Indian hedgehog and syndecans-3 coregulate chondrocyte proliferation and function during XXXX limb skeletogenesis.

@entity705 @entity1573 @entity1184 @entity72309
Hedgehog proteins exert critical roles in embryogenesis and require heparan sulfate proteoglycans (HS-PGs) for action. Indian hedgehog (Ihh) is produced by prehypertrophic chondrocytes in developing long bones and regulates chondrocyte proliferation and other events, but it is not known whether it requires HS-PGs for function. Because the HS-PG @entity72309 is preferentially expressed by proliferating chondrocytes, we tested whether it mediates Ihh action. Primary @entity1573 chondrocyte cultures were treated with recombinant Ihh (rIhh-N) in absence or presence of heparinase I or @entity72309 neutralizing antibodies. While rIhh-N stimulated proliferation in control cultures, it failed to do so in heparinase- or antibody-treated cultures. In reciprocal gain-of-function studies, chondrocytes were made to overexpress @entity72309 by an RCAS viral vector. Cells became more responsive to rIhh-N, but even this response was counteracted by heparinase or antibody treatment. To complement the in vitro data, RCAS viral particles were microinjected in day 4-5 @entity1573 wing buds and effects of @entity72309 misexpression were monitored over time. @entity72309 misexpression led to widespread chondrocyte proliferation and, interestingly, broader expression and distribution of Ihh. In addition, the @entity72309 misexpressing skeletal elements were short, remained @entity705 , lacked osteogenesis, and exhibited a markedly reduced expression of collagen X and osteopontin, products characteristic of @entity1184 chondrocytes and bone cells. The data are the first to indicate that Ihh action in chondrocyte proliferation involves @entity72309 and to identify a specific member of the syndecan family as mediator of hedgehog function.
