Cranial suture obliteration is induced by removal of transforming growth factor (TGF)-beta 3 activity and prevented by removal of TGF-beta 2 activityfrom fetal rat calvaria in vitro

Cranial suture morphogenesis requires soluble, heparin-binding factors secr eted by the dura mater to resist premature osseous obliteration. Elevated l evels of transforming growth factor (TGF)-beta 1, TGF-beta 2, and TGF-beta 3 have previously been noted in cranial sutures undergoing normal and prema ture sutural obliteration. To examine the role of TGF-beta s in regulating cranial suture morphogenesis, an established in vitro, serum-free, calvaria l culture system was used. Tn this system, fetal rat coronal sutures underg o apparently normal suture morphogenesis in the presence of dura mater, but undergo osseous. obliteration in the absence of dura mater. Neutralizing p olyclonal antibodies to TGF-beta 1, TGF-beta 2, or TCF-beta 3 were added to cultures of fetal day 19 rat calvaria, which were harvested at 3, 4, or 5 days, processed for histology, sectioned, and examined. Coronal sutures fro m calvaria cultured in the presence of dura mater resisted obliteration, ei ther alone or in the presence of TCF-beta 1 or TGF-beta 2 neutralizing anti bodies. However, sutures from calvaria cultured in the presence of TGF-beta 3 neutralizing antibodies became obliterated. Conversely, sutures from cal varia cultured in the absence of dura mater became obliterated by bone, eit her alone or in the presence of neutralizing antibodies to TGF-beta 1 or TG F-beta 3. However, those sutures cultured in the presence of neutralizing a ntibodies to TGF-beta 2 were rescued from osseous obliteration.