Engineering Vascularized Adipose Tissue Using the Stromal-Vascular Fraction and Fibrin Hydrogels

Abstract

The development of vascularized and functional adipose tissue substitutes is required to improve soft tissue augmentation. In this study, vascularized adipose tissue constructs were generated using uncultured cells from the stromal-vascular fraction (SVF) of adipose tissue as an alternative cell source to adipose-derived stem cells. SVF cell behavior and tissue formation were compared in a stable fibrin formulation developed by our group and a commercial fibrin sealant (TissuCol; Baxter) upon direct subcutaneous implantation in a nude mouse model. Further, the effect of in vitro adipogenic induction on SVF cell development was investigated by implanting stable fibrin constructs after 1 week of precultivation (adipogenic vs. noninduced control). Constructs were thoroughly analyzed before implantation regarding adipogenic differentiation status, cell viability, and distribution as well as the presence of endothelial cells. Before implantation, in vitro precultivation strongly promoted adipogenesis (under adipogenic conditions) and the formation of CD31(+) prevascular structures by SVF cells (under nonadipogenic conditions). Tissue development in vivo was determined after 4 weeks by histology (hematoxylin and eosin, human vimentin) and quantified histomorphometrically. In stable fibrin gels, adipogenic precultivation was superior to noninduced conditions, resulting in mature adipocytes and the formation of distinct vascular structures of human origin in vivo. Strong neovascularization by the implanted cells predominated in noninduced constructs. Without pretreatment, the SVF in stable fibrin gels displayed only a weak differentiation capability. In contrast, TissuCol gels strongly supported the formation of coherent and well-vascularized adipose tissue of human origin, displaying large unilocular adipocytes. The developed native-like tissue architecture was highlighted by a whole mount staining technique. Taken together, SVF cells from human adipose tissue were shown to successfully lead to adipose tissue formation in fibrin hydrogels in vivo. The results render the SVF a promising cell source for subsequent studies both in vitro and in vivo with the aim of engineering clinically applicable soft tissue substitutes.

Uncultivated stromal vascular fraction is equivalent to adipose‐derived stem and stromal cells on porous polyurethrane scaffolds forming adipose tissue in vivo

“…Whereas the volume stability in vitro of ASC‐seeded PU scaffolds combined with either TissuCol or stable fibrin has been demonstrated previously by our group, TissuCol provides ideal compliance and degradation kinetics to foster adipose tissue formation in vivo . We successfully demonstrated the formation of mature fat pads accompanied by capillaries in macroscopically volume‐stable PU/TissuCol constructs previously seeded with either SVF cells or ASCs.…”

“…Informed consent was given by every participant. The tissue was processed as previously described by our group, and detailed protocols can be found in the Supporting Information in the online version of this article …”

Delivered adipose‐derived stromal cells improve host‐derived adipose tissue formation in composite constructs in vivo

“…The building function of transplanted ASCs was shown by Torio‐Padron et al demonstrating the human origin of the developed adipose tissue in an immunodeficient mouse model by vimentin staining . Other studies support this function of transplanted donor cells contributing to the newly formed adipose tissue by verifying human cells within the developed tissue . In contrast, in a matrigel‐filled tissue engineering chamber with human fat biopsies or ASCs, the new tissue was formed exclusively from murine host cells.…”

Stem cell-derived vasculature: A potent and multidimensional technology for basic research, disease modeling, and tissue engineering

“…In a way, this approach can be considered a hybrid of in situ and prevascularization, as stem cell-derived populations other than the vascular cells themselves are pre-embedded. Vascularized adipose tissue was generated in this manner using stromal-vascular fraction-derived adipose cells embedded in precultivated fibrin gels for soft tissue substitution [90]. A similar strategy has been applied to evaluate the use of both adipose-derived stem cells co-cultured with EC [91] and amniotic-fluid derived stem cells [92] as sources of vascular and perivascular cells for in situ capillary network formation.…”