Abstract
The presence of uniformly small collagen fibrils in tendon repair is believed to play a major role in suboptimal tendon healing. Collagen V is significantly elevated in healing tendons and plays an important role in fibrillogenesis. The objective of this study was to investigate the effect of a particular chain of collagen V on the fibrillogenesis of Sprague-Dawley rat tenocytes, as well as the efficacy of Col V siRNA engineered tenocytes for tendon tissue engineering. RNA interference gene therapy and a scaffold free tissue engineered tendon model were employed. The results showed that scaffold free tissue engineered tendon had tissue-specific tendon structure. Down regulation of collagen V α1 or α2 chains by siRNAs (Col5α1 siRNA, Col5α2 siRNA) had different effects on collagen I and decorin gene expressions. Col5α1 siRNA treated tenocytes had smaller collagen fibrils with abnormal morphology; while those Col5α2 siRNA treated tenocytes had the same morphology as normal tenocytes. Furthermore, it was found that tendons formed by coculture of Col5α1 siRNA treated tenocytes with normal tenocytes at a proper ratio had larger collagen fibrils and relative normal contour. Conclusively, it was demonstrated that Col V siRNA engineered tenocytes improved tendon tissue regeneration. And an optimal level of collagen V is vital in regulating collagen fibrillogenesis. This may provide a basis for future development of novel cellular- and molecular biology-based therapeutics for tendon diseases.
Highlights
Tendons and ligaments are frequently targets of injury from trauma in sports and aging [1,2]
Ultrastructural immunolocalization demonstrated that the homotrimer a1(V)3 was localized at the surface of wide collagen I fibrils as thin filamentous structures and did not regulate fibril assembly, whereas the heterotrimer a1(V)2 a2(V) was buried in the fibril interior and regulated collagen fibrillogenesis [18]
The present study for the first time demonstrated the use of a scaffold-free tissue engineered tendon model for investigating the biological function of collagen V in tendon fibrillogenesis
Summary
Tendons and ligaments are frequently targets of injury from trauma in sports and aging [1,2]. A uniform distribution of small diameter collagen fibrils has been found with poorer mechanical properties than native tissue and shows no improvement of mechanical properties with time[6]. At the early stage of assembly, immature fibril segments is regulated by the NH2-terminal domain of type V collagen [11]. These NH2-terminal domains alter accretion of collagen molecules onto fibrils and lateral growth. Collagen fibrils in tendon and ligament are heterotypic type I/V fibrils and a1(V)2a2(V) is the favored and functional heterotrimer [16,17]. The involvement of collagen V in tendon matrix organization is well established, the functional significance of the particular chains of collagen V in tendon tissue engineering is remained unknown
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