Novel Potential Markers of Myofibroblast Differentiation Revealed by Single-Cell RNA Sequencing Analysis of Mesenchymal Stromal Cells in Profibrotic and Adipogenic Conditions

Molecular characterization of suburothelial fibrosis in murine acute recurrent bladder inflammation

Chronic fibrosis replaces functional organ tissue with scar tissue by overproduction of a thick and stiff extracellular matrix. Bladder fibrosis decreases bladder compliance, ultimately resulting in overactive bladder. The phenoconversion of fibroblasts into myofibroblasts is the defining feature of fibrosis. Recently, regionally distinct populations of bladder platelet-derived growth factor receptor alpha positive (PDGFRα+) cells were identified as fibroblasts. Because of this heterogeneity, the identity of the bladder fibroblast cells that undergo phenotypic conversion into myofibroblasts is not clear. The current study utilized cyclophosphamide (CYP)-induced bladder inflammation to identify and characterize bladder PDGFRα+ cells that become myofibroblasts. We found that suburothelial PDGFRα+ cells and detrusor PDGFRα+ cells display different gene expression profiles. Suburothelial PDGFRα+ cells are more abundant than detrusor PDGFRα+ cells and express higher levels of fibrosis-related genes. CYP-treatment increased the number of suburothelial PDGFRα+ cells, increased Pdgfra, Col1a1, and Fn1 transcription in suburothelial PDGFRα+ cells, and increased α-smooth muscle actin, collagen, and fibronectin protein expression. CYP-treatment likely activated TNF-α and TGF-ß pathways, as indicated by nuclear translocation of SMAD2, SMAD3, and NFκB. In conclusion, we identify suburothelial PDGFRα+ cells as the fibroblast population which convert into myofibroblasts via activation of TNF-α and TGF-ß signaling pathways, due to bladder inflammation.

Inflammatory Cell Interactions in the Rotator Cuff Microenvironment: Insights From Single-Cell Sequencing

Rotator cuff injuries are a common cause of shoulder pain and dysfunction, with chronic inflammation complicating recovery. Recent advances in single-cell RNA sequencing (scRNA-seq) have provided new insights into the immune cell interactions within the rotator cuff microenvironment during injury and healing. This review focuses on the application of scRNA-seq to explore the roles of immune and nonimmune cells, including macrophages, T-cells, fibroblasts, and myofibroblasts, in driving inflammation, tissue repair, and fibrosis. We discuss how immune cell crosstalk and interactions with the extracellular matrix influence the progression of healing or pathology. Single-cell analyses have identified distinct molecular signatures associated with chronic inflammation, which may contribute to persistent tissue damage. Additionally, we highlight the therapeutic potential of targeting inflammation in rotator cuff repair, emphasizing personalized medicine approaches. Overall, the integration of scRNA-seq in studying rotator cuff injuries enhances our understanding of the cellular mechanisms involved and offers new perspectives for developing targeted treatments in regenerative medicine.

Single-cell RNA analysis of chromodomain-encoding genes in mesenchymal stromal cells of the mouse dental pulp

The chromodomain helicase DNA-binding (CHD) and chromobox (CBX) families of proteins play crucial roles in cell fate decisions, differentiation, and cell proliferation in a broad variety of tissues and cell types. CHD proteins are ATP-dependent epigenetic enzymes actively engaged in transcriptional regulation, DNA replication, and DNA damage repair, whereas CBX proteins are transcriptional repressors mainly involved in the formation of heterochromatin. The pleiotropic effects of CHD and CBX proteins are largely dependent on their versatility to interact with other key components of the epigenetic and transcriptional machinery. Although the function and regulatory modes of CHD and CBX factors are well established in many cell types, little is known about their roles during osteogenic differentiation. A single-cell RNA-sequencing analysis of the mouse incisor dental pulp revealed distinct spatiotemporal expression patterns of CHD- and CBX-encoding genes within different clusters of mesenchymal stromal cells (MSCs) representing various stages of osteogenic differentiation. Additionally, genes encoding interaction partners of CHD and CBX proteins, such as subunits of the trithorax-COMPASS and polycomb chromatin remodeling complexes, exhibited differential co-expression behaviors within MSC subpopulations. Thus, CHD- and CBX-encoding genes show partially overlapping but distinct expression patterns in MSCs, suggesting their differential roles in osteogenic cell fate decisions.

Identifying Potential Drug Targets for Keloid: A Mendelian Randomization Study

Keloids are a skin fibrosis disease characterized by troublesome symptoms, a varying degree of recurrence and inevitable side effects from treatments. Thus, identifying their drug targets is necessary. A 2-sample Mendelian randomization analysis was conducted using proteins from the intersection of the deCODE database and "The Druggable Genome and Support for Target Identification and Validation in Drug Development" as the exposure variable. The outcome variable was based on recently published GWAS of keloids. Summary data-based Mendelian randomization and colocalization analysis was employed to distinguish pleiotropy from linkage. Candidate targets underwent drug target analysis. The primary findings were validated through single-cell RNA-sequencing data, Western Blot and immunofluorescence staining on keloids. Seven proteins were identified as potential drug targets for keloids. Among these proteins, Hedgehog-interacting protein, neurotrimin [NTM], KLKB1, and CRIPTO showed positive correlations with keloids, while PLXNC1, SCG3 and PDGFD exhibited negative correlations. Combined with the single-cell RNA-sequencing data, NTM, PLXNC1, and PDGFD were found highly expressed in the fibroblasts. NTM showed a significant increase in keloids as compared to normal scars. In accordance with the analysis, higher levels of protein expression of NTM in keloids compared to normal skin was observed. The identified proteins may be appealing drug targets for keloids treatment with a special emphasis on NTM.

A new cell culture resource for investigations of reptilian gene function

The establishment of CRISPR/Cas9 gene editing in Anolis sagrei has positioned this species as a powerful model for studies of reptilian gene function. To enhance this model, we developed an immortalized lizard fibroblast cell line (ASEC-1) for the exploration of reptilian gene function in cellular processes. We demonstrate the use of this cell line by scrutinizing the role of primary cilia in lizard Hedgehog (Hh) signaling. Using CRISPR/Cas9 mutagenesis, we disrupted the ift88 gene, which is required for ciliogenesis in diverse organisms. We determined that loss of itf88 from lizard cells leads to an absence of primary cilia, a partial derepression of gli1 transcription, and an inability of the cells to respond to the Smoothened agonist, SAG. Through a cross-species analysis of SAG-induced transcriptional responses in cultured limb bud cells, we further determined that ∼46% of genes induced as a response to Hh pathway activation in A. sagrei are also SAG responsive in Mus musculus limb bud cells. Our results highlight conserved and diverged aspects of Hh signaling in anoles and establish a new resource for investigations of reptilian gene function.

The Myofibroblast Fate of Therapeutic Mesenchymal Stromal Cells: Regeneration, Repair, or Despair?

Mesenchymal stromal cells (MSCs) can be isolated from various tissues of healthy or patient donors to be retransplanted in cell therapies. Because the number of MSCs obtained from biopsies is typically too low for direct clinical application, MSC expansion in cell culture is required. However, ex vivo amplification often reduces the desired MSC regenerative potential and enhances undesired traits, such as activation into fibrogenic myofibroblasts. Transiently activated myofibroblasts restore tissue integrity after organ injury by producing and contracting extracellular matrix into scar tissue. In contrast, persistent myofibroblasts cause excessive scarring-called fibrosis-that destroys organ function. In this review, we focus on the relevance and molecular mechanisms of myofibroblast activation upon contact with stiff cell culture plastic or recipient scar tissue, such as hypertrophic scars of large skin burns. We discuss cell mechanoperception mechanisms such as integrins and stretch-activated channels, mechanotransduction through the contractile actin cytoskeleton, and conversion of mechanical signals into transcriptional programs via mechanosensitive co-transcription factors, such as YAP, TAZ, and MRTF. We further elaborate how prolonged mechanical stress can create persistent myofibroblast memory by direct mechanotransduction to the nucleus that can evoke lasting epigenetic modifications at the DNA level, such as histone methylation and acetylation. We conclude by projecting how cell culture mechanics can be modulated to generate MSCs, which epigenetically protected against myofibroblast activation and transport desired regeneration potential to the recipient tissue environment in clinical therapies.

Balance between Pro- and Antifibrotic Proteins in Mesenchymal Stromal Cell Secretome Fractions Revealed by Proteome and Cell Subpopulation Analysis

Multipotent mesenchymal stromal cells (MSCs) regulate tissue repair through paracrine activity, with secreted proteins being significant contributors. Human tissue repair commonly results in fibrosis, where fibroblast differentiation into myofibroblasts is a major cellular mechanism. MSCs' paracrine activity can inhibit fibrosis development. We previously demonstrated that the separation of MSC secretome, represented by conditioned medium (CM), into subfractions enriched with extracellular vesicles (EV) or soluble factors (SF) boosts EV and SF antifibrotic effect. This effect is realized through the inhibition of fibroblast-to-myofibroblast differentiation in vitro. To unravel the mechanisms of MSC paracrine effects on fibroblast differentiation, we performed a comparative proteomic analysis of MSC secretome fractions. We found that CM was enriched in NF-κB activators and confirmed via qPCR that CM, but not EV or SF, upregulated NF-κB target genes (COX2, IL6, etc.) in human dermal fibroblasts. Furthermore, we revealed that EV and SF were enriched in TGF-β, Notch, IGF, and Wnt pathway regulators. According to scRNAseq, 11 out of 13 corresponding genes were upregulated in a minor MSC subpopulation disappearing in profibrotic conditions. Thus, protein enrichment of MSC secretome fractions and cellular subpopulation patterns shift the balance in fibroblast-to-myofibroblast differentiation, which should be considered in studies of MSC paracrine effects and the therapeutic use of MSC secretome.