This study indicates that osteogenic potentials of adipose-derived cells vary by their anatomical sites, with visceral adipose-derived cells exhibiting higher osteogenic potential than those isolated from subcutis. However, the mechanism is still unidentified.

Tissue engineering has emerged as a promising alternative approach to current clinical treatments for restoration of soft tissue defects. The purpose of this study was to investigate adipose tissue formation in vitro and in vivo by using human adipose-derived stromal cells (ADSCs) utilizing a gelatin sponge (Gelform®) as a scaffold. Adipogenic potentials of human ADSCs were demonstrated by Oil-O-red staining and cellular morphology. After seeding human ADSCs in a density of 3 × 10⁶ cells/ml on three-dimensional gelatin sponges, tissue-engineered constructs were exposed to adipogenic differentiation medium for in vitro studies and implanted in the backs of severe combined immunodeficient (SCID) mice for in vivo adipose regeneration. Adipogenesis of ADSC-seeded gelatin sponges was confirmed by Oil-O-red staining after 4 weeks of in vitro incubation. The optical density of the elution from Oil-O-red staining of adipogenic constructs is significantly higher than that of the control group (p < 0.05, n = 4). With short-term in vitro differentiation, adipogenic constructs turned into fat tissue 4 weeks after in vivo implantation, confirmed by biochemical and immunohistochemical examination. No adipogenic-morphological change or fat formation was observed in in vitro or in vivo studies when ADSCs were exposed to a control medium without adipogenic stimulation. These results indicate that engineered adipose tissue can be achieved using human ADSCs and biocompatible and degradable gelatin sponges.

The limitation of current clinical treatment for restoration extended defects of soft tissue associated with trauma, tumor resections, and congenital deformities are well known. This study demonstrates that human bone marrow stromal cells (MSCs) can be utilized to tissue engineer adipose tissue for therapeutic purposes. Adipogenic potentials of monolayer-cultured human MSCs were evaluated by biochemical measurement of an adipogenic differentiation marker (glycerol-3-phosphate dehydrogenase, G-3-PDH) and cellular morphology. After preparation by seeding human MSCs on a 3-dimensional gelatin sponge and exposure to adipogenic differentiation medium, the ex vivo tissue-engineered adipose constructs were assessed histomorphologically and biochemically. Lipid droplets accumulated and expanded within the constructs accompanied by a significant increase of G-3-PDH activity. The present study indicates that bone MSCs could be a cell resource in tissue engineering adipose tissue, while gelatin sponge could be a good scaffold in this approach to improve the outcome of clinical treatment.

Adipose-derived stromal cells (ASCs) possess multiple differentiation potentials and may serve as a cell source, if effectively modulated, for regenerative medicine and tissue engineering. Due to estrogen's function in tissue and organ development through regulating cell proliferation and differentiation, we hypothesized that an estrogen supplement may effectively enhance the multiple differentiation potentials of human ASCs. 17-Beta estradiol (E2) was investigated for modulating in vitro osteogenic and adipogenic differentiation in human ASCs isolated from a healthy female donor. After ASCs' exposure to osteogenic and adipogenic differentiation medium supplemented with different concentrations of E2, osteogenic markers (alkaline phosphatase activity, extracellular matrix, calcium deposition, and osteocalcin expression) and adipogenic parameters (lipid accumulation and differentiated cell population) significantly improved. Estrogen's enhancement is dose dependent and linked to differing alpha and beta estrogen receptors. Our data preliminarily demonstrate that estrogen can modulate the differentiation, and potentially improve the efficiency of ASCs in stem cell-based tissue engineering and regeneration. However, further study is needed to verify the regulatory functions of estrogen on ASC differentiations of donors with different ages and genders.