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Background: Currently, fat graft viability and retention cannot be reliably predicted. The reasons for this variability are not fully understood, although fat processing has been implicated. Objectives: The authors compare the in vitro quantity and in vivo fat retention from lipoaspirate processed by the Revolve system (LifeCell, Bridgewater, New Jersey) compared with centrifugation and decantation. Methods: Ten patients were enrolled in this prospective study. Lipoaspirate from each patient was processed by each of 3 methods: decantation, centrifugation, and the Revolve system. Biochemical characteristics and free oil, adipose, and aqueous phases of the processed fats were determined. Fat grafts were implanted in nude mice; volume retention and quality of the fat grafts were evaluated after 28 days. Viability of retained fat was demonstrated by intact adipocytes and neovascularization on histology. Results: Of the 10 patients, 9 were women and 1 was a man. Mean patient age was 40.7 ± 8.9 years (range, 30-55 years). Fat tissue obtained from all methods had good physiological properties with neutral pH and isotonic salt concentrations. The Revolve system yielded significantly less blood cell debris, a higher percentage of adipose tissue, and a lower percentage of free oil compared with the other 2 methods. Fat tissue retention from Revolve samples was significantly higher (73.2%) than that from decanted samples (37.5%) and similar to that from centrifuged samples (67.7%). Conclusions: The Revolve system produced physiologically compatible, preinjection fat with reduced contaminants and free oil in conjunction with high fat content. In an animal model, volume retention of Revolve-processed fat grafts was significantly greater than decanted samples. The Revolve system presents a fat-processing option that was less time-consuming, easier to use, and more efficient in this study than standard centrifugation or decantation.

During post-natal development, tendons undergo a well orchestrated process whereby extensive structural and compositional changes occur in synchrony to produce a normal tissue. Conversely, during the repair response to injury, structural and compositional changes occur, but in this case, a mechanically inferior tendon is produced. As a result, the process of development has been postulated as a potential paradigm through which improved adult tissue healing may occur. In this study we measured the mechanical, compositional, and structural properties in the post-natal mouse Achilles tendon at 4, 7, 10, 14, 21, and 28 days old. Throughout post-natal development, the mechanical properties, collagen content, fibril diameter mean, and fibril diameter standard deviation increased. Biglycan expression decreased and decorin expression and fiber organization were unchanged. This study provides a new mouse model that can be used to quantitatively examine mechanical development, as well as compositional and structural changes and biological mechanisms, during post-natal tendon development. This model is advantageous due to the large number of genetically modified mice and commercially available assays that are not available in other animal models. A mouse model therefore allows future mechanistic studies to build on this work.

CD44 plays an important role in inflammation and healing. Previous studies have investigated its role in inflammatory diseases and skin wounds; however, the role of CD44 in tendon healing is unknown. Therefore, the aim of this study was to investigate the effect of CD44 in the healing of the patellar tendon in a knockout mouse model. It was hypothesized that in comparison to wild type counterparts, CD44 knockout mice would have decreased material parameters, increased organization, decreased expression of proinflammatory cytokines and increased expression of matrix components during healing. These hypotheses were tested through an in vivo surgical model and mechanical, organizational, and gene expression analyses. Material strength and tissue organization were significantly improved in the CD44 knockout mouse. This could be attributed to increased expression of cytokines and matrix components that are elevated in regenerative healing. This study shows that the absence of CD44 in a mouse patellar tendon injury creates an environment that is conducive to regenerative healing through altered gene expression, resulting in superior material properties and reduced cross-sectional area. Therefore, this study indicates that limiting the role of CD44 may improve healing parameters in adult tendon injury.

Type XIV collagen is a fibril-associated collagen with an interrupted triple helix. This collagen interacts with the fibril surface and has been implicated as a regulator of fibrillogenesis; however, a specific role has not been elucidated. Functional roles for type XIV collagen were defined utilizing a new type XIV collagen-deficient mouse line. This line was produced using a conventional targeted knock-out approach. Col14a1(–/–) mice were devoid of type XIV collagen, whereas heterozygous mice had reduced synthesis. Both mutant Col14a1 genotypes were viable with a grossly normal phenotype; however, mature skin exhibited altered mechanical properties. Prior to evaluating tendon fibrillogenesis in type XIV collagen-deficient mice, the developmental expression patterns were analyzed in wild-type flexor digitorum longus (FDL) tendons. Analyses of mRNA and protein expression indicated tissue-specific temporal expression that was associated with the early stages in fibrillogenesis. Ultrastructural analyses of wild-type and null tendons demonstrated premature fibril growth and larger fibril diameters in tendons from null mice at postnatal day 4 (P4). However, fibril structure in mature tendons was normal. Biomechanical studies established a direct structure/function relationship with reduced strength in P7-null tendons. However, the biomechanical properties in P60 tendons were comparable in null and wild-type mice. Our results indicate a regulatory function for type XIV collagen in early stages of collagen fibrillogenesis with tissue differences.

Purpose Interleukin-10 (IL-10) is a potent anti-inflammatory cytokine shown to inhibit scar formation in fetal wound healing. The role of IL-10 in adult tendon healing and scar formation, however, remains unknown. The objective of this study is to investigate the effect of IL-10 overexpression on the properties of adult healing tendon using a well-established murine model of tendon injury and a lentiviral-mediated method of IL-10 overexpression. Methods A murine model of patellar tendon injury was used and animals divided into 3 groups. Mice received bilateral patellar tendon injections with a lentiviral vector containing an IL-10 transgene (n = 34) or no transgene (n = 34). Control mice (n = 34) received injections of sterile saline. All animals then were subjected to bilateral, central patellar tendon injuries 2 days after injection and were killed at 5, 10, 21, and 42 days after injury. IL-10 content was analyzed by immunohistochemistry (n = 4/group). Tendon healing was evaluated by histology (n = 4/group) and biomechanical analysis (n = 10/group). Results Overexpression of IL-10 in patellar tendon was confirmed after injection of the lentiviral vector. IL-10 immunostaining was increased at day 10 in the IL-10 group relative to that in controls. Histologically, there was no significant difference in angular deviation between groups at day 21, but a trend toward decreased angular deviation in controls relative to that in empty vector group mice was seen at day 42. Biomechanically, the IL-10 group showed significantly increased maximum stress at day 42 relative to that in controls. Percent relaxation showed a trend toward an increase at day 10 and a significant increase at day 42 in the IL-10 group relative to that in controls. Conclusions This study demonstrates successful gene transfer of IL-10 into adult murine patellar tendon using a lentiviral vector. Although the effects of overexpression of IL-10 on adult tendon healing have not yet been fully elucidated, the current study may help to further clarify the mechanisms of tendon injury and repair.