Cranial sutures require tissue interactions with dura mater to resist osseous obliteration in vitro

TLDR

The study uses a chemically defined serum‑free medium to examine how dura mater interacts with developing cranial tissues in vitro. Fetal (days 19–20) and neonatal (day 1) calvarial rudiments were cultured with or without associated dura mater, allowing assessment of suture development in the absence of mechanical tension from dura‑derived fiber tracts. Without dura mater, coronal sutures fused, whereas coculture with dura across a transwell filter prevented fusion, showing that soluble dura‑derived signals—not mechanical tension—are essential for suture maintenance.

Abstract

Abstract A chemically defined serum-free medium, which supports the development of bones and fibrous tissues of rat calvaria from nonmineralized mesenchymal precursor tissues, was employed to investigate tissue interactions between the dura mater and overlying tissues. Fetal calvarial rudiments from stages prior to bone and suture morphogenesis (fetal days 19 and 20) and neonatal calvarial rudiments with formed sutures (day 1) were cultured with and without associated dura mater. Removal of calvaria for in vitro culture allowed the examination of suture morphogenesis in the absence of tensional forces exerted on the sutures via fiber tracts in the dura mater originating in the cranial base. Ossification of frontal and parietal bones proceeded in a fashion comparable to development in vivo, but the cranial (coronal) sutures—primary sites for subsequent skull growth—were obliterated by osseous tissue union in the absence of dura mater. Bony fusion did not occur when rudiments were cocultured with dura mater on the opposite sides of 0.45 μm polycarbonate transwell filters, suggesting that the influence of dura mater on sutural obliteration was mediated by soluble factors rather than cell—cell or cell—matrix interactions. These results indicate that cell signaling mechanisms rather than biomechanical tensional forces are required for morphogenesis of the calvaria.