, determines an increase of bone matrix formation coupled with a decrease of bone resorption, that determines a positive balance of bone modeling.

The large cartilage proteoglycan, aggrecan, was found to vary throughout the ovine physis corresponding to the maturational state of the resident chondrocytes. Two populations of proteoglycan monomer were observed in articular, epiphyseal, and in the resting zone of growth plate cartilage. These proteoglycans contained chondroitin sulfate glycosaminoglycan chains sulfated predominantly in the 4 position along with lesser amounts of chondroitin-6-sulfate and keratan sulfate. In the proliferative zone of the growth plate, chondrocytes synthesize one population of proteoglycan monomer which was significantly larger than monomer populations in articular, epiphyseal, or resting zone and this size increase could be attributed to an increase in its constituent chondroitin sulfate side chains. As these chondrocytes progress through their life cycle they continue to modify the structural characteristics of the aggrecan molecule they synthesize. Thus, in the hypertrophic region of the growth plate, the proteoglycan monomer is larger again than in the proliferative region. Variation in sulfation pattern on aggrecan chondroitin sulfate side chains is also observed in the hypertrophic region with an increasing proportion of unsulfated residues present, which may play a role in the initiation of mineralization. In addition, increasing amounts of the carbohydrate sequence recognized by monoclonal antibody 7-D-4 are observed in the hypertrophic zone.

The effect of zinc on protein synthesis in the femoral-metaphyseal tissues of normal and skeletally unloaded rats was investigated. Skeletal unloading was designed using the model of hindlimb suspension in rats. Animals were fed for 2 or 4 days during the unloading. [3H]Leucine was added to the reaction mixture containing the 5500 g supernatant fraction of the homogenate prepared from the femoral-metaphyseal tissues. In vitro protein synthesis was significantly decreased in the bone tissues from the rats which had undergone unloading for 2 or 4 days. When the metaphyseal tissues were cultured for 24 h in the presence of zinc sulfate (10(-5) M) or beta-alanyl-L-histidinato zinc (AHZ, 10(-5) M), zinc compounds clearly stimulated protein synthesis in the metaphyseal tissues from the 4-day unloaded rats. The zinc effect was also seen in the metaphyseal tissues from normal rats. The addition of zinc sulfate (10(-5) M) or AHZ (10(-7) to 10(-5) M) into the reaction mixture containing the 5500 g supernatant fraction of metaphyseal homogenate from normal or unloaded rats produced a significant increase in protein synthesis. This increase was clearly inhibited in the presence of cycloheximide (10(-7) M). The present result demonstrates that protein synthesis is impaired in the femoral-metaphyseal tissues of rats with skeletal unloading, and that this impairment is clearly restored by zinc supplementation.

MBA-15.4 and MBA-15.6 cell lines are marrow stromal clonal subpopulations and represent various stages of differentiation of the osteoblastic family. These cells vary in terms of morphology, proliferation rate, synthesis of matrix proteins as collagen and noncollagenous proteins, and by their responses to hormones and growth factors. Their differential properties directly reflect the clonal cells' ability to form bone in vivo. When the cells were transplanted at an ectopic site, under the kidney capsule, MBA-15.4 line formed small foci of bone whereas MBA-15.6 cell line formed massive woven bone during the same period of time. In this study, we focused on the histomorphometric analysis of ectopic ossicles formed by the clonal cell lines. Assessments of bone mass changes involved measurements of cellular components, osteoid, and formation of primary bone. The bony tissue formed was condensed, no hemopoiesis was noted, and the ossicle was not remodeled. The histology studies were used for quantitative analysis of the ossicle formation and describe the dynamics of ossicles formed by the individual cell types.

This study compares absolute rates of bone resorption and formation at the organ level in adolescent Sprague-Dawley rats as a function of sex and type of bone. Bone resorption and formation were quantified in rapidly growing male and female rats (4-7 weeks of age) who were multiply prelabeled with [3H]tetracycline. Ten different whole bones were compared: four cranial or appendicular bones and six axial bones. Absolure rate of bone resorption was measured isotopically by the loss of 3H-tetracycline from each whole bone. Bone growth was quantified in terms of relative and absolute increase in bone calcium mass. When the rates of bone resorption (loss of [3H]-tetracycline as percent of whole bone per 3 weeks) were compared between sexes, the six axial bones showed significantly higher rates (P < 0.05-0.001) in males (64-73) than in females (37-66). No significant sex differences were observed in rate for the two cranial and two appendicular bones. During 4-7 weeks of age, a comparison of bone masses showed that only one bone (calvaria) gained more mass in the male and two bones (mandible and humerus) gained more mass in the female. In contrast, five of six axial bones gained more mass in the female. Thus, 7 out of 10 bones were larger in the female. In growing male and female rats, an inverse relationship appears between rate of bone resorption and mass for most of the axial bones; this relationship was not apparent for cranial or appendicular bones. Sexual dimorphism was consistently seen by greater axial bone mass in females. However, greater rates of bone resorption were seen in male axial bones but not in cranial or appendicular bones. It is apparent that the different types of bones are heterogeneous in their rates of resorption and formation during this period of growth.