Acceleration of wound healing by growth hormone-releasing hormone and its agonists

Despite the well-documented action of growth hormone-releasing hormone (GHRH) on the stimulation of production and release of growth hormone (GH), the effects of GHRH in peripheral tissues are incompletely explored. In this study, we show that GHRH plays a role in wound healing and tissue repair by acting primarily on wound-associated fibroblasts. Mouse embryonic fibroblasts (MEFs) in culture and wound-associated fibroblasts in mice expressed a splice variant of the receptors for GHRH (SV1). Exposure of MEFs to 100 nM and 500 nM GHRH or the GHRH agonist JI-38 stimulated the expression of α-smooth muscle actin (αSMA) based on immunoblot analyses as well as the expression of an αSMA-β-galactosidase reporter transgene in primary cultures of fibroblasts isolated from transgenic mice. Consistent with this induction of αSMA expression, results of transwell-based migration assays and in vitro wound healing (scratch) assays showed that both GHRH and GHRH agonist JI-38 stimulated the migration of MEFs in vitro. In vivo, local application of GHRH or JI-38 accelerated healing in skin wounds of mice. Histological evaluation of skin biopsies showed that wounds treated with GHRH and JI-38 were both characterized by increased abundance of fibroblasts during the early stages of wound healing and accelerated reformation of the covering epithelium at later stages. These results identify another function of GHRH in promoting skin tissue wound healing and repair. Our findings suggest that GHRH may have clinical utility for augmenting healing of skin wounds resulting from trauma, surgery, or disease.     

Follistatin production by skin fibroblasts and its regulation by dexamethasone

Activin and follistatin (FS) appear to play a role in the development of the skin and its appendages, in the inflammatory process, angiogenesis, and in wound healing. Although there is information on the expression of activin subunits and receptors in fibroblasts and keratinocytes, there are no reports on the regulation of FS expression in these cells. In the present study we analyzed the splicing variants of FS mRNAs in fibroblasts from genital and nongenital skin by RT-PCR and northern analysis, and examined the induction of FS mRNA and protein by hormones and growth factors in skin fibroblasts from human and nonhuman primates. FS mRNA was highly expressed in all fibroblast strains with similar expression regardless of donor species (human or monkey), donor age (neonate or adult), or the organ from which the fibroblast strains were established (skin or pituitary, genital or non-genital skin). Moreover, the band density corresponding to FS-288 was <5-10% of the value for FS-315 in skin fibroblasts as in all other tissues examined. Fibroblast FS mRNA and protein production were biphasically regulated by dexamethasone: low concentrations (0.01 and 0.1 nM) increased whereas higher concentrations (>1 nM) suppressed FS expression. On the other hand, androgens, activin and PACAP38 were without effect. These data establish cultured skin fibroblasts as a model to study FS gene expression in humans, and support a role for follistatin in the normal immune response and in the anti-inflammatory actions of glucocorticoids.     

Wound angiogenesis as a function of tissue oxygen tension: a mathematical model

Wound healing represents a well orchestrated reparative response that is induced by injuries. Angiogenesis plays a central role in wound healing. In this work, we sought to develop the first mathematical model directed at addressing the role of tissue oxygen tension on cutaneous wound healing. Key components of the developed model include capillary tips, capillary sprouts, fibroblasts, inflammatory cells, chemoattractants, oxygen, and the extracellular matrix. The model consists of a system of nonlinear partial differential equations describing the interactions in space and time of these variables. The simulated results agree with the reported literature on the biology of wound healing. The proposed model represents a useful tool to analyze strategies for improved healing and generate a hypothesis for experimental testing.     

Macrophage migration inhibitory factor: a neuroendocrine modulator of chronic inflammation

The diverse actions of macrophage migration inhibitory factor (MIF) within the immuno-neuroendocrine system are yet to be fully understood, but it is clear that MIF plays a pivotal role in the regulation of both the innate and adaptive immune response. An emerging body of data presently indicates that MIF's position within the cytokine cascade is to act in concert with glucocorticoids to control the 'set point' and magnitude of the immune and inflammatory response. In this article we will review the actions of MIF within the immune system and discuss the overlapping and contrasting aspects of MIF and glucocorticoid biology. In particular we will focus on the role of MIF within the immuno-neuroendocrine interface and suggest molecular mechanisms by which MIF may counter-regulate glucocorticoid function. Finally we will discuss emerging evidence that functional MIF gene-promoter polymorphisms render one susceptible to elevated MIF expression, and the development of an exaggerated immune/inflammatory response that potentiates the progression to chronic inflammatory disease.     

Angiogenic properties of myofibroblasts isolated from normal human skin wounds

During wound healing, angiogenesis plays a crucial role in inducing adequate perfusion of the new tissue, thereby allowing its survival. This angiogenic process contributes to the formation of granulation tissue, alongside myofibroblasts. Myofibroblasts are cells specialized in wound contraction and synthesis of new extracellular matrix. Fibroblasts, considered by some to be at the origin of myofibroblasts, have already been shown to promote neovascularization. Thus, we hypothesized that myofibroblasts play a key role during angiogenic development in wound healing. We isolated myofibroblasts from normal human skin wounds and dermal microvascular endothelial cells (HDMVEC) and fibroblasts from skin. Using an in vitro fibrin-based model, we compared the proangiogenic activity of wound myofibroblasts to that of fibroblasts in the presence of HDMVEC. By immunostaining with collagen IV antibodies, we observed the formation of a capillary network significantly more developed when HDMVEC were cultured with myofibroblasts compared to the network formed in the presence of fibroblasts. The differences between these cell types did not result from a differential secretion of Vascular Endothelial Growth Factor or basic Fibroblast Growth Factor. However, in the presence of myofibroblasts, a significant decrease in matrix metalloproteinase activity was observed. This finding was correlated with a significant increase in Tissue Inhibitor of MetalloProteinase (TIMP)-1 and TIMP-3. Furthermore, inhibition of TIMP-1 secretion using shRNA significantly decreased myofibroblasts induced angiogenesis. These results led to the hypothesis that normal wound myofibroblasts contribute to the vascular network development during wound healing. Our data emphasize the critical role of wound myofibroblasts during healing.     

Topical thyroid hormone accelerates wound healing in mice

Although the physiologic role of thyroid hormone in skin is not well understood, mounting evidence suggests that T3 plays an important role in epidermal proliferation. The goal of this project was to evaluate whether the topical application of supraphysiologic doses of T3 could accelerate wound healing. We evaluated mice treated with topical T3 vs. the same mice receiving vehicle alone (Novasome A). Ten-millimeter diameter (79 mm2) dorsal skin wounds were established in all animals, and wounds were remeasured 4 d after injury. All animals were evaluated twice: once with the T3 treatment and once with the vehicle alone. Daily topical application of 150 ng T3 resulted in 58% greater wound closure relative to wounds on the same animals receiving vehicle alone (P < 0.001). Furthermore, we determined that wound healing-associated keratin 6 protein expression in hair follicle keratinocytes increased in a dose-dependent manner in vivo during topical T3 treatment. The data support our previous hypothesis that T3 is necessary for optimal wound healing. Now, we further suggest that topical thyroid hormone may be an inexpensive agent to hasten healing of certain wounds.     

Prognostic role of macrophage migration inhibitory factor in patients with clear cell renal cell carcinoma

Macrophage migration inhibitory factor (MIF) is a cytokine that mediates the interaction between malignant cells and the innate immune system. Recently, MIF has received attention for its role in tumorigenesis. We evaluated the prognostic role of MIF in clear cell renal cell carcinoma (CCRCC).A total of 152 patients, who underwent nephrectomy for CCRCC were enrolled in this study. Immunohistochemical staining of tissue microarray blocks containing 298 cores—2 cores per CCRCC patient was performed. The relationship between MIF expression and clinicopathological factors was evaluated. Total RNA and protein were extracted from 7 RCC (renal cell carcinoma) cell lines. MIF was knocked down in Caki-2 cells, and a wound healing assay was performed to evaluate migratory activity.Among the 298 cores, 180 (60.4%) were positive for MIF. Multivariate analysis, showed that, CCRCC patients with negative MIF expression exhibited poor disease-free survival (hazard ratio: 2.087, 95% confidence interval: 0.821–5.307, P value: .023) and poor disease-specific survival (hazard ratio: 2.101, 95% confidence interval: 1.009–4.374, P value: .047). The wound healing assay revealed that cell confluence was lower in MIF-deficient Caki-2 cells than in control cells.Negative MIF expression might be an independent prognostic marker for patients with CCRCC.     

Adrenomedullin is both proinflammatory and antiinflammatory: its effects on gene expression and secretion of cytokines and macrophage migration inhibitory factor in NR8383 macrophage cell line

Adrenomedullin (ADM) is a potent vasorelaxant peptide that plays important roles in cardiovascular homeostasis and inflammatory response. ADM derived from macrophages is one of the major sources of ADM that is produced in the inflammatory process. To assess the functions of ADM in inflammation, we studied the temporal changes in ADM production and its effect on secretion of macrophage migration inhibitory factor (MIF) and cytokine response of NR8383 rat macrophages activated by lipopolysaccharide (LPS). NR8383 cells were stimulated by LPS in the absence and presence of exogenous ADM, and the concentrations of ADM, MIF, and proinflammatory cytokines (IL-6, TNF-alpha, and IL-1beta) in the culture media and gene expressions of the cells were measured. We confirmed that the secretion and mRNA expression of ADM in the macrophages were markedly increased by LPS. ADM increased initial secretion of MIF and IL-1beta from both nonstimulated and LPS-stimulated cells, and it also increased basal and LPS-induced IL-6 secretion of the cells by 2- to 15-fold. However, it reduced secretion of TNF-alpha from LPS-stimulated cells by 34-56%. Our results suggest that ADM modulates MIF secretion and cytokine production and plays important roles in both the initiation and propagation of the inflammatory response.     

Angiotensin II promotes integrin-mediated collagen gel contraction by adult rat cardiac fibroblasts

Remodeling is a fundamental cardiac response to injury and involves cardiac fibroblast proliferation and extracellular matrix (ECM) production. Angiotensin II (Ang II) directly promotes these changes in cardiac fibroblasts and thus, plays critical roles in cardiac hypertrophy and wound healing. Osteopontin, fibronectin and laminin mRNA were detected in total RNA harvested from cultured adult rat cardiac fibroblasts. Immunocytochemistry staining of cultured adult rat cardiac fibroblasts grown on coverslips revealed the presence of beta 3 integrins on the surfaces of the cells. In the present study, we investigated the role of Ang II in a model of wound repair using floating collagen gels harboring adult rat cardiac fibroblasts, and we determined which members of the integrin family existed on these cells. The presence of either MPIIIB10, a monoclonal antibody against osteopontin (7.2 micrograms/ml) or RGD (arginine-glycine-aspartate) peptide (10(4) M) had no effect on gel contraction. Osteopontin itself induced gel contraction; however this effect was completely neutralized by MPIIIB10 (7.2 micrograms/ml, RGD peptide (10(4) M) and a monoclonal antibody against rat beta 3 integrin (25 micrograms/ml). We identified alpha v, beta 3 and beta 5 integrins on adult rat cardiac fibroblasts by fluorescence-activated cell sorting and confirmed that RGD peptide and an antibody against beta 3 integrin completely blocked osteopontin-induced gel contraction. These results suggest that Ang II promotes cardiac wound healing and remodeling processes by inducing expression of osteopontin and beta 3 integrin by cardiac fibroblasts.     

Activated protein C stimulates expression of angiogenic factors in human skin cells, angiogenesis in the chick embryo and cutaneous wound healing in rodents

Activated protein C (APC) is a serine protease that plays a central role in physiological anticoagulation, and has more recently been shown to be a potent anti-inflammatory mediator. We show here that APC upregulates the angiogenic promoters, vascular endothelial growth factor (VEGF), monocyte chemoattractant protein-1 (MCP-1), interleukin-8 (IL-8) or matrix metalloproteinase-2 (MMP-2) in cultured human skin fibroblasts (HF), keratinocytes (HK) or umbilical vein endothelial cells (HUVE). In the chick embryo chorio-allantoic membrane assay, APC promoted angiogenesis. In a full-thickness rat skin healing model, a single topical application of APC enhanced wound healing compared to saline control. In summary, our results demonstrate that APC promotes cutaneous wound healing at least partly by stimulation of angiogenesis.     

Angiopoietin-related growth factor (AGF) promotes epidermal proliferation,remodeling, and regeneration

We report here the identification of an angiopoietin-related growth factor (AGF). To examine the biological function of AGF in vivo, we created transgenic mice expressing AGF in epidermal keratinocytes (K14-AGF). K14-AGF mice exhibited swollen and reddish ears, nose and eyelids. Histological analyses of K14-AGF mice revealed significantly thickened epidermis and a marked increase in proliferating epidermal cells as well as vascular cells in the skin compared with nontransgenic controls. In addition, we found rapid wound closure in the healing process and an unusual closure of holes punched in the ears of K14-AGF mice. Furthermore, we observed that AGF is expressed in platelets and mast cells, and detected at wounded skin, whereas there was no expression of AGF detected in normal skin tissues, suggesting that AGF derived from these infiltrated cells affects epidermal proliferation and thereby plays a role in the wound healing process. These findings demonstrate that biological functions of AGF in epidermal keratinocytes could lead to novel therapeutic strategies for wound care and epidermal regenerative medicine.     

Emerging evidence for the role of cardiotrophin-1 in cardiac repair in the infarcted heart

Ischemic heart disease is the most common cause of mortality worldwide. Cardiac fibroblasts and myofibroblasts, i.e., the hypersecretory, muscular, and contractile fibroblastic phenotype variant, play an important role in myocardial healing and are responsible for accumulation of collagen in the infarct scar as well as in viable myocardium. Thus, cardiac fibroblasts and myofibroblasts directly contribute to cardiac stiffness, altered performance, and ultimately to the onset of systolic and diastolic heart failure. Cardiotrophin-1 (CT-1) is a member of the IL-6 superfamily and is elevated in the serum of patients with ischemic heart disease and valvular heart disease; it is also known to induce cardiomyocyte hypertrophy in vitro. The recent, burgeoning awareness of the functions of IL-6 superfamily of cytokines within cardiovascular diseases predicates this summary of CT-1's effect in cardiac wound healing, and particularly after the induction of myocardial infarction. Further, we summarize recent results of cardiac CT-1 expression post-myocardial infarction (post-MI) as well as the effect of CT-1 on cultured primary adult rat cardiac fibroblasts with respect to proliferation and collagen secretion. It would appear that CT-1 plays an important and heretofore largely unrecognized role in infarct scar formation and angiogenesis in the rat model of chronic MI. Further work is required to determine factors that induce CT-1 expression, its interplay with other mediators of cardiac infarct wound healing in the setting of acute cardiac ischemia and chronic post-MI heart failure, and ultimately whether it confers a beneficial effect or contributes to maladaptive cardiac fibrosis.     

Pathophysiological roles of macrophage migration inhibitory factor in gastrointestinal, hepatic, and pancreatic disorders

Macrophage migration inhibitory factor (MIF) is a unique protein, participating in inflammation, immune response, and cell growth. MIF was first discovered as a lymphokine involved in delayed hypersensitivity and various macrophage functions, including phagocytosis, spreading, and tumoricidal activity. It has been reported that MIF is associated with the pathogenesis of a variety of diseases. MIF expression was increased at inflammatory sites in diseases such as rheumatoid arthritis and glomerulonephritis. In experimental inflammatory disease, blockade of MIF bioactivity inhibited the severity of disease activity. On the other hand, MIF expression is also increased in tumor lesions, and MIF plays a role as a cell growth factor. MIF has been reported to be constitutively expressed in gut, liver, and pancreas. In patients with gastritis, inflammatory bowel disease, hepatitis, and pancreatitis, MIF expression was remarkably increased in both the serum and the local lesions. Blockade of MIF bioactivity inhibited and prevented inflammation in experimental gastritis, colitis, hepatitis, and pancreatitis. On the other hand, MIF expression was higher than that in normal tissues in colonic carcinomas and hepatocellular carcinoma both in vivo and in vitro. Blockade of MIF bioactivity successfully inhibited tumor cell growth in vivo and in vitro. MIF plays important roles in the pathogenesis of gastrointestinal, hepatic, and pancreatic disorders.     

Transforming growth factor beta stimulates collagen-matrix contraction by fibroblasts: implications for wound healing.

An important event during wound healing is the contraction of newly formed connective tissue (granulation tissue) by fibroblasts. The role of polypeptide growth factors in the process of wound contraction was investigated by analyzing the influence of transforming growth factor beta (TGF-beta), platelet-derived growth factor on the ability of fibroblasts to contract a collagen matrix in an in vitro system. TGF-beta, but not the other growth factors tested, markedly enhanced the ability of BHK-21,3T3-L1, and human foreskin fibroblasts to contract collagen gels. These results suggest that TGF-beta released from platelets and inflammatory cells at sites of tissue injury stimulates fibroblasts to contract the provisional wound matrix and that this effect contributes to the ability of TGF-beta to accelerate wound healing.