title: Hyaluronidases and CD44 undergo differential modulation during chondrogenesis.
abstract: Hyaluronan, a high-molecular-weight glycosaminoglycan of cartilage, is deposited directly into the extracellular space by hyaluronan synthases, while hyaluronan catabolism is mediated by the hyaluronidases. An in vitro cell culture system has been established in which human dermal fibroblasts are induced to undergo chondrogenesis. Here, we describe the differential modulation of the hyaluronidases and the up-regulation of the hyaluronan receptor, CD44, during such chondrogenesis. Dermal fibroblasts, plated in micromass cultures in the presence of lactic acid and staurosporine for 24 h, were then placed in serum-free, chemically defined medium. At 3 days, RNA was extracted and RT-PCR performed using primers for the hyaluronidase genes. Marked increase in HYAL1 expression was observed, with only moderate increases occurring in HYAL2 and HYAL3. No expression of HYAL4 and PH-20, the sperm-associated hyaluronidase, was detected. RNA levels correlated well with changes in hyaluronidase enzyme activity. Finally, greater expression and staining for the hyaluronan receptor, CD44s, the standard form, were detected. Differential expression of the somatic hyaluronidases and CD44-mediated hyaluronan turnover play a critical role in cartilage development from mesenchymal precursors.
authors.affiliation: Joint Graduate Program in Bioengineering, University of California, Berkeley and San Francisco, California 94143-0775, USA.
authors.forename: Steven B
authors.initials: SB
authors.lastname: Nicoll
authors.forename: Ory
authors.initials: O
authors.lastname: Barak
authors.forename: Antonei B
authors.initials: AB
authors.lastname: Csóka
authors.forename: Rajendra S
authors.initials: RS
authors.lastname: Bhatnagar
authors.forename: Robert
authors.initials: R
authors.lastname: Stern
mesh_terms: D015815:Cell Adhesion Molecules / Q000235:genetics; D002454:Cell Differentiation / Q000187:drug effects; D002478:Cells, Cultured; D020219:Chondrogenesis / Q000187:drug effects / Q000502:physiology*; D016895:Culture Media, Serum-Free / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D006801:Humans; D018960:Hyaluronan Receptors / Q000378:metabolism*; D006821:Hyaluronoglucosaminidase / Q000235:genetics / Q000378:metabolism*; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D019344:Lactic Acid / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019311:Staurosporine / Q000494:pharmacology; D015854:Up-Regulation
chemical_list: D015815:Cell Adhesion Molecules; D016895:Culture Media, Serum-Free; D004791:Enzyme Inhibitors; D018960:Hyaluronan Receptors; D007527:Isoenzymes; D012333:RNA, Messenger; D019344:Lactic Acid; D006821:Hyaluronoglucosaminidase; C066852:hyaluronidase PH-20; D019311:Staurosporine