Spatial transcriptomics reveals a role for sensory nerves in preserving cranial suture patency through modulation of BMP/TGFβ signaling
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ABSTRACT: 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 TGFβ 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/TGFβ 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/TGFβ 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.
Project description:Spatial transcriptomics reveals a role for sensory nerves in preserving cranial suture patency through modulation of BMP/TGFβ signaling
Project description:Cranial sutures separate neighboring skull bones and contain skeletal stem cells that drive bone growth. A key question is how osteogenic activity is controlled to promote bone growth while preventing aberrant bone fusions during skull expansion. Here we integrate single-cell transcriptomics, in vivo expression validation, photoconversion-based lineage tracing, and a zebrafish craniosynostosis model to uncover key developmental transitions regulating bone formation during skull expansion. In addition to conservation of meninges and osteoblast lineage cells between zebrafish and mouse, single-cell transcriptomic analysis of the zebrafish skull reveals distinct subpopulations of suture mesenchyme that undergo transcriptomic changes during suture establishment. While lineage tracing with an osteoblast-specific nlsEOS reporter shows that bone formation largely occurs at suture edges, a subset of mesenchyme cells in the mid-suture region upregulate a suite of genes including BMP antagonists (e.g. grem1a) and pro-angiogenic factors. Further, lineage tracing with grem1a:nlsEOS reveals that this mid-suture subpopulation is largely non-osteogenic. In twist1b; tcf12 mutant zebrafish, a model for the coronal synostosis of Saethre-Chotzen Syndrome, reduction of grem1a+ mid-suture cells correlates with misregulated bone formation and reduced blood vessels at the coronal suture. In addition, combinatorial mutation of BMP antagonists enriched in the mid-suture subpopulation results in increased BMP signaling in the suture, misregulated bone formation, and abnormal suture morphology. These data support roles of a subset of mid-suture mesenchyme in locally promoting BMP antagonism that ensures proper suture morphology.
Project description:Assaying gene expression in sutural bone fragments from patients diagnosed with non-syndromic craniosynostosis. Sutural fragments were collected from both the fused and patent cranial suture of infants during cranial vault reconstruction. Gene expression was compared between the patent and fused sutures using the paired t-test. The aim was to identify thoses genes significantly differentially expressed in fused suture relative to patent. Total RNA isolated from patent and fused human cranial sutures was assayed. Expression in synostosed suture was compared to patent suture.
Project description:IPF is a progressive fibrotic lung disease whose pathogenesis remains incompletely understood. We have previously discovered pathologic mesenchymal progenitor cells (MPCs) in the lungs of IPF patients. IPF MPCs display a distinct transcriptome and create sustained interstitial fibrosis in immune deficient mice. However, the precise pathologic alterations responsible for this fibrotic phenotype remain to be uncovered. Quantitative mass spectrometry and interactomics is a powerful tool that can define protein alterations in specific subcellular compartments that can be implemented to understand disease pathogenesis. We employed quantitative mass spectrometry and interactomics to define protein alterations in the nuclear compartment of IPF MPCs. We identified increased nuclear levels of PARP1, CDK1, and BACH1. Interactomics implicated PARP1, CDK1, and BACH1 as key hub proteins in the DNA damage/repair, differentiation, and apoptosis signaling pathways respectively. Loss of function and inhibitor studies demonstrated important roles for PARP1 in DNA damage/repair, CDK1 in regulating IPF MPC stemness and self-renewal, and BACH1 in regulating IPF MPC viability. Quantitative mass spectrometry combined with interactomics is a powerful tool for defining alterations in key proteins important in uncovering disease mechanisms.
Project description:Assaying gene expression in sutural bone fragments from patients diagnosed with non-syndromic craniosynostosis. Sutural fragments were collected from both the fused and patent cranial suture of infants during cranial vault reconstruction. Gene expression was compared between the patent and fused sutures using the paired t-test. The aim was to identify thoses genes significantly differentially expressed in fused suture relative to patent.
Project description:Polycystic ovary syndrome (PCOS) is a female endocrine disorder characterized by hyperandrogenism, chronic anovulation, and polycystic ovaries. PCOS is often accompanied by symptoms such as insulin resistance, abdominal obesity, and chronic inflammation. Adipose tissue is a crucial endocrine organ involved in metabolic disorders. Metabolic issues and chronic inflammation in PCOS are linked to dysfunctional adipose tissue. Mesenchymal progenitor cells (MPCs) are the precursor cells of adipocytes and can regulate the immune system. In this study, we used induced pluripotent stem cells (iPSCs) from patients with PCOS to derive MPCs and compare the transcriptome profiles between PCOS and HC iPSC-derived MPCs. We also challenged iPSC-derived MPCs with testosterone to assess the impact of androgen on MPCs. We found that 1026 genes differed between PCOS and HC iPSC-derived MPCs. Gene set enrichment analysis showed adipogenesis and metabolic function were reduced, but the inflammatory response was raised in PCOS iPSC-derived MPCs. The critical signals for early adipogenesis, including TGFβ, BMP, WNT, and CEBPA, differed between PCOS and HC iPSC-derived MPCs. After adipogenic induction, mature adipocytes were lower in PCOS iPSC-derived MPCs than HC. Lipolysis, the process involved in fat metabolism, was lower in adipocytes derived from PCOS MPCs than in HC. The testosterone treatment results indicated that genes related to oxidative phosphorylation and fatty acid metabolism were upregulated in HC iPSC-derived MPCs but downregulated in PCOS iPSC-derived MPCs. Short-term androgen stimulation may benefit body functions in HC. The impact of testosterone varied among individuals with HC and PCOS, possibly because of a genetic tendency towards PCOS. This study explains important factors that help us understand PCOS.
Project description:Purpose: The cranial suture is a fibrous joint, and similar to the growth plates of the skeletal long bone, they serve as the major centers of calvarial vault morphogenesis. Our group’s identification of a skeletal stem cell isolated from the mouse tibial growth plate prompted us to investigate whether these skeletal stem cells are also resident in the mouse cranial sutures and if they govern postnatal suture patency or fusion. Results: We preformed a spatio-temporal profiling of the mouse cranial sutures by flow cytometry, demonstrating a significant decrease in the temporal representation of skeletal stem cells in fusing versus patent sutures. Moreover, canonical Wnt signaling has a significant impact on skeletal stem cells proliferation and thus representation within the suture, dictating fate: fusion or patency. Breeding an Axin2+/-LacZ mouse, with enhanced activation of canonical Wnt signaling to a Twist1+/− mouse, harboring a coronal craniosynostosis enriched the skeletal stem cell pool in coronal sutures, thereby preventing Twist1+/− craniosynostosis. Conclusions: Our findings suggest an imbalance and/or decrease in resident skeletal stem cells within the cranial sutures gives rise to craniosynostosis, however, restoring this representation by enriching skeletal stem cells within the suture can maintain patency.
Project description:Purpose: The cranial suture is a fibrous joint, and similar to the growth plates of the skeletal long bone, they serve as the major centers of calvarial vault morphogenesis. Our group’s identification of a skeletal stem cell isolated from the mouse tibial growth plate prompted us to investigate whether these skeletal stem cells are also resident in the mouse cranial sutures and if they govern postnatal suture patency or fusion. Results: We preformed a spatio-temporal profiling of the mouse cranial sutures by flow cytometry, demonstrating a significant decrease in the temporal representation of skeletal stem cells in fusing versus patent sutures. Moreover, canonical Wnt signaling has a significant impact on skeletal stem cells proliferation and thus representation within the suture, dictating fate: fusion or patency. Breeding an Axin2+/-LacZ mouse, with enhanced activation of canonical Wnt signaling to a Twist1+/− mouse, harboring a coronal craniosynostosis enriched the skeletal stem cell pool in coronal sutures, thereby preventing Twist1+/− craniosynostosis. Conclusions: Our findings suggest an imbalance and/or decrease in resident skeletal stem cells within the cranial sutures gives rise to craniosynostosis, however, restoring this representation by enriching skeletal stem cells within the suture can maintain patency.
Project description:Local protein synthesis in sensory neuron axons is necessary for axonal regeneration with the efficiency of regeneration decreasing with age. Because the full repertoire of transcripts in embryonic and adult rat sensory axons is unknown we asked how the pool of mRNAs dynamically changes during ageing. We isolated mRNA from pure axons and growth cones devoid of non-neuronal or cell body contamination. Genome-wide microarray analysis reveals that a previously unappreciated number of transcripts are localised in sensory axons and that this repertoire changes during development toward adulthood. Embryonic sensory axons are enriched in transcripts encoding cytoskeletal-related proteins with a role in axonal outgrowth. Surprisingly, adult axons are highly enriched in mRNAs encoding immune molecules with a role in nociception. To validate our experimental approach we show that Tubulin-beta3 mRNA is present only in embryonic axons where it is locally synthesised. In summary, we show that the population of axonal mRNAs dynamically changes during development, which may partly contribute to the intrinsic capacity of axons at different ages to regenerate after injury and to modulate pain. Pure axonal RNA were extracted from the axons of embryonic and adult dorsal root ganglion neurons, each with 5 biological replicates. The axonal transcriptomes were analysed using Affymetrix Rat Genome 230 2.0 Arrays.