TGF-BETA-1, TGF-BETA-2, AND TGF-BETA-3 EXHIBIT DISTINCT PATTERNS OF EXPRESSION DURING CRANIAL SUTURE FORMATION AND OBLITERATION IN-VIVO ANDIN-VITRO

Cranial sutures function as bone growth centers while themselves remai ning unossified, Rat frontonasal sutures become obliterated by neonata l day 21 (N21), while coronal sutures do not fuse over the life of the animal, Coronal sutures induced to undergo osseous obliteration in vi tro after removal of the dura mater were found to require soluble, hep arin-binding factors present in dura mater to resist osseous obliterat ion, Transforming growth factor beta 1 (TGF-beta 1), beta 2, and beta 3, heparin-binding factors known to regulate bone cell proliferation a nd differentiation, were considered likely candidates, The presence an d distribution of these factors in calvarial tissues both in vivo and in vitro were established by immunohistochemical analysis, while rever se transcription followed by polymerase chain reaction (RT/PCR) was em ployed to determine the presence of transcripts for these factors in m RNA isolated from microdissected dura mater, Results indicated that th e presence of TGF-beta 1 and TGF-beta 2 were associated with developin g coronal and frontonasal sutures, and that the continued presence of these factors was associated with osseous obliteration of the frontona sal suture, However, increased TGF-beta 3 immunoreactivity was associa ted with the coronal suture remaining unossified, RT/PCR demonstrated the presence of transcripts for TGF-beta 1, beta 2, and beta 3 in dura l tissues isolated from rat calvaria, These data support the notion of a role for TGF-beta s in regulating cranial suture morphogenesis and establish the in vitro model as a valid system for examining mechanism s by which growth factors regulate both suture morphogenesis and bone growth at the suture site.