Transplantation of adipose stromal cells promotes neovascularization of random skin flaps

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.

Tetrandrine promotes the survival of the random skin flap via the PI3K/AKT signaling pathway

Flaps are mainly used for wound repair. However, postoperative ischemic necrosis of the distal flap is a major problem, which needs to be addressed urgently. We evaluated whether tetrandrine, a compound found in traditional Chinese medicine, can prolong the survival rate of random skin flaps. Thirty-six rats were randomly divided into control, low-dose tetrandrine (25 mg/kg/day), and high-dose tetrandrine (60 mg/kg/day) groups. On postoperative Day 7, the flap survival and average survival area were determined. After the rats were sacrificed, the levels of angiogenesis, apoptosis, and inflammation in the flap tissue were detected with immunology and molecular biology analyses. Tetrandrine increased vascular endothelial growth factor and Bcl-2 expression, in turn promoting angiogenesis and anti-apoptotic processes, respectively. Additionally, tetrandrine decreased the expression of Bax, which is associated with the induction of apoptosis, and also decreased inflammation in the flap tissue. Tetrandrine improved the survival rate of random flaps by promoting angiogenesis, inhibiting apoptosis, and reducing inflammation in the flap tissue through the modulation of the PI3K/AKT signaling pathway.

Comparative Transcriptomic Analysis of Regenerated Skins Provides Insights into Cutaneous Air-Breathing Formation in Fish

Cutaneous air-breathing is one of the air-breathing patterns in bimodal respiration fishes, while little is known about its underlying formation mechanisms. Here, we first investigated the skin regeneration of loach (Misgurnus anguillicaudatus, a cutaneous air-breathing fish) and yellow catfish (Pelteobagrus fulvidraco, a water-breathing fish) through morphological and histological observations. Then, the original skins (OS: MOS, POS) and regenerated skins (RS: MRS, PRS) when their capillaries were the most abundant (the structural foundation of air-breathing in fish) during healing, of the two fish species were collected for high-throughput RNA-seq. A total of 56,054 unigenes and 53,731 unigenes were assembled in loach and yellow catfish, respectively. A total of 640 (460 up- and 180 down-regulated) and 4446 (2340 up- and 2106 down-regulated) differentially expressed genes (DEGs) were respectively observed in RS/OS of loach and yellow catfish. Subsequently, the two DEG datasets were clustered in GO, KOG and KEGG databases, and further analyzed by comparison and screening. Consequently, tens of genes and thirteen key pathways were targeted, indicating that these genes and pathways had strong ties to cutaneous skin air-breathing in loach. This study provides new insights into the formation mechanism of cutaneous air-breathing and also offers a substantial contribution to the gene expression profiles of skin regeneration in fish.

Translational products of adipose tissue-derived mesenchymal stem cells: Bench to bedside applications

With developments in the field of tissue engineering and regenerative medicine, the use of biological products for the treatment of various disorders has come into the limelight among researchers and clinicians. Among all the available biological tissues, research and exploration of adipose tissue have become more robust. Adipose tissue engineering aims to develop by-products and their substitutes for their regenerative and immunomodulatory potential. The use of biodegradable scaffolds along with adipose tissue products has a major role in cellular growth, proliferation, and differentiation. Adipose tissue, apart from being the powerhouse of energy storage, also functions as the largest endocrine organ, with the release of various adipokines. The progenitor cells among the heterogeneous population in the adipose tissue are of paramount importance as they determine the capacity of regeneration of these tissues. The results of adipose-derived stem-cell assisted fat grafting to provide numerous growth factors and adipokines that improve vasculogenesis, fat graft integration, and survival within the recipient tissue and promote the regeneration of tissue are promising. Adipose tissue gives rise to various by-products upon processing. This article highlights the significance and the usage of various adipose tissue by-products, their individual characteristics, and their clinical applications.

A Feasibility Study on 3D Bioprinting of Microfat Constructs Towards Wound Healing Applications

Chronic wounds affect over 400,000 people in the United States alone, with up to 60,000 deaths each year from non-healing ulcerations. Tissue grafting (e.g., autografts, allografts, and xenografts) and synthetic skin substitutes are common treatment methods, but most solutions are limited to symptomatic treatment and do not address the underlying causes of the chronic wound. Use of fat grafts for wound healing applications has demonstrated promise but these grafts suffer from low cell viability and poor retention at the wound site resulting in suboptimal healing of chronic wounds. Herein, we report on an innovative closed-loop fat processing system (MiniTC^TM) that can efficiently process lipoaspirates into microfat clusters comprising of highly viable regenerative cell population (i.e., adipose stromal cells, endothelial progenitors) preserved in their native niche. Cryopreservation of MiniTC^TM isolated microfat retained cell count and viability. To improve microfat retention and engraftment at the wound site, microfat was mixed with methacrylated collagen (CMA) bioink and 3D printed to generate microfat-laden collagen constructs. Modulating the concentration of microfat in CMA constructs had no effect on print fidelity or stability of the printed constructs. Results from the Alamar blue assay showed that the cells remain viable and metabolically active in microfat-laden collagen constructs for up to 10 days in vitro. Further, quantitative assessment of cell culture medium over time using ELISA revealed a temporal expression of proinflammatory and anti-inflammatory cytokines indicative of wound healing microenvironment progression. Together, these results demonstrate that 3D bioprinting of microfat-laden collagen constructs is a promising approach to generate viable microfat grafts for potential use in treatment of non-healing chronic wounds.

Freeze-dried bovine amniotic membrane as a cell delivery scaffold in a porcine model of radiation-induced chronic wounds

Background

Locoregional stem cell delivery is very important for increasing the efficiency of cell therapy. Amnisite BA (Amnisite) is a freeze-dried amniotic membrane harvested from bovine placenta. The objective of this study was to investigate the retention of cells of the stromal vascular fraction (SVF) on Amnisite and to determine the effects of cell-loaded Amnisite in a porcine radiation-induced chronic wound model.

Methods

Initially, experiments were conducted to find the most suitable hydration and incubation conditions for the attachment of SVF cells extracted from pig fat to Amnisite. Before seeding, SVFs were labeled with PKH67. The SVF cell-loaded Amnisite (group S), Amnisite only (group A), and polyurethane foam (group C) were applied to treat radiation-induced chronic wounds in a porcine model. Biopsy was performed at 10, 14, and 21 days post-operation for histological analysis.

Results

Retaining the SVF on Amnisite required 30 minutes for hydration and 1 hour for incubation. A PKH67 fluorescence study showed that Amnisite successfully delivered the SVF to the wounds. In histological analysis, group S showed increased re-epithelialization and revascularization with decreased inflammation at 10 days post-operation.

Conclusions

SVFs had acceptable adherence on hydrated Amnisite, with successful cell delivery to a radiation-induced chronic wound model.

Role of adipose mesenchymal stem cells and secretome in peripheral nerve regeneration

The use of stem cells is a breakthrough in medical biotechnology which brings regenerative therapy into a new era. Over the past several decades, stem cells had been widely used as regenerative therapy and Mesenchymal Stem Cells (MSCs) had emerged as a promising therapeutic option. Currently stem cells are effective therapeutic agents againts several diseases due to their tissue protective and repair mechanisms. This therapeutic effect is largely due to the biomolecular properties including secretomes. Injury to peripheral nerves has significant health and economic consequences, and no surgical procedure can completely restore sensory and motor function. Stem cell therapy in peripheral nerve injury is an important future intervention to achieve the best clinical outcome improvement. Adipose mesenchymal stem cells (AdMSCs) are multipotent mesenchymal stem cells which are similar to bone marrow-derived mesenchymal stem cells (BM-MSCs). The following review aims to provide an overview of the use of AdMSCs and their secretomes in regenerating peripheral nerves.

Exenatide improves random-pattern skin flap survival via TFE3 mediated autophagy augment

Random-pattern skin flaps are widely applied to rebuild and restore soft-tissue damage in reconstructive surgery; however, ischemia and subsequent ischemia-reperfusion injury lead to flap necrosis and are major complications. Exenatide, a glucagon-like peptide-1 analog, exerts therapeutic benefits for diabetic wounds, cardiac injury, and nonalcoholic fatty liver disease. Furthermore, Exenatide is a known activator of autophagy, which is a complex process of subcellular degradation that may enhance the viability of random skin flaps. In this study, we explored whether exenatide can improve skin flap survival. Our results showed that exenatide augments autophagy, increases flap viability, enhances angiogenesis, reduces oxidative stress, and alleviates pyroptosis. Coadministration of exenatide with 3-methyladenine and chloroquine, potent inhibitors of autophagy, reversed the beneficial effects, suggesting that the therapeutic benefits of exenatide for skin flaps are due largely to autophagy activation. Mechanistically, we identified that exenatide enhanced activation and nuclear translocation of TFE3, which leads to autophagy activation. Furthermore, we found that exenatide activates the AMPK-SKP2-CARM1 and AMPK-mTOR signaling pathways, which likely lead to exenatide's effects on activating TFE3. Overall, our findings suggest that exenatide may be a potent therapy to prevent flap necrosis, and we also reveal novel mechanistic insight into exenatide's effect on flap survival.

Preclinical efficacy of stem cell therapy for skin flap: a systematic review and meta-analysis

Background

A skin flap is one of the most critical surgical techniques for the restoration of cutaneous defects. However, the distal necrosis of the skin flap severely restricts the clinical application of flap surgery. As there is no consensus on the treatment methods to prevent distal necrosis of skin flaps, more effective and feasible interventions to prevent skin flaps from necrosis are urgently needed. Stem therapy as a potential method to improve the survival rate of skin flaps is receiving increasing attention.

Methods

This review followed the recommendations from the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) statements. Twenty studies with 500 animals were included by searching Web of Science, EMBASE, PubMed, and Cochrane Library databases, up until October 8, 2020. Moreover, the references of the included articles were searched manually to obtain other studies. All analyses were conducted using Review Manager V.5.3 software.

Results

Meta-analysis of all 20 studies demonstrated stem cell treatment has significant effects on reducing necrosis of skin flap compared with the control group (SMD: 3.20, 95% CI 2.47 to 3.93). Besides, subgroup analysis showed differences in the efficacy of stem cells in improving the survival rate of skin flaps in areas of skin flap, cell type, transplant types, and method of administration of stem cells. The meta-analysis also showed that stem cell treatment had a significant effect on increasing blood vessel density (SMD: 2.96, 95% CI 2.21 to 3.72) and increasing the expression of vascular endothelial growth factor (VEGF, SMD: 4.34, 95% CI 2.48 to 6.1).

Conclusions

The preclinical evidence of our systematic review indicate that stem cell-based therapy is effective for promoting early angiogenesis by up regulating VEGF and ultimately improving the survival rate of skin flap. In summary, small area skin flap, the administration method of intra-arterial injection, ASCs and MSCs, and xenogenic stem cells from humans showed more effective for the survival of animal skin flaps. In general, stem cell-based therapy may be a promising method to prevent skin flap necrosis.

Improved viability of murine skin flaps using a gelatin hydrogel sheet impregnated with bFGF

Basic fibroblast growth factor (bFGF) promotes epithelial cell proliferation and angiogenesis but its clinical applications are limited by its short half-life and low retention. Recently developed gelatin hydrogel sheets able to release physiologically active substances in a controlled manner have the potential to overcome these issues. In this study, the effects of gelatin hydrogel sheets impregnated with bFGF on flap survival and angiogenesis were examined in a murine skin flap model. A flap of 1 × 3 cm was generated on the backs of 60 C57BL/6 mice. The mice were divided into five groups (n = 12/group): Group I, untreated; Group II, treated with a gelatin hydrogel sheet impregnated with saline; Group III, treated with bFGF (50 µg) without sheets; Groups IV and V, treated with gelatin hydrogel sheets impregnated with 50 and 100 µg of bFGF, respectively. On the seventh day after surgery, the flap survival area and vascular network were examined and hematoxylin and eosin and von Willebrand factor staining were used for histological examinations. The flap survival areas were significantly larger in Groups IV and V than in other groups. The area of new vessels was significantly larger in Group IV than in the other groups. In the murine skin flap model, gelatin hydrogel sheets impregnated with bFGF promoted angiogenesis and improved flap survival. These findings support the use of bFGF-impregnated gelatin hydrogel sheets for improving ischemic flap survival in clinical settings.

Intra-arterial injection of human adipose-derived stem cells improves viability of the random component of axial skin flaps in nude mice

BACKGROUND

Skin flap necrosis is a common postoperative complication in reconstructive surgery. Recent evidence suggests that subcutaneously injected adipose-derived stem cells (ASCs) increase the viability of random skin flaps. Here, we examined whether intra-arterial human ASC administration could improve random component survival of axial skin flaps in nude mice.

METHODS

Human ASCs isolated from a healthy volunteer by liposuction were injected into nude mice through the right femoral artery at a low (1 × 10³ cells), medium (1 × 10⁴ cells), or high (1 × 10⁵ cells) dose. After ASC infusion, right superficial inferior epigastric vessels were ligated to create unipedicled superficial inferior epigastric artery (SIEA) flap with random extension.

RESULTS

Flap survival was higher in mice from all three ASC-treated groups, and particularly the medium-dose group was 30% better, than in the control group. Histological examination demonstrated a significantly higher vascular density in the axial skin flap in nude mice treated with the medium ASC dose than in control mice. PKH26-labeled ASCs were identified in skin flaps of ASC-treated mice; some endothelial cells exhibited positive staining for human HLA-A. Compared to the control group, mice in ASC-treated groups had higher vascular endothelial growth factor levels and lower tumor necrosis factor α, interferon γ, and interleukin-6 levels.

CONCLUSIONS

Intra-arterial human ASC administration increased the survival of axial skin flaps by attenuating inflammatory reactions and enhancing neovascularization. Intra-arterial ASC administration might yield a higher rate of these cells and of engraftment in the skin flaps. This approach may have a therapeutic role in increasing flap survival.

Adipose-derived stem cells: Sources, potency, and implications for regenerative therapies

Adipose-derived stem cells (ASCs) are a subset of mesenchymal stem cells (MSCs) that can be obtained easily from adipose tissues and possess many of the same regenerative properties as other MSCs. ASCs easily adhere to plastic culture flasks, expand in vitro, and have the capacity to differentiate into multiple cell lineages, offering the potential to repair, maintain, or enhance various tissues. Since human adipose tissue is ubiquitous and easily obtained in large quantities using a minimally invasive procedure, the use of autologous ASCs is promising for both regenerative medicine and organs damaged by injury and disease, leading to a rapidly increasing field of research. ASCs are effective for the treatment of severe symptoms such as atrophy, fibrosis, retraction, and ulcers induced by radiation therapy. Moreover, ASCs have been shown to be effective for pathological wound healing such as aberrant scar formation. Additionally, ASCs have been shown to be effective in treating severe refractory acute graft-versus-host disease and hematological and immunological disorders such as idiopathic thrombocytopenic purpura and refractory pure red cell aplasia, indicating that ASCs may have immunomodulatory function. Although many experimental procedures have been proposed, standardized harvesting protocols and processing techniques do not yet exist. Therefore, in this review we focus on the current landscape of ASC isolation, identification, location, and differentiation ability, and summarize the recent progress in ASC applications, the latest preclinical and clinical research, and future approaches for the use of ASCs.

A hydrogel derived from acellular blood vessel extracellular matrix to promote angiogenesis

The biocompatibility and bioactivity of injectable acellular extracellular matrix nominates its use as an optimal candidate for cell delivery, serving as a reconstructive scaffold. In this study, we investigated the feasibility of preparing a blood vessel matrix (BVM) hydrogel, which revealed its pro-angiogenic effects in vitro and its therapeutic effects in an in vivo skin flap model. Aortic and abdominal aortic arteries from pigs were acellularized by Triton-X 100 and confirmed by hematoxylin and eosin and 4,6-diamidino-2-phenylindole staining. Different concentrations of blood vessel matrix hydrogel were generated successfully through enzymatic digestion, neutralization, and gelation. Hematoxylin and eosin staining, Masson’s trichrome staining, collagen type I immunohistochemistry staining, and enzyme-linked immunosorbent assays showed that type I collagen and some growth factors were retained in the hydrogel. Scanning electron microscopy demonstrated the different diametric fibrils in blood vessel matrix hydrogels. A blood vessel matrix hydrogel-coated plate promoted the tube formation of human umbilical vein endothelial cells in vitro. After injection into skin flaps, the hydrogel improved the flap survival rate and increased blood perfusion and capillary density. These results indicated that we successfully prepared a blood vessel matrix hydrogel and demonstrated its general characteristics and angiogenic effects in vitro and in vivo.

Bioactive nanoparticle-based formulations increase survival area of perforator flaps in a rat model

BACKGROUND

Distal flap necrosis is a frequent complication of perforator flaps. Advances in nanotechnology offer exciting new therapeutic approaches. Anti-inflammatory and neo-angiogenic properties of certain metal oxides within the nanoparticles, including bioglass and ceria, may promote flap survival. Here, we explore the ability of various nanoparticle formulations to increase flap survival in a rat model.

MATERIALS AND METHODS

A 9 x 3 cm dorsal flap based on the posterior thigh perforator was raised in 32 Lewis rats. They were divided in 4 groups and treated with different nanoparticle suspensions: I-saline (control), II-Bioglass, III-Bioglass/ceria and IV-Zinc-doped strontium-substituted bioglass/ceria. On post-operative day 7, planimetry and laser Doppler analysis were performed to assess flap survival and various samples were collected to investigate angiogenesis, inflammation and toxicity.

RESULTS

All nanoparticle-treated groups showed a larger flap survival area as compared to the control group (69.9%), with groups IV (77,3%) and II (76%) achieving statistical significance. Blood flow measurements by laser Doppler analysis showed higher perfusion in the nanoparticle-treated flaps. Tissue analysis revealed higher number of blood vessels and increased VEGF expression in groups II and III. The cytokines CD31 and MCP-1 were decreased in groups II and IV.

CONCLUSIONS

Bioglass-based nanoparticles exert local anti-inflammatory and neo-angiogenic effects on the distal part of a perforator flap, increasing therefore its survival. Substitutions in the bioglass matrix and trace metal doping allow for further tuning of regenerative activity. These results showcase the potential utility of these nanoparticles in the clinical setting.

Effects of the traditional Chinese medicine baicalein on the viability of random pattern skin flaps in rats

Background

Random skin flaps are routinely placed during plastic and reconstructive surgery, but the distal areas often develop ischemia and necrosis. Baicalein, a major flavonoid extracted from the traditional Chinese herbal medicine huangqin, Scutellaria baicalensis Georgi, may improve flap viability.

Materials and methods

Rats were randomly divided into baicalein and control groups and they underwent placement of modified McFarlane flaps after intraperitoneal administration of baicalein or vehicle. Flap survival and water content were measured 7 days later, as were angiogenesis, apoptosis, and oxidative stress in ischemic flaps.

Results

Baicalein promoted flap survival, reduced edema, increased mean vessel density, and enhanced vascular endothelial growth factor production at both the translational and transcriptional levels. Baicalein reduced caspase 3 cleavage, increased superoxidase dismutase and glutathione levels, and decreased the malondialdehyde level.

Conclusion

Baicalein promoted flap viability by stimulating angiogenesis and inhibiting apoptosis and oxidation.

Adipose tissue depots and inflammation: effects on plasticity and resident mesenchymal stem cell function

Adipose tissue (AT) is a highly heterogeneous organ. Beside the heterogeneity associated to different tissue types (white, brown, and 'brite') and its location-related heterogeneity (subcutaneous, visceral, epicardial, and perivascular, etc.), AT composition, structure, and functionality are highly dependent on individual-associated factors. As such, the pro-inflammatory state associated to the presence of obesity and other cardiovascular risk factors (CVRFs) directly affects AT metabolism. Furthermore, the adipose-derived stem cells (ASCs) that reside in the stromal vascular fraction of AT, besides being responsible for most of the plasticity attributed to AT, is an additional source of heterogeneity. Thus, ASCs directly contribute to AT homeostasis, cell renewal, and spontaneous repair. These ASCs share many properties with the bone-marrow mesenchymal stem cells (i.e. potential to differentiate towards multiple tissue lineages, and angiogenic, antiapoptotic, and immunomodulatory properties). Moreover, ASCs show clear advantages in terms of accessibility and quantity of available sample, their easy in vitro expansion, and the possibility of having an autologous source. All these properties point out towards a potential use of ASCs in regenerative medicine. However, the presence of obesity and other CVRFs induces a pro-inflammatory state that directly impacts ASCs proliferation and differentiation capacities affecting their regenerative abilities. The focus of this review is to summarize how inflammation affects the different AT depots and the mechanisms by which these changes further enhance the obesity-associated metabolic disturbances. Furthermore, we highlight the impact of obesity-induced inflammation on ASCs properties and how those effects impair their plasticity.

Stem cell and skin rejuvenation

Stem cell-based therapies have been widely used for their abilities to repair and regenerate different types of tissues and organs in cosmetic and plastic surgeries. It involves the clinical application of different types of stem cells. Different stem cells have been reported to be applicable in different areas of cosmetic surgeries like face lipoatrophy, skin rejuvenation, breast enhancement, and body contouring. However, adipose-derived stem cells remain the most widely used by cosmetic surgeons as they have the potential and capability to differentiate into mesenchymal, ectodermal, and endodermal lineages and are easily accessible to harvest. The purpose of this review is to summarize available applications of stem in cosmetic and plastic surgeries.

Maximizing non-enzymatic methods for harvesting adipose-derived stem from lipoaspirate: technical considerations and clinical implications for regenerative surgery

In the past decade, adipose tissue has become a highly interesting source of adult stem cells for plastic surgery and regenerative medicine. The adipose source offers two options for the isolation of regenerative cells: the enzymatic digestion an expensive time-consuming procedure lacking a common standard operating protocol, or the non-enzymatic dissociation methods based on mechanical forces to break the processed adipose tissue. Here, we propose innovative inexpensive non-enzymatic protocols to collect and concentrate clinically useful regenerative cells from adipose tissue by centrifugation of the infranatant fraction of lipoaspirate as first step, usually discarded as a byproduct of the surgical procedure, and by fat shaking and wash as second enrichment step. The isolated cells were characterized according to the criteria proposed by the Mesenchymal and Tissue Stem Cell Committee of the International Society for Cellular Therapy (ISCT) to define human mesenchymal stem cells, and the results were compared with matched lipoaspirate samples processed with collagenase. The results demonstrated the usability of these new procedures as an alternative to fat grafting for treating stem cell-depleted tissues and for specific application requiring minimal or null soft tissue augmentation, such as skin diseases including severe burn and post-oncological scaring, chronic non-healing wounds, and vitiligo.

Microvascular Fragment Transplantation Improves Rat Dorsal Skin Flap Survival

BACKGROUND

The development of flap necrosis distally remains a concern during microsurgical flap transfers because, at least in part, of decreased perfusion. Microvascular fragments (MVFs) are microvessels isolated from adipose tissue that are capable of improving tissue perfusion in a variety of tissue defects. The aim of this study was to determine whether the transplantation of MVFs in a dorsal rat skin flap model can improve flap survival.

METHODS

A 10 × 3 cm flap was raised in a cranial to caudal fashion on the dorsal side of 16 Lewis rats, with the caudal side remaining intact. The rats were equally divided into a treatment group (MVFs) and a control group (sterile saline). At the time of surgery, sterile saline with or without MVFs was injected directly into the flap. Microvessel density was determined after harvesting flap tissue by counting vessels that positively stained for Griffonia simplicifolia lectin I-isolectin B4. Laser Doppler was used to measure blood flow before and after surgery and 7 and 14 days later. Flap survival was evaluated 7 and 14 days after surgery by evaluating the percentage of viable tissue of the flap with photodigital planimetry.

RESULTS

Despite the lack of a significant difference in microvessel density and tissue perfusion, flap survival increased 6.4% (P < 0.05) in MVF-treated animals compared with controls.

CONCLUSIONS

The use of MVFs may be a means to improve flap survival. Future studies are required to delineate mechanisms whereby this occurs and to further optimize their application.

Autologous Stem Cell Transplantation Promotes Mechanical Stretch Induced Skin Regeneration: A Randomized Phase I/II Clinical Trial

Background

Mechanical stretch, in term of skin expansion, can induce effective but limited in vivo skin regeneration for complex skin defect reconstruction. We propose a strategy to obtain regenerated skin by combining autologous stem cell transplantation with mechanical stretch.

Methods

This randomized, blinded placebo-controlled trial enrolled 38 adult patients undergoing skin expansion presenting with signs of exhausted regenerative capacity. Patients randomly received autologous bone marrow mononuclear cell (MNC) or placebo injections intradermally. Follow-up examinations were at 4, 8 weeks and 2 years. The primary endpoint was the volume achieved in relation to the designed size of the expander (expansion index, EI). Secondary endpoints were surface area, thickness and texture of expanded skin. This trial is registered with ClinicalTrial.gov, NCT01209611.

Findings

The MNC group had a significantly higher EI at 4 weeks (mean difference 0.59 [95% CI, 0.03–1.16]; p = 0.039) and 8 weeks (1.05 [95% CI, 0.45–1.66]; p = 0.001) versus controls. At 8 weeks, the MNC group had significantly thicker skin (epidermis: p < 0.001, dermis: p < 0.001) and higher subjective scores for skin quality/texture (24.8 [95% CI, 17.6–32.1]; p < 0.001). The MNC group had more skin surface area (70.34 cm² [95% CI, 39.75–100.92]; p < 0.001). Patients in the MNC group gained up to the quadrupled surface area of expanded skin compared to pre-expansion at the end of expansion. No severe adverse events occurred.

Interpretation

Intradermal transplantation of autologous stem cells represents a safe and effective strategy to promote in vivo mechanical stretch induced skin regeneration, which can provide complex skin defect reconstruction with plentiful of tissue.

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This study shows that intradermally transplanted MNCs in mechanical stretched skin is a safe and feasible clinical application.

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Intradermally transplantation of MNCs can overcome the regenerative limitations of skin.

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The strategy of combining stem cell and microenvironment can provide significant amounts tissue for surgical reconstruction.

Though stem cells are proved to participate in tissue regeneration, there is seldom clinical research combining stem cell and in vivo mechanotransduction to provoke skin regeneration. In this study, we introduce autologous bone marrow stem cells to mechanical stretch induced skin regeneration. The results showed that the potential of autologous stem cells in promoting skin regeneration. The application of stem cell assisted skin expansion can overcome the regenerative limitations of skin to provide significant amounts tissue for surgical reconstruction. The integration of stem cells and mechanical stretch stimuli will engender further advances in in vivo tissue regeneration.

Effects of Acellular Amniotic Membrane Matrix and Bone Marrow-Derived Mesenchymal Stem Cells in Improving Random Skin Flap Survival in Rats

BACKGROUND

The necrotic skin flap represents a great challenge in plastic and reconstructive surgery. In this study, we evaluated the effect of bioscaffolds, acellular amniotic membranes (AAMs), and bone marrow-derived mesenchymal stem cells (BM-MSCs) on random skin flap (RSF) survival in rats by applying a cell-free extracellular matrix scaffold as a supportive component for the growth and proliferation of BM-MSCs on RSFs. AAM matrix scaffolds were created by incubating AMs in ethylenediaminetetraacetic acid 0.05% at 37°C, and cell scrapers were used.

OBJECTIVES

The aim of the present study was to assess the effect of AAM as a scaffold in TE, and combined with transplanted BM-MSCs, on the survival of RSFs and on the biomechanical parameters of the incision-wound flap margins 7 days after flap elevation.

MATERIALS AND METHODS

BM-MSCs and AAMs were transplanted into subcutaneous tissue in the flap area. On the 7th postoperative day, the surviving flap areas were measured using digital imaging software, and the flap tissue was collected for evaluation. Forty rats were randomly divided into four groups of 10 each: group 1 received an AAM injection; group 2 underwent BM-MSC transplantation; group 3 received both AAM injection + BM-MSC transplantation; and group 4 was the control group, receiving only saline.

RESULTS

The survival area in the AAM/BM-MSC group was significantly higher than in the control group (18.49 ± 1.58 versus 7.51 ± 2.42, P < 0.05). The biomechanical assessment showed no significant differences between the experimental groups and the control group (P > 0.05), and there was no correlation with flap survival.

CONCLUSIONS

Our findings showed that the treatment of flaps with BM-MSC and AAM transplantations significantly promoted flap survival compared to a control group. The viability of the flap was improved by combining BM-MSCs with AAM matrix scaffolds.

Novel skin chamber for rat ischemic flap studies in regenerative wound repair

Background

In plastic surgery, skin flap is an important approach to reconstructive wound repairs. The rat dorsal skin flap is a clinically relevant and popular animal model to investigate and evaluate flap survival and necrosis. Nonetheless, flap survival is often unstable with unpredictable outcomes, regardless of previous attempts at design modification.

Methods & Results

In the present study, we report a novel flap chamber that provides stable and reproducible outcomes by separating the dorsal skin flap from its surrounding skin by in situ immobilization. The flap chamber blocks circulation that disturbs flap ischemia from both basal and lateral sides of the flap tissue. Demarcation of skin necrosis is macroscopically evident on the flap and supported by distinct changes in histological architecture under microscopic examination. The utility of the novel skin flap chamber is further proven by applying it to the examination of flap survival in streptozotocin-induced diabetic rats with an increase in skin necrosis. The flap chamber also affords size modifications where a narrower flap chamber increases ischemia and provides manipulable therapeutic windows for studying cell therapies. Accordingly, intradermal injection of endothelial cells 3 days before flap ischemia significantly increases the survival of skin flaps.

Conclusions

The novel flap chamber not only may stabilize the skin flap and provide reproducible outcomes that overcome the shortfalls of the traditional ischemic flap but also may afford size modifications that support research designs and test therapeutic approaches to regenerative repair.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-016-0333-0) contains supplementary material, which is available to authorized users.

Role of adipose-derived stromal cells in pedicle skin flap survival in experimental animal models

The use of skin flaps in reconstructive surgery is the first-line surgical treatment for the reconstruction of skin defects and is essentially considered the starting point of plastic surgery. Despite their excellent usability, their application includes general surgical risks or possible complications, the primary and most common is necrosis of the flap. To improve flap survival, researchers have used different methods, including the use of adipose-derived stem cells, with significant positive results. In our research we will report the use of adipose-derived stem cells in pedicle skin flap survival based on current literature on various experimental models in animals.

In vivo bioimaging analysis of stromal vascular fraction-assisted fat grafting: the interaction and mutualism of cells and grafted fat

BACKGROUND

Unpredictable survival rate of transplanted fat is an obstacle in application of fat grafting. Although recent researches have suggested that adipose-derived stromal vascular fraction (SVF) could promote grafted fat survival, there has been seldom reports on tracing the dynamic change of grafted fat in vivo and on discussing interaction between transplanted SVFs and surrounding fat graft.

METHODS

Fat tissue and SVF separated from luciferase (Luc)-transgenic rats were applied for bioimaging analysis. The Luc-fat (0.2 mL) was subcutaneously injected into the back of nude mice with or without SVFs from 0.2 mL wild type rat fat, with bioimaging at 63 days. Immunohistochemical staining was performed to evaluate the structural integrity. Moreover, to evaluate the influence of surrounding fat tissue to transplanted SVFs, Luc-SVFs separated from 0.2 mL luciferase fat were transplanted to evaluate the influence of surrounding fat tissue to transplanted SVFs.

RESULTS

The bioimaging results showed that fat tissues transplanted with SVFs had higher survival ratio than those transplanted without SVFs (49.99(5.38)% vs. 32.78(3.32)%; P < 0.001). Stromal vascular fraction-assisted fat grafts had more integral structure and less necrosis cysts. The results showed that, with the existence of grafted fat, transplanted SVF survived for a significantly longer time and could contribute to fat graft survival and regeneration by differentiating into structural cells.

CONCLUSION

The results showed that SVF-assisted fat graft had significantly higher survival rate than that transplanted alone. Moreover, our research demonstrated that interaction between grafted fat and SVFs was important in SVF's long-term living and differentiation.

Disturbed angiogenic activity of adipose-derived stromal cells obtained from patients with coronary artery disease and diabetes mellitus type 2

BACKGROUND

Multipotent mesenchymal stem/stromal cells (MSC) including adipose-derived stromal cells (ADSC) have been successfully applied for cardiovascular diseases treatment. Their regenerative potential is considered due to the multipotency, paracrine activity and immunologic privilege. However, therapeutic efficacy of autologous MSC for myocardial ischemia therapy is modest. We analyzed if ADSC properties are attenuated in patients with chronic diseases such as coronary artery disease (CAD) and diabetes mellitus type 2 (T2DM).

METHODS AND RESULTS

ADSC were isolated from subcutaneous fat tissue of patients without established cardiovascular diseases and metabolic disorders (control group, n = 19), patients with CAD only (n = 32) and patients with CAD and T2DM (n = 28). ADSC phenotype (flow cytometry) was CD90(+)/CD73(+)/CD105(+)/CD45(-)/CD31(-) and they were capable of adipogenic and osteogenic differentiation. ADSC morphology and immunophenotype were similar for all patients, but ADSC from patients with CAD and T2DM had higher proliferation activity and shorter telomeres compared to control patients. ADSC conditioned media stimulated capillary-like tubes formation by endothelial cells (EA.hy926), but this effect significantly decreased for patients with CAD (p = 0.03) and with CAD + T2DM (p = 0.017) compared to the control group. Surprisingly we revealed significantly higher secretion of some pro-angiogenic factors (ELISA) by ADSC: vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF) for patients with CAD and HGF and placental growth factor (PlGF) for patients with CAD + T2DM. Among angiogenesis inhibitors such as thrombospondin-1, endostatin and plasminogen activator inhibitor-1 (PAI-1) level of PAI-1 in ADSC conditioned media was significantly higher for patients with CAD and CAD + T2DM compared to the control group (p < 0.01). Inhibition of PAI-1 in ADSC conditioned media by neutralizing antibodies partially restored ADSC angiogenic activity (p = 0.017).

CONCLUSIONS

ADSC angiogenic activity is significantly declined in patients with CAD and T2DM, which could restrict the effectiveness of autologous ADSC cell therapy in these cohorts of patients. This impairment might be due to the disturbance in coordinated network of pro- and anti-angiogenic growth factors secreted by ADSC. Changes in ADSC secretome differ between patients with CAD and T2DM and further investigation are necessary to reveal the MSC-involved mechanisms of cardiovascular and metabolic diseases and develop novel approaches to their correction using the methods of regenerative medicine.

Implications for human adipose-derived stem cells in plastic surgery

Adipose-derived stem cells (ADSCs) are a subset of mesenchymal stem cells (MSCs) that possess many of the same regenerative properties as other MSCs. However, the ubiquitous presence of ADSCs and their ease of access in human tissue have led to a burgeoning field of research. The plastic surgeon is uniquely positioned to harness this technology because of the relative frequency in which they perform procedures such as liposuction and autologous fat grafting. This review examines the current landscape of ADSC isolation and identification, summarizes the current applications of ADSCs in the field of plastic surgery, discusses the risks associated with their use, current barriers to universal clinical translatability, and surveys the latest research which may help to overcome these obstacles.

The survival condition and immunoregulatory function of adipose stromal vascular fraction (SVF) in the early stage of nonvascularized adipose transplantation

Introduction

Adipose tissue transplantation is one of the standard procedures for soft-tissue augmentation, reconstruction, and rejuvenation. However, it is unknown as to how the graft survives after transplantation. We thus seek out to investigate the roles of different cellular components in the survival of graft.

Materials & Methods

The ratios of stromal vascular fraction (SVF) cellular components from human adipose tissue were evaluated using flow cytometry. Human liposuction aspirates that were either mixed with marked SVF cells or PBS were transplanted into nude mice. The graft was harvested and stained on days 1,4,7 and 14. The inflammation level of both SVF group and Fat-only group were also evaluated.

Results

Flow cytometric analysis showed SVF cells mainly contained blood-derived cells, adipose-derived stromal cells (ASCs), and endothelial cells. Our study revealed that most cells are susceptible to death after transplantation, although CD34+ ASCs can remain viable for 14 days. Notably, we found that ASCs migrated to the peripheral edge of the graft. Moreover, the RT-PCR and the immuno-fluorescence examination revealed that although the SVF did not reduce the number of infiltrating immune cells (macrophages) in the transplant, it does have an immunoregulatory function of up-regulating the expression of CD163 and CD206 and down-regulating that of IL-1β, IL-6.

Conclusions

Our study suggests that the survival of adipose tissue after nonvascularized adipose transplantation may be due to the ASCs in SVF cells. Additionally, the immunoregulatory function of SVF cells may be indirectly contributing to the remolding of adipose transplant, which may lead to SVF-enriched adipose transplantation.

Stem cells in plastic surgery: a review of current clinical and translational applications

BACKGROUND

Stem cells are a unique cell population characterized by self-renewal and cellular differentiation capabilities. These characteristics, among other traits, make them an attractive option for regenerative treatments of tissues defects and for aesthetic procedures in plastic surgery. As research regarding the isolation, culture and behavior of stem cells has progressed, stem cells, particularly adult stem cells, have shown promising results in both translational and clinical applications.

METHODS

The purpose of this review is to evaluate the applications of stem cells in the plastic surgery literature, with particular focus on the advances and limitations of current stem cell therapies. Different key areas amenable to stem cell therapy are addressed in the literature review; these include regeneration of soft tissue, bone, cartilage, and peripheral nerves, as well as wound healing and skin aging.

RESULTS

The reviewed studies demonstrate promising results, with favorable outcomes and minimal complications in the cited cases. In particular, adipose tissue derived stem cell (ADSC) transplants appear to provide effective treatment options for bony and soft tissue defects, and non-healing wounds. ADSCs have also been shown to be useful in aesthetic surgery.

CONCLUSIONS

Further studies involving both the basic and clinical science aspects of stem cell therapies are warranted. In particular, the mechanism of action of stem cells, their interactions with the surrounding microenvironment and their long-term fate require further elucidation. Larger randomized trials are also necessary to demonstrate the continued safety of transplanted stem cells as well as the efficacy of cellular therapies in comparison to the current standards of care.

Neuromodulatory nerve regeneration: adipose tissue-derived stem cells and neurotrophic mediation in peripheral nerve regeneration

Peripheral nerve injury requiring nerve gap reconstruction remains a major problem. In the quest to find an alternative to autogenous nerve graft procedures, attempts have been made to differentiate mesenchymal stem cells into neuronal lineages in vitro and utilize these cellular constructs for nerve regeneration. Unfortunately, this has produced mixed results, with no definitive procedure matching or surpassing traditional nerve grafting procedures. This review presents a different approach to nerve regeneration. The literature was reviewed to evaluate current methods of using adipose-derived stem cells (ADSCs) for peripheral nerve regeneration in in vivo models of animal peripheral nerve injury. The authors present cited evidence for directing nerve regeneration through paracrine effects of ADSCs rather than through in vitro nerve regeneration. The paracrine effects rely mainly, but not solely, on the elaboration of nerve growth factors and neurotrophic mediators that influence surrounding host cells to orchestrate in vivo nerve regeneration. Although this paradigm has been indirectly referred to in a host of publications, few major efforts for this type of neuromodulatory nerve regeneration have been forthcoming. The ADSCs are initially "primed" in vitro using specialized controlled medium (not for neuronal differentiation but for sustainability) and then incorporated into a hydrogel base matrix designed for this purpose. This core matrix is then introduced into a natural collagen-based nerve conduit. The prototype design concepts, evidence for paracrine influences, and regulatory hurdles that are avoided using this approach are discussed.

Improved wound healing of postischemic cutaneous flaps with the use of bone marrow-derived stem cells

OBJECTIVES/HYPOTHESIS

To determine if the intravascular delivery of mesenchymal stem cells improves wound healing and blood perfusion to postischemic cutaneous flap tissues.

STUDY DESIGN

Randomized controlled study.

METHODS

A murine model of a cutaneous flap was created based on the inferior epigastric vessels. Mice (n = 14) underwent 3.5 hours of ischemia followed by reperfusion. Bone marrow stromal cells (BMSCs) 1 × 10(6) were injected intravenously. Wound healing was then assessed measuring percent flap necrosis, flap perfusion, and tensile strength of the flap after a period of 14 days. Localization of BMSCs was determined with radiolabeled and fluorescent labeled BMSCs.

RESULTS

Postischemic cutaneous flap tissues treated with BMSCs demonstrated significantly less necrosis than control flaps (P <0.01). Beginning on postoperative day 5, BMSC-treated flaps demonstrated greater blood perfusion than untreated flaps (P <0.01). Tensile strength of BMSC-treated cutaneous flaps was significantly higher (P <0.01), with a mean strength of 283.4 ± 28.4 N/m than control flaps with a mean of 122.4 ± 23.5 N/m. Radiolabeled BMSCs localized to postischemic flaps compared to untreated tissues (P = 0.001). Fluorescent microscopy revealed incorporation of BMSCs into endothelial and epithelial tissues of postischemic flaps.

CONCLUSIONS

This study demonstrates that the intravascular delivery of BMSCs increases wound healing and promotes flap survival following ischemia-reperfusion injury of cutaneous tissue flaps.

Stromal vascular fraction (SVF) cells enhance long-term survival of autologous fat grafting through the facilitation of M2 macrophages

Optimum perfusion may be the key to the endurance, and hence survival, of autologous adipose tissue transportation. Stromal vascular fraction (SVF) cell therapy can greatly improve the survival of fat grafts by enhancing angiogenesis. However, SVF cells are poorly retained in later stages of SVF-assisted adipose tissue transplant. Therefore, it hardly defines the angiogenic effect through long-term transportation. Adipose tissue suffers from acute hypoxia in the early stage of transportation, leading to the recruitment of macrophages. M2 macrophages enhance angiogenesis in adipose transplantation by acting as an angiogenic signal source, promoting tip cell migration and assisting tip cell fusion. Furthermore, the angiogenic and anti-inflammatory micro-environment in the graft created by M2 macrophages may stimulate the transformation of infiltrating macrophages to M2 macrophages. These M2 macrophages may enhance the long-term retention of graft through angiogenesis. Based on these observations, we postulate that the long-term angiogenic effect of SVF cells may be achieved through the facilitation of the M2 macrophages.

Adipose-Derived Stem Cells in Tissue Regeneration: A Review

In 2001, researchers at the University of California, Los Angeles, described the isolation of a new population of adult stem cells from liposuctioned adipose tissue. These stem cells, now known as adipose-derived stem cells or ADSCs, have gone on to become one of the most popular adult stem cells populations in the fields of stem cell research and regenerative medicine. As of today, thousands of research and clinical articles have been published using ASCs, describing their possible pluripotency in vitro, their uses in regenerative animal models, and their application to the clinic. This paper outlines the progress made in the ASC field since their initial description in 2001, describing their mesodermal, ectodermal, and endodermal potentials both in vitro and in vivo, their use in mediating inflammation and vascularization during tissue regeneration, and their potential for reprogramming into induced pluripotent cells.

The subcutaneous adipose tissue reservoir of functionally active stem cells is reduced in obese patients

It has been demonstrated that the adipose tissue, a highly functional metabolic tissue, is a reservoir of mesenchymal stem cells. The potential use of adipose-derived stem cells (ADSCs) from white adipose tissue (WAT) for organ repair and regeneration has been considered because of their obvious benefits in terms of accessibility and quantity of available sample. However, the functional capability of ADSCs from subjects with different adiposity has not been investigated. It has been our hypothesis that ADSCs from adipose tissue of patients with metabolic syndrome and high adiposity may be functionally impaired. We report that subcutaneous WAT stromal vascular fraction (SVF) from nonobese individuals had a significantly higher number of CD90+ cells than SVF from obese patients. The isolated ADSCs from WAT of obese patients had reduced differentiation potential and were less proangiogenic. Therefore, ADSCs in adipose tissue of obese patients have lower capacity for spontaneous or therapeutic repair than ADSCs from nonobese metabolically normal individuals.