|
Back to 2017 Scientific Program ePosters
The Presence of Embryonic Tendon Fibrillogenesis in a Healing Tendon Model
Kavita T. Vakharia, MD; John M. Ingraham, MD
Penn State Hershey Medical Center, Hershey, PA
Introduction: Embryonic tendon fibrillogenesis and ideal post-injury tendon healing both result in highly functional, intricate, and well-organized structures composed primarily of type I collagen fibers, and mediated by fibroblasts. In developing tendon, extracellular recesses in the fibroblast membrane dynamically coordinate fibril assembly and are seen with single or multiple collagen fibrils (Trelstad, 1986). Although they contain extracellular material, the recesses can be found within the body of fibroblast or a cytoplasmic extension (Hyashi, 1979); they have more recently been termed fibropositors (Kadler, 2004). The present study establishes the existence of fibropositors in a healing tendon model, further strengthening the similarities between developing and healing tendon.
Materials and Methods: Thirty adult male Sprague-Dawley rats were studied. The right Achilles tendon was exposed, transected at its midpoint, and directly repaired with a simple permanent monofilament suture. A sham operation (skin incision and closure) was performed on the contralateral control limb. Both limbs were casted nominally for 2 weeks. At 5-day intervals during a 45-day healing period, 3 rats were euthanized. The tendons were dissected; visibly ruptured specimens were eliminated. Healing specimens were sectioned at the repair site, fixed in Karnovsky's solution, embedded, and sectioned for transmission electron microscopy (TEM).
Results: Heterogeneous collagen bundle diameters were observed not only in healing specimens, but also controls; the former, however, showed more variability with a tendency towards less organization, increased extracellular matrix, and numerous small-diameter fibrils. In healing specimens, a large variety of associations were observed within individual fibropositors including one fibril, multiple fibrils, and fibrils with bundles (Figures 1 and 2). These arrangements were frequently plentiful and in close proximity to each other. Fibropositors were also observed in controls.
Conclusion: Fibropositors have a critical role in tendon development, coordinating the assembly of collagen fibril segments into fibrils and bundles. Fibropositors have been observed in cultured human fibroblasts (Kjaer, 2010) and a murine adhesion model (McGrouther, 2009), but this is the first time to our knowledge that fibropositors have been identified in a healing tendon model. Present in early and late healing phases, their role likely involves collagen reorganization, not neosynthesis.
Back to 2017 Scientific Program ePosters
|
