HucMSC-Exo Induced N2 Polarization of Neutrophils: Implications for Angiogenesis and Tissue Restoration in Wound Healing.

Background: Neutrophils rapidly accumulate in large numbers at sites of tissue damage, exhibiting not only their well-known bactericidal capabilities but also playing crucial roles in angiogenesis and tissue repair. While exosomes derived from human umbilical cord mesenchymal stem cells (HucMSC-Exo) have emerged as a promising therapeutic tool, their exact mechanisms of action remain partly elusive. We hypothesize that HucMSC-Exo treatment may modulate neutrophil phenotypes, thereby significantly influencing wound healing outcomes. Methods: HucMSC-Exo were isolated via ultracentrifugation and subsequently administered through subcutaneous injection into full-thickness cutaneous wounds in mice. To determine the impact of host neutrophils on the healing effects of HucMSC-Exo in skin injuries, strategies including neutrophil depletion and adoptive transfer were employed. Flow cytometry was used to evaluate the proportion of N2 subtype neutrophils in both normal and diabetic wounds, and the effect of HucMSC-Exo on this proportion was assessed. Furthermore, the mitochondrial metabolic reprogramming driven by HucMSC-Exo during N2 polarization was investigated through JC1 staining, ATP quantification, fatty acid uptake assays, and assessment of FAO-related genes (Cpt1b, Acadm, and Acadl). Results: Depleting host neutrophils strikingly dampened prohealing effect of HucMSC-Exo on skin injury, while adoptive transfer of bone marrow neutrophils rescued this process. During normal healing process, some neutrophils expressed N2 markers, in contrast, diabetic wounds exhibited a reduced expression of N2 markers. After treatment with HucMSC-Exo, most neutrophils increased the phosphorylation of STAT6, leading to mitochondrial metabolic reprogramming and thus acquired an N2 phenotype. These N2 neutrophils, polarized by HucMSC-Exo, boosted the release of proangiogenic factors, particularly BV8, a myeloid cell-derived proangiogenic factor, and induced angiogenesis thereby favoring tissue restoration. Conclusion: This research uniquely demonstrates the identification of N2 neutrophils in skin injury and shows that HucMSC-Exo could skew neutrophils toward N2 phenotype, enhancing our insight into how cells react to HucMSC-Exo.

Integrated Bioinformatics Analysis Reveals Diagnostic Biomarkers and Immune Cell Infiltration Characteristics of Solar Lentigines.

Background: Solar lentigines (SLs), serving as a prevalent characteristic of skin photoaging, present as cutaneous aberrant pigmentation. However, the underlying pathogenesis remains unclear and there is a dearth of reliable diagnostic biomarkers. Objective: The aim of this study was to identify diagnostic biomarkers for SLs and reveal its immunological features. Methods: In this study, gene expression profiling datasets (GSE192564 and GSE192565) of SLs were obtained from the GEO database. The GSE192564 was used as the training group for screening of differentially expressed genes (DEGs) and subsequent depth analysis. Gene set enrichment analysis (GSEA) was employed to explore the biological states associated with SLs. The weighted gene co-expression network analysis (WGCNA) was employed to identify the significant modules and hub genes. Then, the feature genes were further screened by the overlapping of hub genes and up-regulated differential genes. Subsequently, an artificial neural network was constructed for identifying SLs samples. The GSE192565 was used as the test group for validation of feature genes expression level and the model's classification performance. Furthermore, we conducted immune cell infiltration analysis to reveal the immune infiltration landscape of SLs. Results: The 9 feature genes were identified as diagnostic biomarkers for SLs in this study. And an artificial neural network based on diagnostic biomarkers was successfully constructed for identification of SLs. GSEA highlighted potential role of immune system in pathogenesis of SLs. SLs samples had a higher proportion of several immune cells, including activated CD8 T cell, dendritic cell, myeloid-derived suppressor cell and so on. And diagnostic biomarkers exhibited a strong relationship with the infiltration of most immune cells. Conclusion: Our study identified diagnostic biomarkers for SLs and explored its immunological features, enhancing the comprehension of its pathogenesis.