Matrix composition regulates three-dimensional network formation by endothelial cells and mesenchymal stem cells in collagen/fibrin materials

Abstract

Co-cultures of endothelial cells (EC) and mesenchymal stem cells (MSC) in three-dimensional (3D) protein hydrogels can be used to recapitulate aspects of vasculogenesis in vitro. MSC provide paracrine signals that stimulate EC to form vessel-like structures, which mature as the MSC transition to the role of mural cells. In this study, vessel-like network formation was studied using 3D collagen/fibrin (COL/FIB) matrices seeded with embedded EC and MSC and cultured for 7 days. The EC:MSC ratio was varied from 5:1, 3:2, 1:1, 2:3 and 1:5. The matrix composition was varied at COL/FIB compositions of 100/0 (pure COL), 60/40, 50/50, 40/60 and 0/100 (pure FIB). Vasculogenesis was markedly decreased in the highest EC:MSC ratio, relative to the other cell ratios. Network formation increased with increasing fibrin content in composite materials, although the 40/60 COL/FIB and pure fibrin materials exhibited the same degree of vasculogenesis. EC and MSC were co-localized in vessel-like structures after 7 days and total cell number increased by approximately 70%. Mechanical property measurements showed an inverse correlation between matrix stiffness and network formation. The effect of matrix stiffness was further investigated using gels made with varying total protein content and by crosslinking the matrix using the dialdehyde glyoxal. This systematic series of studies demonstrates that matrix composition regulates vasculogenesis in 3D protein hydrogels, and further suggests that this effect may be caused by matrix mechanical properties. These findings have relevance to the study of neovessel formation and the development of strategies to promote vascularization in transplanted tissues.

Biomimetic Model of Tumor Microenvironment on Microfluidic Platform

“…[25,26] Our results sup port a previous report that a soft fibrin gel promoted the for mation of tumorigenic stem cell like colonies. [27] Although we observed increased proliferation and filopodial projection in the collagen fibrin composite matrix, rigidity alone is insufficient to explain the amplified fibroblast coculture effect with the collagen fibrin mixture.…”

Implanted Cell-Dense Prevascularized Tissues Develop Functional Vasculature That Supports Reoxygenation After Thrombosis

“…46 These positive attributes contribute to this matrix combination receiving increased usage as scaffolding for engineered tissue constructs. [47][48][49] Contracted tissues were chosen for use in this study, because they potentially offer several advantages compared with the disk-shaped implants previously investigated. 25 First, the tissues created in this study initially were relatively compliant before contraction, which began at 2-4 days after tissue creation.…”

CXCL12/Stromal-Cell-Derived Factor-1 Effectively Replaces Endothelial Progenitor Cells to Induce Vascularized Ectopic Bone

“…Moreover, when ECs are combined with multipotent stromal cells (MSCs), communication between both cell types positively influences osteogenic differentiation in vitro [7][8][9][10][11] as well as bone formation in vivo [5][6][7][8]. To this end, an optimal ratio of both cell types leads to higher efficiency in the formation of tubular structures [7,9,12,13] and mineralization [7,9,10] in vitro, when compared with single-cell-type cultures. When implanted in vivo, ectopic implantations show that combined constructs contain higher density of vasculature than the seeding of MSCs alone [9,12,14] and that bone formation is positively affected by the addition of ECs or EPCs [8][9][10].…”

“…To this end, an optimal ratio of both cell types leads to higher efficiency in the formation of tubular structures [7,9,12,13] and mineralization [7,9,10] in vitro, when compared with single-cell-type cultures. When implanted in vivo, ectopic implantations show that combined constructs contain higher density of vasculature than the seeding of MSCs alone [9,12,14] and that bone formation is positively affected by the addition of ECs or EPCs [8][9][10]. At orthotopic locations, some studies claim that there is no beneficial effect on total vessel formation after implantation [6,15], while other results show significantly higher early vascularization using EPCs in combination with MSCs [5,6].…”