Efficacy and mechanism of adenovirus-mediated VEGF-165 gene therapy for augmentation of skin flap viability

VEGF and Other Gene Therapies Improve Flap Survival-A Systematic Review and Meta-Analysis of Preclinical Studies

Surgical flaps are basic tools in reconstructive surgery. Their use may be limited by ischemia and necrosis. Few therapies address or prevent them. Genetic therapy could improve flap outcomes, but primary studies in this field present conflicting results. This systematic review and meta-analysis aimed to appraise the efficacy of external gene delivery to the flap for its survival in preclinical models. This review was registered with PROSPERO (CRD42022359982). PubMed, Embase, Web of Science, and Scopus were searched to identify studies using animal models reporting flap survival outcomes following any genetic modifications. Random-effects meta-analysis was used to calculate mean differences in flap survival with accompanying 95% CI. The risk of bias was assessed using the SYRCLE tool. Subgroup and sensitivity analyses were performed to ascertain the robustness of primary analyses, and the evidence was assessed using the GRADE approach. The initial search yielded 690 articles; 51 were eventually included, 36 of which with 1576 rats were meta-analyzed. VEGF gene delivery to different flap types significantly improved flap survival area by 15.66% (95% CI 11.80-19.52). Other interventions had smaller or less precise effects: PDGF-13.44% (95% CI 3.53-23.35); VEGF + FGF-8.64% (95% CI 6.94-10.34); HGF-5.61% (95% CI 0.43-10.78); FGF 3.84% (95% CI 1.13-6.55). Despite considerable heterogeneity, moderate risk of bias, and low quality of evidence, the efficacy of VEGF gene therapy remained significant in all sensitivity analyses. Preclinical data indicate that gene therapy is effective for increasing flap survival, but further animal studies are required for successful clinical translation.

Current Status of Experimental Animal Skin Flap Models: Ischemic Preconditioning and Molecular Factors

Skin flaps are necessary in plastic and reconstructive surgery for the removal of skin cancer, wounds, and ulcers. A skin flap is a portion of skin with its own blood supply that is partially separated from its original position and moved from one place to another. The use of skin flaps is often accompanied by cell necrosis or apoptosis due to ischemia-reperfusion (I/R) injury. Proinflammatory cytokines, such as nuclear factor kappa B (NF-κB), inhibitor of kappa B (IκB), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and oxygen free radicals are known causative agents of cell necrosis and apoptosis. To prevent I/R injury, many investigators have suggested the inhibition of proinflammatory cytokines, stem-cell therapies, and drug-based therapies. Ischemic preconditioning (IPC) is a strategy used to prevent I/R injury. IPC is an experimental technique that uses short-term repetition of occlusion and reperfusion to adapt the area to the loss of blood supply. IPC can prevent I/R injury by inhibiting proinflammatory cytokine activity. Various stem cell applications have been studied to facilitate flap survival and promote angiogenesis and vascularization in animal models. The possibility of constructing tissue engineered flaps has also been investigated. Although numerous animal studies have been published, clinical data with regard to IPC in flap reconstruction have never been reported. In this study, we present various experimental skin flap methods, IPC methods, and methods utilizing molecular factors associated with IPC.

Dickkopf 2-Expressing Adenovirus Increases the Survival of Random-Pattern Flaps and Promotes Vasculogenesis in a Rat Model

BACKGROUND

Dickkopf 2 (DKK2) has important roles in vertebrate development; it inhibits Wnt signaling-related processes, such as axial patterning, limb development, somitogenesis, and eye formation. However, DKK2 also acts as a Wnt signaling agonist. Dickkopf 2, induced during endothelial cell morphogenesis, promotes angiogenesis in cultured human endothelial cells. In this study, we explored the effect of DKK2-expressing adenovirus on random-pattern flaps using a rodent model.

METHODS

A DKK2-expressing (dE1-RGD/DKK2) adenovirus was generated and 20 Sprague-Dawley rats were randomly divided into 2 groups: a DKK2 group and a control group. Each group was intradermally injected with 1 × 10 plaque-forming units of DKK2-expressing adenovirus (DKK2 group) or control virus (control group) 48 hours before and immediately before surgery. Then, random-pattern dorsal cutaneous flaps of 3 × 9 cm were elevated. Flap survival rates and cutaneous blood flow were measured over time, and immunohistochemical staining was performed 10 days after surgery to detect CD31 and vascular endothelial growth factor (VEGF).

RESULTS

Immunofluorescence staining confirmed the expression of DKK2 in the DKK2 group. The flap survival rate was higher in the DKK2 group (80.0 ± 4.49%) than in the control group (57.5 ± 4.21%; P < 0.05). Blood flow to the most distal compartment was higher in the DKK2 group than the control group during the early postoperative period. Although vascular density was greater in the DKK2 group, there was no difference in the VEGF concentration between groups.

CONCLUSIONS

The findings of the present study suggest that the DKK2-expressing adenovirus increases the survival of the random-pattern cutaneous flap independently of VEGF. The administration of the DKK2-expressing adenovirus into elevated skin flaps increased the number of capillaries and blood flow, thereby improving skin flap survival.

Preemptive treatment with photobiomodulation therapy in skin flap viability

Skin Flap is used in reconstructive plastic surgery. However, complications such as ischemia followed by local necrosis may occur, requiring a new surgical procedure. It is well known that photobiomodulation therapy (PBMT) is an effective technique for improving microcirculation and neoangiogenesis, which contributes positively to the blood supply in the pre and post surgical period. Thus, the objective of the present study was to investigate the effects of preemptive treatment with laser PBMT with different energies on the viability in skin flaps in rats. Sixty-three Wistar rats, male, were randomized into five groups: Control Group (CG) (n = 15): PBMT simulation; Preemptive group 1.1 J laser (GP1) (n = 15): preemptive laser PBMT with 1.1 J of energy per point; Preemptive group 4 J laser (GP4) (n = 15): preemptive PBMT with 4 J of energy per point; Laser group 11 J (G1) (n = 9): PBMT immediately after surgery with 1.1 J of energy per point; Laser group 4 J (G4) (n = 9): TFMB immediately after surgery with 4 J of energy per point. The CG, GP1 and GP4 groups started treatment 72 h prior to surgery and were subdivided into two experimental periods, one of them on the day of the flap and the other along with the other groups on the seventh postoperative day. Three days after the randomization, the animals underwent random skin flap surgery. PBMT was performed with a 660 nm laser at three points. In the first experimental period, a greater number of vessels were found, as well as mast cells in GP1 compared to the CG and greater expression of fibroblast growth factor and vascular endothelial growth factor in the GP1 and GP4 groups compared to the CG. In the second experimental period, GP1 presented a lower percentage of necrotic tissue, a higher number of vessels and a percentage of cells labeled with both VEGF and hypoxia indicible factor alpha (HIF-1α) compared to the CG, FGF in GP1, GP4 and G4 when compared to the CG. Thus, it was concluded that preemptive treatment with PBMT with the application of 1.1 J of energy per point is effective in improving the viability of the skin flap.

Enhanced notch signaling modulates unproductive revascularization in response to nitric oxide-angiopoietin signaling in a mouse model of peripheral ischemia

INTRODUCTION

Arteriolargenesis can be induced by concomitant stimulation of nitric Oxide (NO)-Angiopoietin receptor (Tie)-Vascular Endothelial Growth Factor (VEGF) signaling in the rat mesentery angiogenesis assay. We hypothesized that the same combination of exogenously added growth factors would also have a positive impact on arteriolargenesis and, consequently, the recovery of blood flow in a model of unilateral hindlimb ischemia.

RESULTS AND METHODS

NO-Tie mice had faster blood flow recovery compared to control mice, as assessed by laser speckle imaging. There was no change in capillary density within the ischemic muscles, but arteriole density was higher in NO-Tie mice. Given the previously documented beneficial effect of VEGF signaling, we tested whether NO-Tie-VEGF mice would show further improvement. Surprisingly, these mice recovered no differently from control, arteriole density was similar and capillary density was lower. Dll4 is a driver of arterial specification, so we hypothesized that Notch1 expression would be involved in arteriolargenesis. There was a significant upregulation of Notch1 transcripts in NO-Tie-VEGF compared with NO-Tie mice. Using soluble Dll4 (sDll4), we stimulated Notch signaling in the ischemic muscles of mice. NO-Tie-sDll4 mice had significantly increased capillary and arteriole densities, but impaired blood flow recovery.

CONCLUSION

These results suggest that Dll4 activation early on in revascularization can lead to unproductive angiogenesis and arteriolargenesis, despite increased vascular densities. These results suggest spatial and temporal balance of growth factors needs to be perfected for ideal functional and anatomical revascularisation.

Role of the p38 mitogen-activated protein kinase signaling pathway in estrogen-mediated protection following flap ischemia-reperfusion injury

Ischemia-reperfusion (I/R) injury often occurs during skin flap transplantation and results in tissue damage. Although estrogen treatment significantly alleviates this I/R injury-induced damage, the detailed molecular mechanism is not clear. In this study, a superficial epigastric artery flap I/R injury model was created in adult Wistar rats. Severe necrosis was observed in skin tissue after I/R injury. Histological examination of skin tissue revealed that I/R injury damages skin structure and results in neutrophil infiltration. Inflammation-related parameters, including neutrophil count, tumor necrosis factor-α, and interleukin-10 levels, were increased due to I/R injury. These pathological phenomena were reduced by estradiol treatment. Further investigation found that I/R injury triggers the p38 mitogen-activated protein kinase (p38-MAPK) pathway. The expression levels of p38-MAPK and phosphorylated p38-MAPK were increased after I/R injury. Estradiol increased the expression level of MAPK phosphatase-2, a putative phosphatase of p38, and reduced the levels of p38-MAPK and phosphorylated p38-MAPK. These results suggest that estradiol can improve skin flap survival, possibly by inhibiting neutrophil infiltration and the expression of p38-MAPK. This study provides an explanation for how estrogen alleviates I/R injury-induced damage that occurs during skin flap transplantation. In a rat pathological model, I/R injury leads to skin necrosis, skin structure damage, neutrophil infiltration, and inflammatory cytokine secretion, which are probably downstream effects of activation of the p38-MAPK pathway. On the other hand, estradiol treatment triggers the expression of MAPK phosphatase-2, a putative phosphatase of p38-MAPK, and reduced all examined pathological phenomena. Therefore, estrogen may reduce the deleterious effect of I/R injury on skin flap transplantation through modulating the p38-MAPK pathway.

The Effect of Polydeoxyribonucleotide on Ischemic Rat Skin Flap Survival

Polydeoxyribonucleotide (PDRN) has multiple vascular actions such as angiogenesis and production of a vascular endothelial growth factor (VEGF) through the adenosine A2 receptor stimulation. We applied PDRN on the ischemic flap of rat back and investigated whether it enhances the skin flap survival. A total of 28 Sprague-Dawley rats were divided into 3 groups, namely, PDRN group, control group 1 (no treatment), and group 2 (phosphate-buffered saline injection). On the distally based flap of 3 × 9 cm in size, it was subdermally injected with PDRN or phosphate-buffered saline, which were administered 48 hours prior and immediately after flap elevation. The PDRN group was daily maintained by intraperitoneal administration of PDRN from the postoperative 1st day to 10th day. The mean survival rates of flap in PDRN group [79.5% (6.3%)] are significantly larger than control groups [1, 53.0% (6.9%); 2, 51.7% (6.7%)]. Serial measurements of blood perfusion also showed that the blood flux was significantly increased in almost part of the flap on the 10 days after PDRN injection. The number of CD31 positively stained vessels and expression of VEGF protein were significantly higher in the PDRN group. We propose that administration of PDRN into the ischemic skin flaps increased blood flux to the flap, VEGF expression, and number of capillaries, thereby improving the rat skin flap survival.

Comparison of Laser Doppler and Laser-Assisted Indocyanine Green Angiography Prediction of Flap Survival in a Novel Modification of the McFarlane Flap

BACKGROUND

The McFarlane rat ischemic dorsal skin flap model has been commonly used for clinical vector studies, as well as the testing of noninvasive diagnostics. However, variability of this model secondary to flap contact with the wound bed has led many to question its validity. Here we present a novel modification to the McFarlane skin flap using sterile silicone. We also use this model to test the prognostic efficacy of laser-assisted indocyanine green (ICG) angiography and laser Doppler imaging (LDI).

METHODOLOGY

A 3 × 9-cm dorsal skin flap with a cranially based pedicle was created, centered 1 cm distal to the scapulae. The flap was undermined, and in one of the 2 groups, a sterile silicone sheet was placed onto the wound bed. All flaps were then reapproximated with sutures 1-cm intervals. Clinical assessment and perfusion imaging was performed immediately postoperative, and at 24, 48, and 72 hours postsurgery. Postoperative day 7 clinical assessment was obtained before euthanasia.

RESULTS

A comparative study using silicone blocked versus unblocked models (n = 6 per group) showed that, clinically, both models had equivalent flap survival [8.5 (0.913) vs 9.5 (1.01) cm]. However, a statistically significant increase in perfusion in the mid-third of unblocked models was observed on POD3 [20.28% (2.7%) vs blocked 13.45% (2.5%), P < 0.05], with a similar increase in the distal third on POD7 [18.73% (2.064%) vs 10.91% (4.19%), P < 0.05]. A prognostic study comparing LDI and ICG angiography prediction of POD7 survival at early time points (n = 10) found that LDI underpredicted flap survival at early time points [84.2% (12.03%) on POD0, 87.35% (16.11%) on POD1]. In contrast, ICG was more proficient [100.1% (10.1%) on POD0].

CONCLUSIONS

We present a modification of the McFarlane skin flap model that results in similar clinical results, but with a noted reduction in perfusion inconsistencies noted in unblocked models. The ICG angiography is superior to LDI in predicting POD7 flap necrosis within the first 48 hours postinjury. Future work will focus on histologic validation of our model, and vector efficacy testing.

Propionyl-L-Carnitine Enhances Wound Healing and Counteracts Microvascular Endothelial Cell Dysfunction

Background

Impaired wound healing represents a high cost for health care systems. Endothelial dysfunction characterizes dermal microangiopathy and contributes to delayed wound healing and chronic ulcers. Endothelial dysfunction impairs cutaneous microvascular blood flow by inducing an imbalance between vasorelaxation and vasoconstriction as a consequence of reduced nitric oxide (NO) production and the increase of oxidative stress and inflammation. Propionyl-L-carnitine (PLC) is a natural derivative of carnitine that has been reported to ameliorate post-ischemic blood flow recovery.

Methods and Results

We investigated the effects of PLC in rat skin flap and cutaneous wound healing. A daily oral PLC treatment improved skin flap viability and associated with reactive oxygen species (ROS) reduction, inducible nitric oxide synthase (iNOS) and NO up-regulation, accelerated wound healing and increased capillary density, likely favoring dermal angiogenesis by up-regulation for iNOS, vascular endothelial growth factor (VEGF), placental growth factor (PlGF) and reduction of NADPH-oxidase 4 (Nox4) expression. In serum-deprived human dermal microvascular endothelial cell cultures, PLC ameliorated endothelial dysfunction by increasing iNOS, PlGF, VEGF receptors 1 and 2 expression and NO level. In addition, PLC counteracted serum deprivation-induced impairment of mitochondrial β-oxidation, Nox4 and cellular adhesion molecule (CAM) expression, ROS generation and leukocyte adhesion. Moreover, dermal microvascular endothelial cell dysfunction was prevented by Nox4 inhibition. Interestingly, inhibition of β-oxidation counteracted the beneficial effects of PLC on oxidative stress and endothelial dysfunction.

Conclusion

PLC treatment improved rat skin flap viability, accelerated wound healing and dermal angiogenesis. The beneficial effects of PLC likely derived from improvement of mitochondrial β-oxidation and reduction of Nox4-mediated oxidative stress and endothelial dysfunction. Antioxidant therapy and pharmacological targeting of endothelial dysfunction may represent a promising tool for the treatment of delayed wound healing or chronic ulcers.

Gene therapy using hepatocyte growth factor expressing adenovirus improves skin flap survival in a rat model

Hepatocyte growth factor (HGF) is a potent angiogenic factor that can stimulate the production of blood vessels in ischemic tissue. We investigated whether gene therapy using HGF-expressing adenovirus could enhance skin flap survival. Sprague-Dawley rats were randomly divided into three groups. Rats were subdermally injected with HGF-expressing adenovirus (HGF virus group), recombinant HGF (rhHGF group), or phosphate buffered saline (PBS group) 2 days before and immediately after 3 × 9 cm caudal flap elevation. The survival area of the skin flap, the ratio of blood flow, CD31-positive vessels and, VEGF expression were examined. Skin flap viability was significantly increased in the HGF virus group compared to the rhHGF and PBS groups (71.4% ± 5.9%, 63.8%± 6.4%, and 39.2% ± 13.0%, respectively) (P = 0.025). Furthermore, the blood flow ratio was significantly increased in the HGF virus group. In the HGF virus group, the number of CD31-positive vessels and vascular endothelial growth factor (VEGF) expression were significantly increased. Gene therapy using HGF-expressing adenovirus increase VEGF expression, the number of viable capillaries, and blood flow to the flap, thereby improving skin flap survival.

Effects of natural and recombinant hirudin on VEGF expression and random skin flap survival in a venous congested rat model

We aim to investigate the effects of locally injected natural and recombinant hirudin on vascular endothelial growth factor (VEGF) expression and flap survival in venous congested skin flaps using a rat model. A dorsal random skin flap (10 × 3 cm) was prepared on each of 30 Wistar rats to establish a venous congested model. The rats were randomly divided into 2 treatment groups [receiving subcutaneous injection of either natural hirudin (6 U) or recombinant hirudin (6 U)] and a control group, which received subcutaneous injection of physiologic saline. After treatment, skin flap survival rates were calculated. VEGF messenger RNA levels and VEGF-positive vessel density as a marker for VEGF levels were measured in the flaps during and after treatment. The skin flap VEGF messenger RNA levels increased in the natural hirudin-treated group. The VEGF-positive vessel density was increased in all 3 groups. Statistically significant increases of VEGF levels were observed in the natural and recombinant hirudin-treated groups compared with the control group (P < 0.05). The skin flap survival rates were improved in both hirudin treated groups. Natural and recombinant hirudin can increase VEGF expression in random skin flaps, which can potentially improve random skin flap survival in rats through angio genic mechanisms. Our results showed that hirudin treatment led to an increase in VEGF expression in the congested skin flaps. Natural hirudin demonstrated more pronounced effects than recombinant hirudin. Further studies are needed to understand the specific mechanisms.

Adenovirus-mediated expression of keratinocyte growth factor promotes secondary flap necrotic wound healing in an extended animal model

BACKGROUND

No effective treatments have been found for flap necrosis. Animal models that focus on the initial flap viability are inappropriate for necrotic wound studies. Keratinocyte growth factor (KGF) promotes keratinocyte proliferation with stronger activity and fewer complications and thus may be useful for necrotic flap wound healing.

METHODS

Rats with modified flap necrosis were randomly divided into four groups. An adenoviral vector expressing KGF was injected subdermally in the back of the animals after necrosis began. The expression and effect of KGF was assessed by real-time polymerase chain reaction, enzyme-linked immunoassay, and transwell, and wound healing was monitored.

RESULTS

The plasmid and adenovirus were able to express KGF and stimulate epithelial cell growth (p = 0.029). Histology showed that the necrosis healed fastest in the KGF administration group than in the control groups (p < 0.01). The adenovirus-mediated KGF (Ad-KGF) group had the thickest epithelium on days 15 (p = 0.044) and 25 (p = 0.014). The KGF level in the blood serum soared 10 and 15 days postoperatively (p < 0.01) but returned to baseline by day 25 (p = 0.561). The KGF mRNA levels in vivo increased dramatically in the Ad-KGF group (p = 0.037).

CONCLUSIONS

The extended flap model is applicable in necrotic wound study. Keratinocyte growth factor can promote secondary necrotic flap wound healing, and administration of KGF can be achieved by an adenoviral vector.

Identification of the Fra-1 transcription factor in healing skin flaps transplants: a potential role as a negative regulator of VEGF release from keratinocytes

The molecular mechanisms underlying successful myocutaneous skin flap integration, as well as the ischemic loss of transplanted tissue on surgery, remain largely unknown. In this study we used a mouse model of caudally based skin flaps to determine molecular patterns of acute transplant re-integration. Gene chip-based transcriptional analysis revealed an up-regulation of the transcription factor Fra-1 in murine skin flap tissue. Epidermal keratinocytes at the wound margins represented a dominant cellular source of Fra-1 in mice. Moreover, Fra-1 protein showed a clear nuclear localization. In addition, Fra-1 protein was also present in nuclei of wound margin keratinocytes located near the suture line in human skin flaps. In vitro studies using the human keratinocyte cell line HaCaT showed that epidermal growth factor (EGF) was a potent inducer of Fra-1 expression in keratinocytes. Ablation of Fral-1 protein using a specific Fra-1 small interfering (si)RNA markedly increased the EGF-induced vascular endothelial growth factor (VEGF) expression from keratinocytes. These data suggest the involvement of an injury-induced Fra-1 transcription factor as a regulator of keratinocyte gene expression, which might act as an antagonistic player to restrict epithelial-driven angiogenic responses during normal skin flap integration.

Role of wound macrophages in skin flap loss or survival in an experimental diabetes model

BACKGROUND

Tightly controlled wound inflammation is a central determinant of skin flap survival in healthy mice. This study investigated inflammatory response patterns in caudally pedicled skin flaps in diabetic mice during severely impaired conditions of necrotic skin flap tissue loss.

METHODS

Skin flap biopsies were analysed by RNase protection assay, quantitative real-time polymerase chain reaction, immunohistochemistry, enzyme-linked immunosorbent assay and immunoblotting.

RESULTS

Skin flaps were characterized by the necrotic loss of tissue starting from distal areas of the flaps in diabetic mice. Decay of epidermal and dermal structures within skin flap tissue was paralleled by an immune cell-mediated expression of chemokines (macrophage inflammatory protein 2, macrophage chemoattractant protein 1), cyclo-oxygenase (COX) 2 and inducible nitric oxide synthase (iNOS). Distal regions of necrotic skin flap tissue were infiltrated by excess numbers of neutrophils and macrophages, and the latter were polarized towards a proinflammatory state as they expressed COX-2 and iNOS. Experimental depletion of inflammatory macrophages inhibited necrotic destruction of the distal skin flap tissue in diabetic mice despite the persistence of neutrophil infiltration and inflammation.

CONCLUSION

Wound macrophages play a pivotal role in determining the survival or loss of skin flap tissue under disturbed wound healing conditions in obese diabetic mice.

Hemoglobin vesicles improve wound healing and tissue survival in critically ischemic skin in mice

Local hypoxia, as due to trauma, surgery, or arterial occlusive disease, may severely jeopardize the survival of the affected tissue and its wound-healing capacity. Initially developed to replace blood transfusions, artificial oxygen carriers have emerged as oxygen therapeutics in such conditions. The aim of this study was to target primary wound healing and survival in critically ischemic skin by the systemic application of left-shifted liposomal hemoglobin vesicles (HbVs). This was tested in bilateral, cranially based dorsal skin flaps in mice treated with a HbV solution with an oxygen affinity that was increased to a P(50) (partial oxygen tension at which the hemoglobin becomes 50% saturated with oxygen) of 9 mmHg. Twenty percent of the total blood volume of the HbV solution was injected immediately and 24 h after surgery. On the first postoperative day, oxygen saturation in the critically ischemic middle flap portions was increased from 23% (untreated control) to 39% in the HbV-treated animals (P < 0.05). Six days postoperatively, flap tissue survival was increased from 33% (control) to 57% (P < 0.01) and primary healing of the ischemic wound margins from 6.6 to 12.7 mm (P < 0.05) after HbV injection. In addition, higher capillary counts and endothelial nitric oxide synthase expression (both P < 0.01) were found in the immunostained flap tissue. We conclude that left-shifted HbVs may ameliorate the survival and primary wound healing in critically ischemic skin, possibly mediated by endothelial nitric oxide synthase-induced neovascularization.

Intradermal delivery of plasmid VEGF(165) by electroporation promotes wound healing

Skin flaps are extensively used in reconstructive surgeries to repair large defects and deep wounds, but severe ischemia and necrosis often results in loss of the transplanted tissue. Thus, skin flap models are often used to study the biology of healing and necrosis of acute ischemic wounds. Delivery of exogenous vascular endothelial growth factor (VEGF) to areas of ischemia has shown promise for promoting therapeutic angiogenesis, but its expression must be tightly regulated to avoid adverse effects. In this study, plasmid DNA encoding VEGF(165) (pVEGF) was delivered to the ischemic skin of a rat skin flap model by intradermal injection followed by electroporation (EP) (pVEGFE+). Treatment with pVEGFE+ significantly increased VEGF expression for 5 days after delivery compared to injection of pVEGF without EP (pVEGFE-). The short-term increase in VEGF was sufficient to mediate an upregulation of endothelial nitric oxide synthase, an angiogenic factor that increases vascular permeability. pVEGFE+ significantly increased skin flap perfusion at both days 10 and 14 postoperatively. The observed increase in perfusion with pVEGFE+ correlated with an increase in skin flap healing and survival. Our results demonstrate that pVEGFE+ is a potential nonviral noninvasive therapy to increase perfusion and healing of skin flaps and ischemic wounds.

Adenoviral-mediated expression and local deposition of recombinant tenascin-C perturbs cell-dependent matrix contraction

BACKGROUND

To mimic the wound environment, we have developed a three-dimensional (3-D) fibrin-fibronectin (FN) matrix model that is formed in vitro from purified proteins and approximates the provisional matrix. Tenascin-C, a large extracellular matrix (ECM) glycoprotein, is expressed transiently in tissue adjacent to areas of injury and contacts the provisional matrix in vivo. We have constructed a novel recombinant adenovirus vector (Ad-70Ten) to up-regulate local expression and secretion of a recombinant form of tenascin-C.

METHODS

Ad-70Ten and a control vector were constructed and used to infect cultured mammalian cells. Post-infection monitoring of expression was accomplished by immunoblot and immunohistochemical techniques. Local protein deposition was examined by immunofluorescence. Cell contractility was assessed by ability of infected cells to contract 3-D fibrin-FN matrices. Some matrices also contained lysophosphatidic acid (LPA), an activator of Rho GTPase.

RESULTS

Adenovirus-infected cells demonstrated high recombinant tenascin-C expression and deposited protein at sites of cell-matrix contacts resulting in significantly reduced contractility with 2.5-fold lower contraction of the matrix compared with control cells. Matrix contraction could be restored by treatment with LPA.

CONCLUSION

These results show that endogenous expression of tenascin-C down-regulates cell contractility and strongly suggest that it exerts its effects via a Rho GTPase signaling pathway. Taken with previous findings, these results suggest that tenascin-C acts in both a paracrine and autocrine manner via Rho GTPase pathways. This report demonstrates that recombinant adenovirus infection is a feasible method to induce high expression of large matrix proteins in mammalian cells, allowing better approximation of in vivo circumstances for investigations of locally secreted matrix protein. While the current vector has been constructed for research purposes, it also represents a proof in principle that adenoviral vectors encoding large proteins may have potential benefit in clinical applications.