Identification, content, and distribution of type VI collagen in bovine tendons

Abstract

Tendon composition changes according to differentiation, mechanical load, and aging. In this study, we attempted to identify, localize, and quantify type VI collagen in bovine tendons. Type VI collagen was identified by the electrophoretic behavior of the alpha chains and Western blotting, and by rotary shadowing. Type VI collagen was extracted from powdered tendon with three sequential 24-h extractions with 4 M guanidine-HCl. The amount of type VI collagen was determined by enzyme-linked immunosorbent assay for purely tensional areas and for the compressive fibrocartilage regions of the deep flexor tendon of the digits, for the corresponding fetal and calf tendons, and for the extensor digital tendon. The distal fibrocartilaginous region of the adult tendon was richer in type VI collagen than the tensional area, reaching as much as 3.3 mg/g (0.33%) of the wet weight. Calf tendons showed an accumulation of type VI at the fibrocartilage site. Immunocytochemistry demonstrated that type VI collagen was evenly distributed in the tensional areas of tendons but was highly concentrated around the fibrochondrocytes in the fibrocartilages. The results demonstrate that tendons are variable with regard to the presence and distribution of type VI collagen. The early accumulation of type VI collagen in the region of calf tendon that will become fibrocartilage in the adult suggests that it is a good marker of fibrocartilage differentiation. Furthermore, the distribution of type VI collagen in tendon fibrocartilage indicates that it organizes the pericellular environment and may represent a survival factor for these cells.

Fibrochondrogenesis in Two Embryonic Stem Cell Lines: Effects of Differentiation Timelines

“…Similarly, the resulting constructs contained all three of these matrix components. The presence of collagen VI, recently shown to be particularly important in fibrocartilage development [25][26][27], is very promising in this study. The loss of collagen II by 6 weeks and the increase in collagen I staining, especially in the BG EBs, is suggestive of a transition toward a more fibroblastic lineage.…”

Aggrecan, versican and type VI collagen are components of annular translamellar crossbridges in the intervertebral disc

“…The small islands of rounded cells of a chondrocytic phenotype in the midmeniscus in a matrix rich in anionic proteoglycan (aggrecan) and type II collagen, may be one such example of focal compressive load leading to phenotypic adaptation of intrinsic cell populations [33]. Type VI collagen accumulates in regions of deep flexor digital tendon around nests of cells experiencing focal compressive load and has been suggested as a marker of fibrocartilage differentiation [8]. The supraspinatus tendon of the human rotator cuff contains a number of structurally independent fascicles which can be variably and independently loaded depending on joint angulation.…”

Effect of osteogenic protein‐1 on the matrix metabolism of bovine tendon cells

“…38 Recently, Carvalho et al showed that the bovine digital extensor tendon contains less type VI collagen, which is suggested to be a marker of fibrocartilage differentiation, than the deep flexor tendon. 39 However, it can be hypothesized that a portion of the extensor tendon fibroblastic cells became fibrochondrocytic cells to some extent and produced large PGs when stimulated by rhOP-1 treatment, similar to what is seen in tendons undergoing compressive force. 38 Further research on the precise identification of the large PGs (aggrecan and/or versican) and small PGs (decorin and/or biglycan) produced in response to rhOP-1 stimulation may provide answers to some of these questions.…”