Adult pancreatic stem cells (PSCs) are able to differentiate spontaneously in vitro into various somatic cell types. Stem cells isolated from rat pancreas show extensive self-renewal ability and grow in highly viable long-term cultures. Additionally, these cells express typical stem cell markers such as Oct-4, nestin and SSEA-1. Although differentiation potential is slightly decreasing in long-term cultures, it is possible to keep cell lines up to passage 140. Clonal cell lines could be established from different passages and showed similar characteristics. Remarkably, one clonal cell line, generated from passage 75, showed deviant properties during further culture. Clonal cells formed aggregates, which built tissue-like structures in suspension culture. These generated 3D aggregates produced permanently new cells at the outside margin. Released cells had remarkable size, and closer examination by light microscopy analysis revealed oocyte-like morphology. A comparison of the gene expression patterns between primary cultures of passages 8 and 75, the clonal cell line and the produced oocyte-like cells (OLCs) from tissue-like structures demonstrated some differences. Expression of various germ cell markers, such as Vasa, growth differentiation marker 9 and SSEA-1, increased in the clonal cell line, and OLCs showed additionally expression of meiosis-specific markers SCP3 and DMC1. We here present a first pilot study investigating the putative germ line potential of adult PSCs.
Integration of biomaterials into tissues is often disturbed by unopposed activation of macrophages. Immediately after implantation, monocytes are attracted from peripheral blood to the implantation site where they differentiate into macrophages. Inflammatory signals from the sterile tissue injury around the implanted biomaterial mediate the differentiation of monocytes into inflammatory M1 macrophages (M1) via autocrine and paracrine mechanisms. Suppression of sustained M1 differentiation is thought to be crucial to improve implant healing. Here, we explore whether artificial extracellular matrix (aECM) composed of collagen I and hyaluronan (HA) or sulfated HA-derivatives modulate this monocyte differentiation. We mimicked conditions of sterile tissue injury in vitro using a specific cytokine cocktail containing MCP-1, IL-6 and IFNγ, which induced in monocytes a phenotype similar to M1 macrophages (high expression of CD71, HLA-DR but no CD163 and release of high amounts of pro-inflammatory cytokines IL-1β, IL-6, IL-8, IL-12 and TNFα). In the presence of aECMs containing high sulfated HA this monocyte to M1 differentiation was disturbed. Specifically, pro-inflammatory functions were impaired as shown by reduced secretion of IL-1β, IL-8, IL-12 and TNFα. Instead, release of the immunregulatory cytokine IL-10 and expression of CD163, both markers specific for anti-inflammatory M2 macrophages (M2), were induced. We conclude that aECMs composed of collagen I and high sulfated HA possess immunomodulating capacities and skew monocyte to macrophage differentiation induced by pro-inflammatory signals of sterile injury toward M2 polarization suggesting them as an effective coating for biomaterials to improve their integration.
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