Collagen microgel to simulate the adipocyte microenvironment for in vitro research on obesity.

Obesity is linked to adipose tissue dysfunction, a dynamic endocrine organ. Two-dimensional cultures present technical hurdles hampering their ability to follow individual or cell groups for metabolic disease research. Three-dimensional type I collagen microgels with embedded adipocytes have not been thoroughly investigated to evaluate adipogenic maintenance as instrument for studying metabolic disorders. We aimed to develop a novel tunable Col-I microgel simulating the adipocyte microenvironment to maintain differentiated cells with only insulin as in vitro model for obesity research. Adipocytes were cultured and encapsulated in collagen microgels at different concentrations (2, 3 and 4 mg/mL). Collagen microgels at 3 and 4 mg/mL were more stable after 8 days of culture. However, cell viability and metabolic activity were maintained at 2 and 3 mg/mL, respectively. Cell morphology, lipid mobilization and adipogenic gene expression demonstrated the maintenance of adipocyte phenotype in an in vitro microenvironment. We demonstrated the adequate stability and biocompatibility of the collagen microgel at 3 mg/mL. Cell and molecular analysis confirmed that adipocyte phenotype is maintained over time in the absence of adipogenic factors. These findings will help better understand and open new avenues for research on adipocyte metabolism and obesity. Insight box In the context of adipose tissue dysfunction research, new struggles have arisen owing to the difficulty of cellular maintenance in 2D cultures. Herein, we sought a novel approach using a 3D type I collagen-based biomaterial to adipocyte culture with only insulin. This component was tailored as a microgel in different concentrations to support the growth and survival of adipocytes. We demonstrate that adipocyte phenotype is maintained and key adipogenesis regulators and markers are over time. The cumulative results unveil the practical advantage of this microgel platform as an in vitro model to study adipocyte dysfunction and obesity.

Functionalized Collagen/Poly(ethylene glycol) Diacrylate Interpenetrating Network Hydrogel Enhances Beta Pancreatic Cell Sustenance.

Three-dimensional matrices are a new strategy used to tackle type I diabetes, a chronic metabolic disease characterized by the destruction of beta pancreatic cells. Type I collagen is an abundant extracellular matrix (ECM), a component that has been used to support cell growth. However, pure collagen possesses some difficulties, including a low stiffness and strength and a high susceptibility to cell-mediated contraction. Therefore, we developed a collagen hydrogel with a poly (ethylene glycol) diacrylate (PEGDA) interpenetrating network (IPN), functionalized with vascular endothelial growth factor (VEGF) to mimic the pancreatic environment for the sustenance of beta pancreatic cells. We analyzed the physicochemical characteristics of the hydrogels and found that they were successfully synthesized. The mechanical behavior of the hydrogels improved with the addition of VEGF, and the swelling degree and the degradation were stable over time. In addition, it was found that 5 ng/mL VEGF-functionalized collagen/PEGDA IPN hydrogels sustained and enhanced the viability, proliferation, respiratory capacity, and functionality of beta pancreatic cells. Hence, this is a potential candidate for future preclinical evaluation, which may be favorable for diabetes treatment.

Collagen-mesenchymal stem cell spheroids in suspension promote high adipogenic capacity.

Human mesenchymal stem cells (hMSC) represent a unique and promising platform because of their ability to promote soft tissue regeneration, particularly their ability to differentiate into adipocytes, which are important for adipose tissue regeneration. In this context, type I collagen is the most abundant extracellular matrix component of adipose tissue and can act as a natural spheroid source to support the differentiation process of stem cells. However, spheroids based on collagen and hMSCs without numerous pro-adipogenic factors that can induce adipogenesis have not yet been investigated. In this study, we focused on developing collagen-hMSC spheroids capable of differentiating into adipocyte-like cells in a short time (eight culture days) without adipogenic factors, with potential applications in adipose tissue repair. The physical and chemical properties of the spheroids indicated successful cross-linking of collagen. Upon spheroid development, stability, cell viability, and metabolic activity of the constructs were maintained. During adipogenesis, cell morphology shows significant changes, in which cells change from a fibroblast-like shape to an adipocyte-like shape, and adipogenic gene expression after eight days of cell culture. These results support the utility of collagen-hMSC 3 mg ml-1collagen concentration spheroids to differentiate into adipocyte-like cells in a short time without adverse effects on biocompatibility, metabolic activity, or cell morphology, suggesting that this construct may be used in soft tissue engineering.