Direct conversion of human fibroblasts into therapeutically active vascular wall-typical mesenchymal stem cells.

Cell-based therapies using adult stem cells are promising options for the treatment of a number of diseases including autoimmune and cardiovascular disorders. Among these, vascular wall-derived mesenchymal stem cells (VW-MSCs) might be particularly well suited for the protection and curative treatment of vascular damage because of their tissue-specific action. Here we report a novel method for the direct conversion of human skin fibroblasts towards MSCs using a VW-MSC-specific gene code (HOXB7, HOXC6 and HOXC8) that directs cell fate conversion bypassing pluripotency. This direct programming approach using either a self-inactivating (SIN) lentiviral vector expressing the VW-MSC-specific HOX-code or a tetracycline-controlled Tet-On system for doxycycline-inducible gene expressions of HOXB7, HOXC6 and HOXC8 successfully mediated the generation of VW-typical MSCs with classical MSC characteristics in vitro and in vivo. The induced VW-MSCs (iVW-MSCs) fulfilled all criteria of MSCs as defined by the International Society for Cellular Therapy (ISCT). In terms of multipotency and clonogenicity, which are important specific properties to discriminate MSCs from fibroblasts, iVW-MSCs behaved like primary ex vivo isolated VW-MSCs and shared similar molecular and DNA methylation signatures. With respect to their therapeutic potential, these cells suppressed lymphocyte proliferation in vitro, and protected mice against vascular damage in a mouse model of radiation-induced pneumopathy in vivo, as well as ex vivo cultured human lung tissue. The feasibility to obtain patient-specific VW-MSCs from fibroblasts in large amounts by a direct conversion into induced VW-MSCs could potentially open avenues towards novel, MSC-based therapies.

Dopamine receptor 1 expressing B cells exert a proinflammatory role in female patients with rheumatoid arthritis.

Rheumatoid arthritis (RA) is a chronic rheumatic disease with a clear sex-bias. Recent data indicated a role for dopamine in RA pathogenesis, while dopaminergic pathways can be modulated by estrogens. As defined mechanism of action of dopamine on B cell function in RA are unclear, we aimed to elucidate this, with special focus on sex-differences. Healthy controls (HC, n = 64) and RA patients (n = 61) were recruited. Expression of D1-D5 dopamine receptors (DRs) was investigated by flow cytometry on peripheral blood mononuclear cells (PBMCs). D1-like DRs were stimulated in vitro to assess effects on B cell activation and proliferation. Secretion of cytokines and dopamine content were measured by ELISA. All DRs were expressed on PBMCs of HC and RA patients. Dopamine content in PBMCs, and frequency of D1DR expressing B cells were significantly higher in RA females (p < 0.001). Expression of D1DR on RA B cells correlated positively with disease duration and severity only in women. Combined B cell and D1-like DR stimulation induced higher IL-8 and CCL-3 secretion from PBMCs of female RA patients compared to HC. These results indicate sex-specific differences in dopaminergic pathway in RA, with a proinflammatory feature of the D1DR pathway in women.

Detection of autoreactive CD4+ T cells by MHC class II multimers in HLA-linked human autoimmune diseases.

Recognition of self-peptides in association with distinct HLA class II alleles by autoreactive CD4+ T cells is central for loss of immunological tolerance leading to autoimmune disease. However, identifying immunodominant self-peptides and characterizing autoreactive T cells is challenging. In this issue of the JCI, Falta et al. identify a disease-associated complementarity-determining region 3ß motif specific for beryllium-modified C-C motif ligand 4 (CCL4) and CCL3 self-peptides in patients with chronic beryllium disease (CBD), a granulomatous lung disorder with a known HLA class II allelic association. Detection of these antigen-specific CD4+ T cells by beryllium-pulsed HLA-DP2 tetramers presenting CCL4/CCL3 confirms these autoantigens in humans and mice and enables monitoring in the progress of disease. Detection of autoreactive CD4+ T cells by peptide-MHC class II multimers allows for the detailed characterization of disease-promoting T cells. This knowledge has profound implications for the monitoring and development of targeted therapies in human autoimmune disorders.