Immunological characteristics of human umbilical cord mesenchymal stem cells and the therapeutic effects of their transplantion on hyperglycemia in diabetic rats.

Islet transplantation involves the transplantation of pancreatic islets from the pancreas of a donor to another individual. It has proven to be an effective method for the treatment of type 1 diabetes. However, islet transplantation is hampered by immune rejection, as well as the shortage of donor islets. Human umbilical cord Wharton's jelly-derived mesenchymal stem cells (HUMSCs) are an ideal cell source for use in transplantation due to their biological characteristics and their use does not provoke any ethical issues. In this study, we investigated the immunological characteristics of HUMSCs and their effects on lymphocyte proliferation and the secretion of interferon (IFN)-γ, and explored whether direct cell-to-cell interactions and soluble factors, such as IFN-γ were important for balancing HUMSC-mediated immune regulation. We transplanted HUMSCs into diabetic rats to investigate whether these cells can colonize in vivo and differentiate into pancreatic ß-cells, and whether the hyperglycemia of diabetic rats can be improved by transplantation. Our results revealed that HUMSCs did not stimulate the proliferation of lymphocytes and did not induce allogeneic or xenogeneic immune cell responses. qRT-PCR demonstrated that the HUMSCs produced an immunosuppressive isoform of human leukocyte antigen (HLA-I) and did not express HLA-DR. Flow cytometry revealed that the HUMSCs did not express immune response-related surface antigens such as, CD40, CD40L, CD80 and CD86. IFN-γ secretion by human peripheral blood lymphocytes was reduced when the cells were co-cultured with HUMSCs. These results suggest that HUMSCs are tolerated by the host in an allogeneic transplant. We transplanted HUMSCs into diabetic rats, and the cells survived in the liver and pancreas. Hyperglycemia of the diabetic rats was improved and the destruction of pancreatic cells was partly repaired by HUMSC transplantation. Hyperglycemic improvement may be related to the immunomodulatory effects of HUMSCs. However, the exact mechanisms involved remain to be further clarified.

Impact of perinatal systemic hypoxic-ischemic injury on the brain of male offspring rats: an improved model of neonatal hypoxic-ischemic encephalopathy in early preterm newborns.

In this study, we attempted to design a model using Sprague-Dawley rats to better reproduce perinatal systemic hypoxic-ischemic encephalopathy (HIE) in early preterm newborns. On day 21 of gestation, the uterus of pregnant rats were exposed and the blood supply to the fetuses of neonatal HIE groups were thoroughly abscised by hemostatic clamp for 5, 10 or 15 min. Thereafter, fetuses were moved from the uterus and manually stimulated to initiate breathing in an incubator at 37 °C for 1 hr in air. We showed that survival rates of offspring rats were decreased with longer hypoxic time. TUNEL staining showed that apoptotic cells were significant increased in the brains of offspring rats from the 10 min and 15 min HIE groups as compared to the offspring rats in the control group at postnatal day (PND) 1, but there was no statistical difference between the offspring rats in the 5 min HIE and control groups. The perinatal hypoxic treatment resulted in decreased neurons and increased cleaved caspase-3 protein levels in the offspring rats from all HIE groups at PND 1. Platform crossing times and the percentage of the time spent in the target quadrant of Morris Water Maze test were significantly reduced in the offspring rats of all HIE groups at PND 30, which were associated with decreased brain-derived neurotrophic factor levels and neuronal cells in the hippocampus of offspring rats at PND 35. These data demonstrated that perinatal ischemic injury led to the death of neuronal cells and long-lasting impairment of memory. This model reproduced hypoxic ischemic encephalopathy in early preterm newborns and may be appropriate for investigating therapeutic interventions.

Programming of human umbilical cord mesenchymal stem cells in vitro to promote pancreatic gene expression.

Human umbilical cord mesenchymal stem cells (HUMSCs) are candidates for tissue engineering and may potentially be used for transdifferentiation into pancreatic endocrine cells. The adenoviral vector is effective in transducing genes into stem cells that are refractory to gene delivery by non­viral approaches. qPCR was used to detect the pancreatic endogenous gene expression of HUMSCs transfected by islet cell-specific transcription factors (TFs). In the present study, using adenoviruses, the mouse TFs, pancreatic and duodenal homeobox 1 (pdx1), V-maf musculoaponeurotic fibrosarcoma oncogene homolog A (mafa) and class B basic helix­loop­helix factor neurogenin 3 (ngn3), which are essential for pancreatic cell development, were introduced into HUMSCs to assess the expression of the pancreatic genes, glucagon, pdx1 and nk2 homeobox 2 (nkx2.2). When pdx1, mafa and ngn3 were cotransduced into HUMSCs, the expression of glucagon increased by 21­fold at days 3 and 7 following transduction, while the endogenous pdx1 gene expression was increased by 15­fold at day 3 and decreased by 70% at day 7. When mafa and ngn3 were cotransduced into HUMSCs, there was a 5­fold increase in pdx1 gene expression at day 7, but no activation was observed at day 3. When mafa alone was introduced into HUMSCs, the pdx1 gene expression was elevated by 6­fold at day 3 and decreased by 3­fold at day 7. Transduction of ngn3 alone into HUMSCs induced nkx2.2 gene expression at day 3 but the expression levels were decreased at day 7. However, when pdx1 and ngn3 were cotransduced into HUMSCs, the expression levels of glucagon, pdx1 and nks2.2 were all lower than those observed with pdx1 or ngn3 transduction alone. These results suggested that the transduction of pdx1, mafa and ngn3 genes into HUMSCs induced the expression of the pancreatic genes, glucagon, pdx­1 and nkx2.2, and that the expression was time dependent. In addition, different combinations of the TFs may demonstrate synergistic or antagonistic effects. This data may be beneficial for guiding future studies obtaining mature pancreatic endocrine cells from HUMSCs.