Adipose-derived stem cells accelerate neovascularization in ischaemic diabetic skin flap via expression of hypoxia-inducible factor-1α

Application of Stem Cells Shows Antiinflammatory Effect in an Irradiated Random Pattern Flap Model

BACKGROUND

In reconstructive surgery, local flaps might develop tissue necrosis or partial flap loss especially after previous irradiation, which may be necessary in many tumor entities. The application of stem cells seems promising to improve flap perfusion and might be a possible solution to optimize flap survival.

METHODS

Twenty rats received harvesting of bilateral random pattern fasciocutaneous flaps. The right flaps received 20 Gy ionizing radiation 4 weeks prior to the surgery, while the left flaps served as the non-irradiated control. After flap harvest, four different stem cell mixtures (5 × 106 ASC, ASC-HUVEC, MSC, MSC-HUVEC) were applied under both right and left flaps using 1 mL fibrin glue as the delivery vehicle. Flap size and its necrotic area were examined clinically. Two weeks after the surgery, HE staining and immunohistochemical staining for CD68 and ERG, as well as PCR analysis (Interleukin 6, HIF-1α and VEGF), were performed.

RESULTS

Application of ASCs, ASCs-HUVECs and MSCs resulted in a lower number of CD68-stained cells compared to the no cell group. The expression of Hif1α was higher in the ASC group compared to those in the MSC and previously treated no cell groups. Treatment with MSCs and MSCs-HUVECs prevented shrinking of the flaps in this series.

CONCLUSION

Application of ASCs, MSCs and ASCs-HUVECs was shown to have an antiinflammatory effect. Treatment with MSCs and MSCs-HUVECs can prevent early shrinking of the flaps.

Systematic review of pathologic markers in skin ischemia with and without reperfusion injury in microsurgical reconstruction: Biomarker alterations precede histological structure changes

BACKGROUND

Ischemia and ischemia-reperfusion injury contribute to partial or complete flap necrosis. Traditionally, skin histology has been used to evaluate morphological and structural changes, however histology does not detect early changes. We hypothesize that morphological and structural skin changes in response to ischemia and IRI occur late, and modification of gene and protein expression are the earliest changes in ischemia and IRI.

METHODS

A systematic review was performed in accordance with PRISMA guidelines. Studies reporting skin histology or gene/protein expression changes following ischemia with or without reperfusion injury published between 2002 and 2022 were included. The primary outcomes were descriptive and semi-quantitative histological structural changes, leukocyte infiltration, edema, vessel density; secondary outcomes were quantitative gene and protein expression intensity (PCR and western blot). Model type, experimental intervention, ischemia method and duration, reperfusion duration, biopsy location and time point were collected.

RESULTS

One hundred and one articles were included. Hematoxylin and eosin (H&E) showed inflammatory infiltration in early responses (12-24 h), with structural modifications (3-14 days) and neovascularization (5-14 days) as delayed responses. Immunohistochemistry (IHC) identified angiogenesis (CD31, CD34), apoptosis (TUNEL, caspase-3, Bax/Bcl-2), and protein localization (NF-κB). Gene (PCR) and protein expression (western blot) detected inflammation and apoptosis; endoplasmic reticulum stress/oxidative stress and hypoxia; and neovascularization. The most common markers were TNF-α, IL-6 and IL-1β (inflammation), caspase-3 (apoptosis), VEGF (neovascularization), and HIF-1α (hypoxia).

CONCLUSION

There is no consensus or standard for reporting skin injury during ischemia and IRI. H&E histology is most frequently performed but is primarily descriptive and lacks sensitivity for early skin injury. Immunohistochemistry and gene/protein expression reveal immediate and quantitative cellular responses to skin ischemia and IRI. Future research is needed towards a universally-accepted skin injury scoring system.

ECM proteins and cationic polymers coating promote dedifferentiation of patient-derived mature adipocytes to stem cells

Reprogramming of mature adipocytes is an attractive research area due to the plasticity of these cells. Mature adipocytes can be reprogrammed in vitro, transforming them into dedifferentiated fat cells (DFATs), which are considered a new type of stem cell, and thereby have a high potential for use in tissue engineering and regenerative medicine. However, there are still no reports or findings on in vitro controlling the dedifferentiation. Although ceiling culture performed in related studies is a relatively simple method, its yield is low and does not allow manipulation of mature adipocytes to increase or decrease the dedifferentiation. In this study, to understand the role of physicochemical surface effects on the dedifferentiation of patient-derived mature adipocytes, the surfaces of cell culture flasks were coated with extracellular matrix, basement membrane proteins, and cationic/anionic polymers. Extracellular matrix such as fibronectin and collagen type I, and basement membrane proteins such as collagen type IV and laminin strongly promoted dedifferentiation of mature adipocytes, with laminin showing the highest effect with a DFAT ratio of 2.98 (±0.84). Interestingly, cationic polymers also showed a high dedifferentiation effect, but anionic polymers did not, and poly(diallyl dimethylammonium chloride) showed the highest DFAT ratio of 2.27 (±2.8) among the cationic polymers. Protein assay results revealed that serum proteins were strongly adsorbed on the surfaces of the cationic polymer coating, including inducing high mature adipocyte adhesion. This study demonstrates for the first time the possibility of regulating the transformation of mature adipocytes to DFAT stem cells by controlling the physicochemical properties of the surface of conventional cell culture flasks.

Chorioallantoic Membrane Assay at the Cross-Roads of Adipose-Tissue-Derived Stem Cell Research

With a history of more than 100 years of different applications in various scientific fields, the chicken chorioallantoic membrane (CAM) assay has proven itself to be an exceptional scientific model that meets the requirements of the replacement, reduction, and refinement principle (3R principle). As one of three extraembryonic avian membranes, the CAM is responsible for fetal respiration, metabolism, and protection. The model provides a unique constellation of immunological, vascular, and extracellular properties while being affordable and reliable at the same time. It can be utilized for research purposes in cancer biology, angiogenesis, virology, and toxicology and has recently been used for biochemistry, pharmaceutical research, and stem cell biology. Stem cells and, in particular, mesenchymal stem cells derived from adipose tissue (ADSCs) are emerging subjects for novel therapeutic strategies in the fields of tissue regeneration and personalized medicine. Because of their easy accessibility, differentiation profile, immunomodulatory properties, and cytokine repertoire, ADSCs have already been established for different preclinical applications in the files mentioned above. In this review, we aim to highlight and identify some of the cross-sections for the potential utilization of the CAM model for ADSC studies with a focus on wound healing and tissue engineering, as well as oncological research, e.g., sarcomas. Hereby, the focus lies on the combination of existing evidence and experience of such intersections with a potential utilization of the CAM model for further research on ADSCs.

Extracellular Vesicles Isolated From Hypoxia-Preconditioned Adipose-Derived Stem Cells Promote Hypoxia-Inducible Factor 1α-Mediated Neovascularization of Random Skin Flap in Rats

BACKGROUND

Random flaps are widely used for wound repair. However, flap necrosis is a serious complication leading to the failure of operation. Our previous study demonstrated a great proangiogenic potential of hypoxia-treated adipose-derived stem cells-extracellular vesicles (HT-ASC-EVs). Thus, we aim to evaluate the effect of HT-ASC-EVs in the survival and angiogenesis of random skin flap in rats.

METHODS

Adipose-derived stem cells-extracellular vesicles were respectively isolated from adipose-derived stem cell culture medium of 3 donors via ultracentrifugation. The expression of hypoxia-inducible factor 1α (HIF-1α) and proangiogenic potential of HT-ASC-EVs and ASC-EVs were compared by co-culturing with human umbilical vein endothelial cells. Forty male Sprague-Dawley rats were randomly divided into 3 group (n = 10/group). A 9 × 3-cm random skin flap was separated from the underlying fascia with both sacral arteries sectioned on each rat. The survival and angiogenesis of flaps treated by ASC-EVs or HT-ASC-EVs were also compared. Laser Doppler flowmetry and immunohistochemistry were used to evaluate skin perfusion and angiogenesis of skin flaps on postoperative day 7.

RESULTS

Hypoxia-treated adipose-derived stem cells-extracellular vesicles further improve the proliferation, migration, tube formation with upregulated HIF-1α, and VEGF expression of human umbilical vein endothelial cells in vitro, compared with ASC-EVs. In vivo, postoperatively injecting HT-ASC-EVs suppressed necrosis rate (29.1 ± 2.8% vs 59.2 ± 2.1%) and promoted the angiogenesis of skin flap including improved skin perfusion (803.2 ± 24.3 vs 556.3 ± 26.7 perfusion unit), increased number of CD31-positive cells, and upregulated expression of HIF-1α in vascular endothelium on postoperative day 7, compared with ASC-EVs.

CONCLUSIONS

Intradermal injecting HT-ASC-EVs improve the survival of random skin flap by promoting HIF-1α-mediated angiogenesis in rat model.

The Effect of Adipose Derived Stromal Vascular Fraction on Flap Viability in Experimental Diabetes Mellitus and Chronic Renal Disease

BACKGROUND

The presence of chronic renal disease(CRD) concurrently with diabetes mellitus(DM) increases the flap failure. Adipose derived stromal vascular fraction (SVF) is known to enhance skin flap viability in both healthy and diabetic individuals. The aim of this experimental study was to investigate the effect of SVF on skin flap viability in rats with DM and CRD.

METHODS

48 Sprague-Dawley rats were separated into four groups as follows: group I (control), group II (diabetes mellitus), group III (chronic renal disease), and group IV (diabetes with chronic renal disease).Two dorsal flaps were elevated. Flaps on left side of all groups received 0.5 cc of SVF, while same amount of plasma-buffered saline (PBS) was injected into right side. On postoperative day 7, flaps were harvested for macroscopic, histopathologic and biochemical assessments. Areas of flap survival were measured macroscopically. Blood level of vascular endothelial growth factor (VEGF) was measured after injection of SVF.

RESULTS

Macroscopically, SVF has significantly improved flap viability (p < 0.05). Flap viability percentage was lower in DM and CRD groups when compared with healthy control group. In respect of new capillary formation, there was a statistically significant difference between SVF injected flaps and PBS injected sides (p < 0.05). Similarly, VEGF levels were higher in all study groups and there was a significant difference in comparison to control group (p < 0.05).

CONCLUSIONS

The study showed that injection of SVF increased flap viability via endothelial differentiation and neovascularization. In vivo function of stem cells might be impaired due to uremia and diabetes-related microenviromental changes.

Human stem cells prevent flap necrosis in preclinical animal models: A systematic review

Background and Aim

Adipose-derived mesenchymal stem cells (ADSCs) have been proven effective to prevent distal skin flap necrosis in preclinical models. However, to appropriately translate these findings to clinical trials, the effect of ADSC of human origin (hADSC) needs to be evaluated. We hypothesize that hADSC treatment is as effective as animal ADSC treatment at preventing distal skin flap necrosis in animal flap models.

Methods

Three databases were inquired on August 17, 2020, to evaluate the necrotic flap area after using hADSCs in animal models of ischemic flaps. No publication status or dates were considered. Studies were included if they used hADSCs, measured the surviving or necrotic skin area of flaps, used animal models, and were in English. Studies were excluded if they did not use cells of human origin. The flap survival or necrotic area, perfusion, capillary density, vascular endothelial growth factor secretion and HIF-1α expression were extracted.

Results

Ten studies met inclusion criteria. The mean absolute risk reduction (ARR) in necrotic skin area was 22.37% (95% confidence interval [CI] 16.98-27.76%, P<0.05) for flaps treated with animal ADSCs and 18.04% (95% CI 2.74-33.33%, P<0.05) for flaps treated with hADSCs. The difference between mean ARRs was not statistically significant (4.33%, 95% CI - 34.47-43.13%, P>0.05).

Conclusion

Human ADSCs prevent skin flap necrosis to the same degree as animal ADSCs in rodent and rabbit flap models.

Relevance for Patients

This review found that adipose-derived stem cells of human origin are equally effective at reducing the risk of surgical flap necrosis in preclinical models of small animals as autologous animal cells. The findings in this review should encourage researchers to use human adipose-derived stem cells in animal models of ischemic flaps to accelerate their translation into clinical trials and, eventually, surgical practice. The low immunogenicity of these cells should be leveraged to gain insight into the effects of the products that will be ultimately administered to patients. Furthermore, human adipose-derived stem cells' pro-angiogenic mechanism of action sets this therapy as a promising preventive measure for flap necrosis.

The influence of adipocyte-derived stem cells (ASCs) on the ischemic epigastric flap survival in diabetic rats

Purpose:

To assess the effects of adipocyte-derived stem cell (ASC)-injection on the survival of surgical flaps under ischemia in diabetic rats.

Methods:

Diabetes was induced in 30 male Wistar rats using streptozotocin (55 mg/kg). After eight weeks, epigastric flap (EF) surgery was performed. The animals were divided into control (CG), medium-solution (MG), and ASC groups. The outcomes were: the survival area (SA), the survival/total area rate (S/TR), and expression levels (EL) of genes: C5ar1, Icam1, Nos2, Vegf-a.

Results:

In the ASC group, compared to CG, we observed improved flap SA (CG-420 mm²vs. ASC-720 mm²; p=0.003) was observed. The S/TR analysis was larger in the ASC group (78%) than the CG (45%). This study showed an increase in the Vegf-a EL in the ASC group (2.3) vs. CG (0.93, p=0.0008). The Nos2 EL increased four-fold in the ASC group compared to CG, and C5ar1 EL decreased almost two-fold in the ASC group vs. the CG (p=0.02). There was no difference among the groups regarding Icam1 EL. Compared to the MG, the ASC group had a bigger flap SA (720 mm²vs. 301 mm², respectively), a bigger S/TR (78% vs. 32%, p=0.06, respectively) and increased EL of Vegf-a (2.3 vs. 1.3, respectively). No difference between ASC-group and MG was seen regarding Nos2 (p=0.08) and C5ar1 (p=0.05).

Conclusions:

This study suggests that ASCs increase the survival of EF under IR in diabetic rats.

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.

Hypoxia Promotes Adipose-Derived Stem Cells to Protect Human Dermal Microvascular Endothelial Cells Against Hypoxia/Reoxygenation Injury

BACKGROUND

Microcirculation is important for regulating ischemia-reperfusion (I/R) injury associated with skin flap transplantation surgery. We investigated whether co-culture with adipose-derived stem cells (ADSCs) could protect human dermal microvascular endothelial cells (HDMECs) from I/R injury by inhibiting cell apoptosis and enhancing cell proliferation. We also investigated the effects of hypoxic preconditioning on ADSCs.

MATERIALS AND METHODS

HDMECs were divided into four groups, control, HDMECs in normoxic culture conditions; hypoxia/reoxygenation (H/R), HDMECs in a hypoxic incubator for 8 h then in saturated aerobic culture medium for 24 h; H/R + ADSC(N), HDMECs treated similar to the H/R group then co-cultured with normoxic ADSCs; and H/R + ADSC(H), HDMECs treated similar to the H/R group then co-cultured with hypoxia preconditioned ADSCs.

RESULTS

The rate of HDMECs apoptosis significantly increased in the H/R group, but decreased upon co-culture with ADSCs for 24 h, especially in the H/R + ADSC(H) group. Co-culture with ADSCs, especially hypoxia preconditioned ADSCs, significantly enhanced cell proliferation ability compared with that of the H/R group after 48 h and 72 h, but not after 24 h. Vascular endothelial growth factor levels were significantly higher in the H/R + ADSC(N) and H/R + ADSC(H) groups than in the H/R group.

CONCLUSIONS

ADSCs attenuated H/R injury in endothelial cells by promoting proliferation ability and reducing apoptosis, with an increase in Vascular endothelial growth factor level, especially in the context of hypoxic preconditioning. This approach suggests the potential for an easy and safe method to reduce I/R injury associated with skin flap transplantation surgery.

Adipose-derived mesenchymal stem cells inhibit cell proliferation and migration and suppress extracellular matrix synthesis in hypertrophic-scar and keloid fibroblasts

Pathological scars occur during skin wound healing, and the use of adipose-derived stem cells (ADSCs) is one of the various treatments. The present study aimed to investigate the in vitro effects of ADSCs on the biological properties of hypertrophic scar fibroblasts (HSFs) and keloid fibroblasts (KFs), such as proliferation, migration, and the synthesis of extracellular matrix proteins. Transwell chambers were used to establish a co-culture system of ADSCs with normal skin fibroblasts (NFs), HSFs or KFs. The effect of ADSCs on the proliferation of fibroblasts was evaluated by CCK8 measurement, while the migration ability of fibroblasts was assessed using cell scratch assay. The expression of extracellular matrix proteins was measured by immunoblotting. Co-culture of NFs with ADSCs did not affect cell proliferation and migration, nor the expression of extracellular matrix proteins [collagen-I, collagen-III, fibronectin (FN) and α-smooth muscle actin (α-SMA)] in NFs. However, as with the inhibitor SB431542, ADSCs significantly inhibited cell proliferation and migration and the expression of extracellular matrix proteins (collagen-I, collagen-III, FN and α-SMA), but also suppressed the protein expression of transforming growth factor β1 (TGF-β1), phosphorylated (p-) mothers against decapentaplegic homolog (Smad) 2, p-Smad3 and Smad7 in HSFs and KFs. The results show that ADSCs inhibited cell proliferation and migration and the expression of extracellular matrix proteins in HSCs and KFs in vitro, possibly through inhibition of the TGF-β1/Smad pathway.

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.

An In Vitro Study on Extracellular Vesicles From Adipose-Derived Mesenchymal Stem Cells in Protecting Stress Urinary Incontinence Through MicroRNA-93/F3 Axis

Since the potential roles of extracellular vesicles secreted by adipose-derived mesenchymal stem cells (ADSCs) are not well understood in collagen metabolism, the purpose of this research was to evaluate the effects of ADSCs-extracellular vesicles in stress urinary incontinence and the regulatory mechanism of delivered microRNA-93 (miR-93). ADSCs were isolated and cultured, and ADSCs-extracellular vesicles were extracted and identified. Stress urinary incontinence primary fibroblasts or satellite cells were treated with ADSCs-extracellular vesicles to detect the expression of Elastin, Collagen I, and Collagen III in fibroblasts and Pax7 and MyoD in satellite cells. After transfecting ADSCs with miR-93 mimics or inhibitors, extracellular vesicles were isolated and treated with stress urinary incontinence primary fibroblasts or satellite cells to observe cell function changes. The online prediction and luciferase activity assay confirmed the targeting relationship between miR-93 and coagulation factor III (F3). The rescue experiment verified the role of ADSCs-extracellular vesicles carrying miR-93 in stress urinary incontinence primary fibroblasts and satellite cells by targeting F3. ADSCs-extracellular vesicles treatment upregulated expression of Elastin, Collagen I, and Collagen III in stress urinary incontinence primary fibroblasts and expression of Pax7 and MyoD in stress urinary incontinence primary satellite cells. miR-93 expression was increased in stress urinary incontinence primary fibroblasts or satellite cells treated with ADSCs-extracellular vesicles. Extracellular vesicles secreted by ADSCs could deliver miR-93 to fibroblasts and then negatively regulate F3 expression; ADSCs-extracellular vesicles could reverse the effect of F3 on extracellular matrix remodeling in stress urinary incontinence fibroblasts. miR-93 expression was also increased in stress urinary incontinence primary satellite cells treated by ADSCs-extracellular vesicles. Extracellular vesicles secreted by ADSCs were delivered to satellite cells through miR-93, which directly targets F3 expression and upregulates Pax7 and MyoD expression in satellite cells. Our study indicates that miR-93 delivered by ADSCs-extracellular vesicles could regulate extracellular matrix remodeling of stress urinary incontinence fibroblasts and promote activation of stress urinary incontinence satellite cells through targeting F3.

A clinical perspective on adipose-derived cell therapy for enhancing microvascular health and function: Implications and applications for reconstructive surgery

Restoration of form and function requires apposition of tissues in the form of flaps to reconstitute local perfusion. Successful reconstruction relies on flap survival and its integration with the recipient bed. The flap's precariously perfused hypoxic areas undergo adaptive microvascular changes both internally and in connection with the recipient bed. A cell-mediated, coordinated response to hypoxia drives these adaptive processes, restoring a tissue's normoxic homeostasis via de novo vasculogenesis, sprouting angiogenesis, and stabilizing arterialization. As cells exert prolonged and coordinated effects on site, their use as biological agents merit translational consideration of sourcing angio-competent cells and delivering them to territories enduring microcirculatory acclimatization. Angio-competent cells abound in adipose tissue: a reliable, accessible, and expendable source of adipose-derived cells (ADC). When subject to enzymatic digestion and centrifugation, adipose tissue separates its various ADC: A subset of buoyant oil-dense adipocytes (the tissue's parenchymal component) accumulates on a supra-natant layer, whereas the mesenchymal component remains in the infra-natant sediment, containing the tissue's stromal vascular fraction (SVF), where angio-component cells abound. The SVF can be further manipulated, selected, or culture expanded into more specific stromal subsets (herein defined as adipose stromal cells, ASC). While promising clinical applications for ADC await clinical proof and regulatory authorization, basic science investigation is needed to elucidate the specific ADC mechanisms that influence microvascular growth, remodeling, and function following flap surgery. The objective of this article is to share the clinical perspectives of reconstructive plastic surgeons regarding the use of ADC-based therapies to help with flap tissue integration, revascularization, and wound healing. Specifically, the focus will be on considering the potential for ADC as therapeutic agents and how their clinical application motivates basic science opportunities.

Protective effects of dexmedetomidine on the survival of random flaps

BACKGROUND

Random flaps can be used to repair wounds and improve shape and functional reconstruction, but inflammation and necrosis limit their application. Modified McFarlane flap models were constructed on the backs of rats. We hypothesized that dexmedetomidine (DEX) could improve the survival rate of ischemic random flaps.

METHODS

Sixty rats were randomly divided into three groups: a low-dose DEX group (DEX-L group, 10 μg/kg/D), a high-dose DEX group (DEX-H group, 20 μg/kg/D) and a control group (0.9 % saline equivalent). On day 7 after flap construction, the survival percentage of the flap model was calculated. Hematoxylin and eosin staining (H&E) was used to evaluate the histopathological status of the flaps and microvessel density (MVD). Lead oxide/gelatin angiography was used to detect angiogenesis, and laser Doppler flow imaging (LDF) was used to detect blood perfusion. The levels of superoxide dismutase (SOD) and malondialdehyde (MDA) in the middle areas of the flaps were measured to show the level of oxidative stress. The expressions of Toll-like receptor (TLR4), nuclear factor-kappa B (NF-κB), interleukin (IL)-1β, IL-6, tumor necrosis factor-α (TNF-α) and vascular endothelial growth factor (VEGF) were detected by immunohistochemistry.

RESULTS

DEX significantly increased the average survival percentage of the flaps and reduced ischemia and necrosis of the distal end of the flaps. SOD activity significantly increased, while MDA significantly decreased, indicating that DEX reduces oxidative damage. The expression of inflammatory immunoregulatory proteins (TLR4, NF-κB) was downregulated, and the levels of inflammatory factors (IL-1β, IL-6 and TNF-α) were lower. In addition, DEX upregulated VEGF expression, promoted angiogenesis, and increased blood perfusion.

CONCLUSION

In random flap transplantation, a high dose of DEX is beneficial to flap survival.

Adipogenesis for soft tissue reconstruction

PURPOSE OF REVIEW

It has been increasingly common to use adipose tissue for regenerative and reconstructive purposes. Applications of autologous fat transfer and different stem cell therapies have significant limitations and adipose tissue engineering may have the potential to be an important strategy in the reconstruction of large tissue defects. A better understanding of adipogenesis will help to develop strategies to make adipose tissue more effective for repairing volumetric defects.

RECENT FINDINGS

We provide an overview of the current applications of adipose tissue transfer and cellular therapy methods for soft tissue reconstruction, cellular physiology, and factors influencing adipogenesis, and adipose tissue engineering. Furthermore, we discuss mechanical properties and vascularization strategies of engineered adipose tissue, and its potential applications in the clinical settings.

SUMMARY

Autologous fat tissue transfer is the standard of care technique for the majority of surgeons; however, high resorption rates, poor perfusion within a large volume fat graft and widely inconsistent graft survival are the main limitations. Adipose tissue engineering is a promising field to reach the first goal of producing adipose tissue which has more predictable survival and higher graft retention rates. Advancements of scaffold and vascularization strategies will contribute to metabolically and functionally more relevant adipose tissue engineering.

Transplantation of Adipose-Derived Stem Cells Before Flap Expansion and After Expanded Flap Elevation Result in Different Effects

BACKGROUND

Studies of using mesenchymal stem cells to assist skin and soft tissue expansion have shown that stem cells can improve expansion efficiency through promoting tissue regeneration. However, the issue that whether the flap viability is also improved is unknown.

METHODS

Sixteen pigs were equally divided into 2 groups. A pair of 150 mL expanders was symmetrically inserted into each pig's dorsum. Group 1 received adipose-derived stem cells (ADSCs) injection before expansion, and group 2 received ADSCs grafting after flap elevation. After 4 weeks' expansion, a random flap measuring 2 cm × 16 cm was elevated along the long axis of each expanded flap on the pigs' back. Flap viability was measured at postoperative day 7. Histological analysis and cell tracking were performed. The expression of vascular endothelial growth factor was determined.

RESULTS

The flap viability of the ADSCs-grafted expanded flap (75.5 ± 6.6%) was similar to the control (69.4 ± 8.4%) in group 1 (transplantation before expansion). However, in group 2 (transplantation after flap elevation), the ADSCs-grafted expanded flap had a higher flap viability (92.6 ± 5.7%) compared with control (66.2 ± 7.4%). Moreover, the ADSCs-grafted expanded flap in group 1 showed increased skin thickness, collagen content, cells proliferation, vascularization, and vascular endothelial growth factor expression. Cell tracking showed that the positively stained cell differentiating into an endotheliocyte could be seen in group 2.

CONCLUSIONS

Transplantation of ADSCs before tissue expansion does not improve flap viability but can promote tissue regeneration. Injection of ADSCs after flap elevation can increase the surviving rate of the expanded flap.

Stem cell therapy for chronic skin wounds in the era of personalized medicine: From bench to bedside

With the significant financial burden of chronic cutaneous wounds on the healthcare system, not to the personal burden mention on those individuals afflicted, it has become increasingly essential to improve our clinical treatments. This requires the translation of the most recent benchtop approaches to clinical wound repair as our current treatment modalities have proven insufficient. The most promising potential treatment options rely on stem cell-based therapies. Stem cell proliferation and signaling play crucial roles in every phase of the wound healing process and chronic wounds are often associated with impaired stem cell function. Clinical approaches involving stem cells could thus be utilized in some cases to improve a body's inhibited healing capacity. We aim to present the laboratory research behind the mechanisms and effects of this technology as well as current clinical trials which showcase their therapeutic potential. Given the current problems and complications presented by chronic wounds, we hope to show that developing the clinical applications of stem cell therapies is the rational next step in improving wound care.

Mesenchymal stem cells improve survival in ischemic diabetic random skin flap via increased angiogenesis and VEGF expression

Random skin flaps (RSFs) are cutaneous flaps. Despite the negative impact of diabetes mellitus (DM) on RSF viability, they are commonly used in diabetic patients. In this study, we have assessed bone marrow mesenchymal stem cell (BMMSC) treatment on RSF survival, tensiometrical parameters, angiogenesis, and mast cells (MCs) count in an ischemic RSF model in rats with type 1 DM (T1DM). We induced T1DM in 30 Wistar adult male rats. The animals were assigned to three groups of 10 rats per group as follows: group 1 (control); group 2 (placebo), and group 3 (BMMSCs). A 30  ×  80  mm RSF was created in each rat. On day 7, we measured the viable portion of each RSF. A sample was taken for histological and immunohistochemistry studies, fibroblasts, MCs, angiogenesis, collagen bundle density, and the presence of vascular endothelial growth factor (VEGF)+ cells. An additional sample was taken to evaluate the flap's incision strength. Treatment with BMMSCs (17.8  ±  0.37) significantly increased RSF survival compared with the control (13.3  ±  0.35) and placebo (16.1  ±  0.27) groups (one-way analysis of variance, P  =  .000; least significant difference, P  =  .000, P  =  .002). There was a significant improvement in angiogenesis, as confirmed by stereologic examination. Assessment of VEGF+ cells showed prominent neovascularization in BMMSC-treated RSFs compared with the control and placebo groups. Subdermal injection of BMMSC significantly increased ischemic RSF survival as a result of stimulated neovascularization in T1DM rats. Treatment of diabetic RSF with BMMSCs showed no beneficial effects in the fibroblast number and biomechanical parameters for the repair of ischemic wounds in the rat model. Treatment with BMMSCs significantly increased collagen bundle density.

Hypoxia promotes differentiation of adipose-derived stem cells into endothelial cells through demethylation of ephrinB2

Background

Delivery of endothelial cells into the ischemic tissue is emerging as an alternative approach in revascularization of injured tissues by means of angiogenesis to restore organ function. Adipose-derived stem cells (ASCs) are a readily accessible source of the mesenchymal stem cell with rapid expansion and multidifferentiation potential. The view has emerged that endothelial cells (ECs) differentiated from ASCs is a step forward for adult vascular repair in regenerative medicine and construction of the blood vessel by tissue engineering approach.

Methods

In this study, differentiation of human ASCs (hASCs) into vascular EC lineage was induced by combined treatment of vascular endothelial growth factor (VEGF) and bone morphogenetic protein-4 (BMP4) under hypoxia condition. The expression of CD31, VEGF-R2, and VE-cadherin was determined by immunofluorescent staining, real-time PCR, and western blot analysis. These differentiated cells acquired functional characteristics of mature ECs as determined by their tube formation ability, DiI-ac-LDL uptake, and nitric oxide secretion in vitro. The methylation status in the proximal promoter CpGs was determined by bisulfite sequencing.

Results

hASCs expressed endothelial cell markers including CD31, VEGF-R2, and VE-cadherin by combined treatment of VEGF and BMP4 under hypoxia condition. These differentiated cells exhibited the angiogenesis potential in vitro, and injection of these differentiated cells enhanced angiogenesis in the ischemic hindlimb of diabetic mice. Furthermore, it was found that hypoxia increased significantly EphrinB2 expression EC differentiation, which is greatly downregulated with EphrinB2 blockage. The methylation status in the proximal promoter CpG results showed that methylation of EphrinB2 promoter decreased in hASCs with exposure to hypoxia.

Conclusion

Our data demonstrate that hASCs can be efficiently induced to differentiate into vascular EC lineages which are mediated by demethylation of ephrinB2 under hypoxia condition.

Effect of human adipose-derived regenerative cells on temporomandibular joint healing in immunodeficient rabbits

Increasing research attention has focused on the use of stem cells (SCs) in regenerative and reparative medicine. Adipose-derived regenerative cells (ADRCs) are a relatively cheap and ethical source of SCs. Temporomandibular disorders (TMDs) have been reported with rising incidence over recent decades. The main aims of this study were to evaluate the effects of ADRCs application on the healing of both soft and hard temporomandibular joint (TMJ) tissues, and to assess the possible utilization of ADRCs in TMD treatment. We investigated the effects of human ADRCs on the healing of TMJ defects in immunodeficient rabbits. With no prior cultivation, ADRCs were applied to a surgically created defect in the cartilage of a rabbit TMJ. The healing process and inflammatory response were examined. Our results indicated that ADRCs supported repair processes in soft tissues. However, ADRC treatment induced a significant immune response in both soft and hard tissues, with hard tissues showing a higher level of bone remodelling. Non-differentiated ADRCs can be a promising tool for regenerative medicine of TMJ; however, deeper understanding of their effect on the cellular level is needed.

Assisting Rapid Soft-Tissue Expansion with Adipose-Derived Stem Cells: An Experimental Study in a Pig Model

BACKGROUND

Rapid tissue expansion has been attempted, aiming at shortening the period of conventional expansion. However, it has scarcely been clinically applied because of its drawbacks such as low expansion efficiency and tissue destruction. Adipose-derived stem cell transplantation is a promising therapeutic method in regenerative medicine. However, its effects on rapid expansion remain poorly understood.

METHODS

Twenty-four expanders were implanted in the dorsum of 12 pigs. Rapid expansion persisted for 1 week with 20 ml of saline daily. The increased area of the expanded skin was measured. Histologic and ultrastructural analysis and cell tracking were performed. The expression of vascular endothelial growth factor, fibroblast growth factor-2, and epidermal growth factor was also determined.

RESULTS

The increased area of adipose-derived stem cell-grafted expanded skin (0.91 ± 0.06 cm) was significantly more than the non-adipose-derived stem cell-treated control (0.51 ± 0.05 cm) (p < 0.01). Enhanced tissue regeneration in the adipose-derived stem cell-grafted expanded skin was evidenced by increased skin thickness, proliferating cells, extracellular matrix, and vascularization (113 ± 19/mm versus control 59 ± 14/mm) (all p < 0.05). Higher expression of vascular endothelial growth factor and epidermal growth factor was observed in the adipose-derived stem cell-transplanted expanded skin (p < 0.01 and p < 0.05, respectively), whereas the expression of fibroblast growth factor-2 was higher in the non-adipose-derived stem cell-treated control (p < 0.05). Transmission electron microscopy showed that a high density of collagen fibers could be seen in the adipose-derived stem cell-treated expanded skin. Cell tracking showed that the positively stained cells could be seen.

CONCLUSION

For rapid tissue expansion, adipose-derived stem cell transplantation may limit tissue destruction and improve the expansion efficiency by promoting tissue regeneration.

All-trans retinoic acid improves the viability of ischemic skin flaps in diabetic rat models

AIMS

Endothelial progenitor cells (EPCs) play a critical role in neovascularization, which enhances proliferation under all-trans retinoic acid (ATRA) treatment. However, the effects of ATRA on the skin flap survival in diabetic flap ischemia remains unknown.

METHODS

Ischemic random skin flaps were made in 40 diabetic Sprague-Dawley rats with 20 normal rats used as control in this study. At 7 days postoperatively, the surviving area of each skin flap was measured. Immunofluorescence staining was used to analyze capillary density and EPCs recruited to the flaps. The expression of ANG2 and VEGF was determined by Western blotting. Circulating EPC number was determined by flow cytometry. In vitro tube formation experiment was used to analyze the function of EPCs.

RESULTS

The flap survival rate and capillary density of ATRA-treated flap were significantly increased. Fluorescence-activated cell sorting (FACS) analysis demonstrated a marked increase in systemic CD34+/Flk-1+ EPCs in ATRA-treated rat. The expression of ANG2 and VEGF was increased in diabetic flap tissues under ATRA administration. Furthermore, ATRA administration restored the impaired function of diabetic EPCs in tube formation.

CONCLUSION

ATRA could notably exert preventive effects against skin flap necrosis and promote neovascularization in diabetic rats, which may partially through elevating the expression of ANG2 and VEGF, and augmenting EPC mobilization.

CD54+ rabbit adipose-derived stem cells overexpressing HIF-1α facilitate vascularized fat flap regeneration

Fat flap transplantation is frequently performed in patients suffering from soft tissue defects resulting from disease or trauma. This study explored the feasibility of constructing vascularized fat flaps using rabbit adipose-derived stem cells (rASCs) and collagen scaffolds in a rabbit model. We evaluated rASCs proliferation, paracrine function, adipogenesis, vascularization, and CD54 expression, with or without HIF-1α transfection in vitro and in vivo. We observed that adipogenic differentiation potential was greater in rASCs with high CD54 expression (CD54⁺rASCs) than in those with low expression (CD54^–rASCs), both in vitro and in vivo. HIF-1α overexpression not only augmented this effect, but also enhanced cell proliferation and paracrine function in vitro. We also demonstrated that HIF-1α-transfected CD54⁺rASCs showed enhanced paracrine function and adipogenic capacity, and that paracrine function increases expression of angiogenesis-related markers. Thus, CD54⁺rASCs overexpressing HIF-1α enhanced large volume vascularized fat flap regeneration in rabbits, suggesting CD54 may be an ideal candidate marker for ASCs adipogenic differentiation.

Adipose-derived stem cells improve full-thickness skin grafts in a rat model

To investigate the effects of heterologous adipose-derived stem cells (ADSCs) on autologous full-thickness skin grafts, we designed a first-intention healing model using Wistar rats. We harvested and sutured two full-thickness skin grafts in the dorsal recipient beds of 15 rats, randomized into three groups. In the treatment group, 1 × 10⁶ ADSCs resuspended in saline solution (200 μL) were administered subcutaneously to the skin graft. The control group received only saline solution subcutaneously, whereas the negative control group did not receive any treatment. Compressive dressings were maintained until postoperative day 5. The grafts were assessed by two observers, who checked for the presence of epidermolysis on day 14. Planimetry showed the relative areas of normal skin, redness, ulceration, and contraction. Graft samples were obtained on day 14 and stained with hematoxylin and eosin and Masson's trichrome. Epidermal analysis evaluated thickening, keratosis, acanthosis, hydropic degeneration, and inflammatory infiltrate. Dermal evaluation investigated the absence of hair follicles, granulation tissue formation, presence of inflammatory infiltrate, and collagen deposition. Immunohistochemistry was performed for dermal anti-VEGF and epidermal anti-Ki-67 staining. The ADSC group presented better macroscopic aspects, lower incidence of epidermolysis, and less loss of hair follicles. In addition, the ADSC group presented the lowest frequency of histopathological changes in the dermis and epidermis, as well as the largest subcutaneous and granulation tissue VEGF averages and the weakest Ki-67 staining of the epidermal basal layer. Subcutaneous administration of ADSCs may improve the integration of skin grafts, reducing the deleterious effects of ischemia and reperfusion injury.

In vivo study of a bioactive nanoparticle-gelatin composite scaffold for bone defect repair in rabbits

The purpose is to study the in vivo bioactivity of this scaffold and verify its ability to simulate the characteristics of cancellous bone. Twenty-four adult New Zealand white rabbits were divided into three groups. Bone defects above the femoral condylar of both sides were created. A newly designed bioactive nanoparticle-gelatin composite scaffold was implanted to the experimental side, while the control side was left without implantation. The repair of bone defect was monitored by X-ray examination, gross observation, Micro-CT examination and histological observation of the area of bone defect 4, 8 and 12 weeks after surgery. There was void of new bone tissue in medullary cavity in the bone defect area of the control side. In the experimental side, the composite scaffold displayed excellent biodegradability, bioactivity and cyto-compatibility. With the time laps, new bone tissue grew from the edge to center as revealed by both Micro-CT image and staining biopsy, which complies with the "creeping substitution" process. The mechanical properties of the newly designed bioactive nanoparticle-gelatin composite scaffold and the 3-D structure of new bone tissue are comparable to the surrounding cancellous bones. This newly developed bioactive nanoparticle-gelatin composite scaffold possesses good biocompatibility and in vivo osteogenic capability for bone defect repair. It may be a promising artificial bone grafts.

Detrimental effect of Hypoxia-inducible factor-1α-induced autophagy on multiterritory perforator flap survival in rats

Hypoxia-inducible factor-1α (HIF-1α) plays a key role in angiogenesis, improves flap survival, and activates autophagy. The effect of HIF-1α-induced autophagy is still debatable. Thus, we investigated the effect of HIF-1α-induced autophagy on multiterritory perforator flap survival. In this study, 99 male Sprague-Dawley rats received multiterritory perforator flap procedure and were divided into three groups with 33 each. The dimethyloxalylglycine (DMOG) plus 3-methyladenine (3-MA) group received intraperitoneal injection of DMOG (40 mg/kg) and 3-MA (10 mg/kg). The DMOG group and control group received comparative DMOG and saline respectively. On postoperative day (POD) 7, HIF-1α’s activities of flap survival and perfusion improvement were confirmed in DMOG group, however, its positive effects were further enhanced by co-administration of autophagy inhibitor, 3-MA. On POD 1, vascular endothelial growth factor, mean microvascular density and blood perfusion were not affected by HIF-1α up-regulation or autophagy inactivation. However, HIF-1α-induced autophagy augments apoptosis and oxidative stress. The increased level of apoptosis and oxidative stress was reversed by 3-MA and resulted in further flap survival improvement. In conclusion, HIF-1α-induced autophagy has a detrimental effect on multiterritory perforator flap survival and the flap survival was determined by the combined effects of ischemia and reperfusion injury.

Human adipose-derived stem cell spheroid treated with photobiomodulation irradiation accelerates tissue regeneration in mouse model of skin flap ischemia

Skin flap grafting is a form of transplantation widely used in plastic surgery. However, ischemia/reperfusion injury is the main factor which reduces the survival rate of flaps following grafting. We investigated whether photobiomodulation (PBM) precondition prior to human adipose-derived stromal cell (hASC) spheroid (PBM-spheroid) transplantation improved skin tissue functional recovery by the stimulation of angiogenesis and tissue regeneration in skin flap of mice. The LED had an emission wavelength peaked at 660 ± 20 nm (6 J/cm², 10 mW/cm²). The expression of angiogenic growth factors in PBM-spheroid hASCs was much greater than that of not-PBM-treated spheroid or monolayer-cultured hASCs. From immunochemical staining analysis, the hASCs of PBM-spheroid were CD31⁺, KDR⁺, and CD34⁺, whereas monolayer-cultured hASCs were negative for these markers. To evaluate the therapeutic effect of hASC PBM-spheroid in vivo, PBS, monolayer-cultured hASCs, and not-PBM-spheroid were transplanted into a skin flap model. The animals were observed for 14 days. The PBM-spheroid hASCs transplanted into the skin flap ischemia differentiated into endothelial cells and remained differentiated. Transplantation of PBM-spheroid hASCs into the skin flap ischemia significantly elevated the density of vascular formations through angiogenic factors released by the skin flap ischemia and enhanced tissue regeneration at the lesion site. Consistent with these results, the transplantation of PBM-spheroid hASCs significantly improved functional recovery compared with PBS, monolayer-cultured hASCs, and not-PBM-spheroid treatment. These findings suggest that transplantation of PBM-spheroid hASCs may be an effective stem cell therapy for the treatment of skin flap ischemia.

Current Advancements and Strategies in Tissue Engineering for Wound Healing: A Comprehensive Review

Significance: With an aging population leading to an increase in diabetes and associated cutaneous wounds, there is a pressing clinical need to improve wound-healing therapies. Recent Advances: Tissue engineering approaches for wound healing and skin regeneration have been developed over the past few decades. A review of current literature has identified common themes and strategies that are proving successful within the field: The delivery of cells, mainly mesenchymal stem cells, within scaffolds of the native matrix is one such strategy. We overview these approaches and give insights into mechanisms that aid wound healing in different clinical scenarios. Critical Issues: We discuss the importance of the biomimetic niche, and how recapitulating elements of the native microenvironment of cells can help direct cell behavior and fate. Future Directions: It is crucial that during the continued development of tissue engineering in wound repair, there is close collaboration between tissue engineers and clinicians to maintain the translational efficacy of this approach.

Synthetic matrix of polyether-polyurethane as a biological platform for pancreatic regeneration

AIMS

Several alternative cellular approaches using biomaterials to host insulin-producing cells derived from stem cells have been developed to overcome the limitations of type 1 diabetes treatment (exogenous insulin injection). However, none seem to fulfill all requirements needed to induce pancreatic cells successful colonization of the scaffolds. Here, we report a polymeric platform adherent to the native mice pancreas filled with human adipose stem cells (hASCs) that was able to induce growth of pancreatic parenchyma.

MAIN METHODS

Synthetic polyether-polyurethane discs were placed adjacent to pancreas of normoglycemic and streptozotocin-induced diabetic mice. At day 4 post implantation, 1×10⁶ hASCs were injected intra-implant in groups of normoglycemic and diabetic mice. Immunohistochemistry analysis of the implants was performed to identify insulin positive cells in the newly formed tissue. In addition, metabolic, inflammatory and angiogenic parameters were carried out in those mice.

KEY FINDINGS

This study provides evidence of the ability of a biohybrid device to induce the growth of differentiated pancreas parenchyma in both normoglycemic and streptozotocin-induced diabetic mice as detected by histological analysis. Glucose metabolism and body weight of hyperglycemic mice bearing hASCs implants improved.

SIGNIFICANCE

The synthetic porous scaffold bearing hASC cells placed adjacent to the native animal pancreas exhibits the potential to be exploited in future cell-based type 1 diabetes therapies.

Skin Tissue Engineering: Application of Adipose-Derived Stem Cells

Perception of the adipose tissue has changed dramatically over the last few decades. Identification of adipose-derived stem cells (ASCs) ultimately transformed paradigm of this tissue from a passive energy depot into a promising stem cell source with properties of self-renewal and multipotential differentiation. As compared to bone marrow-derived stem cells (BMSCs), ASCs are more easily accessible and their isolation yields higher amount of stem cells. Therefore, the ASCs are of high interest for stem cell-based therapies and skin tissue engineering. Currently, freshly isolated stromal vascular fraction (SVF), which may be used directly without any expansion, was also assessed to be highly effective in treating skin radiation injuries, burns, or nonhealing wounds such as diabetic ulcers. In this paper, we review the characteristics of SVF and ASCs and the efficacy of their treatment for skin injuries and disorders.

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.

Hypoxia induces glucose uptake and metabolism of adipose‑derived stem cells

It has previously been demonstrated that hypoxia has diverse stimulatory effects on adipose‑derived stem cells (ASCs), however, metabolic responses under hypoxia remain to be elucidated. Thus, the present study aimed to investigate the glucose uptake and metabolism of ASCs under hypoxic conditions, and to identify the underlying molecular mechanisms. ASCs were cultured in 1% oxygen, and experiments were conducted in vitro. As determined by proteomic analysis and western blotting, GAPDH and enolase 1 (ENO1) expression were upregulated under hypoxia. In addition, lactate production was significantly increased, and mRNA levels of glycolytic enzymes, including GAPDH, ENO1, hexokinase 2 (HK2), and lactate dehydrogenase α (LDHα) were upregulated. Hypoxia‑inducible factor 1‑α (HIF‑1α) expression was increased as demonstrated by western blotting, and a pharmacological inhibitor of HIF‑1α significantly attenuated hypoxia‑induced lactate production and expression of glycolytic enzymes. It was also observed that hypoxia significantly increased glucose uptake in ASCs, and glucose transporter (GLUT)1 and GLUT3 expression were upregulated under hypoxia. Pharmacological inhibition of the HIF‑1α signaling pathways also attenuated hypoxia‑induced GLUT1 and GLUT3 expression. These results collectively indicate that hypoxia increases glucose uptake via GLUT1 and GLUT3 upregulation, and induces lactate production of ASCs via GAPDH, ENO1, HK2, and LDHα. Furthermore, HIF‑1α is involved in glucose uptake and metabolism of ASCs.

Angiogenic Synergistic Effect of Adipose-Derived Stromal Cell Spheroids with Low-Level Light Therapy in a Model of Acute Skin Flap Ischemia

Human adipose-derived mesenchymal stem cells (hASCs) are an attractive cell source for tissue engineering. However, one obstacle to this approach is that the transplanted hASC population can decline rapidly in the recipient tissue. The aim of this study was to investigate the effects of low-level light therapy (LLLT) on transplanted spheroid hASCs in skin flaps of mice. hASCs were cultured in monolayers or spheroids. LLLT, hASCs, spheroids and spheroids transplanted with LLLT were applied to the skin flaps. Healing of the skin flaps was assessed by gross evaluation and by hematoxylin and eosin staining and elastin van Gieson staining. Compared with the spheroid group, skin flap healing was enhanced in the spheroid + LLLT group, including the neovascularization and regeneration of skin appendages. The survival of hASCs was enhanced by decreased apoptosis of hASCs in the skin flaps of the spheroid + LLLT group. The secretion of growth factors was stimulated in the spheroid + LLLT group compared with the ASC and spheroid groups. These data suggest that LLLT was an effective biostimulator of spheroid hASCs in the skin flaps, enhancing the survival of hASCs and stimulating the secretion of growth factors.

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.

Prevention of skin flap necrosis by use of adipose-derived stromal cells with light-emitting diode phototherapy

BACKGROUND AIMS

The aim of this study was to investigate the effects of low-level light therapy (LLLT) on transplanted human adipose-derived mesenchymal stromal cells (ASCs) in the skin flap of mice.

METHODS

LLLT, ASC transplantation and ASC transplantation with LLLT (ASC + LLLT) were applied to the skin flap. Immunostaining and Western blot analysis were performed to evaluate cell survival and differentiation and secretion of vascular endothelial growth factor and basic fibroblast growth factor by the ASCs. Vascular regeneration was assessed by means of immunostaining in addition to hematoxylin and eosin staining. In the ASC + LLLT group, the survival of ASCs was increased as the result of the decreased apoptosis of ASCs.

RESULTS

The secretion of growth factors was higher in this group as compared with ASCs alone. ASCs contributed to tissue regeneration through vascular cell differentiation and secretion of angiogenic growth factors. The ASC + LLLT group displayed improved treatment efficacy including neovascularization and tissue regeneration compared with ASCs alone. Transplanting ASCs to ischemic skin flaps improved therapeutic efficacy for ischemia treatment as the result of enhanced cell survival and paracrine effects.

CONCLUSIONS

These data suggest that LLLT is an effective biostimulator of ASCs in vascular regeneration, which enhances the survival of ASCs and stimulates the secretion of growth factors in skin flaps.

Enrichment of Adipose-Derived Stromal Cells for BMPR1A Facilitates Enhanced Adipogenesis

BACKGROUND

Reconstruction of soft tissue defects has traditionally relied on the use of grafts and flaps, which may be associated with variable resorption and/or significant donor site morbidity. Cell-based strategies employing adipose-derived stromal cells (ASCs), found within the stromal vascular fraction (SVF) of adipose tissue, may offer an alternative strategy for soft tissue reconstruction. In this study, we investigated the potential of a bone morphogenetic protein receptor type 1A (BMPR1A)(+) subpopulation of ASCs to enhance de novo adipogenesis.

METHODS

Human lipoaspirate was enzymatically digested to isolate SVF and magnetic-activated cell separation was utilized to obtain BMPR1A(+) and BMPR1A(-) cells. These cells, along with unenriched cells, were expanded in culture and evaluated for adipogenic gene expression and in vitro adipocyte formation. Cells from each group were also labeled with a green fluorescent protein (GFP) lentivirus and transplanted into the inguinal fat pads, an adipogenic niche, of immunocompromised mice to determine their potential for de novo adipogenesis. Confocal microscopy along with staining of lipid droplets and vasculature was performed to evaluate the formation of mature adipocytes by transplanted cells.

RESULTS

In comparison to BMPR1A(-) and unenriched ASCs, BMPR1A(+) cells demonstrated significantly enhanced adipogenesis when cultured in an adipogenic differentiation medium, as evidenced by increased staining with Oil Red O and increased expression of peroxisome proliferator-activating receptor gamma (PPAR-γ) and fatty acid-binding protein 4 (FABP4). BMPR1A(+) cells also formed significantly more adipocytes in vivo, as demonstrated by quantification of GFP+ adipocytes. Minimal formation of mature adipocytes was appreciated by BMPR1A(-) cells.

CONCLUSIONS

BMPR1A(+) ASCs show an enhanced ability for adipogenesis in vitro, as shown by gene expression and histological staining. Furthermore, within an adipogenic niche, BMPR1A(+) cells possessed an increased capacity to generate de novo fat compared to BMPR1A(-) and unenriched cells. This suggests utility for the BMPR1A(+) subpopulation in cell-based strategies for soft tissue reconstruction.

Improved skin flap survival in venous ischemia-reperfusion injury with the use of adipose-derived stem cells

INTRODUCTION

The purpose of this study was to investigate the efficacy of stem cell therapy as an adjuvant treatment for congested skin flap.

METHOD

Sprague-Dawley rats (n = 21) were randomized into three groups. In group I, the flap was sutured without venous ischemia. In group II, the vein was selectively clamped for 4 hours, and complete medium was administered upon clamp removal. In group III, ADSCs were administered upon removing the clamp. On postoperative day 7, the survival areas and the histopathologic findings were assessed. In addition, the expression of heme oxygenase (HO)-1 and nuclear factor (NF)-κB was assessed using immunofluorescent staining and western blot analyses.

RESULTS

Compared with group II, group III showed significantly increased flap survival (31.2% ± 11.9% vs. 51.6% ± 13.6%, P < 0.05). The degree of histological abnormalities was significantly lower in group III than in group II (9.38% ± 1.39 vs. 6.46% ± 2.57, P < 0.05). In addition, in group III, the expression of NF-κB was significantly lower (0.51 ± 0.21 vs. 0.34 ± 0.21, P < 0.05), whereas that of HO-1 was significantly higher (0.25 ± 0.11 vs. 0.43 ± 0.18, P < 0.01). Immunofluorescent staining also showed more HO-1-positive cells in group III than in group II (10.9% ± 1.6% vs. 16.0% ± 1.7%, P < 0.01).

CONCLUSION

Our study demonstrated that treatment with ADSCs significantly increased flap survival in venous ischemia-reperfusion conditions. Further investigation of these protective effects and optimization of the treatment protocol could make cell therapy a viable treatment.

Mesenchymal Stem Cells and Cutaneous Wound Healing: Current Evidence and Future Potential

Human skin is a remarkable organ that sustains insult and injury throughout life. The ability of skin to expeditiously repair wounds is paramount to survival. With an aging global population, coupled with a rise in the prevalence of conditions such as diabetes, chronic wounds represent a significant biomedical burden. Mesenchymal stem cells (MSC), a progenitor cell population of the mesoderm lineage, have been shown to be significant mediators in inflammatory environments. Preclinical studies of MSC in various animal wound healing models point towards a putative therapy. This review examines the body of evidence suggesting that MSC accelerate wound healing in both clinical and preclinical studies and also the possible mechanisms controlling its efficacy. The delivery of a cellular therapy to the masses presents many challenges from a safety, ethical, and regulatory point of view. Some of the issues surrounding the introduction of MSC as a medicinal product are also delineated in this review.

Vascular endothelial growth factor 165-transfected adipose-derived mesenchymal stem cells promote vascularization-assisted fat transplantation

OBJECTIVE

To investigate the effect of vascular endothelial growth factor 165 (VEGF165) and adipose-derived mesenchymal stem cells (ASCs) in promoting the survival of fat grafts, and to provide new methods and theoretical evidence for increasing the survival rate of autologous fat particle grafts.

METHODS

The VEGF165 gene was recombined with the target fragment, and the recombinant gene was introduced into adenovirus pAdEasy-1 system; the virus was then packaged and the titer was detected. The control group received the same processing. ASCs were cultured and subcultured, and then identified with immunohistochemistry and adipogenic differentiation assay. The subsequent experiments were performed in three groups: the VEGF165 gene-virus group, blank virus group, and control group. After the viral solution was transfected into the ASCs, the viral transfection efficiency was detected using a tracing factor, EGFP. The expression of VEGF165 mRNA and protein in the transfected cells were determined. The proliferation of ASCs in each group was detected with the MTT assay.

RESULTS

(1) Recombinant adenoviral vector was constructed successfully in the two groups and the packaging was identified. The viral titer was 2.0 × 10(8) pfu/ml and 1.9 × 10(8) pfu/ml, which was in line with the requirements of the subsequent transfection experiments. (2) Immunohistochemistry and adipogenic differentiation results showed that the culture of ASCs was successful, and the cultured cells could serve as seed cells in this experiment. (3) The RT-PCR analysis showed that the relative optical density of VEGF165 mRNA expression was 0.76 ± 0.05 in the experimental group, and there were statistically significant differences compared with the values obtained for the other two groups (P < 0.05). (4) The western blot analysis showed that the relative optical density of VEGF165 protein expression in the experimental group was significantly higher than that in the other two groups (P < 0.05). (5) The proliferation of ASCs was significantly enhanced after transfection in the experimental group, relative to the other two groups (P < 0.05). This evidence indicated that VEGF165 significantly promoted the proliferation of ASCs.

CONCLUSION

After transfection with the VEGF165-adenoviral vector, ASCs demonstrate sustained expression of the target protein and obviously promote the proliferation of ASCs, which lay the foundation for the in vitro experiments on transplantation of VEGF165 combined with ASCs, for the treatment of tissue defects.