[Promoting the healthy development of the wound repair discipline system with local conditions and Chinese characteristics].

The construction of wound repair discipline system with Chinese characteristics is a process of continuous optimization and improvement. Due to the different conditions and the situations that vary widely from region to region and from hospital to hospital, various forms of wound repair specialty or consortium will exist within a period of time and to a extent plays a key role in promoting the construction of the wound repair discipline system with Chinese characteristics. This article introduced several kinds of construction modes of wound repair specialty or regional alliance of wound repair specialty in recent years. Their successful experience is worth learning and drawing lessons from.

[High-risk sexual behaviors of HIV/AIDS and related factors in young students in Guangzhou].

Objective: To explore high-risk sexual behaviors of HIV/AIDS and related factors in young students in Guangzhou. Methods: A cross-sectional survey was conducted in 5 different types of Guangzhou colleges by convenience sampling with minimum number of classes per grade and 600 samples per school from September to November 2021. The R 4.2.2 software was used to consolidate databases. Simultaneously, a logistic regression model and a decision tree algorithm model, stratifying by whether sexual behaviors had occurred before, were constructed. In each layer, the prediction performance of the two models was evaluated through area under receiver operating characteristic and the confusion matrix, and then the model with high prediction performance was retained. Results: A total of 7 346 students were surveyed. The proportion of the respondents reporting sexual experience were 9.08% (667/7 346), in whom 26.24% (175/667) had risky sexual activity in the past year. The decision tree algorithm model performs well in predicting whether high-risk sexual behaviors have occurred in the past year. When the complexity parameter value is 0.018, and nsplit reaches 4, which means there are 5 leaf nodes in the model, the cross error of the tree will be the smallest. The first best grouping variable in the decision tree was whether to use condoms throughout the first sexual behavior. If condoms were used at their sexual debut, but homosexual practices have occurred in the past year, the probability of risky sexual behavior will increase. If homosexual practices have not occurred in the past year, but the age of sexual debut was below 18 years old while the period of HIV education was after high school, the probability of risk sexual behavior will also increase. Conclusions: AIDS-related risky behaviors of young students still deserved attention. The experience of sexual debut and whether AIDS-related health education has been received before the sexual debut were significant predictors for the occurrence of high-risk sexual behavior. The decision tree algorithm model has particular applicability for predicting and screening potential risk populations.

[Perception of HIV-related behavior and influencing factors among young students in Guangzhou].

Objective: To investigate the risk perception for risky behavior of HIV/AIDS infection among young students and to analyze the related influencing factors. Methods: A cross-sectional survey was conducted in 5 different types of Guangzhou colleges from September to November 2021, in which convenience sampling and a minimum number of classes per grade and 600 samples per school were used according to the national unity program. Disordered multi-classification logistic regression was used to construct a risk perception model and analyze influencing factors in different risk perception levels. Results: A total of 7 346 young students were surveyed, and most rated themselves at low risk of HIV/AIDS infections (90.58%, 6 654/7 346). A total of 89.10% (6 545/7 346) of subjects' perception of their HIV/AIDS infection risk was consistent with their risk behavior, while 10.90% (801/7 346) was inconsistent. Among those inconsistent subjects, 19.10% (153/801) showed underestimating their risk , while 80.90% (648/801) seen overestimating their risk. Disordered multi-classification logistic regression analysis showed that, after controlling for other factors, compared with the non-sexual group, respondents whose first sex age under 18 had a higher rate of underestimating their risk of infection (OR=129.39, 95%CI: 73.28-228.48), as well as a higher rate of overestimated their risk of infection (OR=1.76, 95%CI: 1.04-2.99). First sexual intercourse at age 18 or older was a risk factor for underestimating risk (OR=70.56, 95%CI: 42.72-116.53), but was not statistically associated with overestimating risk. Being female, other school type, non-heterosexual orientation, and self-rated HIV-related knowledge as fair or no knowledge were risk factors for overestimating risk but were not statistically associated with underestimating risk. Conclusions: Overall, young students in universities of Guangzhou have a good risk perception of HIV/AIDS infection. Individual factors, education factors and sexual experience will influence students' risk perception of HIV/AIDS infection. Raising the awareness rate of HIV/AIDS knowledge and delaying the age of first sexual intercourse will improve the risk perception ability of young students.

[Ten key points in the high-quality construction and development of the disciplinary system of wound repair with Chinese characteristics].

Phased major results with construction of the disciplinary system of wound repair with Chinese characteristics have been achieved in the past 30 years. However, some problems in institutional issues still affect the development of the discipline. In this paper, 10 aspects of the impact of discipline construction are put forward which may offer reference for high-quality construction of the disciplinary system of wound repair with Chinese characteristics.

[Research advances of stem cell-based tissue engineering repair materials in promoting the healing of chronic refractory wounds on the body surface].

Repairing chronic refractory wounds on the body surface is a complex medical problem involving all stages of wound healing. In recent years, stem cells (SCs) and tissue engineering (TE) have brought hope for repairing chronic refractory wounds. SCs have excellent regenerative and paracrine effects; various TE strategies have the potential to repair chronic refractory wounds on the body surface and also improve the delivery efficiency of SCs. This article reviews the pathological characteristics of chronic refractory wounds, SCs used to repair chronic refractory wounds, and SC-based TE wound repair strategies.

[Role and prospect of regenerative medicine in early treatment of combat trauma].

The regenerative medicine has made great breakthrough in the repair of combat trauma, showing broad prospects, while the method of regenerative medicine applied in the early treatment of combat trauma is not yet clear. The early treatment of combat trauma includes strict control of bleeding, a large amount of blood transfusion, alleviation of acidosis, and correction of hypothermia and improvement of coagulation dysfunction, etc. This paper focuses on the bio-engineered blood, research and development of homeostatic materials, control of inflammation/infection, regulation of immunity, protection of important organs, establishment of military medical model, research and development of biosensors and drugs, and preventive application of stem cell bank in regenerative and tissue engineering in defense medicine to summarize the role of regenerative medicine in the early treatment of combat trauma, hoping to improve the overall treatment level of combat trauma.

[Continue to promote the construction of the discipline system of wound repair with Chinese characteristics].

The repair of various kinds of complex and difficult-to-heal wounds is a major national demand for disease treatment in new era. Since the National Health Commission approved the establishment of wound repair departments in medical institutions with suitable condition at all levels in 2019, remarkable achievement has been achieved in the construction of the discipline system of wound repair in China in the past 3 years. In this paper, I would like to summarize the fruitful achievements in the field of wound repair in China in the past 3 years and put forward some suggestions for the next development of the discipline.

[Effects of in situ cross-linked graphene oxide-containing gelatin methacrylate anhydride hydrogel on wound vascularization of full-thickness skin defect in mice].

Objective: To prepare graphene oxide (GO)-containing gelatin methacrylate anhydride (GelMA) hydrogel and to investigate the effects of in situ photopolymerized GO-GelMA composite hydrogel in wound vascularization of full-thickness skin defect in mice. Methods: The experimental study method was used. The 50 µL of 0.2 mg/mL GO solution was evenly applied onto the conductive gel, and the structure and size of GO were observed under field emission scanning electron microscope after drying. Human skin fibroblasts (HSFs) were divided into 0 µg/mL GO (without GO solution, the same as below) group, 0.1 µg/mL GO group, 1.0 µg/mL GO group, 5.0 µg/mL GO group, and 10.0 µg/mL GO group treated with GO of the corresponding final mass concentration, and the absorbance value was detected using a microplate analyzer after 48 h of culture to reflect the proliferation activity of cells (n=6). HSFs and human umbilical vein vascular endothelial cells (HUVECs) were divided into 0 µg/mL GO group, 0.1 µg/mL GO group, 1.0 µg/mL GO group, and 5.0 µg/mL GO group treated with GO of the corresponding final mass concentration, and the migration rates of HSFs at 24 and 36 h after scratching (n=5) and HUVECs at 12 h after scratching (n=3) were detected by scratch test, and the level of vascular endothelial growth factor (VEGF) secreted by HSFs after 4, 6, and 8 h of culture was detected by enzyme-linked immunosorbent assay method (n=3). The prepared GO-GelMA composite hydrogels containing GO of the corresponding final mass concentration were set as 0 µg/mL GO composite hydrogel group, 0.1 µg/mL GO composite hydrogel group, 1.0 µg/mL GO composite hydrogel group, and 5.0 µg/mL GO composite hydrogel group to observe their properties before and after cross-linking, and to detect the release of GO after soaking with phosphate buffer solution for 3 and 7 d (n=3). The full-thickness skin defect wounds were made on the back of 16 6-week-old female C57BL/6 mice. The mice treated with in situ cross-linked GO-GelMA composite hydrogel containing GO of the corresponding final mass concentration were divided into 0 µg/mL GO composite hydrogel group, 0.1 µg/mL GO composite hydrogel group, 1.0 µg/mL GO composite hydrogel group, and 5.0 µg/mL GO composite hydrogel group according to the random number table, with 4 mice in each group. The general condition of wound was observed and the wound healing rate was calculated on 3, 7, and 14 d of treatment, the wound blood perfusion was detected by laser Doppler flowmetry on 3, 7, and 14 d of treatment and the mean perfusion unit (MPU) ratio was calculated, and the wound vascularization on 7 d of treatment was observed after hematoxylin-eosin staining and the vascular density was calculated (n=3). The wound tissue of mice in 0 µg/mL GO composite hydrogel group and 0.1 µg/mL GO composite hydrogel group on 7 d of treatment was collected to observe the relationship between the distribution of GO and neovascularization by hematoxylin-eosin staining (n=3) and the expression of VEGF by immunohistochemical staining. Data were statistically analyzed with analysis of variance for repeated measurement, one-way analysis of variance, and Tukey's method. Results: GO had a multilayered lamellar structure with the width of about 20 µm and the length of about 50 µm. The absorbance value of HSFs in 10.0 µg/mL GO group was significantly lower than that in 0 µg/mL GO group after 48 h of culture (q=7.64, P<0.01). At 24 h after scratching, the migration rates of HSFs were similar in the four groups (P>0.05); at 36 h after scratching, the migration rate of HSFs in 0.1 µg/mL GO group was significantly higher than that in 0 µg/mL GO group, 1.0 µg/mL GO group, and 5.0 µg/mL GO group (with q values of 7.48, 10.81, and 10.20, respectively, P<0.01). At 12 h after scratching, the migration rate of HUVECs in 0.1 µg/mL GO group was significantly higher than that in 0 µg/mL GO group, 1.0 µg/mL GO group, and 5.0 µg/mL GO group (with q values of 7.11, 8.99, and 14.92, respectively, P<0.01), and the migration rate of HUVECs in 5.0 µg/mL GO group was significantly lower than that in 0 µg/mL GO group and 1.0 µg/mL GO group (with q values of 7.81 and 5.33, respectively, P<0.05 or P<0.01 ). At 4 and 6 h of culture, the VEGF expressions of HSFs in the four groups were similar (P>0.05); at 8 h of culture, the VEGF expression of HSFs in 0.1 µg/mL GO group was significantly higher than that in 0 µg/mL GO group and 5.0 µg/mL GO group (with q values of 4.75 and 4.48, respectively, P<0.05). The GO-GelMA composite hydrogels in the four groups were all red liquid before cross-linking, which turned to light yellow gel after cross-linking, with no significant difference in fluidity. The GO in the GO-GelMA composite hydrogel of 0 µg/mL GO composite hydrogel group had no release of GO at all time points; the GO in the GO-GelMA composite hydrogels of the other 3 groups was partially released on 3 d of soaking, and all the GO was released on 7 d of soaking. From 3 to 14 d of treatment, the wounds of mice in the 4 groups were covered with hydrogel dressings, kept moist, and gradually healed. On 3, 7, and 14 d of treatment, the wound healing rates of mice in the four groups were similar (P>0.05). On 3 d of treatment, the MPU ratio of wound of mice in 0.1 µg/mL GO composite hydrogel group was significantly higher than that in 0 µg/mL GO composite hydrogel group, 1.0 µg/mL GO composite hydrogel group, and 5.0 µg/mL GO composite hydrogel group (with q values of 10.70, 11.83, and 10.65, respectively, P<0.05 or P<0.01). On 7 and 14 d of treatment, the MPU ratios of wound of mice in the four groups were similar (P>0.05). The MPU ratio of wound of mice in 0.1 µg/mL GO composite hydrogel group on 7 d of treatment was significantly lower than that on 3 d of treatment (q=14.38, P<0.05), and that on 14 d of treatment was significantly lower than that on 7 d of treatment (q=27.78, P<0.01). On 7 d of treatment, the neovascular density of wound of mice on 7 d of treatment was 120.7±4.1 per 200 times of visual field, which was significantly higher than 61.7±1.3, 77.7±10.2, and 99.0±7.9 per 200 times of visual field in 0 µg/mL GO composite hydrogel group, 1.0 µg/mL GO composite hydrogel group, and 5.0 µg/mL GO composite hydrogel group (with q values of 12.88, 7.79, and 6.70, respectively, P<0.01), and the neovascular density of wound of mice in 1.0 µg/mL GO composite hydrogel group and 5.0 µg/mL GO composite hydrogel group was significantly higher than that in 0 µg/mL GO composite hydrogel group (with q values of 5.10 and 6.19, respectively, P<0.05). On 7 d of treatment, cluster of new blood vessels in wound of mice in 0.1 µg/mL GO composite hydrogel group was significantly more than that in 0 µg/mL GO composite hydrogel group, and the new blood vessels were clustered near the GO; a large amount of VEGF was expressed in wound of mice in 0.1 µg/mL GO composite hydrogel group in the distribution area of GO and new blood vessels. Conclusions: GO with mass concentration lower than 10.0 µg/mL had no adverse effect on proliferation activity of HSFs, and GO of 0.1 µg/mL can promote the migration of HSFs and HUVECs, and can promote the secretion of VEGF in HSFs. In situ photopolymerized of GO-GelMA composite hydrogel dressing can promote the wound neovascularization of full-thickness skin defect in mice and increase wound blood perfusion in the early stage, with GO showing an enrichment effect on angiogenesis, and the mechanism may be related to the role of GO in promoting the secretion of VEGF by wound cells.

[Application of limiting antigen avidity enzyme immunoassay for estimating HIV-1 incidence in men who have sex with men].

Objective: To estimate the incidence of HIV-1 infection in men who have sex with men (MSM) in key areas of China through HIV-1 limiting antigen avidity enzyme immunoassay (LAg-Avidity EIA), analyze the deviation from the actual results and identify influencing factors, and provided reference for improving the accuracy of estimation results. Methods: Based on the principle of the cohort randomized study design, 20 cities were selected in China based on population size and the number of HIV-positive MSM. The sample size was estimated to be 700 according to the HIV-1 infection rate in MSM. MSM mobile phone app. was used to establish a detection appointment and questionnaire system, and the baseline cross-sectional survey was conducted from April to November 2019. LAg-Avidity EIA was used to identify the recent infected samples. The incidence of HIV-1 infection was calculated and then adjusted based on the estimation formula designed by WHO. The influencing factors were identified by analyzing the sample collection and detection processes. Results: Among the 10 650 blood samples from the participants, 799 were HIV-positive in initial screening, in which 198 samples (24.78%) missed during confirmation test. Only 621 samples were received by the laboratory. After excluding misreported samples, 520 samples were qualified for testing. A total of 155 samples were eventually determined as recent infection through LAg-Avidity EIA; Based on the estimation formula , the incidence of HIV-1 infection in MSM in 20 cities was 4.06% (95%CI:3.27%-4.85%), it increased to 5.53% (95%CI: 4.45%-6.60%)after the adjusting for sample missing rate. When the sample missing rate and misreporting rate were both adjusted, the incidence of HIV-1 infection in the MSM increased to 5.66% (95%CI:4.67%-6.65%). The actual incidence of HIV-1 infection in MSM in the 20 cities might be between 4.06% and 5.66%. Conclusions: Sample missing and misreporting might cause the deviation of the estimation of HIV-1 infection incidence. It is important to ensure the sample source and the quality of sample collection and detection to reduce the deviation in the estimation of HIV-1 infection incidence.

[Establishment of "Chinese way" for trauma and burn management based on the engineered growth factors research and application].

Innovation and translation application are important topics that have been discussed repeatedly in national community of science and technology in recent years. We do a systemic review about the research and development history of growth factors, their application in trauma and burn management in China, and the conception and experience about the establishment of "Chinese way" for trauma and burn management in the process of constructing a disciplinary system for wound treatment with Chinese characteristics. It is our hope that these precious experiences will provide references and inspiration to our peers, especially the young generation in their research.

[Establishment of integrated emergent medical rescue system for major disaster accidents (safety events) and severe trauma (burn injury and war trauma) in important strategic development regions of China].

Emergent medical rescue and treatment of major disaster accidents (safety events) and severe mass trauma are major national demands. The fast and effective emergent medical rescue depends on the establishment of integrated emergent medical rescue system. This article discusses the importance and necessity of establishing the integrated emergent medical rescue system with Chinese characteristics in important strategic development regions and the specific content of the system.

[Microenvironment control is the only way to achieve perfect wound repair].

With gradually in-depth understanding of wound healing mechanism, the concept and composition of wound microenvironment have been improved and clarified. In the process of wound healing, the external microenvironment and internal microenvironment are both relatively independent and interact with each other, and are always in dynamic change. It is necessary to understand the changing rules and characteristics of wound healing microenvironment from multiple dimensions, such as space and time, so that the process of wound healing can be purposefully regulated and controlled depending on actual circumstance. It helps the adoption of reasonable regenerative medicine technology at the proper time window to realize perfect repair and regeneration after skin and soft tissue injury in the true sense.

[Influence of the stiffness of three-dimensionally bioprinted extracellular matrix analogue on the differentiation of bone mesenchymal stem cells into skin appendage cells].

Objective: To observe the influence of the stiffness of three-dimensionally bioprinted extracellular matrix analogue on the differentiation of bone marrow mesenchymal stem cells (BMSCs) into skin appendage cells. Methods: (1) Sodium alginate of 1 g and 4 g gelatin, 3 g sodium alginate and 8 g gelatin were mixed respectively, and the two mixtures were dissolved in 100 mL ultra-pure water respectively to prepare two sodium alginate-gelatin composite hydrogels, named 1A4G hydrogel and 3A8G hydrogel, which were used in the subsequent experiments. The morphology of the two hydrogels at room temperature, after condensation for 15-30 min at 4 ℃ (the same condensation condition below), after condensation and cross-linking with 25 g/L calcium chloride solution (the same cross-linking condition below), and after condensation and three-dimensional printing with a three-dimensional bioprinter (the same three-dimensional printer below) and cross-linking were observed respectively. Young's modulus (stiffness) of the two kinds of hydrogels was measured by Young's modulus tester after condensation and cross-linking (n=3). Two kinds of hydrogels were cross-linked and freeze-dried, and their pore structure was observed by scanning electron microscope. Two hydrogels were cross-linked and freeze-dried, and the porosity was detected by anhydrous ethanol replacement method (n=3). (2) BMSCs were isolated from femur and tibia of 20 C57BL/6 mice (no limitation with sex, born 7 days) and cultured, and the second passage of cells was used for further test. The BMSCs single cell suspension (1.0×10(7) /mL) was mixed with 1A4G hydrogel and 3A8G hydrogel respectively at 1∶9 volume ratio to prepare BMSCs-loaded 1A4G hydrogel and BMSCs-loaded 3A8G hydrogel for three-dimensional printing. One construct was printed with 1 mL cell-loaded hydrogel (the same dosage for printing below). Mesenchymal stem cells (MSCs) specific medium was added after cross-linking, and the printed constructs were divided into 1A4G group and 3A8G group according to the hydrogel. One construct of each group cultured for 7 days was tested with live/dead kit to count the live cells and dead cells in 50-fold field of view. Nine printed constructs from each of the two groups were taken, and BMSCs of nine wells (1.0×10(6) per well) cultured with 2 mL MSCs specific medium were set as two-dimensional culture group. After 1, 3, 5 day (s) of culture, three printed constructs from 1A4G group and 3A8G group respectively and three wells of cells from two-dimensional culture group were taken to detect the absorbance value in culture medium by cell counting kit 8, denoting the cell proliferation activity. (3) BMSCs-loaded 1A4G hydrogel and BMSCs-loaded 3A8G hydrogel of 10 mL respectively were prepared as in experiment (2), which were respectively mixed with 0.5 mL plantar dermis homogenate extracted from 10 C57BL/6 mice of 1 day postnatal with unknown sex, then three-dimensionally printed, cross-linked, cultured with MSCs specific medium for 3 days and then changed to sweat gland specific medium. The printed constructs were divided into 1A4G group and 3A8G group according to their hydrogel. After 7 days of culture with sweat gland specific medium, the expressions of epithelial cell surface markers cytokeratin-5 (CK5) and CK14, sweat gland cell surface markers CK18 and Na(+) /K(+) -ATPase (NKA), and hair follicle cell surface markers CK17 and alkaline phosphatase (ALP) at protein level in cells of printed constructs in the two groups were detected by immunofluorescence method. The expressions of CK5, CK14, CK18, NKA (detecting ATP1a1), CK17, and ALP at mRNA level in cells of printed constructs in the two groups were detected with real-time fluorescent quantitative reverse transcription polymerase chain reaction (n=3). Data were statistically analyzed with independent sample t test, Fisher's exact probability test, analysis of variance for factorial design, and Bonferroni method. Results: (1) Compared with that of 3A8G hydrogel, 1A4G hydrogel had lower viscosity and better fluidity at room temperature. Both kinds of hydrogels were gel-like after condensation, based on which, the shape of cross-linked hydrogels was uniform and regular, with three-dimensional printing and cross-linking made hrdrogels forming solid crisscross cylindrical constructs. The Young's modulus of 1A4G hydrogel was (52±6) kPa, which was obviously lower than (218±5) kPa of 3A8G hydrogel (t=40.470, P<0.01). The pore structure of the two hydrogels was similar, with all the cross-sections showing porous network structure. The porosity of the two hydrogels was similar (t=0.930, P>0.05). (2) The distribution of live/dead cells between 1A4G group and 3A8G group was similar after 7 days of culture (P>0.05), most of which were live cells. The absorbance value in culture medium of printed constructs among 1A4G group, 3A8G group, and two-dimensional culture group didn't show statistically significant differences after 1, 3, 5 day (s) of culture (P>0.05). Compared with that after 1 day of culture within each group, the absorbance value in culture medium of printed constructs in 1A4G group and 3A8G group was significantly increased after 3 and 5 days of culture (P<0.05 or P<0.01), and the absorbance value in culture medium of cells in two-dimensional culture group was significantly increased after 5 days of culture (P<0.01). Compared with that after 3 days of culture within each group, the absorbance value in culture medium of printed constructs in 1A4G group and 3A8G group and that of cells in two-dimensional culture group was significantly increased after 5 days of culture (P<0.01). (3) After 7 days of culture with sweat gland specific medium, the CK5, CK14, CK18, NKA, CK17, and ALP were positively expressed at protein level in cells of printed constructs in the two groups. After 7 days of culture with sweat gland specific medium, the expressions of CK5, CK14, CK18, and NKA at mRNA level in cells of printed constructs were close between the two groups (t=0.362, 0.807, 0.223, 1.356, P>0.05); the expressions of CK17 and ALP at mRNA level in cells of printed constructs in 3A8G group were 1.96±0.21 and 55.57±11.49, respectively, which were significantly higher than 1.05±0.42 and 2.01±0.27 in 1A4G group (t=3.333, 8.074, P<0.05 or P<0.01). Conclusions: BMSCs cultured three-dimensionally in 1A4G and 3A8G hydrogels tend to differentiate into sweat gland cells, but the BMSCs cultured three-dimensionally in 3A8G hydrogel show a stronger tendency to differentiate into hair follicle cells than the cells cultured in 1A4G hydrogel. It suggests that relatively high stiffness of three-dimensionally bioprinted extracellular matrix analogue facilitates not only differentiation of BMSCs into sweat gland cells, but also their differentiation into hair follicle cells.

[Preparation and preliminary research on the characteristics of modified nano-bioglass hydrogel].

Objective: To explore the preparation and preliminary research on the characteristics of modified nano-bioglass hydrogel. Methods: (1) The nano-bioglass suspension was prepared by adding 67 mL nano-silica suspension into 400 mL saturated calcium hydroxide solution, and its suspension stability was observed. (2) The hydrogel with final mass fraction of 10% gelatin and 1% sodium alginate was prepared and set as control group. On the basis of the hydrogel in control group, the nano-bioglass suspension prepared in experiment (1) was added to prepare the hydrogel with the final mass fraction of 0.5% bioglass, 10% gelatin, and 1% sodium alginate, and the hydrogel was set as the experimental group. The gelling time at 4 and 25 ℃and the dissolution time at 37 ℃ of hydrogel in 2 groups were recorded, and the gelation at 4 and 25 ℃and dissolution condition at 37 ℃of the hydrogel in 2 groups were observed. The hydrogel in 2 groups were collected and cross-linked with 25 g/L calcium chloride solution after cold bath at 4 ℃, and the compression modulus was measured by Young's modulus tester. In addition, the hydrogel in 2 groups were collected and cross-linked as before, and freeze-drying hydrogel was made at -20 ℃. The relative volumes were measured and the porosity of hydrogel in 2 groups was calculated. The number of sample in the experiment was 3. (3) Fibroblasts (Fbs) were isolated and cultured from 12 C57BL/6J mice of 24 hours old and the morphology was observed by inverted microscope, and the third passage of Fbs were cultured for the following experiment. Fbs were collected to make single cell suspension with the cell concentration of 1×10(5)/mL. The single cell suspension was divided into experimental group and control group according the random number table (the same grouping method below), which were added with hydrogel in experimental group and control group prepared in experiment (2), respectively. At culture hour 12, 24, and 48, cells of 3 wells in each group were collected to detect the survival rate by cell counting kit 8 method. (4) The third passage Fbs were collected to prepare the single cell suspension with the cell concentration of (3.0~4.5)×10(7)/mL, which was divided into experimental group and control group, with 1 tube in each group. The single cell suspension in 2 groups were added with green fluorescent probe DIO for staining and then added with 9 mL hydrogel in experimental group and control group prepared in experiment (2), respectively. The mixed solution of Fbs and hydrogel in 2 groups was cross-linked as before to make cell-loaded hydrogel. On culture day 3, the survival of cells in the hydrogel was observed by laser confocal microscope. The cell-loaded hydrogel was prepared as before and without added with green fluorescent probe DIO. On culture day 7, the adhesion and extension of cells in the hydrogel were observed by scanning electron microscope. (5) Twelve 6-week-old female BALB/c-nu nude mice were collected and divided into experimental group and control group, with 6 mice in each group. A round full-thickness skin defect wound with diameter of 1 cm was made on the back of each mouse. Immediately after injury, one cell-loaded hydrogel block in the experimental group and the control group prepared in experiment (4) was placed in the wound of each mouse in the experimental group and the control group, respectively. On post injury day (PID) 7 and 14, 3 nude mice in each group were sacrificed to collect the wound and wound margin tissue, which was stained with hematoxylin-eosin to observe the wound healing. Data were statistically analyzed with independent sample t test. Results: (1) The nano-bioglass particles could be uniformly dispersed in water and had good suspension stability. (2) The hydrogels of the 2 groups were molten at 37 ℃, and no precipitation of particle was observed. The dissolving time of the hydrogel in the experimental group and the control group at 37 ℃ was 5 and 10 min, respectively. The gelation time of the hydrogel in the experimental group and the control group at 25 ℃ was 30 and 180 min, respectively, and the gelation time of the 2 groups at 4 ℃ was 5 and 10 min, respectively. The compression modulus of hydrogel in the experimental group was (53±6) kPa, which was significantly higher than (23±6) kPa in the control group (t=6.364, P<0.01). The porosity of the hydrogel in the experimental group was (86.1±2.1)%, which was similar to (88.2±4.4)% in the control group (t=1.210, P>0.05). (3) The cells were in long fusiform, and the proportion of nuclei was high, which was accorded with the morphological characteristics of Fbs. At culture hour 12, 24, and 48, the survival rate of cells in the experimental group was (84±4)%, (89±4)%, and (130±10)%, which was similar to (89±5)%, (90±4)%, and (130±11)% in the control group, respectively (t=1. 534, 0.611, 0.148, P>0.05). (4) On culture day 3, the cells in the two groups had complete morphology in the hydrogel, no nuclear lysis or disappearance were observed, the cytoplasm remained intact, and the fluorescence intensity of the cells in the experimental group was significantly stronger than that in the control group. On culture day 7, the cells in the experimental group and the control group adhered and stretched in the hydrogel, and the number of cells in the experimental group adhered to the hydrogel was significantly more than that in the control group. On PID 7, the wound area of the nude mice in the control group and the experimental group were reduced, the reduction area of mice in the experimental group was more obvious, and a large amount of inflammatory cells were seen in and around the wound in the 2 groups. On PID 14, the wound area of the nude mice in the control group was larger than that of the experimental group, and the number of inflammatory cells in and around the wound was significantly more than that in the experimental group. Conclusions: Nano-bioglass hydrogel possesses good physical, chemical, and biological properties, cell loading potential, and the ability to promote wound healing, which means it has a good potential in clinical application.

[New concept of chronic wound healing: advances in the research of wound management in palliative care].

With the aggravation of aging of global population and increase of incidence of various chronic diseases and injuries, patients with chronic wounds due to different causes (malnutrition, abnormal metabolism, compression, infection, tumor, etc.) have grown. Especially in some patients at the end of life, chronic wounds have the characteristics of difficult to heal and even unable to heal. There is an urgent need for palliative treatment for such wounds. Palliative treatment of chronic wounds focuses on the management of smell, pain, exudate, bleeding, and infection with the hope to effectively prevent infection, relief pain, improve quality of life, and reduce the economic burden of medical treatment for patients. This paper reviews the related studies of palliative treatment in chronic wounds at home and abroad, and explores the evaluation and management of palliative treatment of different wounds with the aim to provide new management strategies, new materials, and new concept for the treatment of chronic wounds.

[Characteristics of contrast-enhanced ultrasound in alpha-fetoprotein-negative recurrent small hepatocellular carcinoma].

Objective: To investigate the characteristics of contrast-enhanced ultrasound (CEUS) in alpha-fetoprotein (AFP)-negative recurrent small hepatocellular carcinoma (rsHCC). Methods: The imaging characteristics of CEUS were retrospectively analyzed in 132 lesions from 116 patients with rsHCC, including 59 lesions from 51 AFP-negative patients and 73 lesions from 65 AFP-positive patients. The hemodynamic parameters such as contrast-enhanced onset time, time-to-peak, isoenhancement start time, low-enhancement start time, and perfusion mode were compared between two groups. Results: The time-to-peak, isoenhancement start time, low-enhancement start time of AFP-negative group were significantly increased than those in AFP-positive group (23.22±5.08)s vs. (20.30±3.41)s, (59.44±39.75)s vs. (40.75±16.16)s, (102.89±44.45)s vs. (87.08±25.27)s (all of P<0.05). Meanwhile, the proportion of isoenhancement during the portal and late phases in AFP-negative group was significantly higher than those in AFP-positive group (59.3% vs. 37.0%, 16.9% vs. 4.1%; all of P<0.05). However, there was no significant difference between the two groups in the enhancement start time (14.87±6.00)s vs. (14.35±5.30)s (P>0.05) as well as isoenhancement proportion in the arterial phase (94.9% vs. 98.6%, P>0.05). Conclusions: The enhancement pattern of CEUS in AFP-negative rsHCC patients was "fast-in and slow-out" with a diverse and atypical trend. Recognizing its regular features will facilitate the early detection of AFP-negative rsHCC.

[Some thoughts on the coordinated development of burn department and wound repair department].

On November 29, 2019, in order to strengthen the management of the diagnosis and treatment of the chronic refractory wounds, the National Health Commission released a notice that requires the qualified medical institutions in China to establish wound repair department. To ease the concern that the establishment of wound repair department could hinder the construction and development of burn discipline, the authors put forward their views based on the necessity of establishing wound repair department, the space for the respective development of burn department and wound repair department, and how to coordinate the development of burn department and wound repair department. It is hoped that this paper would be used as a reference by doctors in both fields of burn care and wound repair.

[Effects and mechanism of exogenous tumor necrosis factor α on differentiation of mesenchymal stem cells of mice into sweat gland cells in three-dimensional environment].

Objective: To explore the effects and molecular mechanism of tumor necrosis factor α (TNF-α) on differentiation of mesenchymal stem cells of mice into sweat gland cells in a three-dimensional environment. Methods: (1) Five 6-8 week-old female C57BL/6 mice were used, with one 1 cm(2) deep partial-thickness to full-thickness scald wound being created on the back of each mouse with a scald apparatus. One day after injury, the full-thickness skin tissue of the wound was taken, and the concentration of TNF-α in the tissue was detected by enzyme-linked immunosorbent assay. (2) Gelatin in the mass of 0.9 g and 0.3 g sodium alginate were mixed and then dissolved in 30 mL phosphate buffer solution to make hydrogel. Full-thickness skin of the planta of 10 male and female one day newborn C57BL/6 mice was ground into dermal homogenate. The mesenchymal stem cells were isolated from femur and tibia of 10 male and female C57BL/6 mice born for 7 days and cultured. A final density of 1.5×10(5) cells/mL of bioink was made of mixture of 8 mL pre-warmed hydrogel, 1 mL mouse foot dermal homogenate, and 1 mL the second or third passage of mesenchymal stem cell suspensions. The three-dimensional bioprinter was used to print 12 cylindrical blocks arranged in a crisscross pattern in petri dish. The printed blocks were cross-linked with 25 g/L calcium chloride solution for 10 min and then cultured for 12 hours by adding a medium for mesenchymal stem cells. Subsequently, the printed blocks were divided into blank control group and TNF-α treatment group according to the random number table, with 6 plates and 6 blocks in each group. Both groups of printed blocks were cultured with fresh sweat gland induction medium, and a final mass concentration of 20 ng/mL TNF-α was added into the medium of TNF-α treatment group. After 6 hours of culture, the mRNA expression of pluripotency marker Nanog in the mesenchymal stem cells of two plates of each group was detected by real-time fluorescent quantitative reverse transcription polymerase chain reaction (RT-PCR), and the protein expression of Nanog in the mesenchymal stem cells of one plate of each group was detected by Western blotting, both with triplicate samples. After 14 days of culture, the mRNA expression of sweat gland cell markers cytokeratin 14 (CK14), CK18, sodium potassium adenosine triphosphatase protein a1 (ATP1a1), and aquaporin 5 (AQP5) was detected by real-time fluorescent quantitative RT-PCR in the mesenchymal stem cells of 2 plates of each group (n=3), and the protein expression distribution of CK14, CK18, ATP1a1, and AQP5 of the mesenchymal stem cells in one plate of each group was detected by immunofluorescence staining. Data were statistically analyzed with independent sample t test. Results: (1) One day after injury, the mass concentration of TNF-α in the scald wound tissue of mouse was (19±3) ng/mL. (2) After 6 hours of culture, the mRNA and protein expression levels of Nanog in the mesenchymal stem cells of printed blocks in TNF-α treatment group were 0.39±0.04 and 0.36±0.03, respectively, which were significantly lower than 1.00±0.05 and 1.00±0.07 of blank control group (t=16.51, 14.56, P<0.01). (3) After 14 days of culture, the mRNA expression levels of CK18, CK14, ATP1a1, and AQP5 in the mesenchymal stem cells of printed blocks in TNF-α treatment group were 0.38±0.03, 0.42±0.11, 0.23±0.06, and 0.25±0.03, respectively, which were significantly less than 1.00±0.03, 1.00±0.05, 1.00±0.05, 1.00±0.07 of blank control group (t=25.31, 8.31, 17.07, 17.06, P<0.01). (4) After 14 days of culture, the CK18, CK14, ATP1a1, and AQP5 protein were widely distributed in the cytoplasm of mesenchymal stem cells in printed blocks of blank control group, while the distribution of CK18, CK14, ATP1a1, and AQP5 protein in the cytoplasm of mesenchymal stem cells in printed blocks of TNF-α treatment group were significantly reduced in comparison. Conclusions: Exogenous TNF-α inhibits the directional differentiation of mesenchymal stem cells of mice into sweat gland cells in a three-dimensional environment, which may be related to the inhibition of the expression of Nanog mRNA and protein by TNF-α that subsequently results in the down-regulation of multi-directional differentiation potential of mesenchymal stem cells.

[To build a well-developed wound repair department in China with the original mind and mission].

Based on the spirit of the regulations about diagnosis and treatment of chronic skin wounds just issued by National Health Commission, we systematically review the history of the construction of wound repair department in China and discuss the opportunities and challenges faced by the construction of wound repair department in China. We emphasize on seizing historical opportunities and grasping the development direction of the discipline with the original mind and mission to build a well-developed wound repair department in China, so as to benefit the majority of patients.

[Establishment of a wound care discipline system in China: the review of the construction of wound care center with Chinese characteristics in 20 years and prospect].

The construction of wound treatment specialty (center) with Chinese characteristics began in the early 21st century. Based on my personal experience, this paper systematically reviews the key points and characteristics of the specialty (center) construction of wound treatment with Chinese characteristics and its phased progress. Its future development is also prospected.