The potential of the incorporated collagen microspheres in alginate hydrogel as an engineered three-dimensional microenvironment to attenuate apoptosis in human pancreatic islets.

BACKGROUND: Tissue engineering is considered as a promising tool for remodeling the native cells microenvironment. In the present study, the effect of alginate hydrogel and collagen microspheres integrated with extracellular matrix components were evaluated in the decrement of apoptosis in human pancreatic islets. MATERIALS/METHODS: For three-dimensional culture, the islets were encapsulated in collagen microspheres, containing laminin and collagen IV and embedded in alginate scaffold for one week. After that the islets were examined in terms of viability, apoptosis, genes and proteins expression including BAX, BCL2, active caspase-3, and insulin. Moreover, the islets function was evaluated through glucose-induced insulin and C-peptide secretion assay. In order to evaluate the structure of the scaffolds and the morphology of the pancreatic islets in three-dimensional microenvironments, we performed scanning electron microscopy. RESULTS: Our findings showed that the designed hydrogel scaffolds significantly improved the islets viability using the reduction of activated caspase-3 and TUNEL positive cells. CONCLUSIONS: The reconstruction of the destructed matrix with alginate hydrogels and collagen microspheres might be an effective step to promote the culture of the islets.

Exosomes derived from human mesenchymal stem cells preserve mouse islet survival and insulin secretion function.

Islet cell death and loss of function after isolation and before transplantation is considered a key barrier to successful islet transplantation outcomes. Mesenchymal stem cells (MSCs) have been used to protect isolated islets owing to their paracrine potential partially through the secretion of vascular endothelial growth factor (VEGF). The paracrine functions of MSCs are also mediated, at least in part, by the release of extracellular vesicles including exosomes. In the present study, we examined (i) the effect of exosomes from human MSCs on the survival and function of isolated mouse islets and (ii) whether exosomes contain VEGF and the potential impact of exosomal VEGF on the survival of mouse islets. Isolated mouse islets were cultured for three days with MSC-derived exosomes (MSC-Exo), MSCs, or MSC-conditioned media without exosomes (MSC-CM-without-Exo). We investigated the effects of the exosomes, MSCs, and conditioned media on islet viability, apoptosis and function. Besides the expression of apoptotic and pro-survival genes, the production of human and mouse VEGF proteins was evaluated. The MSCs and MSC-Exo, but not the MSC-CM-without-Exo, significantly decreased the percentage of apoptotic cells and increased islet viability following the downregulation of pro-apoptotic genes and the upregulation of pro-survival factors, as well as the promotion of insulin secretion. Human VEGF was observed in the isolated exosomes, and the gene expression and protein production of mouse VEGF significantly increased in islets cultured with MSC-Exo. MSC-derived exosomes are as efficient as parent MSCs for mitigating cell death and improving islet survival and function. This cytoprotective effect was probably mediated by VEGF transfer, suggesting a pivotal strategy for ameliorating islet transplantation outcomes.

Cytoprotective effects of olesoxime on isolated human pancreatic islets in order to attenuate apoptotic pathway.

BACKGROUND AND PURPOSE: Islet transplantation is considered as a promising approach in the treatment of diabetes type 1. In this regard, optimal culture of the pancreatic islets is promising in the success of transplantation. In the present study, the effect of olesoxime, as an antiapoptotic substance, was evaluated on human islet culture. EXPERIMENTAL APPROACH: The pancreatic islets were isolated by mechanical and enzymatic techniques. After overnight recovery, the islets were treated by different concentrations of olesoxime for 24 and 72 h. Then, they were examined in terms of viability, apoptosis, genes and proteins expression including BAX, BCL2, active caspase-3, and insulin. Moreover, the islets function was evaluated through the glucose-induced insulin and C-peptide secretion assay. KEY RESULTS: Our findings showed that the islets increased in apoptosis and the decreased in viability after 72 h; also, insulin and C-peptide secretion reduced. However, in the presence of olesoxime, BAX/BCL2 ratio and the activation of caspase-3 were decreased. Therefore, olesoxime could improve the viability of the islets with the decrease of apoptosis. CONCLUSION: The application of olesoxime can reduce the stressful condition for the islets in vitro and subsequently improve their viability and functionality.

Amelioration of the apoptosis-mediated death in isolated human pancreatic islets by minocycline.

Minocycline functions as a therapeutic drug in different diseases because of its cytoprotective properties. In the present study, we examined the potential of minocycline to decrease the islet loss in pre-transplantation culture stage. Pancreatic islets were isolated from the deceased donors and treated by 0, 2, 10, and 20 µM minocycline for 24 and 72 h. After that, the incubated islets were evaluated for viability and function. Apoptosis markers including Bax, Bcl2, and caspase-3 were determined at gene and protein level. On the other hand, TUNEL assay was used to confirm apoptosis. The functionality of the islets was investigated using glucose-induced insulin and c-peptide secretion assay. After 72 h of incubation, the viability of human islet was drastically decreased, whereas supplementation with minocycline inhibited the cells death. In this regard, the expression of Bax and active Caspase-3 was downregulated, whereas the expression of Bcl2 was upregulated. These consequences suggest that pancreatic islets undergo apoptosis in vitro and minocycline can decelerate or inhibit this process. Our findings identified minocycline as a cytoprotective molecule for preventing human islets death in pre-transplantation culture.