Comparative study of the properties of tendinocytes derived from three different sites in the equine superficial digital flexor tendon

Abstract

This aim of this study was to determine the characteristic differences in tendinocytes derived from three sites of the equine superficial digital flexor tendon (SDFT)-proximally the myotendinous junction (MTJ), mid-metacarpal (mM) and osteotendinous junction (OTJ)-in morphology, proliferation, and ability for synthesis of collagen and matrix metalloproteinases (MMPs). Little difference was observed in cell proliferation. Addition of tumor necrosis factor (TNF) α to the culture medium resulted in increased collagen synthesis by tendinocytes from all three sites. The amount of collagen synthesized by tendinocytes derived from the mM and OTJ was much larger than that synthesized by untreated tendinocytes. A collagen zymogram revealed that proMMP-13 synthesis was increased towards the distal site. However, TNFα treatment resulted in a significant decrease in the amount of proMMP-13 synthesized by tendinocytes from all three sites. On the other hand, a gelatin zymogram showed that the synthesis level of proMMP-9 tended to decrease towards the distal site, but there was little difference between synthesis levels of proMMP-9 before and after TNFα treatment. These results indicated that tendinocytes in the same tendon have different characteristics and that these characterisities would reflect the function of tendinocytes in vivo. Also, the isolated tendinocytes provided much information on the characteristics and properties of tendons for the ECM turnover system and on the responsiveness of tendinocytes to complex inflammatory responses in a tendinopathy condition.Tendon injury, especially in the superficial digital flexor tendon (SDFT), has proved to be a major problem for racehorses. Recent studies have shown that about 10-30% of racehorses suffer from tendonitis (8, 30). Interestingly, tendonitis occurs more frequently in the forelimb, especially in the SDFT rather than the deep digital flexor tendon (DDFT), and rarely occurs in the common digital extensor tendon (CDET) (1, 30). The vulnerability of the SDFT is related to its functions in weight supporting and in accumulation and transmission of elastic force for effective movement. Damage to the SDFT usually occurs during high-speed work or racing competition in which the forelimbs are pulled up to the highest position to bear maximum load or straining power (14,35). Moreover, tendonitis in the SDFT occurs in the mid-metacarpal (mM) site in most cases (1). Therefore, structural properties of the tendons might reflect the occurrence ratio of tendonitis (10). The etiology of tendonitis has been discussed in many reports; however, there is little information regarding the mechanism of tendon degradation. Extracellular matrix (ECM) turnover in a tendon might occur repeatedly and routinely as in other connective tissues (13), and matrix metalloprotein-

Spatiotemporal variations in gene expression, histology and biomechanics in an ovine model of tendinopathy

“…BGN , ADAMTS5 , MMP2 , and MMP13 expression was decreased with increasing distance from the lesion site, in both transected and control tendons, while MMP13 , TIMP2 and COL3A1 showed similar proximal or distal distribution of expression in both transected and control tendons. This commonality supports the suggestion that gene expression of some matrix components by tenocytes is regulated by common biomechanical factors within the regional tendon environment [86]. In transected tendons, COL1A1 expression increased while COL3A1 was decreased with increasing distance from the lesion.…”

Low‐level laser therapy in collagenase‐induced Achilles tendinitis in rats: Analyses of biochemical and biomechanical aspects

“…4,11 The synthesis of MMPs in human tendons can be drastically changed in inflammatory conditions. 12,13 Therefore, the expression of MMP-1, MMP-3, MMP13, IL-1b, cyclooxygenase 2 (COX-2), and some inflammatory mediators, would be related to tendon growing, remodeling or healing. [14][15][16] More specifically, pro-inflammatory cytokines, such as interleukin-1 beta (IL-1b) and tumor necrosis factoralpha (TNFa) can stimulate MMPs synthesis in several kinds of cells, including tendinocytes.…”

“…[14][15][16] More specifically, pro-inflammatory cytokines, such as interleukin-1 beta (IL-1b) and tumor necrosis factoralpha (TNFa) can stimulate MMPs synthesis in several kinds of cells, including tendinocytes. 12,17 Therefore, due to the inflammatory process a degradation of collagen type I and II can be found in tendon tissue, because these collagen types are, in majority, substrates of MMP-13. 12 In tendinopathies increased expression of MMP-1, MMP-9, and MMP-13 have been observed beside decreased type II collagen expression, which consequently might negatively impact in structural integrity of tendon tissue and predispose tendon to rupture.…”

“…12,17 Therefore, due to the inflammatory process a degradation of collagen type I and II can be found in tendon tissue, because these collagen types are, in majority, substrates of MMP-13. 12 In tendinopathies increased expression of MMP-1, MMP-9, and MMP-13 have been observed beside decreased type II collagen expression, which consequently might negatively impact in structural integrity of tendon tissue and predispose tendon to rupture. 18 However, few studies have investigating the role of MMPs on tissue biomechanical properties in musculoskeletal inflammatory disorders.…”

Tenascin-C Expression in Equine Tendon-derived Cells During Proliferation and Migration

“…Although various tendon components, such as collagens, tenascin-C (TN-C), cartilage oligomeric matrix protein (COMP), scleraxis and other matrix components, have been determined [3, 6, 19, 27], information about the many recovery processes of equine tendonitis is very limited. In vitro cell culture systems provide a convenient tool for studying the functions of cells in specific tissues or organs, and the specificity of equine tendon cell lines has been examined [10, 11, 26]. About 60–68% of the dry weight of tendons is collagen [15], and collagen type I (Col I) arranged in tensile-resistant fiber comprises about 60% of the total collagen content.…”