Journal of Cell Science, Vol 110, Issue 21 2691-2701, Copyright © 1997 by Company of Biologists

JOURNAL ARTICLES

Dual action of sonic hedgehog on chondrocyte hypertrophy: retrovirus mediated ectopic sonic hedgehog expression in limb bud micromass culture induces novel cartilage nodules that are positive for alkaline phosphatase and type X collagen

NS Stott and CM Chuong
Department of Pathology, University of Southern California, Los Angeles 90033, USA.

Members of the vertebrate hedgehog gene family (HH) are involved in patterning and modulation of differentiation. Recently it has been shown that ectopic expression of HH gene family members in vivo blocks chondrocyte maturation through activation of a parathyroid hormone related peptide (PTHrP) dependent negative regulatory loop in the perichondrium. However, the direct effect of HH on chondrocyte maturation has not been tested. Here, we studied the effect of retroviral overexpression of the chicken sonic hedgehog gene (Shh) on the growth and maturation of limb bud cells in micromass cultures. Shh is neither expressed nor required for the initiation of cellular condensation in normal micromass cultures. With Shh over-expression, micromass cultures developed novel tightly whorled nodules in addition to the normal Alcian Blue positive cartilage nodules. We characterized the new nodules and showed that they are strongly positive for alkaline phosphatase, enriched in type X collagen and weakly positive for Alcian Blue staining. Shh overexpression also increased cell proliferation, but this cannot account for the formation of the new nodules. This current study shows that misexpression of Shh in in vitro chondrogenic cultures promotes characteristics of hypertrophic chondrocytes. Thus HH has two complementary functions; a direct positive effect on chondrocyte hypertrophy in the absence of PTHrP pathway, and an indirect negative feedback loop through PTHrP to prevent other less differentiated chondrocytes from becoming hypertrophic. These two complementary actions of HH coordinate the progression of cartilage maturation.

This article has been cited by other articles:

				M. K. Tayeh, H.-J. Yen, J. S. Beck, C. C. Searby, T. A. Westfall, H. Griesbach, V. C. Sheffield, and D. C. Slusarski Genetic interaction between Bardet-Biedl syndrome genes and implications for limb patterning Hum. Mol. Genet., July 1, 2008; 17(13): 1956 - 1967. [Abstract] [Full Text] [PDF]

				R. Meech, D. B. Edelman, F. S. Jones, and H. P. Makarenkova The homeobox transcription factor Barx2 regulates chondrogenesis during limb development Development, May 1, 2005; 132(9): 2135 - 2146. [Abstract] [Full Text] [PDF]

				V. Church, T. Nohno, C. Linker, C. Marcelle, and P. Francis-West Wnt regulation of chondrocyte differentiation J. Cell Sci., March 14, 2003; 115(24): 4809 - 4818. [Abstract] [Full Text] [PDF]

				R. A. Deckelbaum, G. Chan, D. Miao, D. Goltzman, and A. C. Karaplis Ihh enhances differentiation of CFK-2 chondrocytic cells and antagonizes PTHrP-mediated activation of PKA J. Cell Sci., July 15, 2002; 115(14): 3015 - 3025. [Abstract] [Full Text] [PDF]

				C. Farquharson, D. Jefferies, E. Seawright, and B. Houston Regulation of Chondrocyte Terminal Differentiation in the Postembryonic Growth Plate: The Role of the PTHrP-Indian Hedgehog Axis Endocrinology, September 1, 2001; 142(9): 4131 - 4140. [Abstract] [Full Text] [PDF]

				B. St-Jacques, M. Hammerschmidt, and A. P. McMahon Indian hedgehog signaling regulates proliferation and differentiation of chondrocytes and is essential for bone formation Genes & Dev., August 15, 1999; 13(16): 2072 - 2086. [Abstract] [Full Text]