Single cell transcriptomic landscape of diabetic foot ulcers

Transcriptomic fingerprint of bacterial infection in lower extremity ulcers

Clinicians and researchers utilize subjective, clinical classification systems to stratify lower extremity ulcer infections for treatment and research. The purpose of this study was to examine whether these clinical classifications are reflected in the ulcer's transcriptome. RNA sequencing (RNA‐seq) was performed on biopsies from clinically infected lower extremity ulcers (n = 44). Resulting sequences were aligned to the host reference genome to create a transcriptome profile. Differential gene expression analysis and gene ontology (GO) enrichment analysis were performed between ulcer severities as well as between sample groups identified by k‐means clustering. Lastly, a support vector classifier was trained to estimate clinical infection score or k‐means cluster based on a subset of genes. Clinical infection severity did not explain the major sources of variability among the samples and samples with the same clinical classification demonstrated high inter‐sample variability. High proportions of bacterial RNA were identified in some samples, which resulted in a strong effect on transcription and increased expression of genes associated with immune response and inflammation. K‐means clustering identified two clusters of samples, one of which contained all of the samples with high levels of bacterial RNA. A support vector classifier identified a fingerprint of 20 genes, including immune‐associated genes such as CXCL8, GADD45B, and HILPDA, which accurately identified samples with signs of infection via cross‐validation. This study identified a unique, host‐transcriptome signature in the presence of infecting bacteria, often incongruent with clinical infection‐severity classifications. This suggests that stratification of infection status based on a transcriptomic fingerprint may be useful as an objective classification method to classify infection severity, as well as a tool for studying host–pathogen interactions.

Single-cell transcriptomics in human skin research: available technologies, technical considerations, and disease applications

Single‐cell technologies have revolutionized research in the last decade, including for skin biology. Single‐cell RNA sequencing has emerged as a powerful tool allowing the dissection of human disease pathophysiology at unprecedented resolution by assessing cell‐to‐cell variation, facilitating identification of rare cell populations and elucidating cellular heterogeneity. In dermatology, this technology has been widely applied to inflammatory skin disorders, fibrotic skin diseases, wound healing complications and cutaneous neoplasms. Here, we discuss the available technologies and technical considerations of single‐cell RNA sequencing and describe its applications to a broad spectrum of dermatological diseases.

Exosomes Derived from Epidermal Stem Cells Improve Diabetic Wound Healing

Diabetic foot ulceration is a major diabetic complication with unmet needs. We investigated the efficacy of epidermal stem cells (ESCs) and ESCs-derived exosomes (ESCs-Exo) in improving impaired diabetic wound healing and their mechanisms of action. In vitro experiments showed that ESCs-Exo enhanced the proliferation and migration of diabetic fibroblasts and macrophages (Mφ), and promoted alternative or M2 Mφ polarization. In wounds of db/db mice, treatment with both ESCs and ESCs-Exo, when compared to fibroblast exosomes (FB-Exo) and PBS control, accelerated wound healing by decreasing inflammation, augmenting wound cell proliferation, stimulating angiogenesis and inducing M2 Mφ polarization. Multiplex protein quantification of wound lysates revealed TGFβ signaling influenced by ESCs-Exo. High-throughput sequencing of small RNAs contained in the ESCs-Exo showed higher proportions of miRNAs when compared to FB-Exo. In silico functional analysis demonstrated that the ESCs-Exo-miRNAs target genes were primarily involved in homeostatic processes and cell differentiation and highlighted regulatory control of PI3K/AKT and TGFβ signaling pathways. This was also validated in vitro. Collectively, our results indicate that ESCs and ESCs-Exo are equally effective in promoting impaired diabetic wound healing and that ESCs-Exo treatment may be a promising and technically advantageous alternative to stem cell therapies.