Protective Effect of Pharmacologic Preconditioning with Pioglitazone on Random-Pattern Skin Flap in Rat is Mediated by Nitric Oxide System

Nephroprotective effect of pioglitazone in a Wistar rat model of adenine‑induced chronic kidney disease

Chronic kidney disease (CKD) is a progressive disease with a high mortality rate and a worldwide prevalence of 13.4%, triggered by various diseases with high incidence. The aim of the present study was to investigate the anti-inflammatory and antifibrotic effect of pioglitazone on kidney in an adenine-induced Wistar rats and the mechanisms possibly involved. CKD was induced in 40 rats. Rats were divided into two groups, which were split into the following sub-groups: i) Therapeutic (pioglitazone administered after renal damage) divided into intact (healthy), adenine (CKD) and adenine/pioglitazone (treatment) and ii) prophylactic (adenine and pioglitazone administered at the same time) split into intact (healthy), adenine (CKD), endogenous reversion (recovery without treatment), adenine/pioglitazone (treatment) and pioglitazone sub-groups. Reverse transcription-quantitative PCR (collagen I, α-SMA and TGF-β), and hematoxylin-eosin, Masson's trichrome and Sirius red staining were performed to measure histological markers of kidney damage, also the serum markers (urea, creatinine and uric acid) were performed, for analyze the effects of pioglitazone. In the adenine/pioglitazone rats of the therapeutic group, renal function parameters such as eGFR increased and serum creatinine decreased from those of untreated rats (CKD), however the renal index, serum urea, abnormalities in renal morphology, inflammatory cells and relative gene expression of collagen I, α-SMA and TGF-β did not change relative to the CKD rats. In adenine/pioglitazone rats, extracellular matrix collagen accumulation was significantly lower than the CKD rats. On the other hand, in adenine/pioglitazone rats of the prophylactic group, the renal index, creatinine, urea, uric acid serum and relative gene expression of collagen I, α-SMA, and TGF-β were significantly lower, as well as the presence of 2,8-dihydroxyadenine crystals, and extracellular matrix collagen compared with CKD rats. In addition, the eGFR in the treatment group was similar to healthy rats, renal morphology was restored, and inflammatory cells were significantly lower. In conclusion, pioglitazone has a nephroprotective effect when administered in the early stages of kidney damage, reducing inflammatory and fibrotic processes and improving glomerular filtration rate. Furthermore, in the late phase of treatment, a tendency to decrease creatinine and increase eGFR was observed.

Chronic Cinacalcet improves skin flap survival in rats: the suggested role of the nitric oxide pathway

Cinacalcet is a calcimimetic medicine that has been used to treat secondary hyperparathyroidism and parathyroid cancer. Various studies have proposed the positive role of calcium and its receptor in skin wound healing. Furthermore, Cinacalcet interacts with other skin repair-related mechanisms, including inflammation and nitric oxide pathways. The present study evaluated the effect of Cinacalcet on the random-pattern skin flap survival. Eighty-four Wistar male rats were used. Multiple doses of Cinacalcet (30, 3, 1, 0.3, and 0.05 mg/kg) were used in 3 different routes of administration before the surgery. Histopathological evaluations, quantitative assessment of IL-6, TNF-α, and nitric oxide (NO), and the expression of calcium-sensing receptor (CaSR) and E-cadherin were evaluated in the skin tissue. To assess the role of NO, a NO synthase inhibitor, N-nitro-L-arginine methyl ester hydrochloride (L-NAME), was used, and histopathological effects were investigated. Cinacalcet pretreatment at the IP chronic 1 mg/kg dose significantly increased the skin flap survival rate and enhanced the NO tissue level compared to the control. However, the administration of L-NAME abolished its protective effects. IP Chronic 1 mg/kg of Cinacalcet could also decline the levels of IL-6 and TNF-α and also increase the expression of CaSR and E-cadherin in the flap tissue compared with the control group. Chronic Cinacalcet at 1 mg/kg could improve skin flap survival, probably mediated by the CaSR, NO, and inflammation-related pathways.

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.

Protective effect of modafinil on skin flap survival in the experimental random-pattern skin flap model in rats: The role of ATP-sensitive potassium channels and nitric oxide pathway

BACKGROUND

The brain-stimulating agent modafinil acts through nitric oxide (NO) and adenosine triphosphate (ATP)-sensitive potassium (KATP) channels, involved in the skin flap survival (SFS). The main aim of this study was to investigate the efficacy of modafinil on SFS in rats through the involvement of NO pathway and KATP channels.

METHODS

Using controlled experiment study design, we enrolled a sample of Wistar male rats. Different doses of modafinil (10, 25, 50, and 100 mg/kg) were injected intraperitoneally (i.p.) before the surgery. L-NAME (non-selective nitric oxide synthase [NOS] inhibitor), aminoguanidine (inducible NOS inhibitor), and 7-nitroindazole (neuronal NOS inhibitor) were administered prior to modafinil. The role of KATP channels was determined by coadministering glibenclamide (KATP channel blocker) or cromakalim (KATP channel opener) with modafinil. The predictor variables were administration of different doses of modafinil, and the coadministration of modafinil with L-NAME, aminoguanidine, 7-nitroindazole, glibenclamide, and cromakalim. The main outcome variables included the percentage of necrotic area (PNA) in flap tissues, histopathological results, vascular endothelial growth factor (VEGF) immunohistochemical (IHC) staining, and nitrite concentrations. Appropriate statistics were computed considering p-value ≤ 0.05 significant.

RESULTS

Modafinil 25 mg/kg was the most effective dose (PNA: 26 [95% CI: 19-33]) vs. control (PNA: 81 [95% CI: 71-92]) (p< 0.001). All NOS inhibitors significantly reversed the protective effect of modafinil (p< 0.001). Non-effective dose of cromakalim had a synergistic effect with the sub-effective dose of modafinil (10 mg/kg), while glibenclamide reversed the effect of modafinil 25 mg/kg (p< 0.001).

CONCLUSIONS

Modafinil increases SFS mediated by NO pathway and KATP channels, which could therefore be a target to improve SFS.

Therapeutic Effects against Tissue Necrosis of Remote Ischemic Preconditioning Combined with Human Adipose-Derived Stem Cells in Random-Pattern Skin Flap Rat Models

INTRODUCTION

Remote ischemic preconditioning (rIPC) is a preventive strategy against ischemia-reperfusion injury. To reduce ischemia-reperfusion injury of random-pattern skin flaps, we investigated the therapeutic effects of rIPC combined with human adipose-derived stem cells (hADSCs) in a rat model.

MATERIAL AND METHODS

In total, 24 female Sprague Dawley rats were divided into four groups (n = 6 each): control (skin flap only), rIPC, hADSCs, and rIPC + hADSCs. rIPC was performed in the hind limb of the rats over three cycles of 5 min of occlusion and 5 min of reperfusion, using a tourniquet. A rectangular (3 × 9 cm) dorsal skin flap was used. hADSCs (5 × 10⁵ cells/100 µL) labeled with fluorescent dye were transplanted into the normal subcutaneous tissue at the skin flap boundary. After 14 days, the therapeutic effects of rIPC and hADSCs were evaluated via analysis of the necrotic flap area, histopathologic assessment, and immunohistochemistry (von Willebrand Factor (vWF) and CD31).

RESULTS

The necrotic area of the skin flap significantly decreased in the rIPC + hADSCs group (32.75 ± 1.43%) compared with the control (40.60 ± 3.27%, P < 0.01) and rIPC groups (38.84 ± 0.77%, P < 0.05). Dye-labeled hADSCs migrated to the skin flap from the injection site. In the rIPC + hADSCs group, the epithelial tissue and skin appendage had regenerated, and the smooth muscle and subcutaneous fat layers were preserved. Many more vWF- and CD31-positive vessels were observed in the rIPC + hADSCs group compared with the other groups.

CONCLUSIONS

The rIPC + hADSCs treatment appeared to reduce skin flap necrosis and activated neovascularization in rats. Therefore, it may be a good strategy for clinical treatment of ischemia-reperfusion injury.

Valproic acid enhances the viability of random pattern skin flaps: involvement of enhancing angiogenesis and inhibiting oxidative stress and apoptosis

Background

Random skin flaps are commonly applied during plastic surgery, but distal flap necrosis limits their clinical applications. Valproic acid (VPA), a histone deacetylase inhibitor and a traditional antiepileptic agent, may promote flap survival.

Materials and methods

Sprague–Dawley rats were randomly divided into VPA-treated and control groups. All rats received VPA or saline by intraperitoneal injections once daily for 7 days after the modified McFarlane flap model was established. On postoperative day 7, flap survival, laser Doppler blood flow, and water content were examined for flap viability, hematoxylin and eosin staining (H&E), immunohistochemistry (IHC), and Western blot analysis, and the status of angiogenesis, apoptosis, and oxidative stress were detected in the ischemic flaps.

Results

VPA increased the survival area, blood flow, and number of microvessels in skin flaps on postoperative day 7 and reduced edema. VPA promoted angiogenesis by enhancing vascular endothelial growth factor (VEGF) mRNA transcription and upregulating VEGF and cadherin 5 expression, inhibited apoptosis via reduction of caspase 3 cleavage, and relieved oxidative stress by increasing superoxide dismutase (SOD) and glutathione (GSH) levels and reducing the malondialdehyde (MDA) level.

Conclusion

VPA promoted random skin flap survival by enhancing angiogenesis and inhibiting oxidative stress and apoptosis.