Wound healing, as a normal biological process in the human body, is achieved through four precisely and highly programmed phases: hemostasis, inflammation, proliferation, and remodeling For a wound to heal successfully, all four phases must occur in the proper sequence and time frame Many factors can interfere with one or more phases of this process, thus causing improper or impaired wound healing This article reviews the recent literature on the most significant factors that affect cutaneous wound healing and the potential cellular and/or molecular mechanisms involved The factors discussed include oxygenation, infection, age and sex hormones, stress, diabetes, obesity, medications, alcoholism, smoking, and nutrition A better understanding of the influence of these factors on repair may lead to therapeutics that improve wound healing and resolve impaired wounds

Factors Affecting Wound Healing

Preeclampsia, a syndrome affecting 5% of pregnancies, causes substantial maternal and fetal morbidity and mortality. The pathophysiology of preeclampsia remains largely unknown. It has been hypothesized that placental ischemia is an early event, leading to placental production of a soluble factor or factors that cause maternal endothelial dysfunction, resulting in the clinical findings of hypertension, proteinuria, and edema. Here, we confirm that placental soluble fms-like tyrosine kinase 1 (sFlt1), an antagonist of VEGF and placental growth factor (PlGF), is upregulated in preeclampsia, leading to increased systemic levels of sFlt1 that fall after delivery. We demonstrate that increased circulating sFlt1 in patients with preeclampsia is associated with decreased circulating levels of free VEGF and PlGF, resulting in endothelial dysfunction in vitro that can be rescued by exogenous VEGF and PlGF. Additionally, VEGF and PlGF cause microvascular relaxation of rat renal arterioles in vitro that is blocked by sFlt1. Finally, administration of sFlt1 to pregnant rats induces hypertension, proteinuria, and glomerular endotheliosis, the classic lesion of preeclampsia. These observations suggest that excess circulating sFlt1 contributes to the pathogenesis of preeclampsia.

/pdf/excess-placental-soluble-fms-like-tyrosine-kinase-1-sflt1-4agajbx36v.pdf

Excess placental soluble fms-like tyrosine kinase 1 (sFlt1) may contribute to endothelial dysfunction, hypertension, and proteinuria in preeclampsia

Background Alterations in circulating soluble fms-like tyrosine kinase 1 (sFlt1), an antiangiogenic protein, and placental growth factor (PlGF), a proangiogenic protein, appear to be involved in th...

https://www.nejm.org/doi/pdf/10.1056/NEJMoa055352

Soluble endoglin and other circulating antiangiogenic factors in preeclampsia.

Although chronic wounds are common, treatment for these disabling conditions remains limited and largely ineffective. In this study, we examined the benefit of bone marrow-derived mesenchymal stem cells (BM-MSCs) in wound healing. Using an excisional wound splinting model, we showed that injection around the wound and application to the wound bed of green fluorescence protein (GFP)(+) allogeneic BM-MSCs significantly enhanced wound healing in normal and diabetic mice compared with that of allogeneic neonatal dermal fibroblasts or vehicle control medium. Fluorescence-activated cell sorting analysis of cells derived from the wound for GFP-expressing BM-MSCs indicated engraftments of 27% at 7 days, 7.6% at 14 days, and 2.5% at 28 days of total BM-MSCs administered. BM-MSC-treated wounds exhibited significantly accelerated wound closure, with increased re-epithelialization, cellularity, and angiogenesis. Notably, BM-MSCs, but not CD34(+) bone marrow cells in the wound, expressed the keratinocyte-specific protein keratin and formed glandular structures, suggesting a direct contribution of BM-MSCs to cutaneous regeneration. Moreover, BM-MSC-conditioned medium promoted endothelial cell tube formation. Real-time polymerase chain reaction and Western blot analysis revealed high levels of vascular endothelial growth factor and angiopoietin-1 in BM-MSCs and significantly greater amounts of the proteins in BM-MSC-treated wounds. Thus, our data suggest that BM-MSCs promote wound healing through differentiation and release of proangiogenic factors. Disclosure of potential conflicts of interest is found at the end of this article.

https://stemcellsjournals.onlinelibrary.wiley.com/doi/epdf/10.1634/stemcells.2007-0226

Mesenchymal stem cells enhance wound healing through differentiation and angiogenesis.

Endothelial nitric oxide synthase (eNOS) is essential for neovascularization. Here we show that the impaired neovascularization in mice lacking eNOS is related to a defect in progenitor cell mobilization. Mice deficient in eNOS (Nos3(-/-)) show reduced vascular endothelial growth factor (VEGF)-induced mobilization of endothelial progenitor cells (EPCs) and increased mortality after myelosuppression. Intravenous infusion of wild-type progenitor cells, but not bone marrow transplantation, rescued the defective neovascularization of Nos3(-/-) mice in a model of hind-limb ischemia, suggesting that progenitor mobilization from the bone marrow is impaired in Nos3(-/-) mice. Mechanistically, matrix metalloproteinase-9 (MMP-9), which is required for stem cell mobilization, was reduced in the bone marrow of Nos3(-/-) mice. These findings indicate that eNOS expressed by bone marrow stromal cells influences recruitment of stem and progenitor cells. This may contribute to impaired regeneration processes in ischemic heart disease patients, who are characterized by a reduced systemic NO bioactivity.

Essential role of endothelial nitric oxide synthase for mobilization of stem and progenitor cells.

We provide anatomic and functional evidence that nicotine induces angiogenesis. We also show that nicotine accelerates the growth of tumor and atheroma in association with increased neovascularization. Nicotine increased endothelial-cell growth and tube formation in vitro, and accelerated fibrovascular growth in vivo. In a mouse model of hind-limb ischemia, nicotine increased capillary and collateral growth, and enhanced tissue perfusion. In mouse models of lung cancer and atherosclerosis, we found that nicotine enhanced lesion growth in association with an increase in lesion vascularity. These effects of nicotine were mediated through nicotinic acetylcholine receptors at nicotine concentrations that are pathophysiologically relevant. The endothelial production of nitric oxide, prostacyclin and vascular endothelial growth factor might have a role in these effects.

Nicotine stimulates angiogenesis and promotes tumor growth and atherosclerosis

Recently, we have discovered an endogenous cholinergic pathway for angiogenesis mediated by endothelial nicotinic acetylcholine receptors (nAChRs). Since angiogenesis plays a major role in wound repair, we hypothesized that activation of nAChRs with nicotine would accelerate wound healing in a murine excisional wound model. In genetically diabetic and control mice full-thickness skin wounds (0.8 cm) were created on the dorsum and topically treated over 7 days with either vehicle (phosphate-buffered saline, PBS) or nicotine (10−8 mol/L, 10−9 mol/L; each, n = 5). Wound size was measured over 14 days followed by resection, histological analysis, and quantitation of vascularity. In diabetic animals an agonist (epibatidine, 10−10 mol/L) or antagonist (hexamethonium, 10−4 mol/L) of nAChRs as well as the positive control basic fibroblast growth factor (bFGF, 25 μg/kg) were also tested. To further study the role of endothelial nAChRs in angiogenesis, we used an ex vivo vascular explant model. In diabetic mice wound healing was markedly impaired. Nicotine significantly accelerated wound healing as assessed by closure rate and histological score. The effects of nicotine were equal to bFGF and were mimicked by epibatidine and blocked by hexamethonium. Histomorphometry revealed increased neovascularization in animals treated with nicotine. Furthermore, capillary-like sprouting from vascular explants was significantly enhanced by nicotine. In conclusion, agonist-induced stimulation of nAChRs accelerates wound healing in diabetic mice by promoting angiogenesis. We have discovered a cholinergic pathway for angiogenesis that is involved in wound healing, and which is a potential target for therapeutic angiogenesis.

/pdf/nicotine-accelerates-angiogenesis-and-wound-healing-in-zchaj8ix74.pdf

Nicotine accelerates angiogenesis and wound healing in genetically diabetic mice.

Background—Many angiogenic factors require endothelium-derived nitric oxide (NO) to exert their effects. Recently, an endogenous competitive antagonist of NO synthase has been characterized: asymmetric dimethylarginine (ADMA). Elevated plasma levels of ADMA reduce NO synthesis in hypercholesterolemia. Accordingly, we hypothesized that hypercholesterolemia impairs angiogenesis by an ADMA-dependent mechanism. Methods and Results—Angiogenesis was assessed with the use of a disk angiogenesis system implanted subcutaneously in normal (E+) mice or apolipoprotein (apo)E-deficient hypercholesterolemic (E−) mice. After 2 weeks, the disks were removed, and the fibrovascular growth area was used as an index of angiogenesis. Basal and fibroblast growth factor–stimulated angiogenesis was impaired in E− mice, associated with an elevation in plasma ADMA. Oral administration of l-arginine reversed the impairment of angiogenesis in E− mice. By contrast, oral administration of l-nitroarginine (an exogenous antagonist of NO...

Angiogenesis Is Impaired by Hypercholesterolemia Role of Asymmetric Dimethylarginine

Background— Developmentally regulated endothelial locus-1 (Del-1) is an extracellular matrix protein that is expressed by endothelial cells during embryological vascular development. We speculated that Del-1 may be reexpressed in ischemia and may be involved in endogenous angiogenesis. Methods and Results— Del-1 protein was detected by immunohistochemistry in murine ischemic hindlimb after femoral artery excision. To determine whether exogenous Del-1 would augment angiogenesis in vivo, Del-1 or vehicle was administered for 3 weeks by intramuscular injection of murine ischemic hindlimbs. Angiogenesis was quantified by gadolinium-MRI perfusion and capillary densitometry. We used a disc angiogenesis system (DAS) to characterize the angiogenic response to vehicle (PBS), Del-1, Del-1 mutant (altered RGD domain), Del-1 minor (truncated discoidin-I–like domain), or basic fibroblast growth factor. After 14 days, the discs were extracted and sectioned to quantify vascular growth by morphometry. Endogenous Del-1 pr...

Developmental Endothelial Locus-1 (Del-1), a Novel Angiogenic Protein Its Role in Ischemia

The present invention features methods for induction of angiogenesis by administration of nicotine or other nicotine receptor agonist. Induction of angiogenesis by the methods of the invention can be used in therapeutic angiogenesis in, for example, treatment of ischemic syndromes such as coronary or peripheral arterial disease.

James J. Jang

Papers

Nicotine stimulates angiogenesis and promotes tumor growth and atherosclerosis

Nicotine accelerates angiogenesis and wound healing in genetically diabetic mice.

Angiogenesis Is Impaired by Hypercholesterolemia Role of Asymmetric Dimethylarginine

Developmental Endothelial Locus-1 (Del-1), a Novel Angiogenic Protein Its Role in Ischemia

Nicotine in therapeutic angiogenesis and vasculogenesis