Thrombin peptide TP508 accelerates closure of dermal excisions in animal tissue with surgically induced ischemia

Therapeutic targets and signaling mechanisms of dasatinib activity against radiation skin ulcer

Objective

To reveal the potential targets and signaling pathways of dasatinib in the treatment of radiation ulcers through network pharmacology and molecular docking technology.

Methods

Pathological targets of radiation ulcers were screened using GeneCards database. At the same time, the pharmacological targets of dasatinib were obtained through SwissTargetPrediction (STP), Binding DB and Drugbank databases. Subsequently, the potential targets of dasatinib for anti-radiation ulcers were obtained after intersection by Venn diagram. Next, a protein-protein interaction (PPI) network was constructed through the STRING database and core targets were screened. Finally, the identified core targets were subjected to GO and KEGG enrichment analysis, co-expression network analysis, and molecular docking technology to verify the reliability of the core targets.

Results

A total of 76 potential targets for anti-radiation ulcer with dasatinib were obtained, and 6 core targets were screened, including EGFR, ERBB2, FYN, JAK2, KIT, and SRC. These genes were mainly enriched in Adherens junction, EGFR tyrosine kinase inhibitor resistance, Focal adhesion, Bladder cancer and PI3K-Akt signaling pathway. Molecular docking results showed that dasatinib binds well to the core target.

Conclusion

Dasatinib may play a role in the treatment of radiation ulcers by regulating EGFR, ERBB2, FYN, JAK2, KIT, and SRC. These core targets may provide new insights for follow-up studies of radiation ulcers.

Dasatinib induces loss of vascular integrity and promotes cutaneous wound repair in mice

BACKGROUND

Inflammatory bleeding due to depletion of platelet glycoprotein VI (GPVI) and C-type lectin-like receptor 2 (CLEC-2) has been proposed as a potential novel mechanism to promote skin wound healing. Dasatinib inhibits a broad range of tyrosine kinases, including Src and Syk, the signaling molecules downstream of GPVI and CLEC-2.

OBJECTIVES

To investigate whether dasatinib affects skin wound healing.

METHODS

A single (4-mm diameter) full-thickness excisional skin wound was generated in mice. Dasatinib (5 or 10 mg/kg) or dimethyl sulfoxide (DMSO) vehicle was intraperitoneally injected daily during the first 4 days. The wound was monitored over 9 days post injury.

RESULTS

Dasatinib induced loss of vascular integrity during the inflammatory phase of wound repair (day 1 to day 3 post injury), which was associated with the inhibition of platelet function stimulated by collagen and rhodocytin, the ligands for GPVI and CLEC-2, respectively. Dasatinib-treated mice, particularly at 5 mg/kg, exhibited accelerated wound closure compared to DMSO-treated controls. Transient bleeding into the wound during the inflammatory phase in dasatinib-treated mice allowed for extravasation of fibrinogen. The increased deposition of fibrinogen and fibrin in the wound on day 3 post injury was associated with the augmented progression of re-epithelialization and angiogenesis, attenuated infiltration of neutrophils and macrophages, and decreased levels of tumor necrosis factor-α (TNF-α).

CONCLUSIONS

Our data show that dasatinib promotes skin wound healing, and the mechanisms include blocking GPVI- and CLEC-2-mediated platelet activation, leading to self-limited inflammatory bleeding and fibrinogen/fibrin deposition, in association with reduced inflammation, increased re-epithelialization, and enhanced angiogenesis.

Peptides from Animal Origin: A Systematic Review on Biological Sources and Effects on Skin Wounds

Background

Skin wounds are closely correlated with opportunistic infections and sepsis risk. Due to the need of more efficient healing drugs, animal peptides are emerging as new molecular platforms to accelerate skin wound closure and to prevent and control bacterial infection.

Aim

The aim of this study was to evaluate the preclinical evidence on the impact of animal peptides on skin wound healing. In addition, we carried out a critical analysis of the studies' methodological quality. Main Methods. This systematic review was performed according to the PRISMA guidelines, using a structured search on the PubMed-Medline, Scopus, and Web of Science platforms to retrieve studies published until August 25, 2020 at 3 : 00 pm. The studies included were limited to those that used animal models, investigated the effect of animal peptides with no association with other compounds on wound healing, and that were published in English. Bias analysis and methodological quality assessments were examined through the SYRCLE's RoB tool.

Results

Thirty studies were identified using the PRISMA workflow. In general, animal peptides were effective in accelerating skin wound healing, especially by increasing cellular proliferation, neoangiogenesis, colagenogenesis, and reepithelialization. Considering standardized methodological quality indicators, we identified a marked heterogeneity in research protocols and a high risk of bias associated with limited characterization of the experimental designs.

Conclusion

Animal peptides show a remarkable healing potential with biotechnological relevance for regenerative medicine. However, rigorous experimental approaches are still required to clearly delimit the mechanisms underlying the healing effects and the risk-benefit ratio attributed to peptide-based treatments.

Nuclear Countermeasure Activity of TP508 Linked to Restoration of Endothelial Function and Acceleration of DNA Repair

There is increasing evidence that radiation-induced damage to endothelial cells and loss of endothelial function may contribute to both acute radiation syndromes and long-term effects of whole-body nuclear irradiation. Therefore, several drugs are being developed to mitigate the effects of nuclear radiation, most of these drugs will target and protect or regenerate leukocytes and platelets. Our laboratory has demonstrated that TP508, a 23-amino acid thrombin peptide, activates endothelial cells and stem cells to revascularize and regenerate tissues. We now show that TP508 can mitigate radiation-induced damage to endothelial cells in vitro and in vivo. Our in vitro results demonstrate that human endothelial cells irradiation attenuates nitric oxide (NO) signaling, disrupts tube formation and induces DNA double-strand breaks (DSB). TP508 treatment reverses radiation effects on NO signaling, restores tube formation and accelerates the repair of radiation-induced DSB. The radiation-mitigating effects of TP508 on endothelial cells were also seen in CD-1 mice where systemic injection of TP508 stimulated endothelial cell sprouting from aortic explants after 8 Gy irradiation. Systemic doses of TP508 that mitigated radiation-induced endothelial cell damage, also significantly increased survival of CD-1 mice when injected 24 h after 8.5 Gy exposure. These data suggest that increased survival observed with TP508 treatment may be due to its effects on vascular and microvascular endothelial cells. Our study supports the usage of a regenerative drug such as TP508 to activate endothelial cells as a countermeasure for mitigating the effects of nuclear radiation.

Systemic administration of thrombin peptide TP508 enhances VEGF-stimulated angiogenesis and attenuates effects of chronic hypoxia

Revascularization of chronic wounds and ischemic tissue is attenuated by endothelial dysfunction and the inability of angiogenic factors to stimulate angiogenesis. We recently showed that TP508, a nonproteolytic thrombin peptide, increases perfusion and NO-dependent vasodilation in hearts with chronic ischemia and stimulates NO production by endothelial cells. In this study, we investigated systemic in vivo effects of TP508 on VEGF-stimulated angiogenesis in vitro using aortic explants in normoxic and hypoxic conditions. Mice were injected with saline or TP508 and 24 h later aortas were removed and cultured to quantify endothelial sprouting. TP508 injection increased endothelial sprouting and potentiated the in vitro response to VEGF. Exposure of control explants to hypoxia inhibited basal and VEGF-stimulated endothelial cell sprouting. This effect of hypoxia was significantly prevented by TP508 injection. Thus, TP508 systemic administration increases responsiveness of aortic endothelial cells to VEGF and diminishes the effect of chronic hypoxia on endothelial cell sprouting. Studies using human endothelial cells in culture suggest that protective effects of TP508 during hypoxia may involve stimulation of endothelial cell NO production. These data suggest potential clinical benefit of using a combination of systemic TP508 and local VEGF as a therapy for revascularization of ischemic tissue.

Pollution dilemma in Asian population: CNG and wound healing

Automobile exhaust constituents contribute significantly to air pollution in urban areas and compressed natural gas (CNG) is considered one of the most promising fuel alternatives for the future. CNG-powered four-stroke engine auto-rickshaws are ubiquitous in South Asian cities as taxi and for commercial transportation. Automotive exhaust contains several toxins, which are overwhelmingly toxic to the processes of wound healing. By utilizing the in vivo mouse model of wound healing, this report analyzes the effects of CNG-powered four-stroke auto-rickshaws smoke solution (4SARSS) on different events of wound healing; dermal matrix regeneration, re-epithelialization and neovascularization. A total of 72 adult mice, divided in eight groups were exposed to 4SARSS for 12 days. A highly significant reduction (P<0.001) in wound closure was observed among all 4SARSS treated groups, at each time point of the experiment. An immature development in both the neoepidermis and the neodermis was observed among all 4SARSS treated wounds with defective re-epithelialization, dermal matrix regeneration and maturation of collagen bundles. Abbott curve, angular spectrum, 3D surface topographies, and histological investigations of wounds explicated highly significant activation (P<0.001) of delayed-neovascularization among 4SARSS treated wounds. All these annotations advocate excessive toxicity of emission from CNG-powered auto-rickshaws to the process of wound healing and people occupationally exposed to this toxic emissions may suffer varying degree of delayed wound healing.

Effect of aged garlic extract on wound healing: a new frontier in wound management

Successful wound healing depends upon angiogenesis, and impaired angiogenesis is a hallmark of the chronic wounds encountered with diabetes and venous or arterial insufficiency. To intervene and improve wound closure, it is essential to investigate the effects of different natural remedies in wound healing. The chicken dorsum skin excisional wound assay was used to investigate the influence of different concentrations of aged garlic solution (AGS) on wound healing. Gross, histopathology, scanning electron microscopy (SEM) and computer-based three-dimensional (3D) image-probing techniques were utilized to determine the effects of AGS on wound closure, re-epithelialization, dermal matrix regeneration, and angiogenesis. Ninety chicks, aged 1 week and divided in 6 groups, were topically exposed to different concentrations of AGS for 6 days: control (group A), 1% (group B), 5% (group C), 10% (group D), 15% (group E), and skin lotion (group F). Different patterns, ranging from incomplete to almost complete wound closure, were observed among different groups with highly significant results (P < 0.001) in group E. Histological investigations revealed a positive augment in the re-epithelialization of all AGS exposed wounds. An increase in the number of new loosely packed collagen and maturation of collagen bundles was observed in all treated wounds at days 4 and 6 post-wounding, respectively. Similar results were achieved through SEM of treated wounds. Histological investigations revealed the profuse dose-dependent neovascularization among AGS-treated wounds. Abbott curve, angular spectrum, and different parameters of 3D surface roughness of wounds were also measured for the precise quantification of angiogenesis. A very highly significant (P < 0.001) increase in angiogenesis was observed among all treated groups. No significant change was observed among control and skin lotion-treated groups. These observations substantiate the beneficial use of AGS in the treatment of wounds. Additional studies are needed to study the specific wound-healing mechanisms of chemical, or group of chemicals, present in AGS.

Total particulate matter and wound healing: an in vivo study with histological insights

OBJECTIVES

Wound healing in the skin is a multifarious orchestration of cellular processes and cigarette smoking may be a cause for delayed wound healing. The aim of this study was to investigate the plausible association between exposures of cigarette total particulate matter (TPM) and wound healing.

METHODS

An in vivo wound healing model of mice was established for determination of assorted events of wound healing, dermal matrix regeneration, re-epithelialization, and neovascularization. A total of 72 adult mice, separated in eight groups, were exposed to TPM for 12 days.

RESULTS

A highly considerable diminution in wound closure (P < 0.001) was pragmatic among all TPM-treated mice from day 6 to day 8 post-wounding. Histological investigations unveiled a noteworthy impede in the outcome of re-epithelialization, dermal matrix regeneration and maturation of collagen bundles among all TPM-exposed wounds. Delayed commencement of neovascularization was pragmatic among all TPM-treated mice, on day 12 post wounding. Abbot curve, angular spectrum, and other different parameters of 3D surface behavior of wounds revealed a very highly significant reduction (P < 0.001) in angiogenesis on days 6 and 8 post-wounding, which points that application of TPM instigates extensive delay in trigging the progression of angiogenesis, resulting in delayed onset of wound healing.

CONCLUSION

Our annotations validate the damaging effects of TPM on wound healing and excessive use of TPM may lead to the production of chronic wounds and oral ulcers.

Toxicological evaluation of the effects of 2-stroke auto-rickshaw smoke solutions on wound healing

Vehicle exhaust from traffic is a widespread air pollutant. The use of 3-wheel auto-rickshaws powered by a 2-stroke engine is widespread in south Asia; exhaust from these vehicles may cause different types of toxicities resulting in different pathologies. The aim of this study was to explore the association between exposure to 2-stroke auto-rickshaw smoke solution (2SARSS) and wound healing. The in vivo model of wound healing was customized to evaluate different stages of wound healing: dermal matrix regeneration, re-epithelialization, and neovascularization. A total of 72 adult mice were divided into 8 groups and exposed to 2SARSS for 12 days. A highly significant reduction (p<0.001) in wound closure was observed among all 2SARSS-treated groups at day 8 post-wounding. Histological examination revealed a significant delay in the outcome of re-epithelialization, dermal matrix regeneration, and maturation of collagen bundles among all 2SARSS-exposed wounds. Delayed activation of neovascularization was seen in the 2SARSS-treated groups at day 12 post-wounding. The Abbot curve, angular spectrum, and several other 3D surface parameters of reverse wound topographies revealed a highly significant reduction (p<0.001) in angiogenesis. These results demonstrate that application of 2SARSS causes a substantial delay in the progression of angiogenesis, resulting in delayed onset of wound healing. These observations validate the damaging effects of 2SARSS on wound healing. Thus, people who are directly or indirectly exposed to this toxic exhaust are expected to have delayed wound healing, which could result in chronic wounds.

Thrombin fragment (TP508) decreases myocardial infarction and apoptosis after ischemia reperfusion injury

BACKGROUND

Myocardial ischemia-reperfusion injury may lead to cardiac dysfunction or death. This study investigates the potential efficacy of a novel thrombin fragment (TP508) on myocardial ischemia-reperfusion injury.

METHODS

Fourteen male Yucatan pigs underwent 60 minutes of mid-left anterior descending coronary artery occlusion followed by 120 minutes of reperfusion. Pigs received either saline vehicle (control, n = 7) or thrombin fragment TP508 (n = 7) as a bolus (0.5 mg/kg) 50 minutes into the ischemic period, followed by continuous intravenous infusion (1.25 mg x kg(-1) x h(-1)) during reperfusion. Myocardial function was monitored throughout the experiments. Monastryl blue/triphenyl tetrazolium chloride staining was utilized to measure the area at risk and infarcted tissue. Apoptosis was assessed by Western blotting and dUTP nick-end labeling (TUNEL) staining. Coronary microvascular reactivity to endothelium-dependent factors (adenosine diphosphate, substance P, A23187) and endothelium-independent factor (sodium nitroprusside) was examined.

RESULTS

Global and regional left ventricular function was not significantly different between groups. Endothelium-dependent coronary microvascular relaxation was greater in the TP508 group and associated with higher endothelial nitric oxide synthase phosphorylation. Both infarct size and TUNEL staining was significantly decreased in the TP508 group compared with the control group (p < 0.05). Expression of the cell survival proteins B-cell lymphoma 2 (2.2-fold, p < 0.05) and heat shock protein-73 (1.6-fold, p < 0.05) was higher in the TP508 group. Expression of the cell-death-signaling proteins poly adenosine diphosphate-ribose polymerase (1.6-fold, p < 0.05), cleaved poly adenosine diphosphate-ribose polymerase (6.4-fold, p < 0.05), and B-cell lymphoma 2/adenovirus E1B 19 kDa-interacting protein 3 (3.8-fold, p < 0.05) was significantly higher in the TP508 group in the ischemic territory.

CONCLUSIONS

This study demonstrates that TP508 decreases infarct size, improves endothelial microvascular function, and induces cell-survival signaling in the setting of ischemia-reperfusion injury. Thus, TP508 may be a useful agent to attenuate myocardial reperfusion injury.

Thrombin related peptide TP508 promoted fracture repair in a mouse high energy fracture model

Background

Thrombin related peptide (TP508) is a 23 amino-acid synthetic peptide that represents a portion of the receptor-binding domain of thrombin molecule. Previous studies have shown that TP508 can accelerate musculoskeletal tissue repair including fracture healing.

Objectives

The aim of this study was to investigate the effect of TP508 on fracture healing in a murine fracture model representing high energy fracture situation.

Methods

Eighty CD 1 mice underwent controlled quadriceps muscle crush and open transverse mid diaphyseal femoral fracture that was then fixed with an external fixator. Animals were randomised into four groups to receive an intra-operative dose of either 100 μg TP508 into the fracture gap; 100 μg TP508 into the surrounding damaged muscle tissues; 10 μg TP508 into the fracture gap, or control equal amount of saline into the fracture gap. Radiographic assessment was performed weekly for 5 weeks; histological analysis was at 3 and 5 weeks post fracture and biomechanical testing of the fractured bone was performed at 5 weeks post fracture.

Results

Mechanical testing data showed that the fracture stiffness was significantly higher in the group receiving 100 μg TP508 into the fracture gap than other groups. Histological and radiographic analysis revealed a trend of increase in bone formation in the 100 μg TP508 injected into the fracture gap group compared to the saline control group. It was noted that the scar tissues was significantly less in Group II comparing with the saline control group and there was increased blood vessel formation in the crushed muscles and fracture gap areas in the groups receiving TP508 comparing to the saline control group.

Conclusion

The results from this study demonstrated the use of thrombin related peptide TP508 in the situation of a high energy fracture can promote fracture healing and reduce the potential complications such as muscle fibrosis and fracture delayed or non-union.

TP508 (Chrysalin) reverses endothelial dysfunction and increases perfusion and myocardial function in hearts with chronic ischemia

Endothelial dysfunction (ED) is characterized by impaired nitric oxide (NO) signaling, decreased NO-dependent vasodilatation, increased vascular inflammation, and diminished response to angiogenic factors. TP508 (Chrysalin), an angiogenic tissue repair peptide, was tested for potential effects on myocardial revascularization and ED using a porcine model of chronic myocardial ischemia. TP508 increased perfusion in ischemic regions up to16-fold (P < .02) and doubled myocardial wall thickening (P < .02) relative to placebo controls. Ischemic arterioles exhibited impaired NO-mediated vasodilation and diminished NO production. TP508 reversed ischemic effects, increasing NO-mediated vasodilation (P < .05), endothelial nitric oxide synthase (eNOS) expression, and NO production. In human endothelial cells, TP508 stimulated eNOS activation (1.84 +/- 0.2-fold; P < .02), increased NO production (85 +/- 18%; P < .02), and prevented hypoxia-induced eNOS downregulation (P < .01). Thus, TP508 reverses ED both in porcine ischemic hearts and cultured human endothelial cells. These results suggest potential therapeutic benefit of TP508 in myocardial revascularization and treatment of ED-related diseases.

TP508 accelerates fracture repair by promoting cell growth over cell death

TP508 is a synthetic 23-amino acid peptide representing a receptor-binding domain of human thrombin. We have previously shown that a single injection of TP508 accelerates fracture healing in a rat femoral fracture model. To understand how TP508 acts at the protein level during fracture healing, we compared the translational profiles between saline-control and fractured femur at six time points after TP508 treatment using the second generation of BD Clontechtrade mark Antibody Microarray. Here, we demonstrate that TP508 accelerates fracture healing by modulating expression levels of proteins primarily involved in the functional categories of cell cycle, cellular growth and proliferation, and cell death. The majority of those proteins are physically interrelated and functionally overlapped. The action of those proteins is highlighted by a central theme of promoting cell growth via balance of cell survival over cell death signals. This appears to occur through the stimulation of several bone healing pathways including cell cycle-G1/S checkpoint regulation, apoptosis, JAK/STAT, NF-kappaB, PDGF, PI3K/AKT, PTEN, and ERK/MAPK.

Thrombin peptide Chrysalin�stimulates healing of diabetic foot ulcers in a placebo-controlled phase I/II study

Thrombin and thrombin peptides play a role in initiating tissue repair. The potential safety and efficacy of TP508 (Chrysalin) treatment of diabetic foot ulcers was evaluated in a 60-subject, prospective, randomized, double-blind, placebo-controlled phase I/II clinical trial. Chrysalin in saline or saline alone was applied topically, twice weekly, to diabetic ulcers with standardized care and offloading. A dose-dependent effect was seen in the per-protocol population where 1 and 10 mug Chrysalin treatment resulted in 45 and 72% more subjects with complete healing than placebo treatment. Chrysalin treatment of foot ulcers more than doubled the incidence of complete healing (p<0.05), increased mean closure rate approximately 80% (p<0.05), and decreased the median time to 100% closure by approximately 40% (p<0.05). Chrysalin treatment of heel ulcers within this population resulted in mean closure rates 165% higher than placebos (p<0.02) and complete healing in 86% (6/7) of ulcers compared with 0% (0/5) of placebo ulcers (p<0.03). Local wound reactions and adverse events (AEs) were equal between groups with no reported drug-related changes in laboratory tests or serious AEs. These results indicate the potential safety and efficacy of Chrysalin for treatment of diabetic foot ulcers.

Thrombin peptide TP508 stimulates cellular events leading to angiogenesis, revascularization, and repair of dermal and musculoskeletal tissues

The thrombin peptide, TP508, also known as Chrysalin (OrthoLogic, Tempe, Arizona), is a twenty-three-amino-acid peptide that represents a portion of the receptor-binding domain of the native human thrombin molecule that has been identified as the binding site for a specific class of receptors on fibroblasts and other cells. Preclinical studies with this peptide have shown that it can accelerate tissue repair in both soft and hard tissues by mechanisms that appear to involve up-regulation of genes that initiate a cascade of healing events. These events include recruitment and activation of inflammatory cells, directed migration of cells (chemotaxis), cell proliferation, elaboration of extra-cellular matrix, and accelerated revascularization of the healing tissues. Early preclinical dermal wound-healing studies showed that TP508 accelerated healing of both incisional wounds and full-thickness excisional wounds in normal and ischemic skin. In all of these studies, the accelerated healing was associated with increased neovascularization across the incision or in the granulating wound bed. Studies in a rat fracture model have also shown that TP508 accelerates the rate of fracture repair. Gene array analysis of fracture callus from control and TP508-treated fractures indicated that TP508 treatment was associated with an up-regulation of early response elements, inflammatory mediators, and genes related to angiogenesis. Similar to what had been seen in dermal wounds, histology from rat fracture callus twenty-one days after treatment indicated that fractures treated with TP508 had significantly more large functional blood vessels than did fractures in the control animals. In vitro studies support these in vivo data and indicate that TP508 may have a direct angiogenic effect by promoting the rate of new vessel growth. The results from phase-1 and phase-2 human clinical studies have shown a positive stimulatory effect of TP508 in the healing of diabetic ulcers and in the repair of fractures to the distal aspect of the radius. Collectively, these studies suggest that TP508 accelerates tissue repair by initiating a cascade of events that lead to an increased rate of tissue revascularization and regeneration.

Impact of sidestream whole smoke solutions on the outcome of wound repair and related angiogenesis

Wound angiogenesis is essential to support the regenerating tissue and any setback in angiogenesis may result in retarded wound repair. Cigarette smoking causes numerous adverse effects, some of which are associated with poor healing. The current experiment was carried out to elucidate the possible detrimental effects of sidestream whole smoke solutions (SSWSS) on wound healing and related angiogenesis, using a well-defined chicken dorsum excision wound assay. Gross, histopathologic, SEM and computer based 3D image-probing modalities were utilized to quantify different detrimental effects of SSWSS on the fundamental processes of wound healing. A total of 160 chicks, aged 1 week, divided in eight groups were topically exposed for 8 days to SSWSS with different nicotine concentrations. At day 6 and day 8 post-wounding, very highly significant reduction (P<0.001) in wound closure was observed among all SSWSS treated groups. Histological and SEM evaluation of SSWSS treated wounds unveiled deteriorated dermal matrix, delayed re-epithelialization and retarded neovascularization. Moreover, image-probing exploration of SSWSS treated wounds also divulge a very highly significant decrease (P<0.001) in angular spectrum, Sa, Sy and Sci, at day 6 post-wounding. Our study suggests that the cumulative effect of different components of SSWSS has a negative impact on wound healing and related angiogenesis. Furthermore, our study demonstrates the effects that can contribute to abnormal healing and may explain why people who are consistently exposed to sidestream smoke suffer from slow healing and excessive scarring of wounds, much like the smokers themselves.

Impaired wound healing by exposure of different mainstream whole smoke solutions of commercial cigarettes

Cigarette smoke has been shown to potentiate wound damage and delayed ulcer healing. The chicken dorsum excisional wound assay was used to elucidate the deleterious effects of different mainstream whole smoke solutions (MSWSS) on the fundamental processes of wound healing. Gross, histopathology, SEM and computer based 3D image probing techniques were utilized to quantify different toxic effects of MSWSS on wound healing. A total of 160 chicks, aged 1 week, divided in eight groups were exposed to MSWSS with different nicotine concentration; 0.2mg (group A), 0.3mg (group B), 0.5mg (group C), 0.6mg (group D), 0.7mg (group E) and 1mg (group F). A very highly significant reduction (P<0.001) in wound closure was observed among all MSWSS treated groups at day 8 post-wounding. Histological investigations revealed a significant impede outcome in the re-epithelialization of all MSWSS exposed wounds. Delayed dermal matrix regeneration and maturation of collagen bundles were observed among all MSWSS treated wounds. Similar results were achieved through SEM of treated wounds. Histological and image probing analysis unveiled the scanty neovascularization among MSWSS treated wounds. Abbot curve, angular spectrum and different other parameters of 3D surface topographies of wounds revealed a very highly significant reduction (P<0.001) in angiogenesis among all MSWSS treated groups. These annotations validate the damaging effects of MSWSS on the healing of wounds.

The non-proteolytically active thrombin peptide TP508 stimulates angiogenic sprouting

Thrombin is a serine protease that promotes platelet aggregation, blood coagulation, and tissue repair. A peptide derived from a non-proteolytically active region of thrombin, TP508, also promotes tissue repair and increased vascularity, yet does not activate platelet and inflammatory cascades. TP508 binds to cells with high affinity and stimulates cells independent of the proteolytically active thrombin receptors (PARs) and thus is considered to activate a non-proteolytically active receptor (non-PAR) pathway. Using a model of angiogenic sprouting, we further defined the angiogenic potential of TP508 and investigated the role of non-proteolytic, thrombin-mediated pathways in angiogenesis. The assay involves measuring angiogenic sprouting from cultured, intact microvessel fragments. In this assay, TP508 stimulated angiogenic sprouting to an extent similar to or greater than the potent angiogenic factor, VEGF. However, TP508 had no significant effect on the number of sprouts that formed per vessel. In contrast to TP508, proteolytically active receptor agonists had no effect or inhibited angiogenic sprouting. The increased sprouting activity stimulated by TP508 was VEGF dependent but did not involve an increase in VEGF mRNA expression above baseline levels. These results suggest that TP508 acts early in angiogenesis and directly on microvascular cells to accelerate sprouting, but not to induce more sprouting, in a manner different than the intact thrombin molecule.

Heparanase accelerates wound angiogenesis and wound healing in mouse and rat models

Orchestration of the rapid formation and reorganization of new tissue observed in wound healing involves not only cells and polypeptides but also the extracellular matrix (ECM) microenvironment. The ability of heparan sulfate (HS) to interact with major components of the ECM suggests a key role for HS in maintaining the structural integrity of the ECM. Heparanase, an endoglycosidase-degrading HS in the ECM and cell surface, is involved in the enzymatic machinery that enables cellular invasion and release of HS-bound polypeptides residing in the ECM. Bioavailabilty and activation of multitude mediators capable of promoting cell migration, proliferation, and neovascularization are of particular importance in the complex setting of wound healing. We provide evidence that heparanase is normally expressed in skin and in the wound granulation tissue. Heparanase stimulated keratinocyte cell migration and wound closure in vitro. Topical application of recombinant heparanase significantly accelerated wound healing in a flap/punch model and markedly improved flap survival. These heparanase effects were associated with enhanced wound epithelialization and blood vessel maturation. Similarly, a marked elevation in wound angiogenesis, evaluated by MRI analysis and histological analyses, was observed in heparanase-overexpressing transgenic mice. This effect was blocked by a novel, newly developed, heparanase-inhibiting glycol-split fragment of heparin. These results clearly indicate that elevation of heparanase levels in healing wounds markedly accelerates tissue repair and skin survival that are mediated primarily by an enhanced angiogenic response.-Zcharia, E., Zilka, R., Yaar, A., Yacoby-Zeevi, O., Zetser, A., Metzger, S., Sarid, R., Naggi, A., Casu, B., Ilan, N., Vlodavsky, I., Abramovitch, R. Heparanase accelerates wound angiogenesis and wound healing in mouse and rat models.

Rat models of skin wound healing: a review

Rats have been widely used in the study of skin wound healing and the efficacy of different treatment modalities. This particular animal species is often selected for its availability, low cost, and small size. To define the current use of rat skin wound healing models, this manuscript provides a review of articles published between 2000 and 2003 that chose rats as their research animals. Of the 55 articles reviewed, it was found that 38.2% of the studies used incisional models and 38.2% used excisional models, with some studies using combinations. The majority of the studies (78.2%) used the rat's dorsum as the wound location. Male Sprague Dawley in the 250-300 gram weight range were the most preferred rats. Sodium pentobarbital/pentobarbitone was the most commonly used anesthetic choice. Similarities and differences in the selected experimental conditions are noted and questions are raised with regard to comparability between studies and the ability to transfer the data from the animal model to the human clinical situation. Attempts to compare studies for the advancement of wound healing knowledge are being hampered by the differences found between the studies. Standardization in reporting could facilitate comparisons and may instigate additional research that favors the inevitable comparisons between the studies. Thus, universal reporting requirements need to be developed for animal wound healing studies.

Localization of heparin cofactor II in injured human skin: a potential role in wound healing

The physiologic function of the serpin heparin cofactor II (HCII) is not fully understood. We have hypothesized that HCII functions as an extravascular inhibitor of thrombin. Thrombin formed at a site of injury has been hypothesized to contribute to migration and proliferation of fibroblasts and smooth muscle cells involved in wound healing. To begin to test our hypothesis, we examined the immunohistochemical localization of HCII in human skin and compared it to that of the closely related serpin, antithrombin (ATIII). In skin specimens with acute wounds, there was diffuse HCII and ATIII staining in areas of hemorrhage. In healing skin wounds ATIII was primarily associated with mast cells, while HCII was associated with mononuclear phagocytes in the dermis. Blood monocytes isolated from healthy donors also stained for HCII protein. However, in situ hydridization and RT-PCR studies failed to show significant HCII mRNA expression either in macrophages in wounded skin or in peripheral blood leukocytes. HCII localization is not due to nonspecific uptake of plasma proteins, since ATIII had a very different distribution in wounded skin. These findings support the notion that HCII could function as an extravascular thrombin inhibitor and might play a role in the regulation of wound healing.

Wound pharmacobiology

Wound healing after major joint surgery involves a series of complex events. Over the past several years, thrombin has emerged as a pivotal participant in wound healing. The high incidence of venous thromboembolism following major joint replacement has made prophylaxis with pharmacologic agents a component of postoperative management. Anticoagulant agents of various classes affect different degrees of thrombin inhibition by virtue of their in vivo mechanisms of action. By inhibiting thrombin activity directly, with or without antithrombin III or other antithrombins, traditional anticoagulants may retard the wound healing process and impair completion. Newer, more selective anticoagulants may provide not only more effective alternatives for venous thromboembolism prophylaxis surrounding major orthopedic procedures, but also an anticoagulant environment more favorable to wound healing.

Thrombin peptide, TP508, stimulates angiogenic responses in animal models of dermal wound healing, in chick chorioallantoic membranes, and in cultured human aortic and microvascular endothelial cells

The alpha-thrombin peptide, TP508, accelerates the healing of full-thickness wounds in both normal and ischemic skin. In wounds treated with TP508, a pattern of increased vascularization is consistently observed both grossly and microscopically when compared to wounds treated with saline. One possible mechanism by which the peptide accelerates wound healing is by promoting revascularization of granulation tissue at the injured site. To evaluate the angiogenic potential of TP508, the peptide was tested in the chick embryo chorioallantoic membrane (CAM), where it increased the density and size of CAM blood vessels relative to controls. Additionally, TP508 stimulated chemokinesis and chemotaxis in a dose-dependent fashion in cultured human aortic and human microvascular endothelial cells. Taken together, these in vivo and in vitro data support an angiogenic role for TP508 in wound healing. A working model is presented to explain how this 23-amino-acid peptide, which lacks proteolytic activity, is generated during wound healing and contributes to the nonproteolytic functions associated with alpha-thrombin during tissue repair.