Background: Signaling by IL-31 involves OSMR␤ and IL-31R␣, which is expressed in different isoforms. Results: Four of five membrane-bound isoforms activate IL-31 signaling, which is counter-regulated by SOCS3. Conclusion: IL-31 responsiveness is controlled by the expression of specific IL-31R␣ isoforms and is negatively regulated by SOCS proteins. Significance: This study provides new insights into the regulation of IL-31 signaling.

Application of in vitro transcribed (IVT) messenger ribonucleic acid (mRNA) is an increasingly popular strategy to transiently produce proteins as therapeutics in a tissue or organ of choice. Here, we focused on the skin and aimed to test if whole human skin tissue explant technology can be used to evaluate the expression efficacy of different IVT Interferon alpha (IFN-α) mRNA constructs in situ, after biolistic delivery. Skin explants were viable and intact for at least five days based on histologic analysis and TUNEL staining. Using GFP reporter mRNA formulations, we found mostly epidermal expression after biolistic delivery. Two out of five sequence-optimized IFN-α mRNA variants resulted in significantly improved IFN-α protein expression in human skin compared to native IFN-α mRNA transfection. IFN-α secretion analysis of the surrounding culture media confirmed these results. We provide a proof-of-concept that IFN-α mRNA delivery into intact human full thickness skin explants can be utilized to test mRNA sequence modifications ex vivo. This approach could be used to develop novel mRNA-based treatments of common epidermal skin conditions including non-melanoma skin cancer, where IFN-α protein therapy has previously shown a strong therapeutic effect.

Multipotent stromal cells are considered attractive sources for cell therapy and tissue engineering. Despite numerous experimental and clinical studies, broad application of stromal cell therapeutics is not yet emerging. A major challenge is the functional diversity of available cell sources. Here, we investigated the regenerative potential of clinically relevant human stromal cells from bone marrow (BMSCs), white adipose tissue, and umbilical cord compared with mature chondrocytes and skin fibroblasts in vitro and in vivo. Although all stromal cell types could express transcription factors related to endochondral ossification, only BMSCs formed cartilage discs in vitro that fully regenerated critical-size femoral defects after transplantation into mice. We identified cell type–specific epigenetic landscapes as the underlying molecular mechanism controlling transcriptional stromal differentiation networks. Binding sites of commonly expressed transcription factors in the enhancer and promoter regions of ossification-related genes, including Runt and bZIP families, were accessible only in BMSCs but not in extraskeletal stromal cells. This suggests an epigenetically predetermined differentiation potential depending on cell origin that allows common transcription factors to trigger distinct organ-specific transcriptional programs, facilitating forward selection of regeneration-competent cell sources. Last, we demonstrate that viable human BMSCs initiated defect healing through the secretion of osteopontin and contributed to transient mineralized bone hard callus formation after transplantation into immunodeficient mice, which was eventually replaced by murine recipient bone during final tissue remodeling.