Expression of heparanase in newborn mouse growth plates

Abstract

Endochondral ossification is tightly regulated by various heparan sulphate (HS)-binding growth factors, such as fibroblast growth factor 2 and Indian hedgehog. However, HS chains immobilized as substituents on cell surface or matrix proteoglycans are limited in the capacity to present these growth factors efficiently to their corresponding signaling receptors. We hypothesize that heparanase, an endo-E-Dglucuronidase, cleaves HS chains at specific sites to yield mobile HS fragments and avails HS-binding growth factors to their targets. Here we aim to map the expression pattern of heparanase in growth plates of both Hspg2¨3/¨3 , a HS-deficient perlecan mouse mutant, and its wildtype littermates by immunohistochemistry. In both mutant and wildtype animals, heparanase protein was detectable in both the pericellular and extracellular matrix of the resting and proliferative zones but not detectable in the pre-hypertrophic zone. In particular, heparanase is localized in the extracellular matrix of the hypertrophic zone where von Kossa staining of calcium deposits were also found. Our results suggest little involvement of HS moieties of perlecan in the distribution of heparanase and HS-mediated maturation process of the growth plate.