Comparison of systemic inflammation response and vital organ damage induced by severe burns in different area

BACKGROUND

In this study, we will establish a stable and optimized rat model that can meet strictly diagnosed criteria and serve as a tool to investigate the potential of novel therapeutics in this preclinical model through comparative analysis of systemic alterations, levels of pro-inflammatory cytokines in serum and infiltrated numbers of inflammatory cells in distant organ between 30% and 50% TBSA with a full-thickness burn.

MATERIALS AND METHODS

The adult male Wistar rats were randomly divided into the following groups: control group, 30% TBSA with a full-thickness burn group, and 50% TBSA with a full-thickness burn group. The blood and serum samples in the 3 groups were collected and detected by blood routine examination and biochemical detection at 6 h, 12 h, 24 h and 48 h post burn. The levels of TNF-α, IL-1β and IL-6 in serum were detected by ELISA. The sections of lung, renal, liver and heart were analyzed by H&E and immunohistochemical staining detection.

RESULTS

Our results showed that temperature in 50% TBSA with a full-thickness burn group was always hypothermia, and lower than 36°C at defined timepoints post burn, that was in 30% TBSA with a full-thickness burn group was lower than 36°C only at 48 h post burn. The levels of TNF-α, IL-1β and IL-6 were significantly increased in 30% and 50% groups at 6 h, 12 h, 24 h and 48 h post burn. The apoptosis in distant organs and the biochemical parameters such as ALT, AST, troponin, CK, CK-MB, LDH, urea and creatinine in 30% and 50% groups were also increased at different degrees at defined timepoints after burn, but changes in 50% group were more obvious than that in 30% group.

CONCLUSION

We choose 50% TBSA with a full-thickness burn to establish a stable and optimized rat model that can meet strictly diagnosed criteria and serve as a tool to investigate the potential of novel therapeutics in this preclinical model.

[Efficacies of fluid resuscitation volume after combined burn-blast injury shock]

OBJECTIVE

To explore the efficacies of resuscitation fluid volume after combined burn-blast injury versus a simple burn.

METHODS

A total of 24 beagle dogs were randomly assigned into 3 groups of normal volume (N), decreased volume (D) and increased volume (I). Fluid volume for group N was calculated with the Parkland formula while groups D and I decreased or increased by 20% respectively. Urinary output (UOP), hemoglobin concentration (HB), cardiac output (CO), intrathoracic blood volume (ITBV), extravascular lung water index (ELWI), oxygen delivery (DO(2)) and oxygen consumption (VO(2)) were determined before and 4, 8, 24, 48 h after injury to evaluate the sufficiency of resuscitation in each group and examine the superiority.

RESULTS

UOP were [(0.41 ± 0.13), (0.77 ± 0.17), (0.30 ± 0.13)] ml · kg(-1) · h(-1) at 4 h post-injury in groups N, I and D respectively. Group I was significantly higher than groups N and D (P < 0.001).It were [(0.59 ± 0.05), (0.88 ± 0.05), (0.53 ± 0.06)] ml · kg(-1) · h(-1) at 24 h post-injury in groups N, I and D respectively. Group I was significantly higher than groups N and D (P < 0.001). CO in group I was remarkably higher than those in groups N and D at 4 h and 8 h post-injury [(1.57 ± 0.19) vs (1.25 ± 0.17), (1.05 ± 0.17) L/min; (1.87 ± 0.20) vs (1.57 ± 0.24), (1.20 ± 0.19) L/min respectively] (P < 0.05); ITBV also significantly increased in group I than two other groups at 4 h and 8 h post-injury [(169 ± 16) vs (140 ± 12), (121 ± 12) ml; (161 ± 14) vs (135 ± 22), (112 ± 12) ml] (P < 0.05). VO2 in group I was significantly higher than that in group N at 24 h post-injury [(129 ± 10) vs (106 ± 12) ml · min(-1) · m(-2)] (P < 0.05). No differences were detected among 3 group in ELWI (P > 0.05).

CONCLUSION

Larger fluid volume may compensate circulatory volume loss sooner, alleviate declining cardiac output better, maintain adequate organ perfusion, promote tissue oxygenation and improve anti-hypervolemia and anti-hypoxia.

[Lay emphasis on the application of negative pressure wound therapy technique in burn surgery]

In recent years, negative pressure wound therapy (NPWT) technique has been widely used in burn surgery, including wound repair, skin grafting, and cosmetic procedures, showing promising clinical results. Based on the literature and clinical experience, the mechanism of NPWT and its clinical application in burn surgery are briefly iterated herewith.

[PROGRESS OF MESENCHYMAL STEM CELL-DERIVED Exosomes IN TISSUE REPAIR]

OBJECTIVE

To comprehensively analyze the recent advancements in the field of mesenchymal stem cells (MSCs) derived exosomes (MSCs-exosomes) in tissue repair.

METHODS

The literature about MSCs-exosomes in tissue repair was reviewed and analyzed.

RESULTS

Exosomes are biologically active microvesicles released from MSCs which are loaded with functional proteins, RNA, and microRNA. Exosomes can inhibit apoptosis, stimulate proliferation, alter cell phenotype in tissue repair of several diseases through cell-to-cell communication.

CONCLUSION

MSCs-exosomes is a novel source for the treatment of tissue repair. Further research of MSCs-exosomes biofunction, paracellular transport, and treatment mechanism will help the transform to clinical application.

[Effects of exogenous pulmonary surfactant on acute lung injury in rats with severe burn-blast combined injury]

OBJECTIVE

To observe the therapeutic effects of exogenous pulmonary surfactant (PS) on acute lung injury induced by severe burn-blast combined injury in a rat model.

METHODS

A total of 180 adult male SD rats were randomly divided into 3 groups of sham, treatment and control (n=60 each). Severe burn-blast combined injury was induced by inflicting rats with a moderate blast injury and a full-thickness burn injury of 25% total body surface area. The treatment and control groups received exogenous PS (2 ml/kg) and saline (2 ml/kg) by trachea respectively. At the time points of 0, 6, 24, 48 and 72 h, 12 rats per timepoint in each group underwent PaO2, PaCO2 and pulmonary function tests respectively. And they were then sacrificed for other analyses. Lung tissues were harvested for histological studies. Their arterial blood samples were collected for blood gas analysis. All data were expressed as mean ± standard deviation and analyzed with SPSS 20.0 (SPSS Inc., Chicago, IL, USA). The differences were considered to be statistically significant at P < 0.05.

RESULTS

After removing death drain during the experiment, 8 rats were put equally into five phase points of the last three groups, the results were analyzed statistically. PaO2: At each timepoint of 6, 24, 48, 72 h, the control group PaO2 were obviously lower than the sham group ((69.55 ± 5.11), (62.05 ± 6.54), (53.24 ± 7.65), (50.00 ± 7.45) vs (93.75 ± 3.41), (94.25 ± 2.19), (93.63 ± 2.33), (93.25 ± 1.83) mmHg (1 mmHg = 0.133 kPa), all P < 0.01); at 6 h treatment group was close to sham group ((92.63 ± 3.74) vs (93.75 ± 3.41) mmHg, P=0.594); at 6 h control group PaO2 decreased to 70 mmHg and then gradually declined. And at each timepoint the treatment group PaO2 was significantly higher than the control group ((92.63 ± 3.74), (87.50 ± 3.34), (78.75 ± 3.11), (71.38 ± 3.74) vs (69.55 ± 5.11), (62.05 ± 6.54), (53.24 ± 7.65), (50.00 ± 7.45) mmHg, all P < 0.01); PaCO2: treatment group PaCO2 was lower than that of control group at 6, 24, 48 h ((45.50 ± 6.79), (49.38 ± 7.52), (54.13 ± 4.82) vs (53.25 ± 2.76), (59.50 ± 6.61), (63.60 ± 7.33) mmHg, all P < 0.01), both treatment and control groups were significantly higher than those in the sham group ((59.63 ± 6.87), (68.88 ± 6.85) vs (36.38 ± 1.85) mmHg, all P < 0.01). No difference existed between the control and treatment groups (P = 0.051). Deep inspiratory capacity, central airway resistance, lung compliance and tissue elasticity, treatment group was significantly better than control group at 24 h (P < 0.05). And it was close to sham group (P > 0.05). The treatment group alveolar structural damage and pulmonary hemorrhage and edema were better than those in the control group.

CONCLUSION

Exogenous pulmonary surfactant (PS) can improve oxygenation and alleviate pulmonary edema and pulmonary capillary membrane permeability of rats with severe burn blast combined injury.

The function of miRNAs and their potential as therapeutic targets in burn-induced insulin resistance (review)

Burns are common accidental injuries. The main clinical manifestations of severe burn injury are insulin resistance and high metabolism. Insulin resistance results in hyperglycemia, which may lead to skeletal muscle wasting and suspended wound healing. It also elevates the risk of infection and sepsis. Studies have indicated that insulin receptor (IR) and insulin receptor substrate 1 (IRS1) are essential factors involved in the regulation of blood glucose levels. Moreover, the suppression of the IR/IRS1 signaling pathway results in insulin resistance. Recent studies have also indicated that miRNAs, which are small non-coding RNAs consisting of 20-23 nucleotides, target the 3'-untranslated region (3'-UTR) of IRS1 mRNA and attenuate protein translation. miRNAs also play an important role in the development of type II diabetes (T2D) and obesity-induced insulin resistance. In the present review, we discuss the involvement of miRNAs in burn-induced insulin resistance through the targeting of the IR/IRS1 signaling pathway. We also discuss the possibility of miRNAs a novel therapeutic target in insulin resistance in burn patients.

Processing of CXCL12 impedes the recruitment of endothelial progenitor cells in diabetic wound healing

High blood sugar levels result in defective wound healing processes in diabetic patients. Endothelial progenitor cells (EPCs) play an important role in vasculogenesis, and thereby contribute to reconstitution of the microcirculation and healing. This study aimed to determine the possible mechanism by which the numbers of circulating EPCs are regulated in response to tissue wounding. In the streptozotocin-induced diabetic mouse model, we found that phagocytes activated by local inflammatory cytokines in the wound interfere with the mobilization and recruitment of EPCs to the lesion area. Specifically, the activated macrophages inactivate CXCL12, the major chemokine for EPC recruitment, via matrix metalloproteinases (MMPs), and thereby prevent local chemotaxis and subsequent homing of EPCs to the wound. The wound healing process is delayed by local administration of inflammatory cytokines, and its rate is increased by MMP inhibitors. This study indicates that local inhibition of MMPs is beneficial for regeneration of damaged vessels, and may explain poor wound healing in diabetic patients, thus demonstrating its potential utility as a local treatment therapy to promote diabetic wound healing.

Contribution of infection and peripheral artery disease to severity of diabetic foot ulcers in Chinese patients

AIM

The objective of the current ongoing study was to evaluate the characteristics of diabetic patients with newly diagnosed foot ulcer in Burn & Plastic Hospital of PLA General Hospital.

METHODS

A total of 1002 consecutive patients presenting with a new foot ulcer between March 2007 and September 2013 were enrolled. All enrolled patients were classified based on presence or absence of collateral infection, disabling comorbidities and peripheral arterial disease (PAD).

RESULTS

Of patients, 70.05% had PAD, which occurred significantly more in elderly adults. Patients with PAD had higher incidence of infection (58.9% vs. 41.5% in non-PAD group) and disabling comorbidities (79% in PAD and 61% in non-PAD; p < 0.038). There was no significant difference observed in depth, size and duration of foot ulcers between the PAD and non-PAD group of enrolled diabetic patients.

CONCLUSIONS

Diabetic foot ulcer is more prominent in patients with PAD that is further reflected by significantly more underlying cases of infection and disabling comorbidity.

Microencapsulated VEGF gene-modified umbilical cord mesenchymal stromal cells promote the vascularization of tissue-engineered dermis: an experimental study

BACKGROUND AIMS

Tissue-engineered dermis (TED) is thought to be the best treatment for skin defect wounds; however, lack of vascular structures in these products can cause slow vascularization or even transplant failure. We assessed the therapeutic potential of microencapsulated human umbilical cord mesenchymal stromal cells (hUCMSCs) expressing vascular endothelial growth factor (VEGF) in vascularization of TED.

METHODS

hUCMSCs were isolated by means of enzymatic digestion and identified by means of testing biological characteristics. hUCMSCs were induced to differentiate into dermal fibroblasts in conditioned induction media. Collagen-chitosan laser drilling acellular dermal matrix (ADM) composite scaffold was prepared by means of the freeze dehydration and dehydrothermal cross-linking method. hUCMSC-derived fibroblasts were implanted on composite scaffolds to construct TED. TED with microencapsulated VEGF gene-modified hUCMSCs was then transplanted into skin defect wounds in pigs. The angiogenesis of TED at 1 week and status of wound healing at 3 weeks were observed.

RESULTS

The collagen-chitosan laser ADM composite has a uniform microporous structure. This composite has been used to grow hUCMSC-derived fibroblasts in vitro and to successfully construct stem cell-derived TED. Microencapsulated VEGF gene-modified hUCMSCs were prepared with the use of a sodium alginate-barium chloride one-step encapsulation technology. Seven days after the transplantation of the stem cell-derived TED and microencapsulated VEGF gene-modified hUCMSCs into the skin defect wounds on the backs of miniature pigs, the VEGF expression increased and the TED had a higher degree of vascularization. Re-epithelialization of the wound was completed after 3 weeks.

CONCLUSIONS

Microencapsulated VEGF gene-modified hUCMSCs can effectively improve the vascularization of TED and consequently the quality of wound healing.

[Experimental study on effect of burn on brown adipose tissue in mice]

OBJECTIVE

To investigate the effect of burn on brown adipose tissue (BAT) in BALB/c mice.

METHODS

Forty 3-4 months old male BALB/c mice with initial body weight of (20 ± 3) g were randomly divided into control group and burn group (n = 20). BALB/c mice in burn group were subjected to a 30% total body surface area (TBSA) full-thickness thermal injury. BALB/c mice in control group were not treated. The body weight and temperature were observed before and after burn. At 7 days after burn, morphological changes of white adipose tissue (WAT) and BAT were observed, the gene and protein expressions of uncoupling protein 1 (UCP-1) were detected.

RESULTS

There was no significant difference in the body weight and body temperature before burn (P > 0.05). At 1, 2, 3, and 4 weeks after burn, the body weight was significantly lower in burn group than in control group (P < 0.05). At 1, 2, 3, and 7 days after burn, the body temperature was significantly higher in burn group than in control group (P < 0.05). At 7 days after burn, the weight of WAT was significantly reduced, and the weight of BAT was significantly increased in burn group (P < 0.05); WAT and BAT cells became smaller, cell number increased, the cytoplasm and mitochondria appeared as compact. The UCP-1 gene and protein expressions of burn group were significantly higher than those of control group (P < 0.05).

CONCLUSION

BAT plays an important role in burn-induced hypermetabolism.

Exogenous connective tissue growth factor preserves the hair-inductive ability of human dermal papilla cells

Connective tissue growth factor influences human dermal papilla cells' hair inductive ability through several signaling pathways.

Human umbilical cord-derived mesenchymal stem cells differentiate into epidermal-like cells using a novel co-culture technique

Human umbilical cord-derived mesenchymal stem cells (hUCMSCs) isolated from human umbilical Wharton's Jelly are a population of primitive and pluripotent cells. In specific conditions, hUCMSCs can differentiate into various cells, including adipocytes, osteoblasts, chondrocytes, neurocytes, and endothelial cells. However, few studies have assessed their differentiation into epidermal cells in vitro. To assess the potential of hUCMSCs to differentiate into epidermal cells, a microporous membrane-based indirect co-culture system was developed in this study. Epidermal stem cells (ESCs) were seeded on the bottom of the microporous membrane, and hUCMSCs were seeded on the top of the microporous membrane. Cell morphology was assessed by phase contrast microscopy, and the expression of early markers of epidermal cell lineage, P63, cytokeratin19 (CK19), and β1-integrin, was determined by immunofluorescence, Western blot, and quantitative real-time PCR (Q-PCR) analyses. hUCMSC morphology changed from spindle-like to oblate or irregular with indirect co-culture with ESCs; they also expressed greater levels P63, CK19, and β1-integrin mRNA and protein compared to the controls (p < 0.01). As compared to normal co-cultures, indirect co-culture expressed significantly greater CK19 protein (p < 0.01). Thus, hUCMSCs may have the capability to differentiate into the epidermal lineage in vitro, which may be accomplished through this indirect co-culture model.

[Advances in the research on the relationship between brown adipose tissue and metabolism in burn and trauma]

Hypermetabolism and insulin resistance are prominent features of trauma including burn injury, surgery, and infection. Hypermetabolism results in insufficiency in energy supply, which induces organ function lesion, immune suppression, high infection rate, and wound healing delay, thus exerting a strong impact on patients' quality of life and prognosis. The molecular mechanism in the occurrence and development of hypermetabolism is very complicated, and it has not been fully elucidated. Recently, brown adipose tissue (BAT) was found to be present not only in rodents but also in humans, and its activity was associated with resting metabolic rate. BAT may become the new target of research in prevention and control of metabolic disorder.

[INFLUENCE OF BURN SERUM ON PROLIFERATION AND ADIPOSE DIFFERENTIATION OF 3T3-L1 PREADIPOCYTES]

OBJECTIVE

To investigate the effect of burn on the fat metabolism by observing the effect of burn serum on the proliferation and adipose differentiation of 3T3-L1 preadipocytes.

METHODS

Forty-eight male Sprague Dawley rats were randomly divided into sham burn group and burn at 1, 4, 7, 14, and 21 days groups, 8 rats in each group. The rats in burn groups were made the full-thickness thermal burns comprising 30% total body surface area. At 1, 4, 7, 14, and 21 days after burn, the serum of burn rats was collected. The rats in sham burn group were not treated as normal control. The proliferation activity of 3T3-L1 cells was detected using MTT method after treated by normal and burn serum. The burn serum having the highest proliferation inhibitory effect was chosen for subsequent study. The growth of 3T3-L1 cells in normal serum group (group A), burn serum group (group B), normal serum and adipogenic induction group (group C), burn serum and adipogenic induction group (group D) was observed using inverted microscope. After 7 days of treatment, the adipocytes was stained by oil red O and the absorbance (A) value was measured. The mRNA and protein levels of preoxisome proliferator-activated receptor γ (PPAR-γ) and lipoprotein lipase (LPL) were detected by real-time quantitative PCR and Western blot.

RESULTS

The proliferation ability of 3T3-L1 cells was significantly reduced in the group treated by 4- or 7-day burn serum (P < 0.05), especially 7-day burn serum treatment group (P < 0.05). Under inverted microscope, the cell morphology in group A and group B had no obvious change, but a large number of fat cells were observed in group C and a few were observed in group D. The positive or weak positive oil red O staining was observed in group C or group D, respectively. The cell counting and A value were significantly higher in group A than in group B, and in group C than in group D (P < 0.05). The mRNA level of PPAR-γ in group B was significantly reduced when compared with that in group A (P < 0.05). No significant difference was found in LPL mRNA levels and protein levels of PPAR-γ and LPL between group A and group B (P > 0.05). The mRNA and protein levels of PPAR-γ and LPL were significantly attenuated in group D when compared with those in group C (P < 0.05).

CONCLUSION

The adipose differentiation of 3T3-L1 preadipocytes can be significantly reduced after treated by 7-day burn serum of rat.

Development of an Animal Model for Burn-Blast Combined Injury and Cardiopulmonary System Changes in the Early Shock Stage

The purposes of this study were to establish an animal model for burn-blast combined injury research and elaborate cardiopulmonary system changes in the early shock stage. In this study, royal demolition explosive or RDX (hexagon, ring trimethylene nitramine) was used as an explosive source, and the injury conditions of the canine test subjects at various distances to the explosion (30, 50, and 70 cm) were observed by gross anatomy and pathology to determine a larger animal model of moderate blast injury. The canines were then subjected to a 35 % total body surface area (TBSA) full-thickness flame injury using napalm, which completed the development of a burn-blast combined injury model. Based on this model, the hemodynamic changes and arterial blood gas analysis after the burn-blast combined injury were measured to identify the cardiopulmonary system characteristics. In this research, RDX explosion and flame injury were used to develop a severe burn-blast injury animal model that was stable, close to reality, and easily controllable. The hemodynamic and arterial blood gas changes in the canine subjects after burn-blast injury changed distinctly from the burn and blast injuries. Blood pressure and cardiac output fluctuated, and the preload was significantly reduced, whereas the afterload significantly increased. Meanwhile, the oxygen saturation (SO2) decreased markedly with carbon dioxide partial pressure (PCO2), and lactic acid (Lac) rose, and oxygen partial pressure (PO2) reduced. These changes suggested that immediate clinical treatment is important during burn-blast injury both to stabilize cardiac function and supply blood volume and to reduce the vascular permeability, thereby preventing acute pneumonedema or other complications.

[Effect and mechanism of dantrolene on skeletal muscle of rats with severe scald injury]

OBJECTIVE

To explore the effect and mechanism of ryanodine receptor antagonist dantrolene on skeletal muscle of rats with severe scald injury.

METHODS

A total of 56 Wistar rats were divided into control, scald and dantrolene treatment groups according to a random digital table. Rats in scald and dantrolene treatment groups were subject to 50% total body surface area (TBSA) full-thickness scald by a 12-second immersion of back and a 6-second immersion of abdomen in 94 °C water and then received an intraperitoneal injection of Ringer's solution. At the same time, the rats in scald group received 5% mannitol through caudal vein while those in dantrolene treatment group received dantrolene 2 mg/kg (dissolved in 5% mannitol). Rats in control group were sham-injured through an immersion of back and abdomen into 37 °C warm water. Tibialis anterior muscle samples were harvested at Days 1, 4 and 7 post-scalding. Changes of skeletal muscle ultrastructure were observed by transmission electron microscope, subcellular calcium ion (Ca(2+)) contents of skeletal muscle (including cytoplasm, mitochondria & sarcoplasm reticulum) were detected by electron probe X-ray microanalysis (EPMA) and the levels of calpain-1 and calpain-2 protein were determined by Western blot. And the activities of calpain were detected by enzyme-linked immunosorbent assay.

RESULTS

In scald group, assorted arrangement appeared immediately at Day 1 post-injury and partial disappearance of Z lines at Day 7 post-injury. There were no significant ultrastructure changes in dantrolene treatment group at Day 1 and 4 post-injury. Curled filament and mild fracture occurred merely in dantrolene treatment group at Day 7 post-injury. The cytoplasmic contents of Ca(2+) were significantly higher in scald group than those in control group at Day 1 and 4 ((0.964 ± 0.060), (0.639 ± 0.067) vs (0.266 ± 0.029) µmol/L respectively, all P < 0.05) while the contents of Ca(2+) within sarcoplasm reticulum were obviously lower in scald group than those in control group at Day 1 and 4 ((0.368 ± 0.060), (0.814 ± 0.089) vs (1.337 ± 0.112) µmol/L respectively, all P < 0.05). However, those subcellular regions in dantrolene treatment group ((0.310 ± 0.069), (0.490 ± 0.039) and (1.241 ± 0.073), (1.161 ± 0.094) µmol/L) had no significant difference with control group (all P > 0.05). Calpain-1 and calpain-2 protein levels in scald group increased significantly at Day 1 and 4 post-injury versus control group (1.371 ± 0.034, 1.214 ± 0.030 vs 0.838 ± 0.017 & 1.464 ± 0.015, 1.390 ± 0.023 vs 0.806 ± 0.026 respectively, all P < 0.05), whereas calpain-1 and calpain-2 protein levels in dantrolene treatment (0.984 ± 0.031, 0.935 ± 0.023 and 0.836 ± 0.014, 0.741 ± 0.020) obviously were lower than those in scald group respectively (all P < 0.05). The activities of calpain in scald and dantrolene treatment groups at Day 1, 4 and 7 post-injury were (8.33 ± 0.21), (9.33 ± 0.21), (10.59 ± 0.18) and (7.76 ± 0.28), (7.86 ± 0.20), (7.91 ± 0.22) µmol/L respectively while the activity of calpain in control group was (7.62 ± 0.19) µmol/L. The activities of calpain in scald group were significantly higher than those in dantrolene treatment and control groups (all P < 0.05) whereas the activities of calpain in dantrolene treatment group had no obvious change versus control group (all P > 0.05).

CONCLUSIONS

Dantrolene offers significant protection from skeletal muscle tissue damage and minimizes the ultrastructural change of tibialis anterior muscle induced by severe scald injury. The mechanism is probably through inhibiting an excessive release of Ca(2+) within sarcoplasm reticulum and down-regulated cytoplasmic expression and activity of calpain-1 and calpain-2.

Guideline for diagnosis, prophylaxis and treatment of invasive fungal infection post burn injury in China 2013

Invasive fungal infection is one of the major complication of severe burns which can induce local or systemic inflammatory response and cause serious substantial damage to the patient. The incidence of fungal infection for burn victims is increasing dramatically during recent years. This guideline, organized by Chinese Society of Burn Surgeons, aims to standardize the diagnosis, prevention and treatment of burn invasive fungal infection. It can be used as one of the tools for treatment of major burn patients.

[Effects of endotoxin/lipopolysaccharide on proliferation and apoptosis of human umbilical cord mesenchymal stem cells]

OBJECTIVE

To investigate the effects of different concentrations of lipopolysaccharide (LPS) on proliferation and apoptosis of human umbilical cord mesenchymal stem cells (hUCMSCs) in vitro, and to explore their possible mechanism.

METHODS

hUCMSCs from umbilical cord tissue of full-term healthy fetus delivered by caesarean section were isolated and cultured in vitro using tissue attachment method. The 3rd passage hUCMSCs were used in the study. Cells were divided into groups A, B, C, D, and E, which were treated with DMEM/F12 medium containing 0, 0.1, 1.0, 10.0, and 100.0 µg/mL of LPS respectively. In groups B, C, D, and E, methyl-thiazole-tetrazolium assay was used to detect proliferative activity of hUCMSCs at post treatment hour (PTH) 12, 24, and 48 (denoted as absorption value), with 5 samples in each group at each time point; apoptosis of hUCMSCs at PBH 24 was identified with acridine orange-ethidium bromide (AO-EB) staining, with 4 samples in each group; apoptotic rate of hUCMSCs was determined by flow cytometer, with 5 samples in each group. Above-mentioned indexes were determined in group A at the same time points. Data were processed with analysis of variance and LSD- t test.

RESULTS

(1) There was no statistically significant difference in proliferative activity of hUCMSCs at PTH 12 among groups A, B, C, D, and E (with t values from -1.67 to 1.33, P values above 0.05). Compared with that of group A, proliferative activity of hUCMSCs was increased in groups B, C, and D at PTH 24 and 48 (with t values from -13.42 to 17.34, P < 0.05 or P < 0.01), especially so in group C. Proliferative activity of hUCMSCs was lower in group E at PTH 24 and 48 than in group A (with t values respectively 8.64 and 17.34, P values below 0.01). (2) Obvious apoptosis of hUCMSCs was observed in group E but not in the other 4 groups with AO-EB staining. (3) Apoptosis rates of hUCMSCs in groups A, B, C, D, and E were respectively (3.1 ± 0.6)%, (2.6 ± 0.7)%, (2.9 ± 0.8)%, (3.1 ± 0.4)%, (25.1 ± 2.7)% (F = 272.19, P < 0.01). Apoptotic rate of hUCMSCs in group B, C, or D was respectively close to that in group A (with t values respectively 1.22, 0.57, -0.14, P values above 0.05), but it was higher in group E than in group A (t = -17.63, P < 0.01).

CONCLUSIONS

hUCMSCs proliferation may be promoted by low concentration of LPS. hUCMSCs proliferation is inhibited or induced to apoptosis along with the increase in concentration of LPS, and it may be related to activation of different major molecular signaling pathways by different concentrations of LPS.

[Advances in the research of the role of mesenchymal stem cell in wound healing]

Wound healing is a dynamic and complicated process, which generally takes three overlapping phases: inflammation, proliferation, and remodeling. If wounds complicated by severe trauma, diabetes, vascular dysfunction disease, or a massive burn injury failed to pass through the three normal phases of healing, they might end up as chronic and refractory wounds. Mesenchymal stem cells (MSCs) play different important roles in the regulation of all the phases of wound healing. MSCs can be recruited into wound and differentiated into wound repair cells, as well as promote wound healing by exerting functions like anti-inflammation, anti-apoptosis, and neovascularization. This review focuses on the role and mechanism of MSCs in each phase of the wound healing process.

[Effects of lipopolysaccharide pretreatment on endotoxin tolerance of human umbilical cord mesenchymal stem cells]

OBJECTIVE

To explore the effects of lipopolysaccharide (LPS) pretreatment on endotoxin tolerance of human umbilical cord mesenchymal stem cells (hUCMSCs) and its possible mechanism.

METHODS

hUCMSCs (1×10(4) cells/well) were exposed to 0, 0.1, 1.0, 10.0, 20.0, 30.0, 40.0, 50.0 µg/ml LPS for 24 h respectively. And the cell viability of hUCMSCs was detected by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT). 1 µg/ml and 50.0 µg/ml LPS were used as pretreatment and apoptosis induction concentrations respectively. Pyrrolidine dithiocarbamate (PDTC) (20 µmol/L, pretreatment for 20 min) was used as a specific inhibitor of nuclear transcription factor NF-κB. hUCMSCs were randomly divided by Stata software into 7 groups: control (A), LPS induction (B), pretreatment + LPS induction (C), PDTC (D), PDTC+ pretreatment + LPS induction (E), pretreatment (F) and PDTC + pretreatment (G). The apoptosis of hUCMSCs was measured by Hoechst 33258 staining and flow cytometry (FCM). The expressions of NF-κB p65 and cellular FLICE-inhibitory protein (c-FLIP) were measured by Western blot.

RESULTS

The cell viability of 0, 0.1, 1.0, 10.0, 20.0, 30.0, 40.0, 50.0 µg/ml LPS groups were 100%, (117.0 ± 8.8)%, (134.7 ± 6.9)%, (105.3 ± 8.3)%, (99.2 ± 8.3)%, (84.2 ± 9.3)%, (66.4 ± 6.6)% and (59.2 ± 8.0)% respectively. In comparison with 0 µg/ml LPS group, the cell viability of 1.0 µg/ml LPS group increased significantly (P = 0.004) while decreased in 40 and 50 µg/ml LPS groups (P = 0.005, 0.002). Hoechst 33258 staining indicated that chromatin of hUCMSCs was distributed evenly in group A; the apoptotic cell in group B dramatically increased; and the apoptotic cell in group C significantly decreased in comparison with that in group B. Apoptotic rates of groups A, B, C, D and E were (2.8 ± 0.8)%, (29.7 ± 3.4)%, (17.8 ± 3.0)%, (2.9 ± 0.4)% and (23.2 ± 2.6)% respectively. Compared with group A, apoptosis rate significantly increased in group B (P < 0.001). The apoptotic rate in group C significantly decreased than that in group B (P < 0.001) while group E was higher than group C (P = 0.015). The levels of NF-κB p65 and c-FLIP in group F (0.851 ± 0.031, 0.534 ± 0.053) was higher than that in group A (0.220 ± 0.021, 0.049 ± 0.009) (both P < 0.001), G (0.418 ± 0.007, 0.299 ± 0.061) (P < 0.001, P = 0.007).

CONCLUSIONS

LPS pretreatment can resist LPS-induced hUCMSCs apoptosis and enhance the ability of endotoxin tolerance. And the mechanism may be related with activating the NF-κB signaling pathway and up-regulating the expression of c-FLIP.