Spatial and temporal expression of molecular markers and cell signals during normal development of the mouse patellar tendon.

Division of Developmental Biology, Cincinnati Children's Hospital Research Foundation, Cincinnati, OH 45229, USA.
Tissue Engineering Part A (Impact Factor: 4.64). 09/2011; 18(5-6):598-608. DOI: 10.1089/ten.TEA.2011.0338
Source: PubMed

ABSTRACT Tendon injuries are common clinical problems and are difficult to treat. In particular, the tendon-to-bone insertion site, once damaged, does not regenerate its complex zonal arrangement. A potential treatment for tendon injuries is to replace injured tendons with bioengineered tendons. However, the bioengineering of tendon will require a detailed understanding of the normal development of tendon, which is currently lacking. Here, we use the mouse patellar tendon as a model to describe the spatial and temporal pattern of expression of molecular markers for tendon differentiation from late fetal life to 2 weeks after birth. We found that collagen I, fibromodulin, and tenomodulin were expressed throughout the tendon, whereas tenascin-C, biglycan, and cartilage oligomeric protein were concentrated in the insertion site during this period. We also identified signaling pathways that are activated both throughout the developing tendon, for example, transforming growth factor beta and bone morphogenetic protein, and specifically in the insertion site, for example, hedgehog pathway. Using a mouse line expressing green fluorescent protein in all tenocytes, we also found that tenocyte cell proliferation occurs at highest levels during late fetal life, and declines to very low levels by 2 weeks after birth. These data will allow both the functional analysis of specific signaling pathways in tenocyte development and their application to tissue-engineering studies in vitro.

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Available from: David Butler, Oct 16, 2014
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    • "During mouse patellar tendon development, all cells in the tendon were found to respond to TGFβ and BMP signaling at all stages examined, including embryonic and postnatal periods (Liu et al., 2012). In vitro micromass culture of chick mesodermal cells with TGFβ demonstrated significant upregulation of tendon markers Scx and Tnmd, with concurrent reduction in cartilage markers. "
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    • "Phase 3: Between 1995 and 2003, our work moved to the tissue/cell level, as we and our collaborators continued to record in vivo tissue forces [32] [33] [34] [35] [36] [37] [38] and initiated studies to identify novel therapies in tissue engineering and functional tissue engineering (FTE) [39] [40] [41] [42] [43] [44] [45] [46] [47] [48] [49]. Phase 4: Our most recent work, between 2004 and 2012, has progressed even smaller to the tissue/cell/molecular levels as we have sought to develop not only design criteria for tissue-engineered tendon and ligament repairs compared to normal tissues [50–74] but also new research directions in " fundamental tissue engineering " at the interface of FTE and developmental biology [75] [76] [77] [78] [79] [80] [81] [82]. What follows are brief summaries of the four phases of our musculoskeletal research. "
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    ABSTRACT: The use of growth differentiation factor 5 (GDF-5) in damaged tendons has been shown to improve tendon repair. It has been hypothesized that further improvements may be achieved when GDF-5 is used to promote cell proliferation and induce tenogenic differentiation in human bone marrow-derived mesenchymal stem cells (hMSCs). However, the optimal conditions required to produce these effects on hMSCs have not been demonstrated in previous studies. A study to determine cell proliferation and tenogenic differentiation in hMSCs exposed to different concentrations of GDF-5 (0, 5, 25, 50, 100 and 500 ng/ml) was thus conducted. No significant changes were observed in the cell proliferation rate in hMSCs treated at different concentrations of GDF-5. GDF-5 appeared to induce tenogenic differentiation at 100 ng/ml, as reflected by (1) a significant increase in total collagen expression, similar to that of the primary native human tenocyte culture; (2) a significant upregulation in candidate tenogenic marker gene expression, i.e. scleraxis, tenascin-C and type-I collagen; (3) the ratio of type-I collagen to type-III collagen expression was elevated to levels similar to that of human tenocyte cultures, and (4) a significant downregulation of the non-tenogenic marker genes runt-related transcription factor 2 and sex determining region Y (SRY)-box 9 at day 7 of GDF-5 induction, further excluding hMSC differentiation into other lineages. In conclusion, GDF-5 does not alter the proliferation rates of hMSCs, but, instead, induces an optimal tenogenic differentiation response at 100 ng/ml.
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