Elevated Shear Stress Modulates Heterogenous Cellular Subpopulations to Induce Vascular Remodeling.

Rationale: Elevated shear stress (ESS) induces vascular remodeling in veins exposed to arterial blood flow, which can lead to arteriovenous (AV) fistula failure. The molecular mechanisms driving remodeling have not been comprehensively examined with a single-cell resolution before. Objective: Using an in vivo animal mode, single-cell RNA sequencing, and histopathology, we precisely manipulate blood flow to comprehensively characterize all cell subpopulations important during vascular remodeling. Methods: AV loops were created in saphenous vessels of rats using a contralateral saphenous vein interposition graft to promote ESS. Saphenous veins with no elevated shear stress (NSS) were anastomosed as controls. Findings: ESS promoted transcriptional homogeneity, and NSS promoted considerable heterogeneity. Specifically, ESS endothelial cells (ECs) showed a more homogeneous transcriptional response promoting angiogenesis and upregulating endothelial-to-mesenchymal transition inhibiting genes (Klf2). NSS ECs upregulated antiproliferation genes such as Cav1, Cst3, and Btg1. In macrophages, ESS promoted a large homogeneous subpopulation, creating a mechanically activated, proinflammatory and thus proangiogenic myeloid phenotype, whereas NSS myeloid cells expressed the anti-inflammatory and antiangiogenetic marker Mrc1. Conclusion: 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.

Avenanthramide and ß-Glucan Therapeutics Accelerate Wound Healing Via Distinct and Nonoverlapping Mechanisms.

Objective: Given the significant economic, health care, and personal burden of acute and chronic wounds, we investigated the dose dependent wound healing mechanisms of two Avena sativa derived compounds: avenanthramide (AVN) and ß-Glucan. Approach: We utilized a splinted excisional wound model that mimics human-like wound healing and performed subcutaneous AVN and ß-Glucan injections in 15-week-old C57BL/6 mice. Histologic and immunohistochemical analysis was performed on the explanted scar tissue to assess changes in collagen architecture and cellular responses. Results: AVN and ß-Glucan treatment provided therapeutic benefits at a 1% dose by weight in a phosphate-buffered saline vehicle, including accelerated healing time, beneficial cellular recruitment, and improved tissue architecture of healed scars. One percent AVN treatment promoted an extracellular matrix (ECM) architecture similar to unwounded skin, with shorter, more randomly aligned collagen fibers and reduced inflammatory cell presence in the healed tissue. One percent ß-Glucan treatment promoted a tissue architecture characterized by long, thick bundles of collagen with increased blood vessel density. Innovation: AVN and ß-Glucan have previously shown promise in promoting wound healing, although the therapeutic efficacies and mechanisms of these bioactive compounds remain incompletely understood. Furthermore, the healed ECM architecture of these wounds has not been characterized. Conclusions: AVN and ß-Glucan accelerated wound closure compared to controls through distinct mechanisms. AVN-treated scars displayed a more regenerative tissue architecture with reduced inflammatory cell recruitment, while ß-Glucan demonstrated increased angiogenesis with more highly aligned tissue architecture more indicative of fibrosis. A deeper understanding of the mechanisms driving healing in these two naturally derived therapeutics will be important for translation to human use.

Nitric oxide-releasing gel accelerates healing in a diabetic murine splinted excisional wound model.

Introduction: According to the American Diabetes Association (ADA), 9-12 million patients suffer from chronic ulceration each year, costing the healthcare system over USD $25 billion annually. There is a significant unmet need for new and efficacious therapies to accelerate closure of non-healing wounds. Nitric Oxide (NO) levels typically increase rapidly after skin injury in the inflammatory phase and gradually diminish as wound healing progresses. The effect of increased NO concentration on promoting re-epithelization and wound closure has yet to be described in the context of diabetic wound healing. Methods: In this study, we investigated the effects of local administration of an NO-releasing gel on excisional wound healing in diabetic mice. The excisional wounds of each mouse received either NO-releasing gel or a control phosphate-buffered saline (PBS)-releasing gel treatment twice daily until complete wound closure. Results: Topical administration of NO-gel significantly accelerated the rate of wound healing as compared with PBS-gel-treated mice during the later stages of healing. The treatment also promoted a more regenerative ECM architecture resulting in shorter, less dense, and more randomly aligned collagen fibers within the healed scars, similar to that of unwounded skin. Wound healing promoting factors fibronectin, TGF-ß1, CD31, and VEGF were significantly elevated in NO vs. PBS-gel-treated wounds. Discussion: The results of this work may have important clinical implications for the management of patients with non-healing wounds.