Ischemia-reperfusion injury of adipofascial tissue: an experimental study evaluating early histologic and biochemical alterations in rats

Cryolipolysis: The future of cryolipolysis

BACKGROUND

Cryolipolysis has revolutionized the field of cosmetic dermatology as a nonsurgical procedure, utilizing controlled cooling to selectively destroy fat cells.

AIMS AND METHODS

This review article will focus on the future prospects of cryolipolysis, considering advancements in current technology as well as innovations that hold promise for the future. We will explore emerging trends in cryolipolysis, considering novel applicator designs, combination therapies, an innovative injectable treatment approach, and the evolving role of this technology in the field of cosmetic dermatology.

CONCLUSION

The future holds promise for advances in cryolipolysis using both the noninvasive topical cooling approach and the novel injectable ice-slurry technology.

Pinocembrin alleviates pyroptosis and apoptosis through ROS elimination in random skin flaps via activation of SIRT3

Random skin flap grafting is the most common skin grafting technique in reconstructive surgery. Despite progress in techniques, the incidence of distal flap necrosis still exceeds 3%, which limits its use in clinical practice. Current methods for treating distal flap necrosis are still lacking. Pinocembrin (Pino) can inhibit reactive oxygen species (ROS) and cell death in a variety of diseases, such as cardiovascular diseases, but the role of Pino in random flaps has not been explored. Therefore, we explore how Pino can enhance flap survival and its specific upstream mechanisms via macroscopic examination, Doppler, immunohistochemistry, and western blot. The results suggested that Pino can enhance the viability of random flaps by inhibiting ROS, pyroptosis and apoptosis. The above effects were reversed by co-administration of Pino with adeno-associated virus-silencing information regulator 2 homolog 3 (SIRT3) shRNA, proving the beneficial effect of Pino on the flaps relied on SIRT3. In addition, we also found that Pino up-regulates SIRT3 expression by activating the AMP-activated protein kinase (AMPK) pathway. This study proved that Pino can improve random flap viability by eliminating ROS, and ROS-induced cell death through the activation of SIRT3, which are triggered by the AMPK/PGC-1α signaling pathway.

Superior Epididymal Artery-Based Paraepididymal Adipofascial Flap: An Experimental Adipofascial Flap Model in the Rat

BACKGROUND

Flap surgery is widely performed in reconstructive surgery. Experimental research is vital to improve flap viability. However, the number of flap models for animals is still limited. In this study, we define a new adipofascial flap in rats that can be used to investigate pedicled flap and/or adipofascial flap physiology.

METHODS

Eight Wistar male rats were used. Under deep anesthesia, paraepididymal adipofascial flaps were harvested. Flap perfusion was assessed using a near-infrared fluorescence imaging system. The length of the flap and the diameter of the flap pedicle were measured.

RESULTS

All animals (n = 8) had sufficient sizes of paraepididymal fat pad, and no animals were lost. The only postoperative complication was testicular hematoma, which was observed in 2 animals. The maximum length of the harvested paraepididymal adipofascial flap was 9.7 cm with a mean of 6.6 cm. The maximum width of the flap was 3.3 cm with a mean of 2.6 cm. The mean pedicle diameter of the paraepididymal adipofascial flap was 1.1 mm. Near-infrared fluorescence imaging revealed adequate perfusion in all flaps.

CONCLUSIONS

The number of reported adipofascial flap models in animals is low, and they are mostly limited to flaps based on epigastric vessels. Superior epididymal artery-based paraepididymal adipofascial flap can be used as a pedicled flap model for studies focusing on adipofascial and/or pedicled flap physiology. Uncomplicated surgical technique and short operative time make this flap a valuable alternative to other flap models.

Critical Ischemia Time, Perfusion, and Drainage Function of Vascularized Lymph Nodes

BACKGROUND

Vascularized lymph node transfer is a promising surgical treatment for lymphedema. This study investigated the effect of ischemia on the lymphatic drainage efficiency of vascularized lymph node flaps and the critical ischemia time of lymph nodes.

METHODS

Twenty-four lymph nodes containing groin flaps in 12 Sprague-Dawley rats were dissected. Clamping of the vascular pedicle was performed for 0, 1, 3, 5, 6, or 7 hours; then, each was allowed to reperfuse by means of the vascular pedicle for 1 hour. Perfusion and ischemic changes were assessed using indocyanine green lymphography; laser Doppler flowmetry; and histologic studies with associated lymphatic vessel endothelial hyaluronan receptor-1, CD68, 4',6-diamidino-2-phenylindole, terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling, and glutathione assay stains.

RESULTS

The mean latency period of the groin lymph node flaps was 247 ± 67, 83 ± 15, 72 ± 42, 30 ± 18, and 245 ± 85 seconds in the 0-, 1-, 3-, 5-, and 6-hour groups, respectively. Perfusion detected by laser Doppler was 85.2 ± 14.5, 87.2 ± 36.7, 129.8 ± 33.7, 140.4 ± 148.5, 156.1 ± 91.4, and 41.2 ± 34.8 perfusion units at ischemia times of 0, 1, 3, 5, 6, and 7 hours, respectively. Cell damage measured by glutathione was 46.8 ± 10.2, 67.7 ± 14.2, 62.8 ± 15.4, 126.6 ± 5.9, 259.0 ± 70.3, and 109.1 ± 27.5 at ischemia times of 0, 1, 3, 5, 6, and 7 hours, respectively. Histologically, as ischemia time increased, hemorrhage and congestion became more severe.

CONCLUSIONS

The critical ischemia time of vascularized lymph nodes is 5 hours in the rodent animal model, verified by indocyanine green lymphatic fluid uptake, laser Doppler perfusion, and histologic assessments. Interestingly, lymphatic drainage and perfusion of vascularized lymph nodes were improved with an increased ischemia time before the critical 5 hours was reached.

Thioredoxin Protects Skin Flaps from Ischemia-Reperfusion Injury: A Novel Prognostic and Therapeutic Target

BACKGROUND

Ischemia-reperfusion injury is inevitable during free-tissue transfer, causing oxidative damage and extensive apoptosis. Thioredoxin is an endogenous protein with antioxidant and antiapoptotic activity in a variety of tissues. This study aims to investigate the protective effects of human thioredoxin-1 on ischemia-reperfusion flaps, and its clinical application value.

METHODS

Sixteen clinical specimens of ischemia-reperfusion flaps were collected and assessed for apoptosis and thioredoxin-1 expression. Eighty mice were administered recombinant human thioredoxin-1 or saline intraperitoneally for 5 days before ischemia-reperfusion. Half of the mice were killed 24 hours after reperfusion. The flap tissues were harvested and detected for the changes of morphology, apoptosis, redox condition, and relative protein expression. The flap survival percentage of the remaining mice was consecutively observed within 7 days of reperfusion.

RESULTS

Thioredoxin-1 abundance was negatively correlated with ischemia-reperfusion-induced apoptosis in human samples and animal models. The survival rate of the ischemia-reperfusion flaps in mice increased significantly following recombinant human thioredoxin-1 pretreatment. Mitigated tissue damage, reduced apoptosis, and more antioxidant activity were observed in recombinant human thioredoxin-1-pretreated flaps. Western blot analysis revealed thioredoxin-1 depletion and a significant increase in apoptosis signal-regulating kinase 1, p-p38, and cleaved caspase-3 abundance in the ischemia-reperfusion flaps, whereas supplementation of recombinant human thioredoxin-1 significantly reduced the apoptosis-related protein expression.

CONCLUSIONS

Thioredoxin-1 exerts its flap-protective role through redox regulation of reactive oxygen species scavenging and antiapoptotic signaling. The authors' research provides evidence that thioredoxin-1 may serve as a potential prognostic and therapeutic target for skin flap ischemia-reperfusion injury.

Noninvasive selective cryolipolysis and reperfusion recovery for localized natural fat reduction and contouring

BACKGROUND

Cryolipolysis is a contemporary method of reducing fat by controlled extraction of heat from adipocytes.

OBJECTIVES

The authors recorded temperature profiles during a single cryolipolysis treatment/recovery cycle (with and without massage) and report on the clinical safety and efficacy of this procedure.

METHODS

In the pilot study group (PSG), the abdomens of 6 patients were treated with cryolipolysis and subdermal temperatures were recorded. In the clinical treatment group (CTG), 112 patients were treated without temperature recordings and results were evaluated through matched comparison of standardized photographs, caliper measurements, ultrasound imaging, and global assessments.

RESULTS

Thirty minutes into the cooling phase, subdermal temperatures of patients in the PSG declined precipitously from pretreatment levels and remained low until the end of treatment. During recovery, subdermal temperatures of the only subject who received massage returned faster and to higher levels than the temperatures of subjects who did not receive massage. Patients in the CTG who were available for follow-up measurements at 6 months (n = 85) demonstrated an average fat reduction of 21.5% by caliper measurements; 6 random patients from this group also showed an average of 19.6% fat reduction by ultrasound imaging at 6 months. Global assessments were highest for the abdomen, hip, and brassiere rolls. Minimal side effects were observed, and patients experienced no significant downtime.

CONCLUSIONS

Noninvasive cryolipolysis results in a predictable and noticeable fat reduction within 6 months and does not cause skin damage. Profiling of subdermal temperatures may provide additional insights for improving clinical effectiveness and safety.

LEVEL OF EVIDENCE

3.

Antioxidant support in composite musculo-adipose-fasciocutaneous flap applications: an experimental study

Free radicals are chemicals that play roles in the etio-pathogenesis of ischaemia-reperfusion injury. Various antioxidants have been used in an attempt to mitigate the damage induced by these chemicals. In the present study, the antioxidative effects of grape seed extract (proanthocyanidin), tomato extract (lycopene), and vitamin C (ascorbic acid) on a composite re-established-flow inferior epigastric artery based rectus abdominis muscle-skin flap model on which experimental ischaemia was induced were investigated. The rats have been administered antioxidants for 2 weeks prior to the surgery and for 2 more weeks thereafter. Macroscopic, histopathological, and biochemical analyses were carried out at the decision of the experiment. It was found that flap skin island necrosis was significantly reduced in the proanthocyanidin, lycopene, vitamin C groups (p < 0.001). Statistical analyses showed significant decreases in inflammation, oedema, congestion, and granulation tissue in the proanthocyanidin and lycopene groups compared to the vitamin C and control groups (p < 0.001). When the viability rates of fat and muscle tissues were examined, significant improvements were found in the proanthocyanidin and lycopene groups in comparison to the other groups (p < 0.001). Serum antioxidant capacity measurements revealed significant differences in the lycopene group compared to all other groups (p < 0.001). It is concluded that lycopene and proanthocyanidin are protective antioxidants in rat composite muscle-skin flap ischaemia-reperfusion models.

Morphological characteristics of the human skin over posterior aspect of heel in the context of pressure ulcer development

The posterior aspect of heel is known as a particularly vulnerable site for pressure ulcer development, however, it is not well understood why this is so. This study was undertaken to identify the morphological characteristics of the skin over posterior aspect of heel in the context of pressure ulcer development. Human skin tissues were obtained from four different sites of the body of 4 aged subjects postmortem: posterior aspect of heel, plantar aspect of heel, sacrum and centre of gluteus maximus. The skin samples were processed for the examination using light microscopy and scanning electron microscopy. The posterior aspect of heel was characterized by a thicker epidermis, denser distribution and larger diameter of capillaries in the papillary layer, 3-dimensional architecture of collagen fibre meshwork in the reticular layer and elliptic adipose tissues situated perpendicularly to the skin surface being surrounded by thick collagen and elastic fibre septa compared to the sacrum. Given our observations in the papillary layer of the posterior aspect of heel, we assume that the tissue of this area may be less tolerant to ischaemia since the tissue has high metabolic demand to provide oxygen and nutrients to the epidermis which protects underlying tissue from external force. In addition, elliptic configuration of adipose tissues in the posterior aspect of heel situated perpendicularly to the skin surface may result in deep lesion if the forces applied exceed the tolerable level since the forces will be concentrated within the elliptic compartments.

Comparison of fibrogenesis caused by dermal and adipose tissue injury in an experimental model

Mammalian skin is composed of three layers, the epidermis, the dermis, and the subcutis, which is composed primarily of adipose tissue. The dermal and adipose tissues are involved simultaneously when partial and full-thickness burns occur, and often induce scar formation. However, little is known about the role of the dermis and adipose tissue injury in scar formation or the difference in fibrogenesis between the two tissues. In this study with female red Duroc pigs, we created flaps of skin with a dermal plane of injury or deeper flaps with an adipose plane of injury on the back. We compared the extent of fibrogenesis by observing the deposition of extracellular matrix as well as the characteristics of cells in the injured area. In skin flaps with a dermal level of tissue injury, scar formation that was characterized by more extracellular matrix deposition and less apoptotic myofibroblasts in the injured area was observed. Our results suggest that scar formation does not correlate with injury at the level of the adipose tissue, and that adipose tissue might serve to alleviate fibrogenesis.

IFATS collection: Fibroblast growth factor-2-induced hepatocyte growth factor secretion by adipose-derived stromal cells inhibits postinjury fibrogenesis through a c-Jun N-terminal kinase-dependent mechanism

Adipose-derived stem/stromal cells (ASCs) not only function as tissue-specific progenitor cells but also are multipotent and secrete angiogenic growth factors, such as hepatocyte growth factor (HGF), under certain circumstances. However, the biological role and regulatory mechanism of this secretion have not been well studied. We focused on the role of ASCs in the process of adipose tissue injury and repair and found that among injury-associated growth factors, fibroblast growth factor-2 (FGF-2) strongly promoted ASC proliferation and HGF secretion through a c-Jun N-terminal kinase (JNK) signaling pathway. In a mouse model of ischemia-reperfusion injury of adipose tissue, regenerative changes following necrotic and apoptotic changes were seen for 2 weeks. Acute release of FGF-2 by injured adipose tissue was followed by upregulation of HGF. During the adipose tissue remodeling process, adipose-derived 5-bromo-2-deoxyuridine-positive cells were shown to be ASCs (CD31-CD34+). Inhibition of JNK signaling inhibited the activation of ASCs and delayed the remodeling process. In addition, inhibition of FGF-2 or JNK signaling prevented postinjury upregulation of HGF and led to increased fibrogenesis in the injured adipose tissue. Increased fibrogenesis also followed the administration of a neutralizing antibody against HGF. FGF-2 released from injured tissue acts through a JNK signaling pathway to stimulate ASCs to proliferate and secrete HGF, contributing to the regeneration of adipose tissue and suppression of fibrogenesis after injury. This study revealed a functional role for ASCs in the response to injury and provides new insight into the therapeutic potential of ASCs.

Emerging role of adipose tissue hypoxia in obesity and insulin resistance

Recent studies consistently support a hypoxia response in the adipose tissue in obese animals. The observations have led to the formation of an exciting concept, adipose tissue hypoxia (ATH), in the understanding of major disorders associated with obesity. ATH may provide cellular mechanisms for chronic inflammation, macrophage infiltration, adiponectin reduction, leptin elevation, adipocyte death, endoplasmic reticulum stress and mitochondrial dysfunction in white adipose tissue in obesity. The concept suggests that inhibition of adipogenesis and triglyceride synthesis by hypoxia may be a new mechanism for elevated free fatty acids in the circulation in obesity. ATH may represent a unified cellular mechanism for a variety of metabolic disorders and insulin resistance in patients with metabolic syndrome. It suggests a new mechanism of pathogenesis of insulin resistance and inflammation in obstructive sleep apnea. In addition, it may help us to understand the beneficial effects of caloric restriction, physical exercise and angiotensin II inhibitors in the improvement of insulin sensitivity. In this review article, literatures are reviewed to summarize the evidence and possible cellular mechanisms of ATH. The directions and road blocks in the future studies are analyzed.

The effects of increased ischemic times on adipose tissue: a histopathologic study using the epigastric flap model in rats

Little study has investigated the ischemic injury of mature adipocytes. This study researched the effects of different ischemic times on fat histology the 7th postischemic day in a rat epigastric flap model. For this study, 24 rats were randomly divided into four groups subjected, respectively, to 1, 2, 3, and 4 h of ischemia. The most severe inflammation and fat necrosis scores were seen in groups 3 and 4 (p < 0.05). According to the findings of this study, it is possible to say that fat tissue undergoes a gross necrosis after 3 or more hours of ischemia. After that ischemic time, the necrotic volume of fat tissue subjected to ischemic insult does not increase with increased ischemic time.

Depletion of glutathione by buthionine sulfoximine decreases random-pattern skin flap viability in rats

BACKGROUND

Glutathione (GSH) is one of the most highly concentrated intracellular antioxidants. Exogenous GSH has been shown to increase random-pattern skin flap survival. However, the effects of endogenous GSH depletion on random-pattern skin flap viability have never been studied.

MATERIALS AND METHODS

To evaluate the effects of systemic glutathione depletion on random-pattern skin flap survival in rats, 28 Wistar albino rats were divided into control, sham, and BSO (buthionine sulfoximide, a selective inhibitor for gamma-glutamylcysteine synthetase) groups. Dorsal, cranial-based random-pattern skin-flaps were elevated and the percentage of flap necrosis was measured in all rats at the postoperative day 7.

RESULTS

BSO-treated rats showed increased skin flap necrosis when compared with untreated animals (P < 0.001). High-dose BSO treatment group had more clinically evident necrosis than low dose group (P < 0.05).

CONCLUSIONS

This study reveals the importance of endogenous GSH for random skin-flap viability.