Comparative immunolocalisation of perlecan, heparan sulphate, fibroblast growth factor-18, and fibroblast growth factor receptor-3 and their prospective roles in chondrogenic and osteogenic development of the human foetal spine.

Abstract

A comparative immunolocalisation study of perlecan, HS, FGF-18 and FGFR-3 in the 12-20-week gestational age human foetal spine was undertaken to identify spatiotemporal associations between these components to provide insights into prospective roles in spinal development. Comparative immunolocalisations of matrix and cell associated components in Histochoice-fixed paraffin-embedded human foetal spinal tissues. The 12-14-week-old human foetal spine was a predominantly cartilaginous structure with the discs displaying a relative paucity of proteoglycan compared to the adjacent cartilaginous vertebral rudiments, notochordal remnants were also observed. HS and perlecan had a widespread distribution throughout the spine at 12 weeks, however, FGF-18 was only localised to the outer AF margins and hypertrophic cell condensations in the vertebral bodies. This contrasted with HS distributions at 14-20 weeks, which were prominent in the developing intervertebral disc (IVD). Ossification centres were also evident centrally within the vertebral rudiments surrounded by small columns of hypertrophic chondrocytes which expressed FGFR-3 and FGF-18 and upregulated levels of perlecan. FGF-18 also had a prominent localisation pattern in the developing IVD and the cartilaginous endplate while FGFR-3 was expressed throughout the disc interspace. This suggested roles for perlecan, FGF-18 and FGFR-3 in chondrogenic and osteogenic events which drive discal development and ossification of the vertebral bodies. The above data supported a role for FGF-18 in discal development and in the terminal osteogenic differentiation of chondroprogenitor cell populations, which promote vertebral ossification during spinal development.