The Adipose Stromal Vascular Fraction as a Complex Cellular Source for Tissue Engineering Applications

Abstract

A major challenge in tissue engineering is the generation of sufficient volumes of viable tissue for organ transplant. The development of a stable, mature vasculature is required to sustain the metabolic and functional activities of engineered tissues. Adipose stromal vascular fraction (SVF) cells are an easily accessible, heterogeneous cell system comprised of endothelial cells, macrophages, pericytes, and various stem cell populations. Collectively, SVF has been shown to spontaneously form vessel-like networks in vitro and robust, patent, and functional vasculatures in vivo. Capitalizing on this ability, we and others have demonstrated adipose SVF's utility in generating and augmenting engineered liver, cardiac, and vascular tissues, to name a few. This review highlights the scientific origins of SVF, the use of SVF as a clinically relevant vascular source, various SVF constituents and their roles, and practical considerations associated with isolating SVF for various tissue engineering applications.

Keywords: adipose tissue; lipoaspirate; stromal vascular fraction; vasculature.

Conflict of interest statement

No competing financial interests exist.

Figures

FIG. 1.

In vivo and In vitro SVF microvasculature. SVF cells from GFP+ rat were suspended in a three-dimensional collagen-I matrix and implanted subcutaneously for 4 weeks. SVF (green fluorescence) spontaneously self-assembled a hierarchical, mature, and patent vasculature. This vasculature anastomoses with the host circulation (GFP− Dextran-TRITC+) and demonstrates evidence of perfusion (GFP+ Dextran-TRITC+). The ability of the SVF cells to self-organize into a functional vasculature has therapeutic implications in a multitude of tissue engineering applications (Image credit: Dr. James Hoying). When SVF cells are plated in vitro, the SVF-derived endothelial cells (Ulex Europaeus Agglutinin-I-fluorescein+) spontaneously self-assemble an endothelial network within the overlying stromal cells. Scale bar = 10×, 200μm. SVF EC, stromal vascular fraction endothelial cells. Color images available online at www.liebertpub.com/teb

FIG. 2.

Manual Processing of lipoaspirate to yield SVF. In Photo 1, lipoaspirate is shown before mechanical breakdown using scissors (Photo 2). This breakdown provides a greater surface area on which the chemical digestion enzyme collagenase can act (Photo 3). After a defined time period of digestion, the resulting slurry is centrifuged, yielding a solution of three key parts as shown in Photo 4: a top layer of buoyant adipocytes, a middle layer of collagenase and remaining tumescent fluids, and a cellular pellet at the bottom containing SVF—a heterogeneous mix of various cell types. Color images available online at www.liebertpub.com/teb