Collagen VI suppresses fibronectin-induced enteric neural crest cell migration by downregulation of focal adhesion proteins

Identification of signaling pathways that specify a subset of migrating enteric neural crest cells at the wavefront in mouse embryos

During enteric nervous system (ENS) development, pioneering wavefront enteric neural crest cells (ENCCs) initiate gut colonization. However, the molecular mechanisms guiding their specification and niche interaction are not fully understood. We used single-cell RNA sequencing and spatial transcriptomics to map the spatiotemporal dynamics and molecular landscape of wavefront ENCCs in mouse embryos. Our analysis shows a progressive decline in wavefront ENCC potency during migration and identifies transcription factors governing their specification and differentiation. We further delineate key signaling pathways (ephrin-Eph, Wnt-Frizzled, and Sema3a-Nrp1) utilized by wavefront ENCCs to interact with their surrounding cells. Disruptions in these pathways are observed in human Hirschsprung's disease gut tissue, linking them to ENS malformations. Additionally, we observed region-specific and cell-type-specific transcriptional changes in surrounding gut tissues upon wavefront ENCC arrival, suggesting their role in shaping the gut microenvironment. This work offers a roadmap of ENS development, with implications for understanding ENS disorders.

Mesenchymal cells regulate enteric neural crest cell migration via RET-GFRA1b trans-signaling

During early development, the enteric nervous system forms from the migration of enteric neural crest cells (ENCCs) from the foregut to the hindgut, where they undergo proliferation and differentiation facilitated by interactions with enteric mesenchymal cells (EMCs). This study investigates the impact on ENCC migration of EMC-ENCC communication mediated by GFRA1b expressed in EMCs. GFRA1-expressing cells in day 11-12 (E11-12) mouse embryos differentiated into smooth muscle cells from E12 onwards. Observations at E12-13.5 revealed high levels of GFRA1 expression on the anti-mesenteric side of the hindgut, correlating with enhanced ENCC migration. This indicates that GFRA1 in EMCs plays a role in ENCC migration during development. Examining GFRA1 isoforms, we found high levels of GFRA1b, which lacks amino acids 140-144, in EMCs. To assess the impact of GFRA1 isoforms on EMC-ENCC communication, we conducted neurosphere drop assays. This revealed that GFRA1b-expressing cells promoted GDNF-dependent extension and increased neurite density in ENCC neurospheres. Co-culture of ENCC mimetic cells expressing RET and GFRA1a with EMC mimetic cells expressing GFRA1a, GFRA1b, or vector alone showed that only GFRA1b-expressing co-cultured cells sustained RET phosphorylation in ENCC-mimetic cells for over 120 min upon GDNF stimulation. Our study provides evidence that GFRA1b-mediated cell-to-cell communication plays a critical role in ENCC motility in enteric nervous system development. These findings contribute to understanding the cellular interactions and signaling mechanisms that underlie enteric nervous system formation and highlight potential therapeutic targets for gastrointestinal motility disorders.

The role of fibronectin in mediating cell migration

Fibronectin (FN) is a major extracellular matrix (ECM) protein involved in a wide range of physiological processes, including cell migration. These FN-mediated cell migration events are essential to processes such as wound repair, cancer metastasis, and vertebrate development. This review synthesizes mainly current literature to provide an overview of the mechanoregulatory role of FN-mediated cell migration. Background on FN structure and role in mechanotransduction is provided. Cell migration concepts are introduced, including the general cell migration mechanism and classification of cell migration types. Then, FN-mediated events that directly affect cell migration are explored. Finally, a focus on FN in tissue repair and cancer migration is presented, as these topics represent a large amount of current research.

mRNA sequencing provides new insights into the pathogenesis of Hirschsprung's disease in mice

PURPOSE

The aim of this study is to use RNA sequencing and RT-qPCR to identify the main susceptibility genes linked to the occurrence and development of Hirschsprung disease in the colonic tissues of EDNRBm1yzcm and wild mice.

METHODS

RNA was extracted from colon tissues of 3 mutant homozygous mice and 3 wild mice. RNA degradation, contamination concentration, and integrity were then measured. The extracted RNA was then sequenced using the Illumina platform. The obtained sequence data are filtered to ensure data quality and compared to the reference genome for further analysis. DESeq2 was used for gene expression analysis of the raw data. In addition, graphene oxide enrichment analysis and RT-qPCR validation were also performed.

RESULTS

This study identified 8354 differentially expressed genes in EDNRBm1yzcm and wild mouse colon tissues by RNA sequencing, including 4346 upregulated genes and 4005 downregulated genes. Correspondingly, the results of RT-qPCR analysis showed good correlation with the transcriptome data. In addition, GO and KEGG enrichment results suggested that there were 8103 terms and 320 pathways in all DEGs. When P < 0.05, 1081 GO terms and 320 KEGG pathways reached a significant level. Finally, through the existing studies and the enrichment results of differentially expressed genes, it was determined that axon guidance and the focal adhesion pathway may be closely related to the occurrence of HSCR.

CONCLUSIONS

This study analyzed and identified the differential genes in colonic tissues between EDNRBm1yzcm mice and wild mice, which provided new insight for further mining the potential pathogenic genes of Hirschsprung's disease.

Extracellular vesicles stimulate smooth muscle cell migration by presenting collagen VI

The extracellular matrix (ECM) supports blood vessel architecture and functionality and undergoes active remodelling during vascular repair and atherogenesis. Vascular smooth muscle cells (VSMCs) are essential for vessel repair and, via their secretome, are able to invade from the vessel media into the intima to mediate ECM remodelling. Accumulation of fibronectin (FN) is a hallmark of early vascular repair and atherosclerosis and here we show that FN stimulates VSMCs to secrete small extracellular vesicles (sEVs) by activating the β1 integrin/FAK/Src pathway as well as Arp2/3-dependent branching of the actin cytoskeleton. Spatially, sEV were secreted via filopodia-like cellular protrusions at the leading edge of migrating cells. We found that sEVs are trapped by the ECM in vitro and colocalise with FN in symptomatic atherosclerotic plaques in vivo. Functionally, ECM-trapped sEVs induced the formation of focal adhesions (FA) with enhanced pulling forces at the cellular periphery. Proteomic and GO pathway analysis revealed that VSMC-derived sEVs display a cell adhesion signature and are specifically enriched with collagen VI. In vitro assays identified collagen VI as playing the key role in cell adhesion and invasion. Taken together our data suggests that the accumulation of FN is a key early event in vessel repair acting to promote secretion of collage VI enriched sEVs by VSMCs. These sEVs stimulate migration and invasion by triggering peripheral focal adhesion formation and actomyosin contraction to exert sufficient traction forces to enable VSMC movement within the complex vascular ECM network.

Intestinal fibrosis in aganglionic segment of Hirschsprung's disease revealed by single-cell RNA sequencing

BACKGROUND

Hirschsprung's disease (HSCR) is a relatively common congenital disability. Accumulating extracellular matrix (ECM) prompts intestinal fibrosis remodelling in the aganglionic segments of HSCR. The contributions of various cellular subsets in the fibrogenesis of HSCR segments are poorly understood.

METHODS

Single-cell transcriptomics from 8 aganglionic segments and 5 normal segments of 7 HSCR subjects and 26 healthy segments of seven healthy donors were analysed. Fibrotic phenotype and alterations were explored using differential expression analysis and single-cell trajectory analysis. Fibrosis-related transcription factors were inferred through single-cell regulatory network inference. Bulk transcriptomic data, proteomic data, immunohistochemistry (IHC) and real-time polymerase chain reaction were used to validate the alterations in the HSCR intestine.

RESULTS

Various collagen, fibronectin and laminin protein-coding genes expression were up-regulated in the stromal and glial cells of the HSCR intestine. The number of fibroblasts and myofibroblasts in the aganglionic segments increased, and more myofibroblasts were activated at an earlier stage in HSCR segments, which infers that there is an intestinal fibrosis phenotype in HSCR segments. The fibrotic regulators POSTN, ANXA1 and HSP70 were highly expressed in the ECM-related cellular subsets in the transitional segments and aganglionic segments. The transcription factor regulatory network revealed that fibrosis-related and megacolon-related NR2F1 in the fibroblasts and glial subsets was up-regulated in the aganglionic segment.

CONCLUSIONS

This work identifies intestinal fibrosis and related regulators in aganglionic segments of HSCR; hence, anti-fibrotic therapy may be considered to prevent HSCR-associated enterocolitis (HAEC), relieve intestinal stricture and improve cell therapy.

Weighted gene co-expression network analysis and CIBERSORT screening of key genes related to m6A methylation in Hirschsprung's disease

Hirschsprung's disease (HSCR) is a neural crest disease that results from the failure of enteric neural crest cells (ENCCs) to migrate to the corresponding intestinal segment. The RET gene, which regulates enteric neural crest cell proliferation and migration, is considered one of the main risk factors for HSCR and is commonly used to construct HSCR mouse models. The epigenetic mechanism of m6A modification is involved in HSCR. In this study, we analyzed the GEO database (GSE103070) for differentially expressed genes (DEGs) and focused on m6A-related genes. Comparing the RNA-seq data of Wide Type and RET Null, a total of 326 DEGs were identified, of which 245 genes were associated with m6A. According to the CIBERSORT analysis, the proportion of Memory B-cell in RET Null was significantly higher than that of Wide Type. Venn diagram analysis was used to identify key genes in the selected memory B-cell modules and DEGs associated with m6A. Enrichment analysis showed that seven genes were mainly involved in focal adhesion, HIV infection, actin cytoskeleton organization and regulation of binding. These findings could provide a theoretical basis for molecular mechanism studies of HSCR.

Recipient colon preoperative treatment with type I collagenase and fibronectin promotes the growth of transplanted enteric neural crest cells into Auerbach's plexus

PURPOSE

Cell-based therapy is a potential treatment option for neurointestinal diseases by serving as a source of neural progenitor cells to replace missing or abnormal enteric neurons. Using an ex vivo transplantation model, we recently demonstrated that treatment with collagenase and fibronectin promotes infiltration of transplanted enteric neural crest cells (ENCCs) toward the colon lumen. The aim of this study was to determine whether this new method also promotes colonization of transplanted ENCCs in vivo.

METHODS

Collagenase was applied locally on the anti-mesenteric area of the recipient colon using filter paper, followed by fibronectin. Neurospheres were generated from ENCCs isolated from fetal mouse intestines and transplanted into the collagenase and fibronectin-treated colon. Engraftment of neurospheres was confirmed by immunofluorescence.

RESULTS

Neurospheres transplanted onto PBS- or fibronectin-treated colons were not observed to infiltrate to the muscle layer. However, when used in combination with type I collagenase and fibronectin in the recipient colon, transplanted neurospheres reached Auerbach's plexus.

CONCLUSION

We demonstrated that transplanted neurospheres grow into Auerbach's plexus in the recipient colon pretreated with collagenase and fibronectin.

Transplanted neural crest cells migrate toward Auerbach's plexus layer instead of the colon surface in recipient colon pretreated with collagenase and fibronectin

The enteric nervous system (ENS) regulates gastrointestinal motility, secretion, and absorption. Developmental ENS dysplasia causes intestinal ganglion dysfunction, including Hirschsprung's disease. Given their potential ability to replenish insufficient neurons, transplantation of enteric neural cells provides the prospect of a cure. In this study, we used an ex vivo mouse colon transplant model to demonstrate that treatment with collagenase and fibronectin altered the migration of transplanted cells from the direction of the colon surface toward the lumen. Collagenase-treated colons exhibited enhanced expression of type III and VI collagens, which inhibited fibronectin-induced enteric neural crest cell (ENCC) migration. Invasion of neurospheres into colon was dependent on preoperative treatment of recipient colon with collagenase and fibronectin, which enhanced neurosphere motility towards the direction of colon lumen. Infiltration of transplanted ENCCs into the colon increased proportionally to the degree of dedifferentiation of surrounding smooth muscle cells, which was induced in a neurosphere-dependent manner in collagenase-treated colon. Furthermore, induction of GDNF expression, a Ret ligand that promotes enteric neural cell migration, was observed in treated colons. Our results suggest that the environment provided by the extracellular matrix of the colon surface affects the direction of transplanted ENCC migration. Moreover, these findings demonstrating that ENCCs can be accepted by the recipient colon will help to refine current strategies for cell therapy.

Roles of Enteric Neural Stem Cell Niche and Enteric Nervous System Development in Hirschsprung Disease

The development of the enteric nervous system (ENS) is highly modulated by the synchronized interaction between the enteric neural crest cells (ENCCs) and the neural stem cell niche comprising the gut microenvironment. Genetic defects dysregulating the cellular behaviour(s) of the ENCCs result in incomplete innervation and hence ENS dysfunction. Hirschsprung disease (HSCR) is a rare complex neurocristopathy in which the enteric neural crest-derived cells fail to colonize the distal colon. In addition to ENS defects, increasing evidence suggests that HSCR patients may have intrinsic defects in the niche impairing the extracellular matrix (ECM)-cell interaction and/or dysregulating the cellular niche factors necessary for controlling stem cell behaviour. The niche defects in patients may compromise the regenerative capacity of the stem cell-based therapy and advocate for drug- and niche-based therapies as complementary therapeutic strategies to alleviate/enhance niche-cell interaction. Here, we provide a summary of the current understandings of the role of the enteric neural stem cell niche in modulating the development of the ENS and in the pathogenesis of HSCR. Deciphering the contribution of the niche to HSCR may provide important implications to the development of regenerative medicine for HSCR.

Gut innervation and enteric nervous system development: a spatial, temporal and molecular tour de force

During embryonic development, the gut is innervated by intrinsic (enteric) and extrinsic nerves. Focusing on mammalian ENS development, in this Review we highlight how important the different compartments of this innervation are to assure proper gut function. We specifically address the three-dimensional architecture of the innervation, paying special attention to the differences in development along the longitudinal and circumferential axes of the gut. We review recent information about the formation of both intrinsic innervation, which is fairly well-known, as well as the establishment of the extrinsic innervation, which, despite its importance in gut-brain signaling, has received much less attention. We further discuss how external microbial and nutritional cues or neuroimmune interactions may influence development of gut innervation. Finally, we provide summary tables, describing the location and function of several well-known molecules, along with some newer factors that have more recently been implicated in the development of gut innervation.

37/67-laminin receptor facilitates neural crest cell migration during enteric nervous system development

Enteric nervous system (ENS) development is governed by interactions between neural crest cells (NCC) and the extracellular matrix (ECM). Hirschsprung disease (HSCR) results from incomplete NCC migration and failure to form an appropriate ENS. Prior studies implicate abnormal ECM in NCC migration failure. We performed a comparative microarray of the embryonic distal hindgut of wild-type and EdnrB^NCC-/- mice that model HSCR and identified laminin-β1 as upregulated in EdnrB^NCC-/- colon. We identified decreased expression of 37/67 kDa laminin receptor (LAMR), which binds laminin-β1, in human HSCR myenteric plexus and EdnrB^NCC-/- NCC. Using a combination of in vitro gut slice cultures and ex vivo organ cultures, we determined the mechanistic role of LAMR in NCC migration. We found that enteric NCC express LAMR, which is downregulated in human and murine HSCR. Binding of LAMR by the laminin-β1 analog YIGSR promotes NCC migration. Silencing of LAMR abrogated these effects. Finally, applying YIGSR to E13.5 EdnrB^NCC-/- colon explants resulted in 80%-100% colonization of the hindgut. This study adds LAMR to the large list of receptors through which NCC interact with their environment during ENS development. These results should be used to inform ongoing integrative, regenerative medicine approaches to HSCR.

Aberrant Distributions of Collagen I, III, and IV in Hirschsprung Disease

BACKGROUND

Hirschsprung disease (HSCR) is the most common congenital gut motility disorder, involving a severe anomaly of the enteric nervous system, and is characterized by functional intestinal obstruction due to lack of intrinsic innervation (aganglionosis) in the distal bowel.

OBJECTIVE

The aim of this study was to examine the distribution patterns of collagens I (Col I), III (Col III), and IV (Col IV) in the enteric nervous system of HSCR patients, to determine whether or not collagen levels are altered in the aganglionic bowel.

METHODS

We measured the expression levels of Col I, Col III, and Col IV in colonic muscle from 129 children with HSCR. The localizations of the 3 collagens and myenteric ganglia were assessed morphologically by immunofluorescence staining. western blots and real-time fluorescence quantitative polymerase chain reaction were performed to examine the relative levels of these collagens in aganglionic, transitional, and ganglionic colon segments.

RESULTS

Immunoreactivities of Col I and Col III were high around and within myenteric ganglia in the ganglionic segment, moderate in the transitional segment, and weak in the aganglionic segment. Col IV immunoreactivity showed the opposite pattern, being lowest in the ganglionic segment and highest in the aganglionic segment.

CONCLUSION

Col I and Col III are decreased and Col IV is increased in the distal colon of patients with HSCR.

Decreased collagen VI in the tunica media of pulmonary vessels during exposure to hypoxia: a novel step in pulmonary arterial remodeling

The development of hypoxic pulmonary hypertension is characterized by the structural remodeling of pulmonary arteries. However, the relationship between changes of arterial cells and the extracellular matrix remains unclear. We focused on the evaluation of the non-fibrillar collagen changes in tunica media induced by a four-day exposure to hypoxia and the correlation of these changes with the pulmonary arterial wall structure modifications. We used 20 adult male Wistar rats. The amount and localization of collagen VI, collagen IV, matrix metalloproteinase (MMP) 2, and MMP9 were tested in pulmonary arteries immunohistochemically. Two-dimensional electrophoresis and messenger RNA (mRNA) expression were used for the subsequent comparison of protein changes in arterial tunica media cells (normoxia/hypoxia). Collagen VI was significantly reduced strictly in the tunica media of conduit arteries of hypoxia-exposed rats; however, its mRNA increased. The amount of collagen IV and its mRNA were not altered. We detected a significant increase of MMP9 strictly in the tunica media. In addition, a significantly increased number of MMP9-positive cells surrounded the arteries. MMP2 and the expression of its mRNA were decreased in tunica media. We conclude that the loss of collagen VI is an important step characterizing the remodeling of pulmonary arteries. It could influence the phenotypic status and behavior of smooth muscle cells and modify their proliferation and migration.

Characterization of plasma fibronectin for migration, proliferation, and differentiation on human articular chondrocytes

Plasma fibronectin (pFN) plays a crucial role in wound healing by binding to integrins and inducing cell migration. It is known to induce the migration and proliferation of mesenchymal progenitor cells in vitro, which play a key role during microfracture in cartilage repair. Endogenous chondrocytes from the native cartilage of the defect rim might aid in cartilage repair. In this study, the effect of pFN on proliferation, migration, and differentiation was tested on human articular chondrocytes. Results showed that treatment with pFN increased the migration of chondrocytes in a range of 1-30 μg/ml as tested with no effect on proliferation. TGFβ3-induced chondrogenesis was not affected by pFN. Especially, gene expression of matrix metalloproteinases was not increased by pFN. Plasma FN fragmentation due to storage conditions could be excluded by SDS-PAGE. Moreover, bioactivity of pFN did not alter during storage at 4°C and 40°C for up to 14 days. Taken together, pFN induces the migration but not proliferation of human articular chondrocytes with no inhibitory effect on chondrogenic differentiation. Additionally, no loss of activity or fragmentation of pFN was observed after lyophilization and storage, making pFN an interesting bioactive factor for chondrocyte recruitment.