Viewing stromal vascular fraction de novo vessel formation and association with host microvasculature using the rat mesentery culture model

Harnessing the angiogenic potential of adipose-derived stromal vascular fraction cells with perfusion cell seeding

BACKGROUND

The rapid formation and long-term maintenance of functional vascular networks are crucial for the success of regenerative therapies. The stromal vascular fraction (SVF) from human adipose tissue is a readily available, heterogeneous cell source containing myeloid lineage cells, mesenchymal stromal cells, endothelial cells and their precursors, and pericytes, which are important for vascular support. Previous studies showed that seeding SVF cells under perfusion and pre-culturing them on three-dimensional (3D) collagen sponges enhances the vascular cell component in vitro while accelerating vascularization and improving human cell engraftment in vivo compared to static pre-culture. However, generating a perfusion-cultured SVF patch over a 5-day period is both costly and challenging for clinical translation. To overcome these limitations, this study explores a no-pre-culture strategy by comparing perfusion-based seeding with static cell loading on 3D sponges. The hypothesis is that perfusion-based seeding enhances in vivo cell engraftment and angiogenic potential by loading different SVF cell subpopulations onto 3D scaffolds during the seeding process.

METHODS

SVF-cells are seeded onto collagen scaffold using two approaches: a closed system perfusion bioreactor for 18 h or static loading onto the sponge surface. The in vitro cell distribution and baseline cytokine profiles were evaluated. Subsequently, human cell engraftment and differentiation were assessed in vivo using a nude rat subcutaneous implantation model. Analyses included the survival of transplanted human cells, the functionality and maturation of newly formed blood vessels within the SVF-patch.

RESULTS

Perfusion seeding significantly reduced the number of myeloid cells and achieved uniform spatial distribution across the construct. Vascular endothelial growth factor release was significantly increased following perfusion culture, whereas pro-inflammatory cytokines such as tumor necrosis factor-α and interleukin-1β were decreased. In the short term, perfusion culture enhanced uniform vascularization and SVF cell engraftment in vivo. However, the long-term differences between the perfusion-seeded and static-seeded groups diminished.

CONCLUSION

Eliminating the need for prolonged pre-culture offers a feasible and cost-effective strategy for advancing regenerative cell-based therapies by reducing pre-culture times while preserving therapeutic efficacy. Perfusion-based seeding offers significant short-term benefits, including enhanced vascularization and cell engraftment, though long-term differences compared to static seeding are minimal. Further investigation is needed to evaluate its potential in a diseased ischemic heart model.

Stromal Vascular Fraction Reverses the Age-Related Impairment in Revascularization following Injury

Adipose-derived stromal vascular fraction (SVF) has emerged as a potential regenerative therapy, but few studies utilize SVF in a setting of advanced age. Additionally, the specific cell population in SVF providing therapeutic benefit is unknown. We hypothesized that aging would alter the composition of cell populations present in SVF and its ability to promote angiogenesis following injury, a mechanism that is T cell-mediated. SVF isolated from young and old Fischer 344 rats was examined with flow cytometry for cell composition. Mesenteric windows from old rats were isolated following exteriorization-induced (EI) hypoxic injury and intravenous injection of one of four cell therapies: (1) SVF from young or (2) old donors, (3) SVF from old donors depleted of or (4) enriched for T cells. Advancing age increased the SVF T-cell population but reduced revascularization following injury. Both young and aged SVF incorporated throughout the host mesenteric microvessels, but only young SVF significantly increased vascular area following EI. This study highlights the effect of donor age on SVF angiogenic efficacy and demonstrates how the ex vivo mesenteric-window model can be used in conjunction with SVF therapy to investigate its contribution to angiogenesis.