Type III and V collagens modulate the expression and assembly of EDA+ fibronectin in the extracellular matrix of defective Ehlers-Danlos syndrome fibroblasts

Background: Alternative splicing of EDA fibronectin (FN) region is a cell type- and development-regulated mechanism controlled by pathological processes, growth factors and extracellular matrix (ECM). Classic and vascular Ehlers-Danlos syndrome (cEDS and vEDS) are connective tissue disorders caused by COL5A1/COL5A2 and COL3A1 gene mutations, leading to an in vivo abnormal collagen flbrillogenesis and to an in vitro defective organisation in the ECM of type V (COLLV) and type III collagen (COLLIII). These defects induce the FN-ECM disarray and the decrease of COLLs and FN receptors, the alpha 2 beta 1 and alpha 5 beta 1 integrins. Purified COLLV and COLLIII restore the COLL-FN-ECMs in both EDS cell strains. Methods: Real-time PCR, immunofluorescence microscopy, and Western blotting were used to investigate the effects of COLLS on FN1 gene expression. EDA region alternative splicing, EDA(+)-FN-ECM assembly, alpha 5 beta 1 integrin and EDA(+)-FN-specific alpha 9 integrin subunit organisation, alpha 5 beta 1 integrin and FAK co-regulation in EDS fibroblasts. Results: COLLV-treated cEDS and COLLIII-treated vEDS fibroblasts up-regulate the FN1 gene expression, modulate the EDA(+) mRNA maturation and increase the EDA(+)-FN levels, thus restoring a control-like FN-ECM, which elicits the EDA(+)-FN-specific alpha 9 beta 1 integrin organisation, recruits the alpha 5 beta 1 integrin and switches on the FAK binding and phosphorylation. Conclusion: COLLS regulate the EDA(+)-FN-ECM organisation at transcriptional and post-transcriptional level and activate the alpha 5 beta 1-FAK complexes. COLLS also recruit the alpha 9 beta 1 integrin involved in the assembly of the EDA(+)-FN-ECM in EDS cells. General significance: The knowledge of the COLLs-ECM role in FN isotype expression and in EDA(+)-FN-ECM-mediated signal transduction adds insights in the ECM remodelling mechanisms in EDS cells. (c) 2012 Elsevier B.V. All rights reserved.