Attachment, Viability and Adipodifferentiation of Pre-adipose Cells on Silk Scaffolds with and Without Co-expressed FGF-2 and VEGF

Abstract

Background/aim: For application of stem cells and progenitor cells in regenerative medicine, scaffolds for carrying the cells play a key role. One promising biomaterial for scaffold generation is silk because of its mechanical strength, good cytocompatibility and low immunogenicity. Furthermore, bioengineering of silk proteins enable co-expression of various growth, differentiation and angiogenic factors on silk fibers, which may promote cell growth, differentiation and angiogenesis. This study aimed to test cytocompatibility and growth/differentiation of pre-adipose cells on scaffolds with and without expressed growth factors fibroblast growth factor-2 (FGF-2) and vascular endothelial growth factor (VEGF).

Materials and methods: Disk-form scaffolds of 15×3 mm (diameter × thickness) were manufactured in two different densities using silk with and without expressed growth factors FGF-2 or VEGF. Pre-adipose cells were prepared from fatty tissues of patients undergoing operation. Cells (1.6×10(6)) were seeded onto each of the silk-scaffold disks, that were placed into wells of 12-well culturing plates. Adipose-differentiation was induced using differentiation medium containing DMEM/F-12, insulin, pantothenate, biotin, triiodothyronine (T3), transferrin, dexamethasone, isobuthylmethylxanthine and rosiglitazone. Cells on the scaffolds were visualized using a confocal microscope. Viability and adiponectin were measured on days 0, 7 and 14. Expression of adipose-differentiation markers was assessed by means of real-time polymerase chain reaction (RT-PCR).

Results: Pre-adipose cells attached well onto the silk fibers. The highest initial viability was measured on the low-density scaffolds with expressed VEGF. Adipose-differentiation was evident in visible oil droplets and significantly increased adiponectin protein levels were seen in ELISA. Furthermore, increased expression of adipose-differentiation genes were measured in RT-PCR. Adipose-differentiation was more profound in cells on high-density scaffolds. In concordance, viability of cells on high-density scaffolds did not increase, while that of cells on low-density scaffolds doubled over the 14-day experimental period. Slightly enhanced adipose-differentiation was observed in cells on scaffolds with expressed FGF-2 or VEGF.

Conclusion: Silk scaffolds exhibit excellent cytocompatibility for human pre-adipose cells and have application potential in tissue engineering and regenerative medicine. VEGF and FGF-2 expressed on silk fibers could have a potential positive effect on pre-adipose cells, while the effect of VEGF should be further addressed in vivo.

Keywords: Adipose tissue engineering; adipocyte differentiation; incorporated growth factors; pre-adipose cells; silk fibroin scaffolds.