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Effects of TGF‐β1 and triiodothyronine on cartilage maturation: In vitro analysis using long‐term high‐density micromass cultures of chick embryonic limb mesenchymal cells
Author(s) -
Mello Maria A.,
Tuan Rocky S.
Publication year - 2006
Publication title -
journal of orthopaedic research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.041
H-Index - 155
eISSN - 1554-527X
pISSN - 0736-0266
DOI - 10.1002/jor.20233
Subject(s) - chondrogenesis , endochondral ossification , mesenchymal stem cell , medicine , microbiology and biotechnology , cartilage , endocrinology , mesenchyme , transforming growth factor , biology , chondrocyte , calcification , chemistry , anatomy
Endochondral ossification is initiated by differentiation of mesenchymal cells into chondrocytes, which produce a cartilaginous matrix, proliferate, mature, and undergo hypertrophy, followed by matrix calcification, and substitution of cartilage by bone. A number of hormones and growth factors have been implicated in this process. Using in vitro, long‐term, high‐density, micromass cultures of chick embryonic mesenchyme, that recapitulate the process of chondrogenesis, chondrocyte maturation, and hypertrophy, we have investigated the importance of a balance between proliferation and apoptosis in cartilage maturation, focusing specifically on the effects of transforming growth factor‐β1 (TGF‐β1) and the thyroid hormone, triiodothyronine (T3). Our results showed that TGF‐β1 stimulates proliferation, by week 2 of culture, and T3 inhibits proliferation by week 3. Cell size increases in cultures treated with T3. Collagen type X is expressed in all culture, and delay in matrix deposition is seen only in the cultures treated with TGF‐β1. T3 stimulates alkaline phosphatase activity, but not calcification. T3 enhances apoptosis, as seen by TUNEL staining, and internucleosomal DNA fragmentation. The results support the roles of T3 and TGF‐β in cartilage maturation, i.e., TGF‐β stimulates proliferation and suppresses hypertrophy, while T3 stimulates hypertrophy and apoptosis. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 24:2095–2105, 2006