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Over the last decade, there has been an increasing interest among researchers for human mesenchymal stromal cells (MSC). Their regenerative properties, multilineage differentiation capacity and immunomodulatory properties make them promising candidates for treatment in various conditions. Emerging biotechnology companies specialized in cellular and regenerative therapies have been focusing their interest on MSC-based therapies, and their use in clinical trials has steadily increased. Notably, MSC are currently tested in clinical trials addressing unmet medical needs in the field of bone fracture repair and more specifically in non-union and delayed union fractures where the bone repair process is impaired. Although MSC can be isolated from various tissues, the most commonly studied sources are bone marrow (BM) and adipose tissue (Ad). In this article, we reviewed the literature directly comparing BM- and Ad-MSC for their in vitro characteristics and in vivo osteogenic potential to determine which source of MSC would be more appropriate for bone fracture repair. As considerable variations in experimental settings between studies were found, our review was based on studies meeting specific sets of criteria, notably regarding donors’ age and gender. This review of side-by-side comparisons suggests that while BM-and Ad-MSC share common general characteristics, BM-MSC have a higher intrinsic osteogenic capacity in vitro and bone repair potential in vivo.

Recoverin is a calcium-sensing protein which is involved in the transduction of light in vertebrate photoreceptors. It is also detected in other retina cell types in which its function is not yet elucidated, and is an autoantigen in a cancer-associated degenerative disease of the retina. Recently, hippocalcin, an homologous protein of recoverin, belonging to the same family of fatty acylated EF-hand calcium binding proteins was described in mammals. The immunohistochemical studies presented in this paper demonstrate, that, in the retina of the lamprey, an Agnathan considered the living ancestor of actual jawed vertebrates, recoverin was present in all photoreceptors and, to a lesser extent in subpopulations of amacrine and ganglion cells whereas hippocalcin was detected in numerous amacrine and ganglion cells and in the inner segments of long photoreceptors. The existence of these calcium-binding proteins shows that they have a high degree of conservation during evolution. Their presence in the same cells that in jawed vertebrates (photoreceptors and ganglion cells for recoverin; amacrine and ganglion cells for hippocalcin) suggests that some retinal functions are well conserved but because they were also found in different cell types than in other species (amacrine for recoverin; photoreceptors for hippocalcin), they may have functions more specific to the lamprey retina.

Cerebellar syndrome has been described after acute lithium intoxication in human. Neuropathological studies have demonstrated neuronal loss and spongiosis in the cerebellum. We describe an animal model of acute lithium-induced cerebellar degeneration. Five hours following administration of lithium chloride (250 mg/kg, i.p.), the cerebellar white matter of seven rats out 14 exhibited extensive spongiform changes. Microdialysis study in the rat cerebellar cortex demonstrated basal concentrations of dopamine (DA), hydroxy-3-methoxyphenylacetic acid (HVA) and 5-hydroxy-3-indolacetic acid (5-HIAA). These metabolites were unaffected by acute lithium intoxication suggesting that the cerebellar toxicity is not due to a modification of dopaminergic or serotoninergic neurotransmission.

Odorant stimulation of receptor cells results in a calcium influx that activates the transduction pathway. The olfactory neurons extend axons to the olfactory bulb where they synapse onto mitral cells. Ca(2+)-acceptors also may participate in subsequent processing of olfactory information. The present study describes the distribution of calmodulin, calretinin, calbindin-D28k and neurocalcin during rat main olfactory bulb development. From postnatal day 1 (P1) we observed in the olfactory nerve layer a thin external bundle containing calbindin and calretinin whereas calmodulin was present in a large internal bundle. In tufted cells, neurocalcin immunoreactivity was detected at P10 and increased until P20. In mitral cells calmodulin was intensively immunoreactive at P1 but decreased during development to disappear at adulthood whereas calretinin was weakly labelled at P1 but raised in intensity until P20. In granule cells calbindin-D28k and calretinin were detected from P1. Giant neurons were positive for both calretinin and calbindin-D28k from postnatal day 20.

Odorant stimulation of receptor cells results in a calcium influx that activates the transduction pathway. Ca2+ acceptors, such as calmodulin, may mediate between the change in intracellular calcium and the conductance mechanism underlying the initial electrical event. Ca2+ acceptors also may participate in subsequent processing of olfactory information. The identification and characterization of these molecules, therefore, should provide important information about the complex signal transduction pathway involving calcium in olfaction as well as other sensory systems. The present study describes the distribution of six calcium-binding proteins in the rat main olfactory epithelium during postnatal development to determine when different Ca2+ acceptors can be detected and whether they segregate into different layers or portions of the epithelium. Calmodulin, calretinin, calbindin-D28k, neurocalcin, and recoverin were detected immunohistochemically in olfactory receptors but not in basal cells. S-100 immunoreactivity was restricted to glial cells primarily around the cribriform plate. During postnatal development (from P1 to P20), calmodulin, calretinin, calbindin-D28k, and neurocalcin formed a gradient of immunoreactivity descending from the central to the lateral areas in the nasal cavity, whereas recoverin was expressed only in sporadic, mature receptors in the proximal region of the mucosa. At P20, the immunoreactivity pattern for each calcium-binding protein was identical to the adult profile, indicating that the olfactory epithelium had reached maturity by this stage. Olfactory nerve fiber bundles displayed a differential staining pattern from P1 until adulthood for calbindin-D28k and calretinin (internal portions of bundles). Differential calmodulin immunoreactivity of olfactory nerves (large external portions of bundles) appeared at P10. The immunoreactivity of the nerve fiber bundles may reflect a further degree of organization relevant to odor discrimination.

The post-natal developmental expression in rat retina of four calcium-binding proteins belonging to the calmodulin-troponin-C family was investigated by immunohistochemistry using anti-calbindin-D28k, anti-calretinin, anti-hippocalcin and anti-neurocalcin polyclonal antibodies on paraffin sections from Wistar rat retinae aged from post-natal days 1 (P1), 5 (P5), 10 (P10), 20 (P20) to adulthood (8 weeks). Immunoblot using anti-hippocalcin and homogenates proteins from retina, cerebellar cortex, hippocampus and cerebellum was also performed. Hippocalcin immunoreactivity in adult rat retina was demonstrated by both immunohistochemistry and Western blot. During post-natal development, calbindin-D28k, calretinin and neurocalcin immunoreactivity were detected at P1 in ganglion cells, whereas hippocalcin immunoreactivity was seen later at P5 in this cell layer. In the amacrine cell layer, neurocalcin immunoreactivity was detected at P5 and hippocalcin at P10. Calbindin-D28k was labelling the immature horizontal cell, calretinin was detected in nearly all ganglion cells and in some amacrine cells since P1. These three calcium-binding proteins do not seem to play a role in synaptogenesis which takes place later. We confirmed that calbindin-D28k appeared to be a good marker for horizontal cells. The presence of hippocalcin, a myristoylated calcium-binding protein belonging to the recovering subfamily and previously localized in few brain areas has been detected for the first time in retina.

Nonunion fractures can cause severe dysfunction and are often difficult to treat mainly due to a poor understanding of their physiopathology. Although many aspects of impaired fracture healing have been extensively studied, little is known about the cellular and molecular mechanisms leading to atrophic nonunion. Therefore, the aim of the present study was to assess the pools and biological functions of bone marrow-derived mesenchymal stem cells (hMSCs) and circulating endothelial progenitor cells (EPCs) in atrophic nonunion patients compared to healthy subjects, and the systemic levels of growth factors involved in the recruitment, proliferation and differentiation of these cells. In nonunions, the pool of hMSCs was decreased and their proliferation delayed. However, once committed, hMSCs from nonunions were able to proliferate, differentiate into osteoblastic cells and mineralize in vitro as efficiently as hMSCs from healthy subjects. In parallel, we found altered serum levels of chemokines and growth factors involved in the chemotaxis and proliferation of hMSCs such as leptin, interleukin-6 (IL-6) and its soluble receptor, platelet-derived growth factor-BB (PDGF-BB), stem cell factor (SCF) and insulin-like growth factor-1 (IGF-1). Moreover, we showed that the number of EPCs and their regulating growth factors were not affected in nonunion patients. If nonunion is generally attributed to a vascular defect, our results also support a role for a systemic mesenchymal and osteogenic cell pool defect that might be related to alterations in systemic levels of factors implicated in their chemotaxis and proliferation.

Calretinin immunoreactivity was localized during chick embryonic cervical spine development from day 4 until day 16. A transitory expression of calretinin could be seen from embryonic day 5 to embryonic day 15 in the mesenchymal cells forming the intervertebral disc. Calretinin was most abundant at embryonic day 8 when a maximal proliferation of cells occurred. At embryonic day 12, calretinin positive fibroblasts were located along the fibers forming the annulus fibrosus. At embryonic day 16, calretinin immunoreactivity could no more be detected in the cervical column. In conclusion, an intracellular calcium binding proteins belonging to the calmodulin/troponin C superfamily, appeared to be a marker for the disc formation.

Calbindin-D28k, calretinin, and recoverin, three intracellular calcium-binding proteins belonging to the troponin C/calmodulin superfamily, were immunohistochemically localized in chick pineal during development [from embryonic day 16 (E16) to postnatal day 14 (P14)]. At E18, only calretinin immunoreactivity could be detected in nuclei from follicular pinealocytes. With development, calretinin immunoreactivity expanded from nucleus to cytoplasm, and calretinin immuno-positive cell number increased. At P14 almost al pinealocytes were calretinin positive. Calbindin-D28k immunoreactivity was not detected before E20. During development, many follicular and parafollicular pinealocytes became strongly calbindin-D28k positive, reaching a peak both in intensity and in number at P7; thereafter their number decreased. In addition to pinealocytes, neuron-like cells appeared calbindin-D28k positive at E20 and calretinin positive at P7. Recoverin, a myristoylated protein isolated from vertebrate photoreceptor and which might participate in the inactivation of the phototransduction cascade, was transiently expressed in follicular and parafollicular pinealocytes from P1 to P14 with a maximal expression at P7. This transitory expression may coincide with a transitory light sensitivity period in chick pinealocytes, before complete maturity of the pineal gland.

In pineal gland, melatonin is synthesized in pinealocytes. Pharmacological studies using calmodulin antagonists suggested that melatonin synthesis was regulated through calmodulin. However, immunohistochemical studies showed that calmodulin could only be detected in pineal glial cells, and not in pinealocytes. To further investigate this discrepancy, we have tried to detect calmodulin not seen by immunohistochemical methods. We have used rat and chicken pineal homogenate supernatants and Triton X-100-treated pellets denatured by sodium dodecyl sulfate, subjected to electrophoresis and immunoblotting using anti-calmodulin antibodies. Two different IgG (#465 and #860) purified from anti-calmodulin sera were used. In rat pineal homogenate supernatants, calmodulin could be detected by immunoblotting using both antibodies. Some calmodulin could also be detected in the Triton-treated pellet fractions, but no additional cross-reacting bands were detected. However, in both chicken pineal homogenate supernatants and Triton-extracted pellets, in addition to a calmodulin immunoreactive band, two other proteins with approximate molecular masses (M(r)) of 56 kDa and 60 kDa were detected using anti-calmodulin #465. For comparison, similar immunoblot experiments were performed for detection of calbindin-D28K and calretinin, two other calcium binding proteins expressed in different pineal cell populations. Interestingly, Triton extraction of chicken pineal pellets revealed additional bands cross-reacting with each antibody. Anti-calbindin-D28K cross-reacted strongly with a M(r) = 68 kDa protein and weakly with a M(r) = 56 kDa protein. Anti-calretinin cross-reacted strongly with a M(r) = 93 kDa protein and weakly with a M(r) = 56 kDa protein.

Neurocalcin, a newly discovered calcium-binding protein belonging to the recoverin-like superfamily, was detected immunohistochemically in tufted cells from the rat olfactory bulb. More precisely, only periglomerular tufted cells and some tufted cells from the external plexiform layer were expressing neurocalcin. Western blot analysis has confirmed the presence of neurocalcin in rat olfactory bulb. Lack of neurocalcin immunoreactivity in mitral cells and periglomerular cells favor a different phylogenic origin between tufted and mitral or periglomerular cells.

Calcium ions play a critical role in neural development. Insights into the ontogeny of Ca2+ homeostasis were gained by investigating the developmental expression of two E-F hand calcium-binding proteins. Calretinin and calbindin were monitored through their immunoreactivity in the developing chick cerebellum (from E6 to E20). Calbindin was detected from E13 and in Purkinje cells only. Intensity of labelling increased with Purkinje cell development. Calretinin presented a transitory immunoreactivity between E11 and E20 in the internal granular cell layer. This cell layer contains cells which will differentiate into Golgi and granular cells which are calretinin-negative in adult chick cerebellum. Calretinin immunoreactivity presented a peak (both in number of cells and in intensity) at E15 and fell dramatically after E20 while calbindin immunoreactivity was restricted to the Purkinje cells and increased with the development of these cells.

Three parent peptides were shown to coexist in four rat brain regions: PHI(1–27)NH2 (peptide with an N-terminal histidine and a C-terminal isoleucinamide commonly called PHI), PHI-Gly (PHI(

Calcium plays a fundamental role in the cell as second messenger and is principally regulated by calcium-binding proteins. Although these proteins share in common their ability to bind calcium, they belong to different subfamilies. They present, in general, specific developmental and distribution patterns. Most Purkinje cells express the fast and slow calcium buffer proteins calbindin-D28k and parvalbumin, whereas basket, stellate and Golgi cells the slow buffer parvalbumin only. They are, almost all, calretinin negative. Granule, Lugaro and unipolar brush cells present an opposite immunoreactivity profile, most of them being calretinin positive while lacking calbindin-D28k and parvalbumin. The developmental pattern of appearance of these proteins seems to follow the maturation of neurons. Calbindin-D28k appears early, shortly after cessation of mitosis when neurons become ready to start migration and differentiation while parvalbumin is expressed later in parallel with an increase in neuronal activity. The other proteins are generally detected later. During development, some of these proteins, like calretinin, are transiently expressed in specific cellular subpopulations. The function of these proteins is not fully understood, although strong evidence supports a prominent role in physiological settings with altered calcium concentrations. These proteins regulate and are regulated by intracellular calcium level. For example, they may directly or indirectly enable sensitization or desensitization of calcium channels, and may further block calcium entry into the cells, like the calcium-sensor proteins, that have been shown to be potent and specific modulators of ion channels, which may allow for feedback control of current function and hence signaling. The absence of calcium buffer proteins results in marked abnormalities in cell firing; with alterations in simple and complex spikes or transformation of depressing synapses into facilitating synapses. Calcium-binding protein implication in resistance to degeneration is still a controversial issue. Neurons rich in calcium-binding proteins, especially calbindin-D28k and parvalbumin, seem to be relatively resistant to degeneration in a variety of acute and chronic disorders. However other data support that an absence of calcium-binding proteins may also have a neuroprotective effect. It is not unlikely that neurons may face a dual action mechanism where a decrease in calcium-binding proteins has a first short-term beneficial effect while it becomes detrimental for the cell over the long term.

Profound morphological modifications occur during postnatal development of the rat pineal gland. We have immunohistochemically followed those events from postnatal day 1 to 20 by using three cytoarchitectonic markers (S-100, calbindin-D28k, and calretinin) that belong to the calmodulin/troponin C calcium-binding protein family. In the developing rat pineal, anticalbindin-D28k antibody labels three cell types: immature and mature astrocytes and perivascular type II pinealocytes. During development, calbindin-D28k positive cells migrate from the base of the pineal stalk into the superficial part of the pineal. Calbindin-D28k, usually used as a neuronal marker in the central nervous system, recognizes in rat pineal precursor astrocytes 5 days before S-100 and labels a subpopulation somewhat different from S-100 positive astrocytes. Calretinin immunoreactivity appeared in the postero-superior part of the pineal and was abundant until postnatal day 5, then its density dramatically felt to leave, after postnatal day 20, an occasional population of cells whose morphology is compatible with neuron-like cells.

Calmodulin, calbindin-D28k and calretinin are calcium-binding proteins largely distributed in the bipolar olfactory receptor cells. In the olfactory epithelium their distribution seemed to be random. Using immunohistochemistry we have examined their localization in rat olfactory axons extending to the olfactory bulb. Sections were analyzed both horizontally and vertically. Almost all fibers were immunoreactive for one of the three intracellular calcium-binding proteins whose distribution was not random among the bundles. Three different subclasses of fibers could be detected: calbindin-D28k and calretinin immunoreactivities were restricted to external fibers whereas calmodulin immunoreactivity was intense, abundant and largely distributed throughout the internal portion of the olfactory nerve. This additional degree of organization detected in the olfactory axons might play a role in odor discrimination.

Calmodulin distribution in the chicken pineal organ was investigated by immunohistochemistry. Calmodulin immunoreactivity was detected in ependymocytes in the follicular zone and in interstitial cells in the parafollicular zone. No calmodulin immunoreactivity was detected in pinealocytes. Lack of calmodulin immunoreactivity in pinealocytes raises questions about its proposed function in melatonin synthesis as suggested by pharmacological studies using calmodulin antagonists. The calmodulin distribution was comparable to that of S100, a glial cell marker. Two other markers, calbindin-D28k and calretinin, which in neuroanatomical studies give excellent cytoarchitectonic staining, in the chick pineal permitted the detection of two subclasses of pinealocytes. One was darkly stained by calbindin-D28k and rare. The other was very abundant and calretinin positive. In the parafollicular zone, calbindin-D28k and/or calretinin antibodies allowed us to visualize cells presenting a neuron-like morphology. Calretinin immunoreactivity was detected in nearly all pinealocytes in which hydroxy-indol-O-methyl transferase was also located. Comparison between the lack of calmodulin and the presence of calretinin, belonging to the same calcium-binding protein family, in chick pinealocytes raises the hypothesis about a possible role of calretinin in melatonin synthesis.