Introduction Tendinopathy, a pathological condition caused by tendon overuse, adversely affects millions of people in athletic and occupational settings worldwide. The underlying molecular mechanisms in the development of tendinopathy are poorly understood, however, increased mast cell numbers have been detected in human patellar tendinopathy specimens. Mast cells are known to increase fibroblast proliferation and collagen production leading to fibrosis in some tissues. The present study was carried out to determine the effects of mast cells on isolated human tendon fibroblasts (tenocytes) and explore a possible role for mast cells in the development of tendinopathy.
Methods Primary human tenocytes were isolated from hamstring tendons of healthy donors. Light and electron microscopy were used to examine a physical association between mast cells (HMC-1) and tenocytes, in vitro. Collagen gel contraction assay was used to examine the effects of mast cells on isolated tenocytes. Cell viability and proliferation was assessed by MTS assay. Gene expression was quantitated by qPCR.
Results HMC-1 mast cells were shown by light and electron microscopy to physically bind to primary tenocytes through adherent junctions. Immunostaining for stem cell factor (SCF), a mast cell growth factor, showed homogeneous expression of this protein on the surface of tenocytes. Additionally, qPCR showed an increase in tenocyte SCF mRNA expression in the presence of mast cells. In other experiments, both mast cells and mast cell sonicates were shown to induce tenocyte mediated contraction of collagen gel, which appeared to be driven by TGF-β1. MTS assay showed a mast cell mediated increase in tenocyte survival and proliferation.
Discussion These findings suggest that either through physical association with tenocytes and/or release of mediators, mast cells could play a role in the regulation and activation of tenocytes. Further studies are underway to investigate the molecular mechanisms of mast cell-tenocyte interactions and whether these could play a role in the pathogenesis of tendinopathy.
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