Generation of a pancreas derived hydrogel for the culture of hiPSC derived pancreatic endocrine cells.

Stem cell-derived ß-cells (SC-BCs) represent a potential source for curing diabetes. To date, in vitro generated SC-BCs display an immature phenotype and lack important features in comparison to their bona-fide counterparts. Transplantation into a living animal promotes SC-BCs maturation, indicating that components of the in vivo microenvironment trigger final SC-BCs development. Here, we investigated whether cues of the pancreas specific extracellular matrix (ECM) can improve the differentiation of human induced pluripotent stem cells (hiPSCs) towards ß-cells in vitro. To this aim, a pancreas specific ECM (PanMa) hydrogel was generated from decellularized porcine pancreas and its effect on the differentiation of hiPSC-derived pancreatic hormone expressing cells (HECs) was tested. The hydrogel solidified upon neutralization at 37 °C with gelation kinetics similar to Matrigel. Cytocompatibility of the PanMa hydrogel was demonstrated for a culture duration of 21 days. Encapsulation and culture of HECs in the PanMa hydrogel over 7 days resulted in a stable gene and protein expression of most ß-cell markers, but did not improve ß-cell identity. In conclusion, the study describes the production of a PanMa hydrogel, which provides the basis for the development of ECM hydrogels that are more adapted to the demands of SC-BCs.

Erythropoietin gene expression in renal carcinoma is considerably more frequent than paraneoplastic polycythemia.

Signalling by erythropoietin (EPO) is increasingly recognised as a relevant mechanism in tumour biology, potentially leading to enhanced proliferation, angiogenesis and therapy resistance. Paraneoplastic polycythemia by cancerous overproduction of EPO is a rare event, but most frequently seen in patients with renal cell carcinoma (RCC). The majority of clear cell RCC displays a strong activation of the transcription factor regulating EPO, the Hypoxia-inducible Factor (HIF). Therefore, it is unclear why only a small minority of patients develop polycythemia. We studied 70 RCC for EPO gene and HIFalpha isoform expression. 34% of all RCC showed expression of EPO mRNA in RNase protection assays, which were almost exclusively of the clear cell type. Only 1 patient presented with polycythemia. In situ hybridisation revealed that expression of EPO was in the tumour cells. Expression of EPO mRNA was always associated with activation of HIF, which could involve HIF-1alpha and/or HIF-2alpha. The frequency of EPO gene expression in RCC is therefore much higher than the prevalence of polycythemia. Furthermore, activation of HIF appears necessary for EPO gene expression in RCC, but is clearly not the only determinant. Further to the reported expression of EPO receptors in tumour tissues, the finding of widespread expression of EPO in RCC supports the recent notion of an involvement of this system in paracrine or autocrine effects of tumour cells.