TISSUE INTERACTIONS WITH UNDERLYING DURA-MATER INHIBIT OSSEOUS OBLITERATION OF DEVELOPING CRANIAL SUTURES

Cranial sutures play a critical role in calvarial morphogenesis, servi ng as growth centers during skull development. Both biomechanical tens ile forces originating in the cranial base and biochemical factors pre sent in dura mater have been postulated as determinants of suture morp hogenesis and patency. A rat transplant model free of the putative bio mechanical influence of the dura and cranial base was used to investig ate the role of the dura mater in both the initial morphogenesis and m aintenance of sutures during skull growth. Day 19 fetal presumptive (F 19) and day 1 neonatal differentiated (N1) coronal sutures, including associated frontal and parietal bones, were transplanted with or witho ut underlying dura mater to the center of adult parietal bones. After 1, 2, and 3 weeks, transplanted tissues were examined histologically a nd histomorphometrically to determine whether sutures formed and wheth er they were obliterated by ossification in the absence of dura mater. Both F19 and N1 sutures remained patent for 2 weeks either in the pre sence or the absence of transplant dura mater. However, at 3 weeks, in the absence of transplant dura mater, sutures were obliterated by bon e, while in the presence of dura mater sutures resisted ossification, demonstrating an essential requirement for interactions with the trans plant dura mater in maintaining functional sutures. Both F19 and N1 tr ansplants showed comparable bone growth (cross-sectional surface area) , regardless of the presence of transplant dura mater. These experimen ts suggest that tissue interactions of a biochemical nature, rather th an biomechanical forces generated through the cranial base, are requir ed to maintain the suture as a non-ossified growth center. Furthermore , while the presence of dura mater was essential for maintenance of su ture patency, fetal dura mater was not required for initial suture for mation. (C) 1993 Wiley-Liss,Inc.