Scarless healing is considered as the most ideal mode of wound repair. This ability generally exists in the early period of mammalian embryos, however it gradually turns to scar healing with the development of the embryos. This phenomenon is the result of the interaction of multiple biological functions, and the mechanism is still uncertain. This article deals with a systematical review of literature concerning the mechanism of scarless healing based on the recent experimental studies, hoping to provide evidence for the treatment of wounds to realize scarless healing in adult.
Adult ; Animals ; Cicatrix ; prevention & control ; Fetus ; physiology ; Humans ; Wound Healing ; physiology

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.

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 preliminarily observe the effects of application of micro-negative pressure in children with small-area deep partial-thickness burn. Methods: From January 2016 to August 2018, 64 children with small-area deep partial-thickness burn who were admitted to the Department of Burn Surgery of the First Affiliated Hospital of Naval Medical University were recruited in this prospective randomized controlled study. According to the random number table, they were divided into negative pressure group [18 boys and 14 girls, aged (3.9±1.6) years with total burn area of (5.5±2.2)% total body surface area (TBSA)] and conventional group [20 boys and 12 girls, aged (3.8±1.7) years with total burn area of (5.8±1.6)% TBSA], with 32 patients in each group. After admission, simple debridement was performed in the patients of 2 groups. After that, the children in negative pressure group were treated with micro-negative pressure with negative pressure material replaced every 3 to 5 days. Children in conventional group were treated with silver sulfadiazine cream with dressing change every other day. On post injury day (PID) 14 and 21, general wound observation was performed, the wound healing rate was calculated, the exudates from the wounds were cultured and the positive detection rate was calculated. The number of patients requiring surgical skin grafting was recorded and the rate of surgical skin grafting was calculated, and the complete wound healing time was recorded in the patients of 2 groups. Scar formation was evaluated by the Vancouver Scar Scale (VSS) in 3, 6, and 12 months after wound healing. Data were processed with chi-square test, t test, Bonferroni correction, and analysis of variance for repeated measurement. Results: (1) On PID 14, all the necrotic tissue in the wounds of patients in negative pressure group was removed, with few exudates, and most of the wounds had been epithelialized; most of necrotic tissue in the wounds of patients in conventional group was removed, with more exudates and smaller wound healing area than those in negative pressure group. On PID 21, most of the wounds of patients in negative pressure group were healed, and the exudates were rare, while the wound healing area of patients in conventional group was significantly smaller than that in negative pressure group with more exudates. (2) On PID 14 and 21, the wound healing rates [(49.8±3.3)% and (95.8±2.4)%] of patients in negative pressure group were significantly higher than those in conventional group [(40.0±3.2)% and (75.3±2.5)%, t=11.899, 33.461, P<0.01]. (3) On PID 14 and 21, the positive detection rates of wound bacteria of patients in negative pressure group were significantly lower than those in conventional group (χ²=6.275, 5.741, P<0.05). (4) The rate of surgical skin grafting of patients in negative pressure group was significantly lower than that in conventional group (χ²=5.333, P<0.05). (5) The complete wound healing time of patients in negative pressure group [(23.9±2.3) d] was significantly shorter than that in conventional group [(27.9±1.8) d, t=-7.806, P<0.01]. (6) In 3, 6, and 12 months after wound healing, the VSS scores [(6.9±1.8), (5.6±1.4), (3.4±1.5) points] of patients in negative pressure group were significantly lower than those in conventional group [(9.0±1.5), (7.4±2.0), (5.7±1.6) points, t=-4.987, -4.127, -5.988, P<0.01]. Conclusions In comparison with routine dressing change, the treatment of application of micro-negative pressure in children with small-area deep partial-thickness burn can significantly improve the wound healing rate and rate of surgical skin grafting, decrease the wound infection rate, shorten the wound healing time, and improve the wound healing quality.