Mechanisms driving the initiation and direction of endothelial sprouting in organotypic co‐culture of aorta and spinal cord tissues

Abstract

The resumption of blood supply in spinal cord (SC) after injury is a prerequisite of its recovery. To expose the mechanisms of damaged SC revascularization we have used an organotypic SC/aortic fragments (AF) co‐culture where, as we showed previously, damaged SC tissue induces AF cell sprouting but repels them away. Supplementation of culture medium with exogenous VEGF‐A165 redirects the migrating aortic endothelial cells towards SC tissue. This effect and the pattern of sFlt1 expression (a soluble form of VEGFR1) suggest that the low level of SC‐secreted VEGF and the presence of sFlt1 in SC slices together prevent the migration of aortic CD31+ cells to the SC in the absence of exogenous VEGF. VEGF‐A165 supplementation sequesters this inhibitory activity of sFlt1 by direct binding thus allowing CD31+ cell migration in to SC tissue. Proteome analysis has shown that migration/proliferation of CD31+ and αSMA+ aortic cells in neuronal culture medium used in our SC/AF model (which obstruct sprouting by itself) was resumed by combined action of several pro‐ (aFGF, bFGF, Osteopontin, TF, IGFBP2, SDF1) and anti‐angiogenic (Endostatin/Collagen18) factors. The mutual influence of AF and SC tissues is a key factor balancing these factors and thus driving endothelial sprouting in SC injury zone.

Osteopontin Promotes Angiogenesis in the Spinal Cord and Exerts a Protective Role Against Motor Function Impairment and Neuropathic Pain after Spinal Cord Injury

“…According to a recent study involving aorta and spinal cord tissue co-cultures, OPN was identified as one of the proangiogenic factors (Endostatin/Collagen18) that revived the migration/proliferation of CD31+ and αSMA+ aortic cells in neuronal culture medium. Moreover, it was produced by both spinal cord tissue and aortic fragments 39 . For the first time, our study confirms OPN’s proangiogenic role after SCI in animal models, as evidenced by the revocation of CD31 immunofluorescent signal enhancement after SCI in OPN knockdown mice.…”

“…Moreover, it was produced by both spinal cord tissue and aortic fragments. 39 For the first time, our study confirms OPN's proangiogenic role after SCI in animal models, as evidenced by the revocation of CD31 immunofluorescent signal enhancement after SCI in OPN knockdown mice. OPN could promote angiogenesis through VEGF and/or AKT pathways, 40,41 as we detected potential modulation of VEGF and AKT phosphorylation mediated by OPN post-SCI in this study.…”