Angiogenesis in a 3D model containing adipose tissue stem cells and endothelial cells is mediated by canonical Wnt signaling

Abstract

Adipose-derived stromal cells (ASCs) have gained great attention in regenerative medicine. Progress in our understanding of adult neovascularization further suggests the potential of ASCs in promoting vascular regeneration, although the specific cues that stimulate their angiogenic behavior remain controversial. In this study, we established a three-dimensional (3D) angiogenesis model by co-culturing ASCs and endothelial cells (ECs) in collagen gel and found that ASC-EC-instructed angiogenesis was regulated by the canonical Wnt pathway. Furthermore, the angiogenesis that occurred in implants collected after injections of our collagen gel-based 3D angiogenesis model into nude mice was confirmed to be functional and also regulated by the canonical Wnt pathway. Wnt regulation of angiogenesis involving changes in vessel length, vessel density, vessel sprout, and connection numbers occurred in our system. Wnt signaling was then shown to regulate ASC-mediated paracrine signaling during angiogenesis through the nuclear translocation of β-catenin after its cytoplasmic accumulation in both ASCs and ECs. This translocation enhanced the expression of nuclear co-factor Lef-1 and cyclin D1 and activated the angiogenic transcription of vascular endothelial growth factor A (VEGFA), basic fibroblast growth factor (bFGF), and insulin-like growth factor 1 (IGF-1). The angiogenesis process in the 3D collagen model appeared to follow canonical Wnt signaling, and this model can help us understand the importance of the canonical Wnt pathway in the use of ASCs in vascular regeneration.

Blood vessel development: 3D culture models implicate key signaling pathway

Stem cells found in fat help promote new blood vessel formation by activating an evolutionarily conserved pathway crucial to development. Yunfeng Lin and colleagues from Sichuan University in Chengdu, China, cultured connective tissue cells (stromal cells), which are rich in stem cells, from mouse fat, with endothelial cells from mouse brain in a collagen gel, creating three-dimensional (3D) cellular models of blood vessel development. By applying different chemicals that either activate or repress proteins involved in the Wnt pathway, the researchers showed that Wnt signals from the stromal cells affected blood vessel length, density and sprouting, and did so by promoting the movement of an important regulatory protein into the cell nucleus. The blood vessels formed in these 3D models proved functional when implanted into mice, highlighting the potential of this system for studying vascular regeneration.

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