title: Extracellular matrix synthesized by clonal osteogenic cells is osteoinductive in vivo and in vitro: role of transforming growth factor-beta 1 in osteoblast cell-matrix interaction.
abstract: ROB-C26 (C26) is a multipotential, clonal cell line known to express several members of the TGF-beta superfamily and to become more osteoblastic (e.g., express higher levels of alkaline phosphatase) upon treatment with 10(-6)M retinoic acid (RA). We hypothesize that the expression of this more osteoblastic phenotype subsequent to RA exposure is the result of the treated cell's extracellular matrix (ECM) becoming a repository and active source of putative osteoinductive growth factors including, specifically, select members of the TGF-beta superfamily. To test this hypothesis, we isolated the ECM from RA-treated and untreated C26 cells and assessed them for their ability to promote osteogenic differentiation in vivo and in vitro. We then explored whether the latter activities could be attributed specifically to TGF-beta 1. We found that the ECM of treated cells isolated by cell lysis and extensive washing induced endochondral bone formation in vivo when implanted into the thigh muscles of athymic nude mice and stimulated alkaline phosphatase (ALP) activity in vitro in freshly plated C26 cells. This latter stimulation was comparable to levels observed with direct RA treatment. This latter in vitro activity was only very partially mimicked by the ECM prepared from untreated cells and not duplicated at all by RA-treated collagen or the ECM from another RA-treated multipotential cell line. Moreover, the in vivo osteoinductive effect of the treated C26 cell ECM was not duplicated by comparable ECM prepared from untreated cells.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: University of California at San Francisco, USA.
authors.forename: M D
authors.initials: MD
authors.lastname: Kirk
authors.forename: A J
authors.initials: AJ
authors.lastname: Kahn
mesh_terms: D000469:Alkaline Phosphatase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D001846:Bone Development / Q000187:drug effects / Q000235:genetics; D002454:Cell Differentiation / Q000187:drug effects / Q000235:genetics; D002460:Cell Line; D005109:Extracellular Matrix / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*; D051379:Mice; D008819:Mice, Nude; D010006:Osteoblasts / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D010012:Osteogenesis / Q000187:drug effects; D010641:Phenotype; D016212:Transforming Growth Factor beta / Q000096:biosynthesis* / Q000235:genetics; D014212:Tretinoin / Q000494:pharmacology
chemical_list: D000906:Antibodies; D016212:Transforming Growth Factor beta; D014212:Tretinoin; D000469:Alkaline Phosphatase