Type I collagen production and growth factor expression in developing and adult human bone

• Main Author: Beeton, C. A.
• Published: University of Cambridge 2000
• Subjects: 612
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.596525

The study focused on the expression of the precursor to type I collagen (type I procollagen), type X collagen, transforming growth factor beta (TGFβ) isoforms. TGFβ receptors (TGFβ R) and parathyroid hormone related peptide (PTHrP) in the growing and adult human skeleton <I>in vivo</I> to determine the changes in production of type I collagen and the expression of growth factors associated with cellular maturation in the vertebral growth plate using normal developing human bone obtained at post mortem from three gestational ages; 25-30 weeks (Group 1), 37-40 weeks (Group 2) and 2 - 3 months post-natal (Group 3). Type I procollagen and type X collagen are maximally expressed by hypertrophic and mineralising chondrocytes in the cartilage of all groups. TGFβ1, TGFβ2 and TGFβ3 expression also increased with increased cellular maturation. However, less TGFβ1 was observed in bone whereas higher expression of TGFβ2 was seen. Similar expression of TGFβ RI and RII was observed in individual samples. Both receptors were absent in the resting chondrocytes but were consistently expressed at further stages of cartilage maturation with occasional expression in the bone. PTHrP was maximally expressed by the upper hypertrophic chondrocytes with lower levels of expression observed in the proliferating chondrocytes and mineralised bone. This study also investigated the production of type I collagen at both the mRNA and protein levels, and TGFβ isoforms at the mRNA level in iliac crest bone biopsies obtained before and three months following liver transplantation. The results suggest that the increased bone turnover observed following liver transplantation is accompanied by an increase in type I collagen production and TGFβ1 expression.