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Abstract: Loss of adipose tissue can occur due to congenital and acquired lipoatrophies, trauma, tumor resection, and chronic disease. Clinically, it is difficult to regenerate or reconstruct adipose tissue. The extensive microvsacular network present in adipose, and the sensitivity of adipocytes to hypoxia, hinder the success of typical tissue transfer procedures. Materials that promote the formation of vascularized adipose tissue may offer alternatives to current clinical treatment options. A number of synthetic and natural biomaterials common in tissue engineering have been investigated as scaffolds for adipose regeneration. While these materials have shown some promise they do not account for the unique extracellular microenvironment of adipose. Adipose derived hydrogels more closely approximate the physical and chemical microenvironment of adipose tissue, promote preadipocyte differentiation and vessel assembly in vitro, and stimulate vascularized adipose formation in vivo. The combination of these materials with techniques that promote rapid and stable vascularization could lead to new techniques for engineering stable, vascularized adipose tissue for clinical application. In this review we discuss materials used for adipose tissue engineering and strategies for vascularization of these scaffolds. Clinical Relevance: Materials that promote formation of vascularized adipose tissue have the potential to serve as alternatives or supplements to existing treatment options, for adipose defects or deficiencies resulting from chronic disease, lipoatrophies, trauma, and tumor resection. [Copyright &y& Elsevier]

Abstract: Chronic exposure to reducing sugars due to diabetes, aging, and diet can permanently modify extracellular matrix (ECM) proteins. This non-enzymatic glycosylation, or glycation, can lead to the formation of advanced glycation end products (AGE) and crosslinking of the ECM. This study investigates the effects of glycation on the properties of type I collagen gels. Incubation with glucose-6-phopshate (G6P), a reducing sugar that exhibits similar but more rapid glycation than glucose, modified the biological and mechanical properties of collagen gels. Measures of AGE formation that correlate with increased complications in people with diabetes, including collagen autofluorescence, crosslinking, and resistance to proteolytic degradation, increased with G6P concentration. Rheology studies showed that AGE crosslinking increased the shear storage and loss moduli of type I collagen gels. Fibroblasts cultured on glycated collagen gels proliferated more rapidly than on unmodified gels, but glycated collagen decreased fibroblast invasion. These results show that incubation of type I collagen gels with G6P increases clinically relevant measures of AGE formation and that these changes altered cellular interactions. These gels could be used as in vitro models to study ECM changes that occur in diabetes and aging. [Copyright &y& Elsevier]

Abstract: Biomaterials that induce adipogenesis may ultimately serve as alternatives to traditional tissue reconstruction and regeneration techniques. In addition, these materials can provide environments for studying factors that regulate adipogenesis. The present study investigates the potential of adipose-derived matrices to induce adipogenesis in vitro and in vivo. Solutions containing basement membrane proteins and growth factors were extracted from subcutaneous adipose tissue. These extracts could be induced to form gels by either incubating the solutions at 37°C or adjusting the pH to 4.0. The adipose extracts promoted rapid preadipocyte aggregation and formation of lipid-loaded colonies in vitro. Differentiation on adipose-derived gels was greater than tissue culture dishes and the tumor-derived product Matrigel™ (p <0.05). Significant adipose formation was observed when adipose-derived gels were implanted around a rat epigastric pedicle bundle. Adipose levels in these gels were significantly greater than Matrigel™ (p <0.05). The duration of adipose formation depended on the mechanism for gelling the solutions, with acid gelled matrices having greater adipose levels at 6 weeks than temperature gelled matrices. These adipose-derived hydrogels promote rapid adipogenesis in vitro and in vivo. They may lead to new materials for adipose tissue engineering, and provide an environment for studying cell–matrix interactions in adipogenesis. [Copyright &y& Elsevier]