Mesenchymal stem cells cultured as spheroids (MSC-Sph) : A tool for improving pancreatic islet transplantation outcome

OLIVEIRA, TC; FORNI, MF; SANTOS, AF; WAILEMANN, RAM; TERRA, LF; GIMENO, ML; GOMES, VM; FORTUNA, V; PERONE, MJ; SOGAYAR, MC; LABRIOLA, L

Congreso; International Pancreas & Islet Transplant Association; International Xenotransplantation Association and Cell Transplant Society; 2015

INTRODUCTION: Type 1 diabetes is a chronic disease caused by autoimmune destruction of pancreatic beta cells leading to insulin deficiency and consequent metabolism impairment. Pancreatic islet transplantation is a therapeutic alternative however, both islet isolation technique and allorecognition by immune system undermine beta cell viability. One of the strategies investigated in islet transplantation is the co-transplantation of mesenchymal stem cells in order to improve graft function, either in relation to the modulation of immune response or by a increased vascularity of the islet. Recent studies from Darwin Prockop and collaborators showed aggregation of bone marrow derived MSCs as spheroids (MSC-Sph) enhances their secretion of modulators of inflammation and immunity. It is worth mentioning that this cell type has not yet been tested in the context of islet transplantation. Furthermore there is an evident benefit of making use of skin cells since they are of easy access and provide the possibility of using cells obtained from the receptor themselves. Therefore, we set out to assess whether co-transplantation of MSC-Sph cells, enriched from skin primary cultures, influence islet viability and functionality, improving the outcome of transplantation. MATERIAL AND METHODS: Primary cultures of human skin tissue were subjected to adherent and suspension culture steps to enrich MSC-Sph population and further characterized by flow cytometry (FC). MSC-Sph cells were co-cultured with mouse splenocytes to assess cytokines secretion. Mouse islets kept in co-culture with MSC-Sph conditioned medium were submitted to viability and functional assays. MSC-Sph cells were injected into immunodeficient nude mice testes to check for tumorigenicity. RESULTS AND DISCUSSION: The MSC-Sph cells FC analysis showed an enrichment of CD105+ and double-positive CD105+/CD90+ populations, with no significant enrichment of negative markers (CD34, CD45, HLA-DR). The culture of murine splenocytes with MSC-Sph resulted in modulation of immune secretory profile, with both decrease of proinflamatory (IFNγ, IL-2) and increase in anti-inflammatory (IL-10) cytokines. Murine testes showed no signs of tumor formation after six months of MSC-Sph injection. MSC-Sph-conditioned medium inhibited cytokine-induced beta-cell death, while exposure to conditioned medium from primary skin cells showed no cytoprotective effect. Moreover, the presence of MSC-Sph-conditioned medium did not hamper glucose-stimulated insulin release. CONCLUSIONS: These results pointed MSC-Sph as important tools for increasing islet transplantation outcome since they displayed promising effects on both islet viability as well as immunomodulation.