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The induction of adequate vascularization, a major challenge in tissue engineering, has been tried with numerous methods but with unsatisfactory results. Adipose tissue, an active endocrine organ with dense vasculature, secretes a wide number of angiogenic and adipogenic factors and seems an attractive source for these bioactive factors. We produced a novel cell-free extract from mature human adipose tissue (adipose tissue extract [ATE]) and analyzed the ability of this extract to induce angiogenesis and adipogenesis in vitro and studied the cytokine and growth factor composition of ATE with ELISA and cytokine array. We demonstrate that ATE, when added as cell culture supplement, effectively induced triglyceride accumulation in human adipose stem cells at concentrations from 200 μg/mL upward in less than a week and caused elevated levels of adipocyte differentiation markers (proliferator-activated receptor gamma and acyl-CoA-binding protein) when treated with at least 350 μg/mL of ATE. ATE induced angiogenesis from 450 μg/mL upward after a week in vitro. ATE contained numerous angiogenic and adipogenic factors, for example, vascular endothelial growth factor, basic fibroblast growth factor, interleukin-6, adiponectin, angiogenin, leptin, and insulin-like growth factor-I, as well as lower levels of a wide variety of other cytokines. We here present a novel cell-free angiogenesis- and adipogenesis-inducing agent that is cell-free and easy to produce, and its effect is dose dependent and its composition can be easily modified. Therefore, ATE is a promising novel agent to be used for angiogenesis induction to overcome the challenge of vascularization and for adipogenesis induction in a wide variety of tissue engineering applications in vitro and in vivo. ATE is also efficient for reproduction and modeling of natural adipogenesis in vitro for, for example, obesity and diabetes studies.

The aim of this study was to compare the effects of novel three-dimensional composite scaffolds consisting of a bioactive phase (bioactive glass or beta-tricalcium phosphate [beta-TCP] 10 and 20 wt%) incorporated within a polylactic acid (PLA) matrix on viability, distribution, proliferation, and osteogenic differentiation of human adipose stem cells (ASCs). The viability and distribution of ASCs on the bioactive composite scaffolds was evaluated using Live/Dead fluorescence staining, environmental scanning electron microscopy, and scanning electron microscopy. There were no differences between the two concentrations of bioactive glass and beta-TCP in PLA scaffolds on proliferation and osteogenic differentiation of ASCs. After 2 weeks of culture, DNA content and alkaline phosphatase (ALP) activity of ASCs cultured on PLA/beta-TCP composite scaffolds were higher relative to other scaffold types. Interestingly, the cell number was significantly lower, but the relative ALP/DNA ratio of ASCs was significantly higher in PLA/bioactive glass scaffolds than in other three scaffold types. These results indicate that the PLA/beta-TCP composite scaffolds significantly enhance ASC proliferation and total ALP activity compared to other scaffold types. This supports the potential future use of PLA/beta-TCP composites as effective scaffolds for tissue engineering and as bone replacement materials.

Human adipose stem cells (ASCs) combined with osteostimulative material provide an attractive approach for clinical bone regeneration. The effect of calcium phosphate (Ca-P) surface treatment of three-dimensional bioactive glass scaffolds on the attachment, proliferation, and osteogenic differentiation of ASCs was studied. Three types of bioactive glass scaffolds (nontreated, thick and thin Ca-P treated) were compared. All scaffold types supported ASC attachment, spreading, and proliferation equally as detected by scanning electron microscopy, fluorescence staining, and DNA measurement. Indices of osteogenic differentiation including the expression of osteopontin and alkaline phosphatase (ALP) were consistently higher in the nontreated and thin Ca-P-treated scaffolds when compared with thick Ca-P-treated scaffolds at 2 weeks. ASCs cultured on nontreated bioactive glass scaffolds showed significantly higher ALP activity when compared with both thin and thick Ca-P-treated scaffolds after 1 week in culture, but these differences equalized between the three scaffolds by the 2-week time point. In conclusion, osteogenic differentiation appears to be delayed on the Ca-P surface-treated scaffolds. This delay is more pronounced with thick Ca-P treatment of the scaffolds.