C‐X‐C motif chemokine ligand 12 (CXCL12; Stromal Cell‐Derived Factor 1 [SDF‐1]), most notably known for its role in embryogenesis and hematopoiesis, has been implicated in tumor pathophysiology and neovascularization. However, its cell‐specific role and mechanism of action have not been well characterized. Previous work by our group has demonstrated that hypoxia‐inducible factor (HIF)‐1 modulates downstream CXCL12 expression following ischemic tissue injury. By utilizing a conditional CXCL12 knockout murine model, we demonstrate that endothelial‐specific deletion of CXCL12 (eKO) modulates ischemic tissue survival, altering tissue repair and tumor progression without affecting embryogenesis and morphogenesis. Loss of endothelial‐specific CXCL12 disrupts critical endothelial–fibroblast crosstalk necessary for stromal growth and vascularization. Using murine parabiosis with novel transcriptomic technologies, we demonstrate that endothelial‐specific CXCL12 signaling results in downstream recruitment of non‐inflammatory circulating cells, defined by neovascularization modulating genes. These findings indicate an essential role for endothelial‐specific CXCL12 expression during the neovascular response in tissue injury and tumor progression.

Elevated shear stress induces vascular remodeling in veins exposed to arterial blood flow, which can lead to arterio-venous (AV) fistula failure. The molecular mechanisms driving remodeling have not been comprehensively examined with single cell resolution before. Using an in vivo animal mode, single-cell RNA-sequencing (scRNA-seq), and histopathology, we precisely manipulate blood flow to comprehensively characterize all cell subpopulations important during vascular remodeling. AV loops were created in saphenous vessels of rats using a contralateral saphenous vein interposition graft to promote elevated shear stress (ESS). Saphenous veins with no elevated shear stress (NSS) were anastomosed as controls. ESS promoted transcriptional homogeneity, and NSS cells promoted considerable heterogeneity. Specifically, ESS ECs showed a more homogeneous transcriptional response promoting angiogenesis and upregulating Endothelial-to-Mesenchymal-Transition (EndMT) inhibiting genes (Klf2). NSS ECs upregulated anti-proliferation genes such as Cav1, Cst3 and Btg1. In macrophages, ESS promoted a large homogeneous subpopulation, creating a mechanically activated pro-inflammatory M1-like, thus pro-angiogenic myeloid phenotype, while NSS myeloid cells expressed the anti-inflammatory and anti-angiogenetic marker Mrc1. ESS activates unified gene expression profiles to induce adaption of the vessel wall to hemodynamic alterations. Targeted depletion of the identified cellular subpopulations may lead to novel therapies to prevent excessive venous remodeling, intimal hyperplasia, and AV fistula failure.

Hypertrophic scarring (HTS) is an abnormal process of wound healing that results in excessive scar tissue formation. Over the past decade, we have demonstrated that mechanotransduction—the conversion of mechanical stimuli into cellular responses—drives excessive fibrotic scar healing. A mouse model to assess human-like hypertrophic scarring would be an essential tool for examining various therapeutics and their ability to reduce scarring and improve healing. Specifically, our laboratory has developed a murine wound model that increases mechanical strain to promote human-like HTS. This protocol utilizes biomechanical loading devices, made from modified 13 mm palatal expanders, whose arms are placed on either side of the incision and distracted incrementally apart in order to apply continuous tension across the wound bed during healing. Over nearly two decades of use, this model has been significantly advanced to improve efficacy and reproducibility. Using the murine HTS model, significant dermal fibrotic scars can be induced to be histologically comparable to human hypertrophic scars. This murine model provides an environment to develop biologics involved in the treatment of HTS and mechanotransduction-related conditions such as foreign body response.

Diabetes is a major growing public health concern, but the impact on cellular impairments in chronic wounds remains incompletely understood. Fibroblasts, key players in all phases of wound healing, are particularly responsive to mechanotransduction. Here, we characterize fibroblast heterogeneity in genetically induced and pathophysiological diabetic murine wounding models across all wound healing phases. Full-thickness excisional wounds were created on the dorsum of C57BL/6 non-diabetic wild-type (WT) mice (N-DB), WT-mice fed a high-fat diet to create pathophysiologic diabetes (P-DB), and leptin-receptor-deficient mice, a genetically induced diabetic model (G-DB). Tissue was submitted for single-cell RNA sequencing at postoperative days (PODs) 0, 2, 7 and 30. Both G-DB and P-DB significantly impaired wound healing compared to N-DB. N-DB expressed distinct myeloid-like Cd14+/C1qa+ angiogenic fibroblasts at PODs 2, and 7. Mechanotransduction pathways FAK and MAPK were consistently upregulated in N-DB fibroblasts and depleted in both diabetic models. G-DB upregulated WNT-activated Dpp4+ fibrotic fibroblasts at POD7 compared to N-DB. Thus, mechanotransduction pathways are present in physiologically healing fibroblasts and are selectively depleted in both pathophysiologic and genetically induced diabetes. In genetically induced diabetes, overactivation of canonical and non-canonical WNT pathways overwhelms cells and impairs healing processes. Transcriptomic insights into these mechanotransducive perturbations may lead to new therapies for diabetic wound repair.

IntroductionDeferoxamine (DFO), an iron-chelator, has been shown to promote hypoxia-inducible factor (HIF)-1α signaling and neovascularization, which could both prevent and promote healing of chronic wounds such as pressure ulcers. Although preclinical applications for wound healing have been extensively studied, clinical trials have not been performed. In this review, we highlight and discuss the latest developments on the use of DFO as a local treatment for pressure ulcers.Areas coveredWe review and critically discuss literature on deferoxamine treatment, focusing on its local application for pressure ulcers. We also highlight clinical trial challenges that have limited FDA approval of DFO in different disease settings. Expert opinionThe unique delivery and skin penetrating abilities of the Deferoxamine Intradermal Delivery Patch (DIDP) makes it a promising system for transdermal drug delivery. Further research, especially human clinical trials, is needed to validate current promising findings from animal models and optimize drug doses in various disease settings.