| BackgroundScar is a natural product of surgical wound.However,excessive collagen deposition would result in pathological scarring,which not only influences appearance,but also causes pain,itching and other symptoms.Additionally,it may lead to joint movement disorders,and bring both psychological and physiological stress to patients.How to restrain scar formation after surgery is constantly a clinical difficulty in the department of plastic surgery.Skin mechanical tension could promote pathological scar formation after surgery,appearing higher and wider than the normal skin.Although the use of tension-reducing suture in skin deeper layer could reduce the internal tension,it is temporary for suture to retain its strength against skin tension and still prone to pathological scarring.Thus,it is crucial to find out a method which could persistently reduce skin mechanical tension around incision.At present,there have been many methods for prevention and treatment of pathological scarring,among which silicone occlusive sheeting is the first choice for its exact effectiveness and convenient usage.However,it cannot reduce skin tension to inhibit scar widening.Elastic silicone occlusive sheeting is a new drug,which has good tensile elasticity to reduce skin tension and potential to inhibit scar widening.However,there is no trial involving elastic silicone occlusive sheeting on its effectiveness of inhibiting surgical scar formation.Although skin mechanical tension is identified as a key regulator of pathological scar formation,the underlying mechanism has not been completely understood.Studies have shown that the persistence of myofibroblasts is one of the main causes of pathological scarring.Most myofibroblasts come from fibroblasts.Compared with fibroblasts,myofibroblasts,identified by expression ofα-smooth muscle actin,have the ability of contractility and could secrete more extracellular matrix secretion.They appear temporarily during normal skin wound healing and then disappear through apoptosis.However,the persistence of myofibroblasts can lead to excessive collagen deposition,resulting in pathological scar formation.It has been reported that skin mechanical tension promotes the transformation of fibroblasts to myofibroblasts,resulting in excessive collagen deposition in the new granulation tissue of the wound,which is closely related to pathological scar formation.However,the mechanism behind it remains unclear.Transient receptor potential canonical channel-6 is a nonselective Ca2+channel protein,which is widely distributed in human tissue.Recent studies show that TRPC6 is associated with wound healing,controlling the transformation of fibroblasts into myofibroblasts.Meanwhile,TRPC6 is a kind of stretch-activated ion channels that open directly through stretching cell membrane.Thus,we assumed that mechanical tension mediated the transformation of fibroblasts into myofibroblasts and pathological scar formation by regulating TRPC6 and activating related intracellular signaling pathways.To solve the above problems,we first compared the mechanical properties between elastic silicone occlusive sheeting and silicone occlusive sheeting to determine the reduced tension around the incision.Then,we conducted a randomized controlled study to compare the effects of elastic silicone occlusive sheeting versus silicone occlusive sheeting on scar formation after surgery.Finally,we preliminarily discussed the mechanism of mechanical tension promoting hypertrophic scar formation after surgery.Contents and Methods1.Compare the mechanical properties between elastic silicone occlusive sheeting and silicone occlusive sheetingThe force parameters of elastic silicone occlusive sheeting and silicone occlusive sheeting were measured via Electro Force 3100 instrument,and compared by the stress-strain curve.The optimal lengths of elastic silicone occlusive sheeting and silicone occlusive sheeting after stretching were measured in patients’skin.We calculated resilience to compare the reduced tension of the two types of silicone occlusive sheeting on the incision.2.Compare the effects of elastic silicone occlusive sheeting versus silicone occlusive sheeting on scar width and appearance after surgeryA single-center,prospective,randomized,assessor-blinded,and split-scar trial was conducted.74 patients who had undergone conventional open thyroidectomy were continuously enrolled from August to October 2021.After patient enrollment,the wound was divided into left and right half and then randomly divided into elastic silicone occlusive sheeting group and silicone occlusive sheeting group.In both groups,sheetings were applied3-7 days after removal,and replaced once 5-7 days after removal.Scar width,VSS score,pain/itch VAS score and PSD score were used to compare effects between the two groups.3.Discuss the mechanism of mechanical tension promoting the transformation of dermal fibroblasts into myofibroblastsThis experiment was divided into two parts:in vivo experiment and in vitro experiment.In vivo,surgical tension incision model was established on the back of mice.The mice were divided into high-stretched group and low-stretched group.In the high-stretched group,a regular hexagonal full-layer skin defect with a base edge of 1cm was made around T1 level on the back of mice,while in the low-stretched group,a full-layer horizontal skin incision with a length of 2cm was made at the same site.The wounds of both groups were immediately sutured.On the 9th and 14th days after operation,standardized digital images were taken with a labeled standard scale next to each wound to compare the width of scar tissue between the two groups.At the same time,part of the scar tissue was dissected and immediately fixed in 4%paraformaldehyde for over 48h,then embedded with paraffin.HE staining as well as Masson’s trichrome staining were performed to compare the area of scar tissue and collagen deposition between the two groups.Immunohistochemistry was performed to test the distribution and expression of TRPC6.Additionally,part of the scar tissue was used to extract the protein of the scar tissue and Western Blot was performed to compare the expression of TRPC6 andα-SMA between the two groups,clarifying the possible relationship between the expression of TRPC6 and incision tension as well as the transformation of fibroblasts into myofibroblasts.In vitro,The Flexcell（?）FX-5000TM system was used to simulate the in vitro tension model,and the dermal fibroblasts isolated from the skin of the second-generation C57BL/6J mice were cultured on Bioflex（?）six-well plates and divided into mechanically-stretched group and control group.The dermal fibroblasts in the mechanically-stretched group were subjected to cyclic tension at a frequency of 0.1 Hz（6 cycles/min）with a maximal increase in surface area of 10%for 4h and 8h and the dermal fibroblasts in the control group were not stretched.Western Blot and immunofluorescence were performed to detect the expression change of protein TRPC6 to determine the induced effect of mechanical tension on TRPC6expression.Meanwhile,the possible role of TRPC6 in the transformation of fibroblasts into myofibroblasts induced by skin mechanical tension was preliminarily investigated by RT-q PCR and Western Blot to detect the changes of TRPC6,α-SMA and Col-1 in dermal fibroblasts of the two groups.Results1.The mechanical properties between elastic silicone occlusive sheeting and silicone occlusive sheetingThe elastic silicone occlusive sheeting could reduce the tension of 2.43-3.95N around the incision.By contrast,the silicone occlusive sheeting could reduce the tension of 0-0.288N around the incision.2.The effects of elastic silicone occlusive sheeting versus silicone occlusive sheeting on the inhibition of scar formation after surgery（1）A total of 74 patients after conventional open thyroidectomy were included in this study,among which 61 patients completed the 6-month follow-up.（2）6 months after surgery,mean scar width（our primary outcome measure）on the silicone occlusive sheeting group was significantly wider than that on the elastic silicone occlusive sheeting group（1.02±0.64 mm versus 0.47±0.25 mm,respectively,P<0.01）.（3）6 months after surgery,the VSS score of the elastic silicone occlusive sheeting group was significantly lower than that of the silicone occlusive sheeting group（3.93±0.93 versus4.49±0.96,respectively,P<0.01）.Among its subscore,the pigmentation score（1.07±0.51）and vascularity score（0.89±0.52）of the elastic silicone occlusive sheeting group were significantly lower than those of the silicone occlusive sheeting group（1.25±0.51 and1.21±0.58,respectively）,and the difference was statistically significant（P<0.01）.（4）6 months after surgery,the mean pain VAS score was 0.77±0.42 on the silicone occlusive sheeting group and 0.82±0.50 on the elastic silicone occlusive sheeting group（P=0.083）.（5）6 months after surgery,the mean itching VAS score was 0.31±0.47 on the silicone occlusive sheeting group versus 0.36±0.48 on the elastic silicone occlusive sheeting group（P=0.083）.（6）6 months after surgery,the PSD score was 4.25±0.47 in the elastic silicone occlusive sheeting group and 3.79±0.80 in the silicone occlusive sheeting group（P<0.01）.3.The role of TRPC6 in skin mechanical tension inducing the transformation of dermal fibroblasts into myofibroblasts（1）In vivo,gross observation showed that the width of incision scar tissue in high-stretched group was wider than that in low-stretched group.Results of HE staining showed that the area of incision scar tissue in high-stretched group was larger than that in low-stretched group.Results of Masson’s trichrome staining showed that compared with the low-stretched group,there was more collagen deposition in the dermal layer in the high-stretched group.These results suggested that an animal model of surgical tension incision in mice was successfully established.Results of immunohistochemistry showed that compared with that in normal skin,the expression of TRPC6 was significantly increased in the incision scar tissue and the expression of TRPC6 in the high-stretched group was higher than that in the low-stretched group.Western Blot assay showed significant increases in the expression of protein TRPC6 andα-SMA in the high-stretched group compared with that in the low-stretched group.（2）In vitro,the expression of protein TRPC6 in dermal fibroblasts of the mechanically-stretched group significantly increased compared with that of the control group according to Western Blot assay and immunofluorescence results,which was in a time-dependent manner.Additionally,RT-q PCR and Western Blot analysis showed that the m RNA and protein levels of TRPC6,α-SMA and Col-1 in dermal fibroblasts of the mechanically-stretched group were increased simultaneously compared with those of the control group.Conclusions1.The tension reduction degree of elastic silicone occlusive sheeting is better than that of silicone occlusive sheeting.2.Compared with silicone occlusive sheeting,elastic silicone occlusive sheeting can effectively inhibit scar widening and further improve the scar appearance.3.Results both from vivo and vitro indicate that mechanical tension may induce transformation of fibroblasts into myofibroblasts through TRPC6,thus promoting scar formation.4.This study provides an important experimental and theoretical basis for clinical use of elastic silicone occlusive sheeting to inhibit scar formation after surgery. |
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