There are multiple signaling communication modalities for the biological activities of single cells or groups of cells. The elucidated modalities include neuronal electrical signal communication, long-distance communication mediated by hormones, and short-range signal communication secreted by cells into the extracellular environment, etc. Recently, many studies have shown that mechanical forces are also extensively involved in the information exchange between cells or between cells and the external environment, especially in the signal communication among epithelial cells or between epithelial cells and the extracellular matrix. The cell communication triggered by mechanical forces is instantaneous and rapid, and it affects various activities of both individual epithelial cells and epithelial cell clusters. The mediators of cell communication induced by mechanical forces include actin, myosin, cytoskeleton, and adherens junctions, etc. These mediators trigger processes such as ion flow, activation of signaling pathways, and regulation of transcription factors through mechanical signals, thereby interfering with cell behaviors. This article elaborates on the impacts of mechanical forces on epithelial cells from multiple aspects, including biological signals, three-dimensional folding, collective migration, cell metabolism, carcinogenesis, and epithelial-mesenchymal transition.

Objective To investigate the role of scar epithelial cells and its potential molecular mechanisms in the efficacy of low-energy CO2 fractional laser treating post-burn scars.Methods The model of post-major burn scars on the back of rat was established.Three rats with post-major burn scars received 30 mJ low-energy CO2 fractional laser treatment to detect the activation of scar epidermal cells.Epidermal tissue of scars was isolated for RNA sequencing to screen activated pathways.Subsequently,18 rats with post-major burn scars were randomly divided into 3 groups(n=6):the control group without laser treatment,the laser group receiving 30 mJ CO2 fractional laser treatment,and the laser+inhibitor group receiving laser treatment and intra-scar injection of IWR-1(a Wnt/β-catenin pathway inhibitor),to verify the activation status and effects of the selected pathways.Hematoxylin-eosin staining,Masson staining,and Western blotting were used to detect the proliferation of epithelial cells and fibroblasts,the activation of Wnt/β-catenin pathway,as well as the improvement of scar profiles.Results After low-energy laser treatment,there was a significant increase in the number of Ki67-positive,proliferating cell nuclear antigen(PCNA)-positive,cytokeratin 19(CK19)-positive,and p63-positive cells in the scar epithelial tissue.RNA sequencing coupled with literature analysis identified Wnt/β-catenin pathway as a potential candidate pathway.In the confirmatory experiment,compared to the control group,the Wnt/β-catenin pathway was activated in scar epithelial cells in the laser group 5 d post-laser intervention.After 30 d laser intervention,dermal collagen exhibited a more loosened arrangement,with reduced dermal thickness and significantly less α-smooth muscle actin(α-SMA)-positive fibroblasts compared to the control group.CollagenⅠ,collagen Ⅲ,and the relative ratio of collagen Ⅰ to Ⅲ in the laser group were at a lower level than those in the control group.Administration of the Wnt/β-catenin pathway inhibitor blocked the activation of the Wnt/β-catenin pathway induced by low-energy laser,the proliferation of scar epithelial cells and the improvement of scar profiles.Conclusion Low-energy CO2 fractional laser treatment can activate the Wnt/β-catenin pathway of scar epithelial cells,thereby activating epithelial cells and yielding significant scar improvements.

There are multiple signaling communication modalities for the biological activities of single cells or groups of cells. The elucidated modalities include neuronal electrical signal communication, long-distance communication mediated by hormones, and short-range signal communication secreted by cells into the extracellular environment, etc. Recently, many studies have shown that mechanical forces are also extensively involved in the information exchange between cells or between cells and the external environment, especially in the signal communication among epithelial cells or between epithelial cells and the extracellular matrix. The cell communication triggered by mechanical forces is instantaneous and rapid, and it affects various activities of both individual epithelial cells and epithelial cell clusters. The mediators of cell communication induced by mechanical forces include actin, myosin, cytoskeleton, and adherens junctions, etc. These mediators trigger processes such as ion flow, activation of signaling pathways, and regulation of transcription factors through mechanical signals, thereby interfering with cell behaviors. This article elaborates on the impacts of mechanical forces on epithelial cells from multiple aspects, including biological signals, three-dimensional folding, collective migration, cell metabolism, carcinogenesis, and epithelial-mesenchymal transition.

Currently, there are limited strategies for convenient and rapid wound repair in clinical practice. In recent years, in-situ cell electrospinning (IS-CE) technology, developed from in-situ electrospinning (IS-E) technology, has emerged. IS-CE technology involves encapsulating living cells within micro-nanofibers to construct living fibrous tissue scaffolds in situ, making some progress in wound repair applications. However, this technology still faces limitations such as low cell survival rate and poor fiber stability. This article provides a comprehensive review on the current status of both IS-E and IS-CE technologies, as well as the application of IS-CE technology in wound repair. In addition, the advantages, limitations, and improvement methods of IS-CE technology applied in wound treatment are emphatically discussed, aiming to provide insights for its application in tissue engineering and wound repair.

Objective:To explore the properties of gelatin-polyethylene glycol hydrogel loaded with silver nanoparticle (AgNP) Chlorella (hereinafter referred to as the composite hydrogel) and its effects on healing of infected full-thickness skin defect wounds in mice. Methods:The research was an experimental research. The simple gelatin-polyethylene glycol hydrogel (hereinafter referred to as the simple hydrogel) and the composite hydrogel were prepared, and the appearance and injectability of the two hydrogels were observed at 55 and 37 ℃, and under the irradiation of 808 nm near-infrared light, respectively. An electronic universal testing machine was employed to assess the tensile and compressive stress-strain properties of both types of hydrogels at room temperature. Additionally, the cyclic compressive stress-strain properties of the composite hydrogel were examined at 80% of the maximum compressive stress. Staphylococcus aureus or Escherichia coli solution was added to phosphate buffer solution (PBS), simple hydrogel, and composite hydrogel, respectively. The part of composite hydrogel containing Staphylococcus aureus or Escherichia coli solution was irradiated with near-infrared light for 5 minutes. After each sample was incubated for 6 h, the dilution plating method was used to detect and calculate the mortality rates of the two bacteria at 24 h of culture ( n=5). The discarded foreskin tissue was taken from a 6-year-old healthy boy admitted to the Department of Urology of the First Affiliated Hospital of Naval Medical University for circumcision. Primary human fibroblasts (HFbs) were isolated using the enzyme extraction method, routinely cultured to the 3 rd to 6 th passages for subsequent cellular experiments. Composite hydrogel extracts with final mass concentrations of 100.0, 50.0, 25.0, 12.5, and 0 mg/mL were respectively prepared and used to culture HFbs, and the cell proliferation after 24 h of culture was detected using a cell counting kit 8 ( n=3). A total of twenty 6-8 weeks old C57BL/6J female mice were utilized, and a full-thickness skin defect was surgically created on the back of each mouse. The wounds were infected with Staphylococcus aureus solution. The infected mice were divided into blank control group, simple hydrogel group, composite hydrogel group, and combined treatment group according to the random number table, and the wounds were treated with PBS, simple hydrogel, composite hydrogel, and composite hydrogel+light irradiation (under the irradiation of 808 nm near-infrared light for 5 min), respectively, with 5 mice in each group. On post injury day (PID) 0 (immediately after the first wound treatment), 3, 7, and 14, an overall assessment of wound exudation and healing were conducted, and the wound healing rates on PID 7 and 14 were calculated ( n=5). On PID 14, hematoxylin-eosin staining was performed to observe histopathological changes in the mouse wound. Results:Both simple hydrogel and composite hydrogel were in a solution state at 55 ℃ and transition to a gel state when cooling to 37 ℃. After the two hydrogels were irradiated by near-infrared light, only the composite hydrogel reheated up and returned to the solution state again with injectability. The maximum tensile stress of the composite hydrogel was up to 301.42 kPa, with a corresponding strain of 87.19%; the maximum compressive stress was up to 413.79 kPa, with a corresponding strain of 91.67%, which was similar to the tensile and compressive properties of the simple hydrogel. After 10 compression cycles, the maximum compressive stress of the composite hydrogel still reached 84.1% of the first compressive stress. After 24 h of culture, the mortality rate of Staphylococcus aureus treated with simple hydrogel was significantly higher than that treated with PBS ( P<0.05); the mortality rates of Escherichia coli and Staphylococcus aureus treated with composite hydrogel alone were significantly higher than those treated with simple hydrogel ( P<0.05); the mortality rates of Escherichia coli and Staphylococcus aureus treated with composite hydrogel+light irradiation were significantly higher than those treated with composite hydrogel alone ( P<0.05). After 24 h of culture, compared with that cultured in composite hydrogel immersion solution with final mass concentration of 0 mg/mL, the proliferation activity of HFbs cultured in composite hydrogel immersion solution with final mass concentrations of 25.0 and 50.0 mg/mL was significantly enhanced ( P<0.05), while the proliferation activity of HFbs cultured in composite hydrogel immersion solution with final mass concentration of 100 mg/mL was significantly decreased ( P<0.05). On PID 0 and 3, more purulent secretions were seen in the wounds of mice in blank control group and simple hydrogel group, while only a small amount of exudate was observed in the wounds of mice in composite hydrogel group, and no obvious infection was observed in the wounds of mice in combined treatment group. On PID 7 and 14, the wound healing rates of mice in simple hydrogel group were significantly higher than those in blank control group ( P<0.05); the wound healing rates of mice in composite hydrogel group were significantly higher than those in simple hydrogel group ( P<0.05); the wound healing rates in combined treatment group were significantly higher than those in composite hydrogel group ( P<0.05). On PID 14, the wounds of mice in blank control group exhibited a high infiltration of inflammatory cells with no new epithelial layer observed; the wounds of mice in simple hydrogel group displayed a short length of newly formed epithelium with a small amount of inflammatory cells; the wounds of mice in composite hydrogel group exhibited continuous formation of new epithelium and a large amount of immature granulation tissue; the wounds of mice in combined treatment group showed continuous epithelialization with less immature granulation tissue. Conclusions:The prepared composite hydrogel exhibits excellent thermosensitivity, photothermal properties, and injectability, as well as excellent mechanical properties, antibacterial properties, and biocompatibility, and can promote the healing of infected full-thickness skin defect wounds in mice.

Research of in-situ induced repair and regeneration is a multi- and inter-disciplinary field, which is of important potentials in the treatment of both large-area deep burns and chronic wounds such as diabetic skin ulcers. In-situ forming injectable hydrogels which are hydrogel-like biomaterials that can spontaneously gelatinize in physiological condition when applied in local wounds have been explored in recent years. This kind of biomaterials contain extracellular matrix, in which cells promoting wound repairing can be added if required, and can work as release-controlled carriers for active peptides such as growth factors to simulate local wound microenvironment and induce the repair and regeneration. Herein, characteristics and function of promoting wound repair and regeneration about in-situ forming injectable hydrogels were reviewed, including material types and their relevant working mechanisms, advantages, existing problems, etc.

Objective:To investigate the clinical effects of negative pressure wound therapy (NPWT) in treating the poor healing of incisions after different abdominal operations.Methods:The retrospective observational study was conducted. From June 2019 to December 2020, 42 patients with poor healing of incisions after abdominal surgery were admitted to Center of Burns and Trauma of the First Affiliated Hospital of Naval Medical University, including 29 males and 13 females, aged 23-81 years. The disease course of poor healing of abdominal incision was 3-60 d. The preoperative examination of patients was completed after admission, and NPWT was used after debridement. According to the dehiscence level of incision, the negative pressure value of -10.64 to -6.65 kPa was set. The incisions were sutured in the second stage when the incisions had good blood circulation. The cause of abdominal surgery, the dehiscence level and the cause of poor healing of abdominal incision were investigated, and the final healing of abdominal incision and the occurrence of complication were observed.Results:The causes of abdominal operations in this group of patients who ocurred poor healing of abdominal incisions were ranked according to the composition ratio, with the top 4 causes being colon cancer (9 cases, accounting for 21.4%), bile duct disease (8 cases, accounting for 19.0%), liver cancer (5 cases, accounting for 11.9%), and appendicitis (4 cases, accounting for 9.5%). There were 25 cases (59.5%) with dehiscence of abdominal incision in the deep fascia layer, and the other 17 cases (40.5%) with dehiscence of abdominal incision in the superficial fascia layer. The causes of poor healing of abdominal incision were ranked according to the composition ratio, with the top 3 causes being infection (24 cases, accounting for 57.1%), fat liquefaction (11 cases, accounting for 26.2%), and suture reaction (5 cases, accounting for 11.9%). The blood circulation in 40 patients was improved after being treated with NPWT, and the incisions were sutured in the second stage. The incisions healed well when the suture lines were removed in the second to third week. Intestinal fistula and bile leakage developed during the NPWT treatment, respectively in the other 2 patients, in which negative pressure equipment was removed subsequently, and the incisions healed after adequate drainage and conventional dressing changes.Conclusions:NPWT is effective in treating poor healing of abdominal incision after different abdominal surgeries. The clinicians need to comprehensively assess the patient's condition to determine when and how to use NPWT to avoid the occurrence of intestinal fistula, bile leakage, and other complications.

Vitiligo is a common depigmented disease, and currently there is no specific treatment. In clinical practice, common treatments include topical or oral drugs, phototherapy and surgery. Surgical interventions mainly include tissue and cellular grafting. Tissue grafting techniques include punch/mini grafting, split-thickness skin grafting, epidermal suction blister grafting, and cellular grafting techniques include cultured and non-cultured autologous melanocyte grafting. These surgical treatments are safe and effective for patients with stable, localized vitiligo or those irresponsive to other therapies.

Autologous split-thickness skin grafting is still an important procedure for the repair of skin defect. However, there are some obvious limitations, such as new injury to skin donor sites and insufficient skin source, etc. It is an ideal goal to develop tissue-engineered skin to realize permanent replacement of skin defect. After decades of development, a variety of tissue-engineered skins have been put into the market for applications, but it is still a long way to achieve regenerative repair of skin defect. In this article, we summarize the status of various tissue-engineered skins, and then make a preliminary discussion on the opportunities and challenges on development of tissue-engineered skin.

Objective:To evaluate the efficacy and safety of cell sheets containing allogeneic keratinocytes and fibroblasts in the treatment of partial-thickness burn wounds.Methods:The cell sheets containing allogeneic keratinocytes and fibroblasts were constructed using polyurethane biofilm as carrier. Then gross observation and histological observation were conducted. From April 2016 to December 2017, Changhai Hospital of Naval Medical University recruited patients with acute partial-thickness burn wounds that met the inclusion criteria for this prospective and positively self-controlled clinical trial. Recruitment of 40 acute partial-thickness burn wounds were planned with each selected single wound being not smaller than 10 cm×10 cm and not more than 5% total body surface area (TBSA). Each wound was equally divided into two areas, which were recruited into cell sheet group and conventional treatment group according to the random number table. The wounds in cell sheet group were covered by cell sheet and then sterile gauze as secondary dressings. Depending on the wound healing and exudation, the sterile gauze was replaced every 1 to 3 day (s) after the treatment was started, and the cell sheet was replaced every 7 days (namely dressing changing). The wounds in conventional treatment group were covered by sulfadiazine silver cream gauze and then dressed with sterile gauze, with the dressings changed every 2 to 3 days depending on wound exudation. On treatment day 5, 7, 10, and 14, the wound healing rates in the two groups were calculated. The complete wound healing time, the total number of dressing changes, and the status of wound infection during treatment were recorded. The Visual Analogue Scale was used to score the pain at the first dressing change. Scar formation of patients was followed up for 6 to 12 months after injury. Safety indicators including vital signs, laboratory examination indexes, and adverse reactions during treatment were observed. Data were statistically analysed with Wilcoxon rank sum test and Bonferroni correction.Results:(1) Each prepared cell sheet had a diameter of about 8 cm and was about 49 cm 2 in size, containing 2 or 3 layers of keratinocytes and fibroblasts. (2) A total of 43 patients were enrolled, of whom 3 patients dropped out of the study. Of the 40 patients who completed the treatment, there were 22 males and 18 females who were aged 1 to 57 year (s), with total burn area of 2% to 26% TBSA. (3) On treatment day 5, 7, 10, and 14, the wound healing rates in cell sheet group were significantly higher than those in conventional treatment group ( Z=4.205, 4.258, 3.495, 2.521, P<0.05 or P<0.01). The complete wound healing time in cell sheet group was 7 (6, 8) days, which was significantly shorter than 11 (7, 14) days in conventional treatment group ( Z=4.219, P<0.01). The total number of wound dressing changes in cell sheet group was 1 (1, 2) times, which was significantly less than 6 (4, 7) times in conventional treatment group ( Z=5.464, P<0.01). (4) The wounds in cell sheet group in 31 patients healed before the first dressing change. The pain score of wounds in the first dressing change in cell sheet group of 9 patients was 1 (0, 1) point, while the pain score of wounds in the first dressing change in conventional treatment group of 40 patients was 2 (1, 3) points. There was no obvious infection in the wounds in both groups of 40 patients before the wound healing. Nine patients completed the follow-up after the trial. In 6 patients, no scar formation was observed in cell sheet group or conventional treatment group. The color of wounds in cell sheet group was consistent with normal skin, and there was only a small amount of pigment deposition in the wounds of conventional treatment group. Three patients developed pigment deposition only in the wounds of cell sheet group but obvious scars in conventional treatment group. (5) The abnormal fluctuations of vital signs including body temperature, blood pressure, heart rate, respiratory rate, and laboratory examination indexes of all patients during treatment were alleviated through the process of burn wound healing. No obvious adverse reactions or abnormalities related to the treatment were observed. Conclusions:The cell sheet containing allogeneic keratinocytes and fibroblasts can reduce the number of dressing changes, accelerate wound epithelialization, shorten wound healing time, reduce pain during dressing change in the treatment of partial-thickness burn wounds, and it may reduce scar hyperplasia after wound healing because of accelerating wound epithelization. Its clinical application is simple, safe, and effective.