Adipose tissue stromal vascular fraction in the treatment of full thickness burns in rats

Efficacy of stromal vascular fraction and enzyme-free mechanical isolation therapy in experimental full thickness burn wounds

BACKGROUND

Autologous cell suspensions obtained by a stromal vascular fraction (SVF) and enzyme-free mechanical isolation (EMI) are an alternative in the treatment of burn wounds. In this study, we aimed to investigate the effect of autologous cell suspensions obtained by SVF and EMI on full-thickness skin burn wounds.

METHODS

A total of 45 male Sprague-Dawley rats were divided into three groups, SVF group, EMI group, and SVF + EMI group. The groups were also classified as the first, second, and third week of the burn to reveal the effect of the treatment on the burn in the early, middle, and late stages. For treatment, 0.2 ml SVF or 0.2 ml EMI was injected subcutaneously into the burn lesions of the subjects. Histopathological examination was performed on the burn wounds taken at the end of the experiment, and Ki67, CD44, CD73, CD90, and CK17 expressions were evaluated.

RESULTS

Histological examination revealed that there was no improvement in the control samples, but the skin was multicellular, vascularization was present. Histologic scores in all groups was significantly better than control, and SVF + EMI was the best group in terms of recovery (p < 0.05). Ki67, CK17, CD44, CD73, and CD90 expressions were significantly higher in the treatment groups compared to the control (p < 0.05).

CONCLUSION

We found in our study that both applications significantly increased the healing of the burn wound. Moreover, SVF + EMI application provided more improvement than SVF or EMI alone.

The effect of stromal vascular fraction in an experimental frostbite injury model

BACKGROUND

Despite current treatment modalities, frostbite remains an injury with a poor prognosis which may cause functional morbidities. Several experimental and clinical studies have demonstrated that stromal vascular fraction is an autologous mixture, which can improve wound healing and vasculogenesis. The aim of this study was to show the beneficial effects of stromal vascular fraction on experimental frostbite healing.

MATERIAL AND METHODS

Stromal vascular fraction (SVF) was harvested from 5 rats after excision of the inguinal fat pads. Another 20 rats were separated into 2 groups of 10 as the SVF group and the control group. A frostbite injury was created on each rat using a cryoprobe frozen with liquid nitrogen (-196 °C). SVF was applied to the SVF group and phosphate-buffered saline to the control group. All injections were performed subcutaneously within the frostbite injury area. Biopsies were performed on days 5 and 14 for histopathological and immunochemical evaluations. The tissue perfusion rates of both groups were assessed on day 14 using indocyanine green angiography (SPY system).

RESULTS

The increase in mean tissue perfusion was 373.3% ( ± 32.1) in the SVF group and 123.8% ( ± 16.3) in the control group (p < 0.001). The macroscopic wound reduction rates of the SVF and control groups were 25.5% ( ± 19.1) and 18.0% ( ± 5.9), respectively on day 5%, and 78.2% ( ± 9.2) and 57.3% ( ± 16.7) on day 14 (p = 0.007; p = 0.003). Acute inflammation and the fibrosis gradient were significantly decreased in the SVF group compared to the control group (p = 0.004, p = 0.054 respectively on day 14). Granulation tissue amount, re-epithelialization score and neovascularization were significantly increased in the SVF group (p = 0.006, p = 0.010 and p = 0.021, respectively on day 14).

CONCLUSIONS

The study results demonstrated that SVF increases frostbite wound healing by increasing tissue perfusion rate, neovascularization and re-epithelialization, and modulating acute inflammation and fibrosis.

Treatment of experimentally induced partial-thickness burns in rats with different silver-impregnated dressings

PURPOSE

To evaluate the morphometric, macroscopic and microscopic aspects of experimentally induced partial-thickness burns in rats treated with different silver-based dressings.

METHODS

Wistar rats were used, divided into six treatments: saline (NaCl 0.9%); silver sulfadiazine 1%; Silvercel; Mepilex Ag; Aquacel Ag and Acticoat. The animals were monitored daily and euthanized at 7, 14 and 30 days after injury induction (DAI).

RESULTS

At 7 DAI, necrosis/crust was greater in control, silver sulfadiazine and Mepilex Ag treatments, granulation tissue was induced by Aquacel Ag, polymorphonuclear infiltrate (PMN) infiltration was intensified by Mepilex Ag; mononuclear infiltrate (MN) infiltration and angiogenesis were increased by Silvercel. At 14 DAI, hemorrhage was decreased by Silvercel and Mepilex Ag, PMN infiltration increased by Acticoat. At 30 DAI, angiogenesis was greater in the Acticoat treatment and fibroblasts were increased by Acticoat and Mepilex Ag. Collagen was induced at 14 DAI by silver sulfadiazine and Aquacel Ag and, at 30 DAI, by silver sulfadiazine and Silvercel treatments.

CONCLUSIONS

Silvercel and Acticoat presented better results than the other products. However, all the dressings were better than the control at some point during the process, and may contribute to the healing of partial thickness burns. Silvercel and Aquacel Ag treatments induced better cosmetic outcomes regarding wound closure and scarring.

Adipose stromal vascular fraction: a promising treatment for severe burn injury

Thermal skin burn injury affects both adults and children globally. Severe burn injury affects a patient's life psychologically, cosmetically, and socially. The pathophysiology of burn injury is well known. Due to the complexity of burn pathophysiology, the development of specific treatment aiding in tissue regeneration is required. Treatment of burn injury depends on burn severity, size of the burn and availability of donor site. Burn healing requires biochemical and cellular events to ensure better cell response to biochemical signals of the healing process. This led to the consideration of using cell therapy for severe burn injury. Adult mesenchymal stem cells have become a therapeutic option because of their ability for self-renewal and differentiation. Adipose stromal vascular fraction (SVF), isolated from adipose tissues, is a heterogeneous cell population that contains adipose-derived stromal/stem cells (ADSC), stromal, endothelial, hematopoietic and pericytic lineages. SVF isolation has advantages over other types of cells; such as heterogeneity of cells, lower invasive extraction procedure, high yield of cells, and fast and easy isolation. Therefore, SVF has many characteristics that enable them to be a therapeutic option for burn treatment. Studies have been conducted mostly in animal models to investigate their therapeutic potential for burn injury. They can be used alone or in combination with other treatment options. Treatment with both ADSCs and/or SVF enhances burn healing through increasing re-epithelization, angiogenesis and decreasing inflammation and scar formation. Research needs to be conducted for a better understanding of the SVF mechanism in burn healing and to optimize current techniques for enhanced treatment outcomes.

Hydrogel-based dressings in the treatment of partial thickness experimentally induced burn wounds in rats

Purpose:

To compare four commercially available hydrogel formulations in the healing of partial thickness burns experimentally induced in rats.

Methods:

Wistar rats were used, and after the burn wound induction they were divided into the following treatment groups: G1) NaCl 0.9%; G2) 1% silver sulfadiazine; G3) Debrigel™; G4) Safgel™; G5) Dersani™; G6) Solosite™. The animals were followed during seven, 14 and 30 days after the injury induction. Morphometric, macroscopic and microscopic evaluations were performed.

Results:

The treatment with Dersani™ induced better results during the inflammatory and proliferative phases of the healing process (p<0.05). The animals treated with Safgel™ presented better scaring in the remodeling phase (p<0.05), and the treatment with Dersani™ and Solosite™ induced greater wound closure (p<0.05).

Conclusions:

The hydrogel-based dressings presented beneficial outcomes in the healing of burn wounds experimentally induced in rats due to their ability in maintain the humidity of the wound, in removing the exudate, in promoting cell migration and collagen production during the different phases of the healing process.

Synergistic efficacy of colistin and silver nanoparticles impregnated human amniotic membrane in a burn wound infected rat model

Antimicrobials used to treat burn wound infections have become multidrug-resistant, thus delaying wound healing. When combined with silver nanoparticles, antibiotics create a multifaceted antibacterial mechanism of action to which bacteria are incapable of developing resistance. Similarly, the amniotic membrane has been found to lower the bacterial number. The purpose of the current study was to observe the antibacterial activity of combined topical colistin with silver nanoparticles and decellularized human amniotic membrane as a dressing in burn wounds infected with bacteria with the goal of promoting faster healing. Bacteria commonly isolated from burn wounds and the most sensitive topical antibiotic were identified. Colistin, silver nanoparticles and combined colistin with silver nanoparticles were impregnated into decellularized human amniotic membranes. These wound dressings were evaluated in third-degree multidrug-resistant bacterial infected thermal burns induced in rats. Out of a total of 708 pus samples from burn wounds, Pseudomonas aeruginosa was the most prevalent pathogen 308 (43.5%), followed by Klebsiella pneumoniae 300 (42.4%). Topical colistin was 100% sensitive for both bacteria. Overall, maximum wound contraction (p < 0.05), and increased collagen deposition (+++) with no isolation of bacteria from wound swabs were noted on day 21 for the combined colistin with silver nanoparticle-loaded human amniotic membrane dressing group. Our study concluded that the increased antimicrobial activity of the novel combination of colistin and silver nanoparticle-loaded decellularized human amniotic membrane manifested its potential as an effective burn wound dressing.

The Combination of Stromal Vascular Fraction Cells and Platelet-Rich Plasma Reduces Malondialdehyde and Nitric Oxide Levels in Deep Dermal Burn Injury

Introduction

Thermal burns release reactive oxygen species, which cause profound systemic and local changes. Stromal vascular fraction cells (SVFs) combined with platelet-rich plasma accelerate burn wound healing. This study investigated the effect of a combination of locally injected SVFs and PRP on malondialdehyde (MDA) and nitric oxide (NO) serum and tissue levels in a deep dermal burn model in Wistar rats.

Methods

Thirty-six adult Wistar rats weighing between 150 and 250 grams were used in this study to establish a deep dermal degree burn wound model. They were randomly divided into 4 groups: locally injected the combination SVFs and PRP, the Vaseline group, the placebo group, and healthy Wistar rats (the normal control group). MDA and NO levels in blood serum and burn wound tissue were measured at 8, 24, and 48 hours. Data were analyzed with one-way ANOVA followed by multiple comparisons tests and regression tests.

Results

Local injection of SVFs and PRP in combination affected blood MDA, tissue MDA, blood NO and tissue NO levels, with reductions of 0.257µmol/L, 0.427 µmol/L, 21.78nmol/mg, and 23.777nmol/mg, respectively. Injection of SVFs and PRP in combination reduced tissue MDA levels by 1.282 times, NO blood levels by 2.305, and NO tissue levels by 2.377 times compared to Vaseline application.

Conclusion

The combination of SVFs and PRP undeniably reduced the MDA and NO levels in blood and tissue compared to those in the Vaseline and placebo groups. The injection of these two preparations in combination inhibited the local and systemic stress oxidative response, as illustrated by the decreased MDA and NO levels in blood serum and tissue.

The Effects of Adipose Derived Stromal Vascular Fraction and Platelet-Rich Plasma on Bone Healing of a Rat Model With Chronic Kidney Disease

BACKGROUND

Chronic kidney disease (CKD) impairs osteoblast/osteoclast balance and damages bone structure with diminished mineralization and results in bone restoration disorders. In this study, we investigate the effects of adipose-derived stromal vascular fraction and platelet-rich plasma (PRP) on bone healing model in rats with CKD.

METHODS

Sprague-Dawley rats were separated into 4 groups. All groups except group I (healthy control) had CKD surgery using 5/6 nephrectomy model. All groups had intramedullary pin fixation after receiving bone fracture using drilling tools. Group II rats were used as control group for CKD. Group III rats received PRP treatment on fracture site. Group IV rats received PRP and stromal vascular fraction treatment on fracture site.Weight loss and blood samples were followed at the time of kidney surgery, third, sixth, and 12th weeks. Bone healing and callus formations were compared, biomechanically, radiologically, histopathologically, and immunohistochemically. Osteoblastic transformation of stem cells was assessed with DiI staining.

RESULTS

Negative effects of CKD on bone healing were reduced by increasing mechanical, histological, radiological, and biochemical properties of the bone with stromal vascular fraction and PRP treatments. Although thickness of callus tissue delayed bone healing process, it also enhanced biomechanical features and bone tissue organization.

CONCLUSIONS

Platelet-rich plasma and adipose-derived stromal vascular fraction treatments were effective for bone healing in animal model, which can be promising for clinical trials.

Combination of platelet rich plasma and stromal vascular fraction on the level of vascular endothelial growth factor in rat subjects experiencing deep dermal burn injury

Background

The healing process of burns includes coagulation, inflammation, and remodeling. Vascular endothelial growth factor (VEGF) is involved throughout this healing process. Stem cells from the platelet-rich plasma (PRP) with stromal vascular fraction (SVF) can increase concentrations of growth factors, including VEGF. This is expected to accelerate burn healing. The aim of this study was to determine the effect of a combination of PRP and SVF on VEGF levels in a rats model of deep dermal burn wound healing.

Materials and methods

This is an experimental research study in rats using a post-test control group design with 4 groups: A) control, B) Vaseline, C) topical PRP and SVF, and D) PRP and SVF injection. Burn wounds were induced according to the modified Guo method.

Results

In a rats model of deep dermal wound healing, topical Vaseline significantly increased serum VEGF compared to control. Topical application and injection of stem cells also significantly increased serum VEGF compared to control and Vaseline. The VEGF concentration was significantly higher following injection of PRP and SVF, suggesting that the injection route is more effective at increasing VEGF levels compared to the topical application of stem cells.

Conclusion

The combination of PRP and SVF, either by injection or topical application, can increase VEGF levels during the healing process from deep dermal burns.

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Stem cells can increase concentrations of growth factors.

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Topical application and injection of stem cells significantly increased serum VEGF compared to control.

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The VEGF concentration was significantly higher following injection of PRP and SVFs.

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The injection route of stem cells is more effective at increasing VEGF levels compared to the topical application.

Therapeutic Targeting of Neutrophil Extracellular Traps Improves Primary and Secondary Intention Wound Healing in Mice

Background

Neutrophils are the first responders in wound healing after injury that mediate pro- and anti-inflammatory activities i.a. through the formation of extracellular traps (NETs). However, excessive NETs presence in wound tissue can cause local hyperinflammation and -coagulation resulting in delayed wound healing. To improve wound healing, we aimed to examine the role of NETs and DNase1 on primary and secondary wound healing.

Methods

The study included 93 C57BL/6 mice, with 3 different genotypes: wildtype, Pad4-, and DNase1-Knockout (KO). Pad4-KO mice show limited NETs formation, while DNase1-KO mice cannot disintegrate them. All 3 genotypes were included in (1) a laparotomy group and (2) a thermal injury group. Animals in both groups either received DNase1 or a vehicle i.p. post wound induction and wound assessment and euthanasia were conducted. Laparotomy and burn scars were assessed using the stony brook scar evaluation scale and modified Yeong scale respectively. Tissue was analyzed histologically using H&E staining. Ly6g, Collagen I and III, SMA, and Fibrinogen were visualized and neutrophils activation (NE, MPO) and NETs (H3cit) formation assessed.

Results

All animals survived with no complications. DNase1 treatment led to a significantly improved scar appearance in both groups, which was also seen in Pad4-KO mice. In the laparotomy group DNase1 improved collagen deposition and fibrin concentration was significantly reduced by DNase1 treatment. Markers of neutrophil activation were significantly reduced in the treatment and Pad4-KO group. In the thermal injury group wound closure time was significantly reduced after DNase1 treatment and in the Pad4-KO group. Even though inflammation remained high in the thermal injury model over time, neutrophil activation and NETs formation were significantly reduced by DNase1 treatment compared to controls.

Discussion

Primary and secondary intention wound healing is improved by targeting NETs through DNase1 treatment or genetic KO, as assessed by wound closure time and scar appearances. Additionally, wound stability was not affected by DNASE treatment. The results suggest that overall wound healing is accelerated and DNase1 appears to be a promising option to reduce scar formation; which should be evaluated in humans.

Combination of platelet-rich plasma and stromal vascular fraction on the level of transforming growth factor-β in rat subjects experiencing deep dermal burn injury

INTRODUCTION

The combination of stromal vascular fraction (SVF) and platelet-rich plasma (PRP) is effective at increasing the concentration of growth factors including transforming growth factor-β (TGF-β). The increase in this growth factor is expected to accelerate the healing of burns. This study aims to determine the effect of giving a combination of SVFs and PRP on TGF-β levels in the healing process of deep dermal burns.

METHODS

This was an experimental study in 64 rats using a post-test control group design consisting of 1 group of SVFs and PRP combination injection treatment group, 1 group given a topical combination of SVFs and PRP, 1 group given Vaseline, and 1 control group.

RESULTS

There was a significant difference in TGF-β levels between the deep dermal burns group that was given a combination of SVFs and PRP injection and topical, the Vaseline group, and the control group with p-value <0.05.

CONCLUSION

The combination of SVFs and PRP increases the level of TGF-β in the healing process of deep dermal burns.

Expression levels and significance of miR-184 and miR-126 in burned rats

Expression levels and significance of miR-184 and miR-126 in burned rats were investigated. A total of 30 healthy rats were selected to construct a burn rat model, and another 10 healthy rats as the control group. The modeled rats were divided into groups I, II and III according to burn area, 10 for each group. The reverse transcription-quantitative polymerase chain reaction (RT-q.PCR) was used to detect the expression of miR-184 and miR-126 in the serum of three groups of burned rats, and ELISA was employed to detect the expression levels in peripheral blood and the correlation. There was no difference in the expression levels of miR-184 and miR-126 among the four groups of rats before modeling (P>0.05). Those of miR-184 and miR-126 at each time point were lower than those at the previous one in groups I, II and III (P<0.05). There was no significant change in the expression levels of miR-184 and miR-126 in the control group (P>0.05). At the same time point, those of miR-184 and miR-126 decreased with the increase of burn degree, and the difference was statistically significant between every two groups (P<0.05). The results of Pearson's correlation analysis revealed that the expression level of miR-184 was positively correlated with that of miR-126 (r=0.832, P=0.002). miR-184 and miR-126 were positively correlated with burn degree (r=0.901, P=0.001, r=0.775, P=0.001) and time after burn (r=0.732, P=0.004, r=0.753, P=0.002). The expression levels of miR-184 and miR-126 decrease in burned rats. The changes of their levels may be used as a reference standard for clinical efficacy evaluation to evaluate burn degree, preventing burn wounds from deepening.

Photobiomodulation associated to cellular therapy improve wound healing of experimental full thickness burn wounds in rats

Adipose derived stromal vascular fraction (SVF) is a method of cell therapy potentially applicable for treatment of full thickness burns. Here we investigated if the association of photobiomodulation (PBM) with SVF therapy could improve wound healing in experimentally induced full thickness burn wounds in rats compared to the topical agent 2% silver sulfadiazine in a dose-dependent manner. Sixty-six male Wistar rats were divided in 4 groups containing 5 animals each which received the following treatments: 2% sulfadiazine (SD), SVF, SVF plus PBM at 30 mW (SVFL30), and SVF plus PBM at 100 mW (SVFL100). Two donor animals were used for each experimental series with 3, 7 and 30 days. Digital photography, microscopic analysis with Hematoxilin and Eosin (H&E), quantification of collagen type I by picrosirius red staining analysis and wound contraction evaluation were performed in order to quantify the results. At day 3 SVF alone or combined with PBM promoted increased early inflammatory response compared to SD. At day 7 SVFL30 and SVFL100 enhanced inflammatory cells infiltration, angiogenesis and fibroblast content compared to SVF and SD groups. At day 30 collagen concentration and wound contraction were higher in SVFL30 when compared to the other groups. In conclusion PBM promotes a synergistic outcome with SVF therapy with a dose dependent effect potentializing wound healing of experimental full thickness burns in rats through amplification of early inflammatory response, enhanced angiogenesis, fibroblast content, accentuated wound contraction and collagen concentration.

Formation of Adipose Stromal Vascular Fraction Cell-Laden Spheroids Using a Three-Dimensional Bioprinter and Superhydrophobic Surfaces

The therapeutic infusion of adipose-derived stromal vascular fraction (SVF) cells for the treatment of multiple diseases, has progressed to numerous human clinical trials; however, the often poor retention of the cells following implantation remains a common drawback of direct cell injection. One solution to cellular retention at the injection site has been the use of biogels to encapsulate cells within a microenvironment before and upon implantation. The current study utilized three-dimensional bioprinting technology to evaluate the ability to form SVF cell-laden spheroids with collagen I as a gel-forming biomatrix. A superhydrophobic surface was created to maintain the bioprinted structures in a spheroid shape. A hydrophilic disc was printed onto the hydrophobic surface to immobilize the spheroids during the gelation process. Conditions for the automated rapid formation of SVF cell-laden spheroids were explored, including time/pressure relationships for spheroid extrusion during bioprinting. The formed spheroids maintain SVF viability in both static culture and dynamic spinner culture. Spheroids also undergo a time-dependent contraction with the retention of angiogenic sprout phenotype over the 14-day culture period. The use of a biphilic surface exhibiting both superhydrophobicity to maintain the spheroid shape and a hydrophilicity to immobilize the spheroid during gel formation produces SVF cell-laden spheroids that can be immediately transplanted for therapeutic applications.