Identifying dysregulated immune cell subsets following critical volumetric muscle loss with pseudo-time trajectories

Volumetric muscle loss (VML) results in permanent functional deficits and remains a substantial regenerative medicine challenge. A coordinated immune response is crucial for timely myofiber regeneration, however the immune response following VML has yet to be fully characterized. Here, we leveraged dimensionality reduction and pseudo-time analysis techniques to elucidate the cellular players underlying a functional or pathological outcome as a result of subcritical or critical VML in the murine quadriceps, respectively. We found that critical VML presented with a sustained presence of M2-like and CD206hiLy6Chi "hybrid" macrophages whereas subcritical defects resolved these populations. These macrophage subsets may contribute to fibrogenesis in critical VML, especially in the presence of TGF-β. Furthermore, several T cell populations were significantly elevated in critical VML compared to subcritical injuries. Specifically, there was a significant increase of CD127+ T cells at days 3 and 7, and upregulated CD127 expression may indicate aberrant IL-7 signaling in critical VML. These results demonstrate a dysregulated immune response in critical VML that is unable to resolve the chronic inflammatory state and transition to a pro-regenerative microenvironment. These data provide important insights into potential therapeutic strategies which could reduce the immune cell burden and pro-fibrotic signaling characteristic of VML.

MAGT1 gene mutation causes myositis and CD127 expression downregulation

X-linked immunodeficiency with Magnesium defect, Epstein-Barr virus infection, and Neoplasia (XMEN) is a primary immune deficiency caused by mutations in MAGT1 and is characterized by chronic infection with Epstein-Barr virus (EBV), CD4 lymphopenia, severe chronic viral infections, and defective T-lymphocyte activation. Herein, we described an XMEN patient carrying a MAGT1 p.Arg331* mutation that presented with prominent muscle involvement. The PET-CT and lower limbs MRI showed diffuse muscle inflammation. Histopathology staining revealed the infiltrated lymphocytes were stained with CD3, CD20, and EBER. We monitored the patient’s in-depth immunophenotype at the first visit and after two months of oral Mg 2+ supplementation. We noticed obviously decreased CD127 expression in CD4 + T cells, which could be reversed by Mg 2+ supplementation. Our findings suggested that the decreased CD127 expression may be an additional biomarker of XMEN.

Decreased CD127 Expression on CD4+ T-Cells and Elevated Frequencies of CD4+CD25+CD127− T-Cells in Children with Long-Lasting Type 1 Diabetes

Pathobiology of type 1 diabetes (T1D) is predominantly associated with T-cell-related actions. Homeostasis of majority of T-cells is critically dependent on signals mediated by CD127 (interleukin-7 receptor, IL-7R). In contrast, regulatory T-cells express very little CD127 and thereby may be delineated by CD4+CD25+CD127− phenotype. Here we aimed to analyze CD127 expression on CD4+ and CD8+ T-cells and enumerate CD4+CD25+CD127− T-cells in long-lasting T1D. T-cells were analyzed by flow cytometry and immunologic data were correlated with vascular, metabolic, and inflammatory parameters. We demonstrated significantly decreased CD127 levels on CD4+, but not CD8+, T cells in T1D pediatric patients. Interestingly, frequencies of CD4+CD25+CD127− T-cells were significantly enhanced in T1D children and correlated well with frequencies of CD34+CD144+ endothelial progenitor cells and CD4+CD25− T-cells. Levels of CD127 on both CD4+ and CD8+ T-cells in T1D patients were not correlated to each other or HbA1C. Interestingly, however, CD127 levels on CD4+ T-cells were significantly correlated to frequencies of CD4+CD25+CD127− T-cells, whereas CD127 levels on CD8+ T-cells were significantly correlated to concentrations of VEGF and triglycerides. Our data indicate that CD127 expression is differentially modulated on CD4+ and CD8+ T-cells in the course of T1D. Moreover, we demonstrated that, in contrast to recent-onset T1D, long-lasting T1D is associated with enhancement of T-cells with regulatory phenotype.