GSE174313
Spatial transcriptomics reveals a role for sensory nerves in preserving cranial suture patency through modulation of BMP/TGFß signaling
The patterning and ossification of the mammalian skeleton requires the coordinated actions of both intrinsic bone morphogens and extrinsic neurovascular signals, which function in a temporal and spatial fashion to control mesenchymal progenitor cell (MPC) fate. Here we show genetic inhibition of Tropomyosin receptor kinase A (TrkA) sensory nerve innervation of the developing cranium results in premature calvarial suture closure, associated with a decrease in suture MPC proliferation. In vitro, axons from peripheral afferent neurons derived from DRGs of wild type mice induce MPC proliferation in a spatially-restricted manner via a soluble factor when co-cultured in microfluidic chambers. Comparative spatial transcriptomic analysis of the cranial sutures in vivo confirmed a positive association between sensory axons and proliferative MPCs. SpatialTime analysis across the developing suture revealed regional-specific alterations in BMP and TGFß signaling pathway transcripts in response to TrkA inhibition. RNA sequencing of DRG cell bodies following direct axonal co-culture with MPCs confirmed alterations in BMP/TGFß signaling pathway transcripts. Among these, the BMP inhibitor FSTL1 (Follistatin-like 1) replicated key features of the neural-to-bone influence, including mitogenic and anti-osteogenic effects via inhibition of BMP/TGFß signaling. Taken together, our results demonstrate that sensory nerve-derived signals, including FSTL1, function to coordinate cranial bone patterning by regulating MPC proliferation and differentiation in the suture mesenchyme. Overall design: P0 calvaria were isolated from TrkAF592A homozygous (mutant) and heterozygous (control) mice in which mothers were treated with 1NMPP1 via their drinking water from the time of conception through birth. Sagittal sutures and flanking parietal bones were dissected out, stacked and fresh frozen in OCT. Frozen sections were applied to the 10X Visium spatial transcriptomics gene expression platform and processed according to manufacturers protocols. Following sequencing, alignment and image registration was conducted using SpaceRanger.