Proliferation and differentiation of adipose-derived stem cells on naturally derived scaffolds

The effect of source animal age upon extracellular matrix scaffold properties

Biologic scaffold materials composed of mammalian extracellular matrix (ECM) are commonly used for the repair and reconstruction of injured tissues. An important, but unexplored variable of biologic scaffolds is the age of the animal from which the ECM is prepared. The objective of the present study was to compare the structural, mechanical, and compositional properties of small intestinal submucosa (SIS)-ECM harvested from pigs that differed only in age. Degradation product bioactivity of these ECM materials was also examined. Results showed that there are distinct differences in each of these variables among the various age source ECM scaffolds. The strength and growth factors content of ECM from 3-week-old animals is less than that of ECM harvested from 12, 26 or >52-week-old animals. The elastic modulus of SIS-ECM for 3 week and >52-week-old source was less than that of the 12 and 26 week source. Degradation products from all age source ECMs were chemotactic for perivascular stem cells, with the 12 week source the most potent, while the oldest source caused the greatest increase in proliferation. In summary, distinct differences exist in the mechanical, structural, and biologic properties of SIS-ECM harvested from different aged animals.

The use of decellularized adipose tissue to provide an inductive microenvironment for the adipogenic differentiation of human adipose-derived stem cells

The development of an engineered adipose tissue substitute, capable of supporting reliable, predictable, and complete fat tissue formation, would be of significant value in the fields of plastic and reconstructive surgery. Towards the goal of engineering an optimized microenvironment for adipogenesis, a decellularization strategy was developed for adipose tissue, which yielded 3-D scaffolds with preserved extracellular matrix architecture. A significant volume of scaffolding material could be obtained from a human tissue source that is commonly discarded. Histology, immunohistochemistry, and scanning electron microscopy confirmed the efficacy and reproducibility of the approach, and also indicated that the basement membrane was conserved in the processed matrix, including laminin and collagen type IV. Seeding experiments with human adipose-derived stem cells indicated that the decellularized adipose tissue (DAT) provided an inductive microenvironment for adipogenesis, supporting the expression of the master regulators PPARgamma and CEBPalpha, without the need for exogenous differentiation factors. High levels of adipogenic gene expression and glycerol-3-phosphate dehydrogenase activity were observed in the induced DAT scaffolds, as compared to cells grown in monolayer or cell aggregate culture. The protein data emphasized the importance of the cell donor source in the development of tissue-engineering strategies for large-volume soft tissue regeneration.

Tissue engineering with adipose-derived stem cells (ADSCs): current and future applications

Soft-tissue loss presents an ongoing challenge in plastic and reconstructive surgery. Standard approaches to soft-tissue reconstruction include autologous tissue flaps, autologous fat transplantation and alloplastic implants. All of these approaches have disadvantages, including donor-site morbidity, implant migration and absorption and foreign body reaction. Stem cell application has recently been suggested as a possible novel therapy. Adipose-derived stem cells (ADSCs) are an abundant, readily available population of multipotent progenitor cells that reside in adipose tissue, which is an easily accessible and abundant source of putative stem cells for translational clinical research. Their therapeutic use in pre-clinical studies and experimental clinical trials has been well documented. We present the current strategies of tissue engineering with ADSC and we discuss the possible future applications of this new method in the field of plastic and reconstructive surgery. Complete understanding of the mechanisms of interactions among adipose stem cells, growth factors and biomaterials in tissue engineering is still lacking. Adipose tissue stem cell-based regenerative strategies hold tremendous promise, although this potential must be balanced against stringent standards of scientific and clinical investigation, before developing 'off-the-shelf' tissue engineering products.

In vivo osteogenic differentiation of human adipose-derived stem cells in an injectable in situ-forming gel scaffold

The sol-to-gel transition occurring at around body temperature makes the MPEG-PCL diblock copolymer an ideal candidate material for use as an injectable in situ-forming gel containing human adipose tissue-derived stem cells (hADSCs). The sol can be prepared at room temperature, and the gel forms at body temperature. Solutions of the copolymer containing hADSCs and osteogenic factors injected into rats formed gel scaffolds at the injection sites. The gels thus formed showed the interconnective pore structure required to support growth, proliferation, and differentiation of hADSCs. Bromodeoxyuridine-labeled hADSCs were confirmed to be present in gels formed in vivo. Bone formation was observed only in gel implants containing both hADSCs and osteogenic factors. Subcutaneous implantation of the in situ-forming gel scaffold demonstrated that hADSCs embedded in the gel stimulated much lower host tissue responses than did the gel alone, probably because of the unique immunomodulatory properties of hADSCs. In conclusion, our data on hADSCs embedded in an in situ gel scaffold suggest that this formulation may provide numerous benefits as a noninvasive alternative for tissue-engineered bone formation.

Adipose-derived stem cells for soft tissue reconstruction

In soft tissue repair, there are several surgical options such as nondegradable, inert, synthetic, biodegradable implants or autologous tissue transplantation. However, the potential of using autologous adult stem cells derived from fat tissue is quickly becoming a clinical reality. The possibility of using an abundant source of extraneous tissue as a soft tissue implant has significant implications for plastic and reconstructive surgeons. This strategy would be particularly useful after tumor removal or trauma. The ability of adult stem cells derived from adipose tissue (termed adipose-derived stem cell) to proliferate and differentiate in vivo or in vitro is actively being studied owing to the potential implementation in reconstructive surgery. This review describes innovative research strategies and discusses the first clinical studies involving adipose-derived stem cells as a motif for soft tissue reconstruction.