The current state of knowledge on how to improve skin flap survival: A review

The Mitochondrial Transplantation: A New Frontier in Plastic Surgery

Challenges such as difficult wound healing, ischemic necrosis of skin flaps, and skin aging are prevalent in plastic surgery. Previous research has indeed suggested that these challenges in plastic surgery are often linked to cellular energy barriers. As the powerhouses of the cell, mitochondria play a critical role in sustaining cellular vitality and health. Fundamentally, issues like ischemic and hypoxic damage to organs and tissues, as well as aging, stem from mitochondrial dysfunction, which leads to a depletion of cellular energy. Hence, having an adequate number of high-quality, healthy mitochondria is vital for maintaining tissue stability and cell survival. In recent years, there has been preliminary exploration into the protective effects of mitochondrial transplantation against cellular damage in systems such as the nervous, cardiovascular, and respiratory systems. For plastic surgery, mitochondrial transplantation is an extremely advanced research topic. This review focuses on the novel applications and future prospects of mitochondrial transplantation in plastic surgery, providing insights for clinicians and researchers, and offering guidance to patients seeking innovative and effective treatment options.

Biologic Brachytherapy: Genetically Modified Surgical Flap as a Therapeutic Tool-A Systematic Review of Animal Studies

Surgical flaps are rudimentary tools in reconstructive surgery, especially following extensive solid tumour resections. They cover skin and soft tissue defects but are prone to ischaemia and necrosis. Since their primary aim is reconstruction, they rarely exhibit a therapeutic activity against the treated disease. Attempts have been made to develop a new therapeutic strategy-biologic brachytherapy, which uses genetically engineered surgical flaps as a drug delivery vehicle, allowing the flap tissue to act as a "biologic pump". This systematic review summarizes the preclinical evidence on using genetically modified surgical flaps. A literature search was conducted in PubMed, EMBASE, Scopus and Web of Science. The initial literature search yielded 714 papers, and, eventually, seventy-seven studies were included in qualitative analysis. The results show that genetic enhancement of flaps has been used as a local or systemic therapy for numerous disease models. Frequently, it has been used to increase flap survival and limit ischaemia or promote flap survival in a non-ischemic context, with some studies focusing on optimizing the technique of such gene therapy. The results show that genetically modified flaps can be successfully used in a variety of contexts, but we need more studies to implement this research into specific clinical scenarios.

β-Caryophyllene promotes the survival of random skin flaps by upregulating the PI3K/AKT signaling pathway

BACKGROUND

Flap transplantation is a widely used plastic repair technique in surgical procedures, aimed at addressing skin defects resulting from diverse wounds and diseases. However, due to the insufficient blood supply after flap surgery, the occurrence of ischemia-reperfusion injury, and an excessive sterile inflammatory response, flaps frequently develop complications (e.g., partial or complete ischemic necrosis). These complications have adverse effects on wound healing and repair. β-Caryophyllene (BCP) is a bicyclic sesquiterpene that is widely present in plants. It mitigates oxidative stress and inflammatory responses, demonstrates neuroprotective and analgesic properties, and serves a protective function in organs or tissues subjected to ischemia-reperfusion injury. However, no study has confirmed whether BCP can be used in the field of flap transplantation to improve the flap survival rate.

METHODS

To assess the impact of BCP on random flap survival, we constructed a modified McFarlane random flap model on the rat. After 7 consecutive days of gavage with different doses of BCP, we measured the survival area ratio, angiogenesis, blood perfusion, tissue inflammation level, apoptosis-related protein levels, and the PI3K/AKT signaling pathway expression of the random flap.

RESULTS

BCP treatment increased the survival area of the flap in a dose-dependent manner after random flap transplantation in rats. BCP mainly promoted the formation of tissue blood vessels, improved flap blood perfusion, limited the local inflammatory response, and reduced apoptosis. In addition, we demonstrated that BCP works primarily by promoting the PI3K/AKT signaling expression while enhancing the phosphorylation of AKT. Administration of wortmannin, a selective inhibitor of PI3K, eliminated the effects of BCP.

CONCLUSION

BCP can promote the survival of random flaps by upregulating the PI3K/AKT signaling pathway, increasing tissue blood perfusion, and limiting the inflammatory response and apoptosis.

Tetrahydropalmatine promotes random skin flap survival in rats via the PI3K/AKT signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Flap necrosis is the most common complication after flap transplantation, but its prevention remains challenging. Tetrahydropalmatine (THP) is the main bioactive component of the traditional Chinese medicine Corydalis yanhusuo, with effects that include the activation of blood circulation, the promotion of qi, and pain relief. Although THP is widely used to treat various pain conditions, its impact on flap survival is unknown.

AIM OF THE STUDY

To explore the effect and mechanism of THP on skin flap survival.

MATERIALS AND METHODS

In this study, we established a modified McFarlane flap model, and the flap survival rate was calculated after 7 days of THP treatment. Angiogenesis and blood perfusion were evaluated using lead oxide/gelatin angiography and laser Doppler, respectively. Flap tissue obtained from zone II was evaluated histopathologically, by hematoxylin and eosin staining, and in assays for malondialdehyde content and superoxide dismutase activity. Immunofluorescence was performed to detect interleukin (IL)-6, tumor necrosis factor (TNF)-α, hypoxia-inducible factor (HIF)-1α, Bcl-2, Bax, caspase-3, caspase-9, SQSTM1/P62, Beclin-1, and LC3 expression, and Western blot to assess PI3K/AKT signaling pathway activation and Vascular endothelial growth factor (VEGF) expression. The role played by the autophagy pathway in flap necrosis was examined using rapamycin, a specific inhibitor of mTOR.

RESULTS

Experimentally, THP improved the survival rate of skin flaps, promoted angiogenesis, and improved blood perfusion. THP administration reduced the inflammatory response, oxidative stress, and apoptosis in addition to inhibiting autophagy via the PI3K/AKT/mTOR pathway. Rapamycin partially reversed these effects.

CONCLUSION

THP promotes skin flap survival via the PI3K/AKT signaling pathway.

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.

M2 macrophage-derived exosomes induce angiogenesis and increase skin flap survival through HIF1AN/HIF-1α/VEGFA control

BACKGROUND

Skin flap transplantation is a routine strategy in plastic and reconstructive surgery for skin-soft tissue defects. Recent research has shown that M2 macrophages have the potential for pro-angiogenesis during tissue healing.

METHODS

In our research, we extracted the exosomes from M2 macrophages(M2-exo) and applied the exosomes in the model of skin flap transplantation. The flap survival area was measured, and the choke vessels were assessed by morphological observation. Hematoxylin and eosin (H&E) staining and Immunohistochemistry were applied to assess the neovascularization. The effect of M2-exo on the function of Human umbilical vein endothelial cells (HUVECs) was also investigated. We also administrated 2-methoxyestradiol (2-ME2, an inhibitor of HIF-1α) to explore the underlying mechanism. We tested the effects of M2-Exo on the proliferation of HUVECs through CCK8 assay and EdU staining assay.

RESULTS

The survival area and number of micro-vessels in the skin flaps were increased in the M2-exo group. Besides, the dilation rate of choke vessels was also enhanced in the M2-exo group. Additionally, compared with the control group, M2-exo could accelerate the proliferation, migration and tube formation of HUVECs in vitro. Furthermore, the expression of the pro-angiogenesis factors, HIF-1α and VEGFA, were overexpressed with the treatment of the M2-exo. The expression of HIF1AN protein level was decreased in the M2-exo group. Finally, treatment with HIF-1α inhibitor reverses the pro-survival effect of M2-exo on skin flaps by interfering with the HIF1AN/HIF-1α/VEGFA signaling pathway.

CONCLUSION

This study showed that M2-exosomes promote skin flap survival by enhancing angiogenesis, with HIF1AN/HIF-1α/VEGFA playing a crucial role in this process.

Desmopressin enhances random-pattern skin flap survival in rats: Possible role of vasopressin Type-1a and 2 receptors

BACKGROUND

Many drugs have been explored for their role in improving skin flap survival. 1-deamino-8-D-arginine vasopressin (DDAVP or desmopressin) is a synthesized form of anti-diuretic hormone (ADH) and a selective agonist for vasopressin type-2 receptors (V2 receptors). Desmopressin has been shown to improve endothelial function, induce vasodilation, and reduce inflammation. We aimed to evaluate its efficacy in enhancing flap survival and assess the role of vasopressin receptors in this process.

MATERIALS AND METHODS

We randomly assigned six male Wistar rats to each study group. Different doses of desmopressin were injected intraperitoneally to find the most effective amount (8 μg/rat). SR-49059, a selective V1a receptor antagonist, was given at 2μg/rat before providing the most effective dose of desmopressin (8μg/rat). Histopathological assessments, quantitative measurements of interleukin-1β (IL-1β), Tumor necrosis factor-alpha (TNF-α), and Nuclear Factor-κB (NF-κB), optical imaging, and measurement of the expression levels of V2 receptor in the rat skin tissue were performed.

RESULTS

Desmopressin (8μg/rat) significantly reduced the mean percentage of necrotic area compared to the control group (19.35% vs 73.57%). Histopathological evaluations revealed a notable reduction in tissue inflammation, edema, and degeneration following administration of desmopressin (8). The expression of the V2 receptor was increased following desmopressin administration. It also led to a reduction in IL-1β, TNF-α, and NF-κB levels. The protective effect of desmopressin on flap survival was reversed upon giving SR-49059. The optical imaging revealed enhanced blood flow in the desmopressin group compared to the control group.

CONCLUSIONS

Desmopressin could be repurposed to improve flap survival. V1a and V2 receptors probably mediate this effect.