Mechanical receptor-related mechanisms in scar management: a review and hypothesis

Deciphering Pain and Pruritus in Keloids from the Perspective of Neurological Dysfunction: Where Are We Now?

Keloids are a typical skin fibroproliferative disease that can cause severe aesthetic and functional concerns. Pain and pruritus are the most common clinical symptoms of keloids, but the mechanisms underlying these symptoms remain unclear. The peripheral nervous system plays a pivotal role in the transmission of superficial sensation signals. Mounting evidence has shown potential correlations between disturbance in the peripheral nervous system and pain and pruritus in keloids. Here, we summarize the role of neurological dysfunction in the development of pain and pruritus, with a specific focus on neuroanatomical alterations, the dysfunction of sensory nerves, and neurogenic inflammation.

Tension-sensitive HOX gene expression in fibroblasts for differential scar formation

BACKGROUND

Scar formation is a common end-point of the wound healing process, but its mechanisms, particularly in relation to abnormal scars such as hypertrophic scars and keloids, remain not fully understood. This study unveils a novel mechanistic insight into scar formation by examining the differential expression of Homeobox (HOX) genes in response to mechanical forces in fibroblasts derived from normal skin, hypertrophic scars, and keloids.

METHODS

We isolated fibroblasts from different scar types and conducted RNA sequencing (RNA-Seq) to identify differential gene expression patterns among the fibroblasts. Computational modeling provided insight into tension alterations following injury, and these findings were complemented by in vitro experiments where fibroblasts were subjected to exogenous tensile stress to investigate the link between mechanical tension and cellular behavior.

RESULTS

Our study revealed differential HOX gene expression among fibroblasts derived from normal skin, hypertrophic scars, and keloids. Computational simulations predicted injury-induced tension reduction in the skin, and in vitro experiments revealed a negative correlation between tension and fibroblast proliferation. Importantly, we discovered that applying mechanical tension to fibroblasts can modulate HOX gene expression, suggesting a pivotal role of mechanical cues in scar formation and wound healing.

CONCLUSION

This study proposes a model wherein successful wound healing and scar formation are critically dependent on maintaining tensional homeostasis in the skin, mediated by tension-sensitive HOX genes. Our findings highlight the potential of targeting mechanotransduction pathways and tension-sensitive HOX gene expression as therapeutic strategies for abnormal scar prevention and treatment, offering a new perspective on the complex process of scar formation.

Efficacy of stromal vascular fraction in the treatment of scars: A systematic review and meta-analysis

OBJECTIVE

Our aim was to assess the effectiveness of stromal vascular fraction (SVF) in treating scars using the latest meta-analysis.

METHODS

We used PubMed, Embase, Cochrane, and Web of Science to search the studies used to evaluate the efficacy of SVF in scar treatment. At least one of the following outcome measures were reported: vascularity, pigmentation, thickness, relief, pliability, surface area, pain, itching and color.

RESULTS

A total of four eligible articles comprising 145 patients (64 SVF patients and 81 non-SVF patients) were included. The findings of this meta-analysis indicated that SVF had significant therapeutic effects in terms of vascularity (SMD/MD, 95% CI: -1.12, -0.02; p = 0.04), itching (SMD/MD, 95% CI: -0.61, -0.13; p = 0.002), POSAS (SMD/MD, 95% CI: -5.93, -1.47; p = 0.001), and thickness (SMD/MD, 95% CI: -1.04, -0.35; p < 0.001). In terms of OSAS (SMD/MD, 95% CI: -9.14, 0.59; p = 0.09), pigmentation (SMD/MD, 95% CI: -1.02, 0.06; p = 0.08), relief (SMD/MD, 95% CI: -1.14, 0.16; p = 0.14), surface area (SMD/MD, 95% CI: -0.91, 0.26; p = 0.27), PSAS (SMD/MD, 95% CI: -7.20, 0.49; p = 0.09), pain (SMD/MD, 95% CI: -0.87, 0.07; p = 0.10), pliability (SMD/MD, 95% CI: -0.57, 0.01; p = 0.06), and color (SMD/MD, 95% CI: -1.78, 0.48; p = 0.26), there were no significant statistical differences.

CONCLUSION

In view of the heterogeneity and potential selective bias, further large-scale, prospective, and multicenter clinical trials are needed to confirm the efficacy and reliability of SVF in the treatment of scars.

Compression Therapy in Dermatology

The benefit of lower limb compression therapy is not limited to chronic venous insufficiency or/and lymphoedema. Thanks to its anti-edema and anti-inflammatory effects, compression therapy is considered a beneficial adjuvant therapy to treat atypical wounds, inflammatory dermatoses, cellulitis, and traumatic wounds in the absence of contraindications. Strict contraindications are limited to severe peripheral arterial disease and decompensated heart failure. The variability of commercially available compression materials and systems, such as short-stretch bandages, multi-component systems, zinc oxide bandages, medical adaptive compression systems, ulcer compression stockings or medical compression stockings, facilitates the adaptation of compression therapy to the individual needs of each patient. Compared to venous leg ulcers, low pressures of 20mmHg are often sufficient to treat dermatological disorders, with higher patient tolerance and compliance.

[Translated article] Compression Therapy in Dermatology

The benefit of lower limb compression therapy is not limited to chronic venous insufficiency or/and lymphoedema. Thanks to its anti-edema and anti-inflammatory effects, compression therapy is considered a beneficial adjuvant therapy to treat atypical wounds, inflammatory dermatoses, cellulitis, and traumatic wounds in the absence of contraindications. Strict contraindications are limited to severe peripheral arterial disease and decompensated heart failure. The variability of commercially available compression materials and systems, such as short-stretch bandages, multi-component systems, zinc oxide bandages, medical adaptive compression systems, ulcer compression stockings or medical compression stockings, facilitates the adaptation of compression therapy to the individual needs of each patient. Compared to venous leg ulcers, low pressures of 20mmHg are often sufficient to treat dermatological disorders, with higher patient tolerance and compliance.

NRP1 transduces mechanical stress inhibition via LATS1/YAP in hypertrophic scars

Hypertrophic scar (HS) is an abnormal fibrous hyperplasia of the skin caused by excessive tissue repair in response to skin burns and trauma, which restricts physical function and impairs patients' quality of life. Numerous studies have shown that pressure garment therapy (PGT) is an effective treatment for preventing hypertrophic scars. Herein, we found that mechanical stress stimulates the neuropilin 1 (NRP1) expression through screening GSE165027, GSE137210, and GSE120194 from Gene Expression Omnibus (GEO) database and bioinformatics analysis. We verified this stimulation in the human hypertrophic scar, pressure culture cell model, and rat tail-scar model. Mechanical compression increased LATS1 and pYAP enrichment, thus repressing the expression of YAP. Functionally, the knockdown of NRP1 promoted the expression of LATS1, thus decreasing the expression of YAP and inhibiting endothelial cell proliferation. Furthermore, co-immunoprecipitation analysis confirmed that NRP1 binds to YAP, and mechanical compression disrupted this binding, which resulted in the promotion of YAP relocation to nuclear. In conclusion, our results indicated that NRP1 transduces mechanical force inhibition by inhibiting YAP expression. Mechanical pressure can release YAP bound to NRP1, which explains the phenomenon that mechanical stress increases YAP in the nucleus. Strategies targeting NRP1 may promote compression therapy with optimal and comfortable pressures.

Compression therapy in dermatology

Compression therapy is a conservative therapy that can be used in many patients with dermatological conditions, especially those associated with edema. In addition to its well-established use in venous and lymphatic disorders, there is increasing evidence that compression therapy supports the healing of inflammatory dermatoses. The presence of edema, regardless of its etiology, is an indication for the use of compression therapy. Nowadays, a variety of materials and treatment options are available for compression therapy, each with their own advantages and disadvantages. Often, compression therapy with low resting pressures is sufficient for effective therapy and is better tolerated by patients. The main contraindications to compression therapy are advanced peripheral arterial disease and decompensated heart failure. Individual factors and economic considerations should be taken into account when deciding on compression therapy with the patient. Patient self-management should be encouraged whenever possible. This requires education and support tools.

Kompressionstherapie in der Dermatologie

Die Kompressionstherapie ist eine konservative Therapie, die bei vielen Patienten mit dermatologischen Krankheiten durchgeführt werden kann, insbesondere wenn diese mit Ödemen assoziiert sind. Neben den wissenschaftlich sehr gut belegten Indikationen bei venösen und lymphatischen Erkrankungen, gibt es auch zunehmend wissenschaftliche Hinweise, dass durch die Kompressionstherapie die Abheilung entzündlicher Dermatosen unterstützt wird. Wenn Ödeme vorliegen, handelt es sich, unabhängig von deren Genese, um einen Einsatz im Rahmen der Zulassung der Kompressionstherapie.

Für die Kompressionstherapie stehen heute verschiedene Materialien und Versorgungsoptionen mit systemspezifischen Vor‐ und Nachteilen zur Verfügung. Oft ist eine Kompressionstherapie mit niedrigen Ruhedruckwerten für einen Therapieerfolg ausreichend und wird von den Patienten besser toleriert. Als wichtigste Kontraindikationen der Kompressionstherapie sind die fortgeschrittene periphere arterielle Verschlusskrankheit und die dekompensierte Herzinsuffizienz zu beachten.

Bei der gemeinsam mit dem Patienten getroffenen Entscheidung für eine Kompressionstherapie, sollten individuelle Faktoren und wirtschaftliche Aspekte berücksichtigt werden. Wann immer möglich, ist ein Selbstmanagement des Patienten zu unterstützen. Hierfür sind Edukation und Hilfsmittel erforderlich.

Matrix stiffness-induced α-tubulin acetylation is required for skin fibrosis formation through activation of Yes-associated protein

Skin fibrosis, a pathological process featured by fibroblast activation and extracellular matrix (ECM) deposition, makes a significant contribution to morbidity. Studies have identified biomechanics as the central element in the complex network of fibrogenesis that drives the profibrotic feedback loop. In this study, we found that the acetylation of α-tubulin at lysine 40 (K40) was augmented in fibrotic skin tissues. Further analysis showed that α-tubulin acetylation is required for fibroblast activation, including contraction, migration, and ECM deposition. More importantly, we revealed that biomechanics-induced upregulation of K40 acetylation promotes fibrosis by mediating mechanosensitive Yes-associated protein S127 dephosphorylation and its cytoplasm nucleus shuttle. Furthermore, we demonstrated that the knockdown of α-tubulin acetyltransferase 1 could rescue the K40 acetylation upregulation caused by increased matrix rigidity and ameliorate skin fibrosis both in vivo and in vitro. Herein, we highlight the critical role of α-tubulin acetylation in matrix stiffness-induced skin fibrosis and clarify a possible molecular mechanism. Our research suggests α-tubulin acetylation as a potential target for drug design and therapeutic intervention.

Beyond the Scar: A Basic Science Review of Wound Remodeling

Significance: Increasing development of experimental animal models has allowed for the study of scar formation. However, many pathophysiological unknowns remain in the longest stage of healing, the remodeling stage, which may continue for a year or more. The wound healing process results in different types of scarring classified as normal or pathological depending on failures at each stage. Failures can also occur during wound remodeling, but the molecular mechanisms driving the wound remodeling process have yet to be investigated. Recent Advances: While the current understanding of wound repair is based on investigations of acute healing, these experimental models have informed knowledge of key components of remodeling. This review examines the components that contribute to collagen organization and the final scar, including cell types, their regulation, and signaling pathways. Dysregulation in any one of these components causes pathologic healing. Critical Issues and Future Directions: As wounds continue to remodel months to years after reepithelialization, new models to better understand long-term remodeling will be critical for improving healing outcomes. Further investigation of the contributions of fibroblasts and cell signaling pathways involved during remodeling as well as their potential failures may inform new approaches in promoting regenerative healing beyond reepithelialization.

Identification and characterization of four immune-related signatures in keloid

A keloid is a fibroproliferative disorder of unknown etiopathogenesis that requires ill-defined treatment. Existing evidence indicates that the immune system plays an important role in the occurrence and development of keloid. However, there is still a lack of research on the immune-related signatures of keloid. Here we identified immune-related signatures in keloid and explored their pathological mechanisms. Transcriptomic datasets (GSE7890, GSE92566, and GSE44270) of keloid and normal skin tissues were obtained from the Gene Expression Omnibus database. The overlap of differentially expressed genes and immune-related genes was considered as differentially expressed immune-related genes (DEIGs). Functional analysis, expression, and distribution were applied to explore the function and characteristics of DEIGs, and the expression of these DEIGs in keloid and normal skin tissues was verified by immunohistochemistry. Finally, we conducted interactive network analysis and immune infiltration analysis to determine the therapeutic potential and immune correlation. We identified four DEIGs (LGR5, PTN, JAG1, and DKK1). In these datasets, only GSE7890 met the screening criteria. In the GSE7890 dataset, DKK1 and PTN were downregulated in keloid, whereas JAG1 and LGR5 were upregulated in keloid. In addition, we obtained the same conclusion through immunohistochemistry. Functional analysis indicated that these four DEIGs were mainly involved in stem cell, cell cycle, UV response, and therapy resistance. Through interactive network analysis, we found that these DEIGs were associated with drugs currently used to treat keloid, such as hydrocortisone, androstanolone, irinotecan, oxaliplatin, BHQ-880, and lecoleucovorin. Finally, many immune cells, including CD8⁺ T cells, resting memory CD4⁺ T cells, and M1 macrophages, were obtained by immune infiltration analysis. In conclusion, we identified four immune signaling molecules associated with keloid (LGR5, PTN, JAG1, and DKK1). These immune-related signaling molecules may be important modules in the pathogenesis of keloid. Additionally, we developed novel therapeutic targets for the treatment of this challenging disease.

Skin Wound Tension Reduction Device Combined with Ablative Fractional Carbon Dioxide Laser to Reduce Scar Formation After Excision of Pediatric Facial Skin Lesions: A Prospective Cohort Study

Purpose

To investigate the efficacy of skin wound tension reduction device (SWTRD) combined with ablative fractional carbon dioxide laser (CO2-AFL) for the prevention of scar formation following the excision of facial cutaneous lesions in children.

Methods

Patients undergoing surgical excision of facial cutaneous lesions in our hospital between May 2019 and April 2021 were enrolled. After the excision of facial cutaneous lesions and based on the personal intents and conditions, patients were assigned to undergo SWTRD combined with CO2-AFL. Outcome evaluations were as follows: defect size, incision width, scar width, the Vancouver Scar Scale (VSS) and University of North Carolina 4P Scar Scale (UNC4P).

Results

A total of 25 pediatric patients (mean age, 9.88 years) were enrolled in the study. Following the treatment of SWTRD+CO2-AFL, scar widths were relatively narrow and the appearance of the incision scars was significantly improved. A significant reduction in the patient-reported UNC4P scores at 6 months (3, 1–4) was observed when compared with that at 2 months (0, 0–1) after surgery (p<0.001). A similar reduction in the VSS scar scale was also evident (6 months: 1, 0.75–2.5 vs 2 months: 6.5–8.5; p<0.001).

Conclusion

Combined SWTRD and CO2-AFL treatment effectively modulates the scar formation after the incision is healed and resulting in preventing scar widening, leading to the improvement of scar appearance, reduction in wound pain and pruritus and its overall prognosis.

Silencing of Nesprin-2 inhibits the differentiation of myofibroblasts from fibroblasts induced by mechanical stretch

Mechanical force plays a pivotal role in the pathogenesis of hypertrophic scar (HTS). Dermal fibroblasts and myofibroblasts are the key cells involved in HTS. Myofibroblasts in HTS possess different biochemical and biophysical characteristics by which myofibroblasts are often distinguished from fibroblasts. The role of mechanotransducers outside the nucleus in the pathogenesis of HTS has been reported in many studies. However, the role of Nesprin‐2 in HTS is not clear. Hence, we aim to construct a cell model of HTS and explore the role of Nesprin‐2 in this process. Myofibroblasts and fibroblasts were isolated from HTS and healthy skin tissues of the same patient. Fibroblasts were exposed to cyclic stretch with 10% magnitude and a frequency of 0.1 Hz for 3 days, 5 days, and 7 days, respectively. After the cell model was confirmed, fibroblasts transfected with siRNA targeting human Nesprin‐2 were exposed to cyclic stretch. The mechanical behaviour and biochemical reaction of the dermal fibroblasts were analysed. The stretched fibroblasts at day 5 showed the same mechanotransductive and biochemical features as unstretched myofibroblasts. Mechanical strain could induce the myofibroblasts differentiation and a cell model of HTS was established successfully at day 5. The expressions of lamin A/C, alpha‐smooth muscle actin, transforming growth factor beta 1, and collagen type I in fibroblasts were reduced by the silencing of Nesprin‐2. Mechanical strain could induce the myofibroblasts differentiation and silencing of Nesprin‐2 could block the mechanical stimulation of terminal myofibroblasts differentiation. Nesprin‐2 might be a potential target to treat the HTS.

Combination of 1,064-nm Neodymium-doped Yttrium Aluminum Garnet Laser and Steroid Tape Decreases the Total Treatment Time of Hypertrophic Scars: An Analysis of 40 Cases of Cesarean-Section Scars

BACKGROUND

The 1,064-nm neodymium-doped yttrium aluminum garnet (Nd:YAG) laser (Cutera, Inc., Brisbane, CA) and steroid tape (fludroxycortide tape) have been used to treat keloids and hypertrophic scars.

OBJECTIVE

To evaluate the efficacy of contact-mode 1,064-nm Nd:YAG laser therapy and steroid tape for hypertrophic cesarean-section scars versus conservative therapy (steroid tape only).

MATERIALS AND METHODS

A medical record review identified 40 consecutive Japanese patients who had hypertrophic scars (total Japan Scar Workshop Scar Scale [JSS] 2015 evaluation scores of 9 to 12) for more than 1 year after a vertical cesarean section and who were treated at our scar-specialist clinic from July 2015 to December 2017. All 40 patients continued treatment until the total JSS score dropped below 3. Recurrence was defined as a ≥1-point increase in the total JSW score 6 months after achieving a total JSS score <3.

RESULTS

The patients had a mean age of 34.2 years. The test (n = 25) and control (n = 15) groups took on average 16.9 and 24.3 months to achieve a total JSS score <3, respectively (p < .01). In the following 6 months, none of the scars recurred.

CONCLUSION

Nd:YAG laser treatment effectively decreased the total treatment time of hypertrophic cesarean-section scars. An algorithm for treating mild and severe hypertrophic cesarean-section scars is proposed.

Current potential therapeutic strategies targeting the TGF-β/Smad signaling pathway to attenuate keloid and hypertrophic scar formation

Aberrant scar formation, which includes keloid and hypertrophic scars, is associated with a pathological disorganized wound healing process with chronic inflammation. The TGF-β/Smad signaling pathway is the most canonical pathway through which the formation of collagen in the fibroblasts and myofibroblasts is regulated. Sustained activation of the TGF-β/Smad signaling pathway results in the long-term overactivation of fibroblasts and myofibroblasts, which is necessary for the excessive collagen formation in aberrant scars. There are two categories of therapeutic strategies that aim to target the TGF-β/Smad signaling pathway in fibroblasts and myofibroblasts to interfere with their cellular functions and reduce cell proliferation. The first therapeutic strategy includes medications, and the second strategy is composed of genetic and cellular therapeutics. Therefore, the focus of this review is to critically evaluate these two main therapeutic strategies that target the TGF-β/Smad pathway to attenuate abnormal skin scar formation.

MiR-486-5p inhibits the hyperproliferation and production of collagen in hypertrophic scar fibroblasts via IGF1/PI3K/AKT pathway

Background: This study explored the function and mechanism of miR-486-5p in HSFBs.Methods: Qualitative real-time-polymerase chain reaction (qRT-PCR) was performed to detect the expression of miR-486-5p in HS and hypertrophic scar fibroblasts (HSFBs). Viability, migration, invasion ability, apoptosis, and expressions of Collagen I, Collagen III, α-SMA and Cleaved caspase-3 in HSFBs after transfection with miR-486-5p mimic or inhibitor were measured by CCK-8, wound-healing, transwell, and Western blot, respectively. Interaction between miR-486-5p and IGF1 was predicted by Targetscan version 7.2 and further confirmed by dual-luciferase assay, and functional rescue experiments were conducted to verify the predicted molecular mechanism. The activation of PI3K/AKT pathway was also analyzed by Western blot.Results: MiR-486-5p was low-expressed in HS and HSFBs, and that overexpression of miR-486-5p suppressed the viability, migration, invasion, and expressions of Collagen I, Collagen III, and α-SMA of HSFBs, meanwhile, it also promoted apoptosis and Cleaved caspase-3 expression in HSFBs. Moreover, IGF1 was targeted by miR-486-5p, and increased viability, migration, invasion, and collagens expressions, the activation of PI3K/Akt pathway, and decreased apoptosis and Cleaved caspase-3 induced by miR-486-5p inhibitor could be partly alleviated by siIGF1.Conclusions: Overexpressed miR-486-5p inhibited the hyperproliferation and excessive production of collagen in HSFBs via IGF1/PI3K/AKT pathway.

Effectiveness of topical silicone gel and pressure garment therapy for burn scar prevention and management in children: a randomized controlled trial

Objective:

To determine the effectiveness of silicone and pressure garments (alone and in combination) in children receiving scar management post-burn.

Design:

Multicentre, parallel-group, randomized controlled trial.

Setting:

Hospital outpatient clinics, colocated research centre, or the participant’s home.

Participants:

Children (0–18 years) referred for burn scar management.

Interventions:

Participants were randomized to (1) topical silicone gel only, (2) pressure garment therapy only, or (3) combined topical silicone gel and pressure garment therapy.

Main measures:

Primary outcomes included scar thickness and itch intensity at the primary end-point of six months post-burn injury. The outcome assessor and data analyst were blinded for scar thickness.

Results:

Participants (N = 153; silicone n = 51, pressure n = 49, combined n = 53) had a median (inter-quartile range) age of 4.9 (1.6, 10.2) years and percent total body surface area burn of 1% (0.5%, 3%) and were 65% male. At six months post-burn injury, intention-to-treat analysis identified thinner scars in the silicone (n = 51 scar sites) compared to the combined group (n = 48 scar sites; mean difference (95% confidence interval) = –0.04 cm (–0.07, –0.00), P = 0.05). No other between-group differences were identified for scar thickness or itch intensity at six months post-burn.

Conclusion:

No difference was identified in the effectiveness of silicone and pressure interventions alone. No benefit to a combined silicone and pressure intervention was identified for the prevention and management of abnormal scarring in children at six months post-burn injury, compared to the silicone or pressure interventions alone.

Combination therapy using non-ablative fractional laser and intralesional triamcinolone injection for hypertrophic scars and keloids treatment

Combinations of various treatment modalities were shown to be more effective than monotherapy when treating hypertrophic scars and keloids. This study was conducted to assess the effectiveness of combination therapy with non-ablative fractional laser and intralesional steroid injection. From May 2015 to June 2017, a total of 38 patients with hypertrophic scars or keloids were evaluated. The control group of 21 patients received steroid injection alone, and 17 patients (the combined group) received 1550-nm erbium-glass fractional laser treatment and steroid injection simultaneously. The mean number of treatment sessions was statistically fewer in the combined group than in the control group (6.95 vs 5.47, P = .042). There was a significant difference in the patient's scale in the combined group (14.62 vs 22.82, P = .005); however, the observer's scale was not significantly different (17.92 vs 20.55, P = .549). The recurrence rate was 38.1% (8/21) in the control group and 35.3% (6/17) in the combined groups and showed no significant difference (P = .859). However, the mean remission period was statistically longer in the combined group (3.00 months vs 4.17 months, P = .042). Combination therapy with non-ablative fractional laser and intralesional steroid injection showed better results for the treatment of hypertrophic scars and keloids with fewer treatment sessions, better patient satisfaction, and longer remission periods.

Bone marrow concentrate-induced mesenchymal stem cell conditioned medium facilitates wound healing and prevents hypertrophic scar formation in a rabbit ear model

Background

Hypertrophic scars (HSs) are formed via an aberrant response to the wound healing process. HSs can be cosmetic or can result in functional problems. Prolonged proliferation and remodeling phases disrupt wound healing, leading to excessive collagen production and HS formation. However, there are currently no satisfactory drugs to prevent HS formation. Mesenchymal stem cell (MSC) conditioned medium (CM) has therapeutic effects on wound healing and preventing HS formation. Bone marrow concentrate (BMC) contains various growth factors and cytokines that are crucial for regeneration and has been applied in the clinical setting. In this study, we evaluated the effects of BMC-induced MSC CM on HS formation in a rabbit ear model.

Methods

We established a rabbit ear wound model by generating full-thickness wounds in the ears of rabbits (n = 12) and treated wounds with MSC CM, BMC CM, or BMC-induced MSC CM. Dermal fibroblasts from human hypertrophic scar were stimulated with transforming growth factor beta 1 (TGF-β1) for 24 h and cultured in each culture medium for 72 h. We measured the hypertrophic scar (HS) formation during the skin regeneration by measuring the expression of several remodeling molecules and the effect of these conditioned media on active human HS fibroblasts.

Results

Our results showed that BMC-induced MSC CM had greater antifibrotic effects than MSC CM and BMC CM significantly attenuated HS formation in rabbits. BMC-induced MSC CM accelerated wound re-epithelization by increasing cell proliferation. Additionally, BMC-induced MSC CM also inhibited fibrosis by decreasing profibrotic gene and protein expression, promoting extracellular matrix turnover, inhibiting fibroblast contraction, and reversing myofibroblast activation.

Conclusions

BMC-induced MSC CM modulated the proliferation and remodeling phases of wound healing, representing a potential wound healing agent and approach for preventing HS formation.

Electronic supplementary material

The online version of this article (10.1186/s13287-019-1383-x) contains supplementary material, which is available to authorized users.

Effect of poly(dimethylsiloxane)-block-poly(oligo (ethylene glycol) methacrylate) amphiphilic block copolymers on dermal fibroblast viability and proliferation

In this work, well-defined poly(dimethylsiloxane)-b-poly(oligo (ethylene glycol) methacrylate) (PDMS-b-POEGMA) amphiphilic block copolymers were synthesized and their effect on human dermal fibroblast were investigated. Anionic ring opening polymerization (ROP) and atom transfer radical polymerization (ATRP) were used to synthesis the block copolymers. The molecular weight of synthesized copolymers ranged from 1000 to 2300 Da by changing the number of both PDMS and POEGMA units. It was found that the copolymer having low molecular weight decreased the fibroblast viability and proliferation by inducing apoptosis. It was proved by flow cytometry and TUNEL assay that human dermal fibroblast experienced apoptosis after exposure to synthesized amphiphilic copolymers. The results of this work suggest the use of PDMS-b-POEGMA amphiphilic copolymers with low molecular weight for hypertrophic scars remediation.

Skin Changes During Ageing

The skin provides the primary protection for the body against external injuries and is essential in the maintenance of general homeostasis. During ageing, resident cells become senescent and the extracellular matrix, mainly in the dermis, is progressively damaged affecting the normal organization of the skin and its capacity for repair. In parallel, extrinsic factors such as ultraviolet irradiation, pollution, and intrinsic factors such as diabetes or vascular disease can further accelerate this phenomenon. Indeed, numerous mechanisms are involved in age-induced degradation of the skin and these also relate to non-healing or chronic wounds in the elderly. In particular, the generation of reactive oxygen species seems to play a major role in age-related skin modifications. Certainly, targeting both the hormonal status of the skin or its surface nutrition can slow down age-induced degradation of the skin and improve healing of skin damage in the elderly. Skin care regimens that prevent radiation and pollution damage, and reinforce the skin surface and its microbiota are among the different approaches able to minimize the effects of ageing on the skin.

Analysis of Mechanical Behavior of Dermal Fibroblasts Obtained From Various Anatomical Sites in Humans

PURPOSE

Facial skin fibroblasts imposed with cyclic stretch at 10% magnitude display considerable mechanotransduction properties and biochemical reactions in our previous study. However, it is poorly understood how these shared traits are fully parallel to the common features across all fibroblasts derived from different skin-based anatomical regions in response to cyclic stretch stimulation. Thus, the purpose of this study was to evaluate the effects of various cyclic stretches on fibroblasts derived from multiple anatomical skin sites of human bodies, and the optimal stretch magnitude was defined based on the changes to cell mechanical behavior.

METHODS

Fibroblasts from skin areas of the scalp, anterior chest, suprapubic, axilla, and planta were cultured and characterized in vitro. Cyclic stretch at 0%, 5%, 10%, 15%, and 20% magnitudes was imposed at a loading frequency of 0.1 Hz for 48 hours, and thereafter, the mechanical behavior and biochemical reaction of the dermal fibroblasts were analyzed.

RESULTS

Dermal fibroblasts from various anatomical sites preconditioned with varying cyclic stretch led to an evident increase in the cell proliferation ability, the expression of integrin β1 and p130 Crk-associated substrate messenger RNA and protein, and the productions of type I collagen and transforming growth factor β1, most importantly in a strain magnitude-dependent manner with the peak appearing in the range of 10% to 15% magnitude cyclic stretch.

CONCLUSIONS

These findings may facilitate the subsequent studies on the conversion of normal skin fibroblasts into hypertrophic scar cells, which should be considered in an interpretation of the mechanisms of hypertrophic scarring and skin mechanics.

Extracorporeal shock wave therapy with low-energy flux density inhibits hypertrophic scar formation in an animal model

Hypertrophic scar is characterized by excessive deposits of collagen during skin wound healing, which could become a challenge to clinicians. This study assessed the effects of the extracorporeal shock wave therapy (ESWT) on hypertrophic scar formation and the underlying gene regu-lation. A rabbit ear hypertrophic scar model was generated and randomly divided into three groups: L-ESWT group to receive L-ESWT (energy flux density of 0.1 mJ/mm2), H-ESWT (energy flux density of 0.2 mJ/mm2) and sham ESWT group (S-ESWT). Hypertrophic scar tissues were then collected and stained with hematoxylin and eosin (H&E) and Masson's trichrome staining, respectively, to assess scar elevation index (SEI), fibroblast density and collagen fiber arrangement. Expression of cell proliferation marker proliferating cell nuclear antigen (PCNA) and α-smooth muscle actin (α-SMA) were assessed using RT-PCR and immunohistochemistry in hypertrophic scar tissues. H&E staining sections showed significant reduction of SEI and fibroblast density in both ESWT treatment groups compared to S-ESWT, but there was no dramatic difference between L-ESWT and H-ESWT groups. Masson's trichrome staining showed that collagen fibers were more slender and broader and oriented in parallel to skin surface after administration of ESWT compared to control tissues. At the gene level, PCNA‑positive fibroblasts and α-SMA-positive myofibroblasts were significantly decreased after L-ESWT or H-ESWT compared to the controls. Furthermore, there was no significant difference in expression of PCNA mRNA between L-ESWT or H-ESWT and S-ESWT, whereas expression of α-SMA mRNA significantly decreased in L-ESWT compared to that of H-ESWT and S-ESWT (P=0.002 and P=0.030, respectively). In conclusion, L-ESWT could be effective on suppression of hypertrophic scar formation by inhibition of scar elevation index and fibroblast density as well as α-SMA expression in hypertrophic scar tissues of the rabbit model.

Cosmetic outcomes of cesarean section scar; subcuticular suture versus intradermal buried suture

OBJECTIVE

The objective of the study was to compare cosmetic outcomes and overall satisfaction rate of cesarean section scar between conventional subcuticular suture and intradermal buried vertical mattress.

METHODS

Patients were enrolled to the study by chart review. A scar assessment was obtained retrospectively through a telephone survey. The patient component of the patient and observer scar assessment scale (POSAS) was utilized along with the overall satisfaction of the patient regarding their cesarean section scar and their willingness to choose the same skin closure technique when anticipating their next cesarean section.

RESULTS

A total of 303 cases of cesarean section was recruited, 102 finished telephone surveys were calculated for the analyses. Subcuticular suture was regarded as control group (n=52) and intradermal buried suture as test group (n=50). The PSAS score of the test group (mean, 21.8) was lower than that of the control group (mean, 28), with a statistical significance (P=0.02). Overall satisfaction rate did not differ between the two groups. Two parameters of the PSAS score and the level of overall satisfaction showed significant correlation (Pearson's r, -0.63; P<0.01).

CONCLUSION

We suggested the use of intradermal buried vertical mattress as a cosmetically superior skin closure method for application in cesarean sections over subcuticular stitch.

In vivo terahertz reflection imaging of human scars during and after the healing process

We use terahertz imaging to measure four human skin scars in vivo. Clear contrast between the refractive index of the scar and surrounding tissue was observed for all of the scars, despite some being difficult to see with the naked eye. Additionally, we monitored the healing process of a hypertrophic scar. We found that the contrast in the absorption coefficient became less prominent after a few months post-injury, but that the contrast in the refractive index was still significant even months post-injury. Our results demonstrate the capability of terahertz imaging to quantitatively measure subtle changes in skin properties and this may be useful for improving scar treatment and management.

Naringenin attenuates fibroblast activation and inflammatory response in a mechanical stretch-induced hypertrophic scar mouse model

The pathogenesis and therapy of hypertrophic scars (HS) have not yet been established. The aim of the present study was to investigate the potential effect of naringenin on HS and its underlying mechanisms. The mouse model of HS was prepared by a mechanical stretch device and then treated with naringenin at various concentrations. Histological studies were performed to evaluate scar hypertrophy by hematoxylin and eosin, as well as Masson's trichrome staining. The activation of HS fibroblasts was determined based on reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR), western blotting and immunohistochemical staining. Following observing the retention of inflammation cells by immunohistochemistry, the cytokines, including tumor necrosis factor (TNF)‑α, interleukin (IL)‑1β, IL‑6 and transforming growth factor (TGF)‑β1, mRNA and protein levels were quantitated by RT‑qPCR, ELISA and western blotting methods. As a result, naringenin significantly inhibited the formation of HS in a concentration‑dependent manner. In addition, naringenin inhibited fibroblast activation and inflammatory cell recruitment. In addition, mRNA and protein expression levels of TNF‑α, IL‑1β, IL‑6 and TGF‑β1 were downregulated following naringenin treatment. The current study highlighted a new pharmacological activity of naringenin on HS. The mechanism of action of naringenin was associated with the inhibition of fibroblast activation and local inflammation. These results suggested that naringenin may serve as a novel agent for treatment of HS.

Evidence-Based Scar Management: How to Improve Results with Technique and Technology

BACKGROUND

Scars represent the visible sequelae of trauma, injury, burn, or surgery. They may induce distress in the patient because of their aesthetically unpleasant appearance, especially if they are excessively raised, depressed, wide, or erythematous. They may also cause the patient symptoms of pain, tightness, and pruritus. Numerous products are marketed for scar prevention or improvement, but their efficacy is unclear.

METHODS

A literature review of high-level studies analyzing methods to prevent or improve hypertrophic scars, keloids, and striae distensae was performed. The evidence from these articles was analyzed to generate recommendations. Each intervention's effectiveness at preventing or reducing scars was rated as none, low, or high, depending on the strength of the evidence for that intervention.

RESULTS

For the prevention of hypertrophic scars, silicone, tension reduction, and wound edge eversion seem to have high efficacy, whereas onion extract, pulsed-dye laser, pressure garments, and scar massage have low efficacy. For the treatment of existing hypertrophic scars, silicone, pulsed-dye laser, CO2 laser, corticosteroids, 5-fluorouracil, bleomycin, and scar massage have high efficacy, whereas onion extract and fat grafting seem to have low efficacy. For keloid scars, effective adjuncts to excision include corticosteroids, mitomycin C, bleomycin, and radiation therapy. No intervention seems to have significant efficacy in the prevention or treatment of striae distensae.

CONCLUSION

Although scars can never be completely eliminated in an adult, this article presents the most commonly used, evidence-based methods to improve the quality and symptoms of hypertrophic scars, as well as keloid scars and striae distensae.

A Systematic Review on the Effect of Mechanical Stretch on Hypertrophic Scars after Burn Injuries

Objective/Background

To review the effect of mechanical stretch on hypertrophic scars after burn injuries.

Methods

A systematic review of all controlled trials related to the effect of mechanical stretch on post burn hypertrophic scars was conducted. Studies of conservative scar managements that applied mechanical forces parallel to the scar surface, including stretching exercise, massage, and splinting, were appraised. Eligible studies published in English between 1995 and 2016 were extracted from The Cochrane Library, MEDLINE, CINAHL, Science direct, SPORTDiscus, and Physiotherapy Evidence Database Scale (PEDro). The journals were further screened with inclusion and exclusion criteria. PEDro was selected for further analysis and appraisal.

Results

There were 853 articles identified. After a standardized screening mechanism stipulated, only nine full-text articles were selected for critical appraisal using PEDro. There were five articles of high quality, two of fair quality, and two of poor quality. Detailed training regime and outcomes of nine studies were summarised, including two studies with stretching exercise, six studies with massage, and one study with splinting. The physical parameters of scar assessments and the range of motion on affected areas were compared.

Conclusion

From extensive literature search, there was no strong evidence indicating the positive effect of mechanical stretch using stretching exercise, massage, or splinting on hypertrophic scars. A firm conclusion cannot be drawn for the discrepancy of outcome measures and varied effectiveness. Most of the included studies lacked objective evaluation or control group for comparison. Further high quality studies with larger sample size and using standardized measurements are needed.

Current concepts related to hypertrophic scarring in burn injuries

Scarring following burn injury and its accompanying aesthetic and functional sequelae still pose major challenges. Hypertrophic scarring (HTS) can greatly impact patients' quality of life related to appearance, pain, pruritus and even loss of function of the injured body region. The identification of molecular events occurring in the evolution of the burn scar has increased our knowledge; however, this information has not yet translated into effective treatment modalities. Although many of the pathophysiologic pathways that bring about exaggerated scarring have been identified, certain nuances in burn scar formation are starting to be recognized. These include the effects of neurogenic inflammation, mechanotransduction, and the unique interactions of burn wound fluid with fat tissue in the deeper dermal layers, all of which may influence scarring outcome. Tension on the healing scar, pruritus, and pain all induce signaling pathways that ultimately result in increased collagen formation and myofibroblast phenotypic changes. Exposure of the fat domes in the deep dermis is associated with increased HTS, possibly on the basis of altered interaction of adipose-derived stem cells and the deep burn exudate. These pathophysiologic patterns related to stem cell-cytokine interactions, mechanotransduction, and neurogenic inflammation can provide new avenues of exploration for possible therapeutic interventions.

Development of a novel CsA-PLGA drug delivery system based on a glaucoma drainage device for the prevention of postoperative fibrosis

The formation of a scar after glaucoma surgery often leads to unsuccessful control of intraocular pressure, and should be prevented by using a variety of methods. We designed and developed a novel drug delivery system (DDS) comprising cyclosporine A (CsA) and poly(lactic-co-glycolic acid) (PLGA) based on a glaucoma drainage device (GDD) that can continuously release CsA to prevent postoperative fibrosis following glaucoma surgery. The CsA@PLGA@GDD DDS was observed by field emission scanning electron microscopy and revealed an asymmetric pore structure. Thermogravimetric analysis was performed to measure the weight loss and evaluate the thermal stability of the CsA@PLGA@GDD DDS. The in vitro drug release profile of the DDS was studied using high performance liquid chromatography, which confirmed that the DDS released CsA at a stable rate and maintained adequate CsA concentrations for a relatively long time. The biocompatibility of the DDS and the inhibitory effects on the postoperative fibrosis were investigated in vitro using rabbit Tenon's fibroblasts. The in vivo safety and efficacy of the DDS were examined by implanting the DDS into Tenon's capsules in New Zealand rabbits. Bleb morphology, intraocular pressure, anterior chamber reactions, and anterior chamber angiography were studied at a series of set times. The DDS kept the filtration pathway unblocked for a longer time compared with the control GDD. The results indicate that the CsA@PLGA@GDD DDS represents a safe and effective strategy for preventing scar formation after glaucoma surgery.

A Combined In Vitro Imaging and Multi-Scale Modeling System for Studying the Role of Cell Matrix Interactions in Cutaneous Wound Healing

Many cell types remodel the extracellular matrix of the tissues they inhabit in response to a wide range of environmental stimuli, including mechanical cues. Such is the case in dermal wound healing, where fibroblast migrate into and remodel the provisional fibrin matrix in a complex manner that depends in part on the local mechanical environment and the evolving multi-scale mechanical interactions of the system. In this study, we report on the development of an image-based multi-scale mechanical model that predicts the short-term (24 hours), structural reorganization of a fibrin gel by fibroblasts. These predictive models are based on an in vitro experimental system where clusters of fibroblasts (i.e., explants) were spatially arranged into a triangular geometry onto the surface of fibrin gels that were subjected to either Fixed or Free in-plane mechanical constraints. Experimentally, regional differences in short-term structural remodeling and cell migration were observed for the two gel boundary conditions. A pilot experiment indicated that these small differences in the short-term remodeling of the fibrin gel translate into substantial differences in long-term (4 weeks) remodeling, particularly in terms of collagen production. The multi-scale models were able to predict some regional differences in remodeling and qualitatively similar reorganization patterns for the two boundary conditions. However, other aspects of the model, such as the magnitudes and rates of deformation of gel, did not match the experiments. These discrepancies between model and experiment provide fertile ground for challenging model assumptions and devising new experiments to enhance our understanding of how this multi-scale system functions. These efforts will ultimately improve the predictions of the remodeling process, particularly as it relates to dermal wound healing and the reduction of patient scarring. Such models could be used to recommend patient-specific mechanical-based treatment dependent on parameters such as wound geometry, location, age, and health.

An updated review of mechanotransduction in skin disorders: transcriptional regulators, ion channels, and microRNAs

INTRODUCTION

The skin is constantly exposed and responds to a wide range of biomechanical cues. The mechanobiology of skin has already been known and applied by clinicians long before the fundamental molecular mechanisms of mechanotransduction are elucidated.

MATERIALS AND METHODS

Despite increasing knowledge on the mediators of biomechanical signaling such as mitogen-associated protein kinases, Rho GTPases or FAK-ERK pathways, the key elements of mechano-responses transcription factors, and mechano-sensors remain unclear. Recently, canonical biochemical components of Hippo and Wnt signaling pathway YAP and β-catenin were found to exhibit undefined mechanical sensitivity. Mechanical forces were identified to be the dominant regulators of YAP/TAZ activity in a multicellular context. Furthermore, different voltage or ligand sensitive ion channels in the cell membrane exhibited their mechanical sensitivity as mechano-sensors. Additionally, a large number of microRNAs have been confirmed to regulate cellular behavior and contribute to various skin disorders under mechanical stimuli. Mechanosensitive (MS) microRNAs could not only be activated by distinct mechanical force pattern, but also responsively target MS sensors such as e-cadherin and cytoskeleton constituent RhoA.

CONCLUSION

Thus, a comprehensive understanding of this regulatory network of cutaneous mechanotransduction will facilitate the development of novel approaches to wound healing, hypertrophic scar formation, skin regeneration, and the progression or initiation of skin diseases.

New approach to the understanding of keloid: psychoneuroimmune-endocrine aspects

The skin is a dynamic and complex organ that relies on the interrelation among different cell types, macromolecules, and signaling pathways. Further, the skin has interactions with its own appendages and other organs such as the sebaceous glands and hair follicles, the kidney, and adrenal glands; systems such as the central nervous system; and axes such as the hypothalamic–pituitary–adrenal axis. These continuous connections give the skin its versatility, and when an injury is caused, some triggers start a cascade of events designed to restore its integrity. Nowadays, it is known that this psychoneuroimmune–endocrine intercommunication modulates both the homeostatic condition and the healing process. In this sense, the skin conditions before a trauma, whether of endogenous (acne) or exogenous origin (injury or surgical incision), could regulate the process of tissue repair. Most skin diseases such as psoriasis and atopic dermatitis, among others, have in their pathophysiology a psychogenic component that triggers integrated actions in the nervous, immune, and endocrine systems. However, fibroproliferative disorders of wound healing, such as hypertrophic scar and keloid, are not yet included in this listing, despite showing correlation with stress, especially with the psychosocial character. This review, by understanding the “brain–skin connection”, presents evidence that allows us to understand the keloid as a psychomediated disease.

Mechanical tension promotes skin nerve regeneration by upregulating nerve growth factor expression

This study aimed to explore the role of mechanical tension in hypertrophic scars and the change in nerve density using hematoxylin-eosin staining and S100 immunohistochemistry, and to observe the expression of nerve growth factor by western blot analysis. The results demonstrated that mechanical tension contributed to the formation of a hyperplastic scar in the back skin of rats, in conjunction with increases in both nerve density and nerve growth factor expression in the scar tissue. These experimental findings indicate that the cutaneous nervous system plays a role in hypertrophic scar formation caused by mechanical tension.

Updated scar management practical guidelines: non-invasive and invasive measures

Hypertrophic scars and keloids can be aesthetically displeasing and lead to severe psychosocial impairment. Many invasive and non-invasive options are available for the plastic (and any other) surgeon both to prevent and to treat abnormal scar formation. Recently, an updated set of practical evidence-based guidelines for the management of hypertrophic scars and keloids was developed by an international group of 24 experts from a wide range of specialities. An initial set of strategies to minimize the risk of scar formation is applicable to all types of scars and is indicated before, during and immediately after surgery. In addition to optimal surgical management, this includes measures to reduce skin tension, and to provide taping, hydration and ultraviolet (UV) protection of the early scar tissue. Silicone sheeting or gel is universally considered as the first-line prophylactic and treatment option for hypertrophic scars and keloids. The efficacy and safety of this gold-standard, non-invasive therapy has been demonstrated in many clinical studies. Other (more specialized) scar treatment options are available for high-risk patients and/or scars. Pressure garments may be indicated for more widespread scarring, especially after burns. At a later stage, more invasive or surgical procedures may be necessary for the correction of permanent unaesthetic scars and can be combined with adjuvant measures to achieve optimal outcomes. The choice of scar management measures for a particular patient should be based on the newly updated evidence-based recommendations taking individual patient and wound characteristics into consideration.

Systems-based approaches toward wound healing

Wound healing in the pediatric patient is of utmost clinical and social importance because hypertrophic scarring can have aesthetic and psychological sequelae, from early childhood to late adolescence. Wound healing is a well-orchestrated reparative response affecting the damaged tissue at the cellular, tissue, organ, and system scales. Although tremendous progress has been made toward understanding wound healing at the individual temporal and spatial scales, its effects across the scales remain severely understudied and poorly understood. Here, we discuss the critical need for systems-based computational modeling of wound healing across the scales, from short-term to long-term and from small to large. We illustrate the state of the art in systems modeling by means of three key signaling mechanisms: oxygen tension-regulating angiogenesis and revascularization; transforming growth factor-β (TGF-β) kinetics controlling collagen deposition; and mechanical stretch stimulating cellular mitosis and extracellular matrix (ECM) remodeling. The complex network of biochemical and biomechanical signaling mechanisms and the multiscale character of the healing process make systems modeling an integral tool in exploring personalized strategies for wound repair. A better mechanistic understanding of wound healing in the pediatric patient could open new avenues in treating children with skin disorders such as birth defects, skin cancer, wounds, and burn injuries.

Can single use negative pressure wound therapy be an alternative method to manage keloid scarring? A preliminary report of a clinical and ultrasound/colour-power-doppler study

Keloid scarring represents a pathological healing where primary healing phenomenon is deviated from normal. Pico is a single use negative pressure wound therapy system originally introduced to manage open or just closed wounds. Pico dressing is made of silicone, and distributes an 80 mmHg negative pressure across wound bed. Combination of silicon layer and continuous compression could be a valid method to manage keloid scarring. Since November 2011, three patients were enrolled and evaluated before negative pressure treatment, at end of treatment (1 month) and 2 months later, through Vancouver Scar Scale (VSS), Visual Analog Scale (VAS) and a scoring system for itching. Ultrasound (US) and colour-power-doppler (CPD) examination was performed to evaluate thickness and vascularisation of the scar. One patient was discharged from study after 1 week. In last two patients, VSS, VAS and itching significantly improved after 1 month therapy and the results were stable after 2 months without any therapy. At end of therapy, the 'appearance of palisade vessels' disappeared in both cases at CPD exam; US showed a thickness reduction (average 43·8%). We propose a well-tolerated, non invasive treatment to manage keloid scarring. Prospective studies are necessary to investigate whether these preliminary observations are confirmed.

Risk factors for hypertrophic surgical scar development after thyroidectomy

Postoperative neck scarring is a major concern for patients who undergo thyroid surgery; however, the treatments for hypertrophic scars are generally considered by patients to provide unsatisfactory outcomes. Therefore, risk factors should be identified and prevention of these factors is considered to be critical in management. We reviewed the medical records of 96 thyroidectomy patients who were divided into two groups based on scar type: patients with hypertrophic (n = 61) and linear flat scars (n = 35). Multivariable logistic regression model was developed to identify risk factors for developing hypertrophic scar. There was no significant difference between the two groups in terms of age, gender ratio, tumor type, and type of operation. Multivariable analysis showed that hypertrophic scar development was associated with scars located within 1 cm above the sternal notch (odds ratio [OR] = 5.94, p = 0.01), prominent sternocleidomastoid muscles (OR = 12.03, p < 0.01), and a high body mass index (OR = 1.33, p = 0.01). The area under the receiver operating characteristic curve for risk factors was 0.85. Development of hypertrophic scar after thyroidectomy was found to be associated with specific preoperative factors such as incision site near the sternal notch, prominent sternocleidomastoid muscles, and high body mass index.

Keloids: prevention and management

Keloids result from an abnormal wound-healing process in which the normal regulatory pathways during tissue regeneration and scar remodeling are disrupted. While the pathogenesis of keloids continues to be investigated, numerous treatment options exist. Although prevention of keloid formation is the best management, early recognition of keloid formation is integral in treatment and prevention of recurrence. Surgical resection with adjuvant silicone gel sheeting or triamcinolone injection is common, but can still result in recurrence. New treatments include chemotherapeutics such as 5-fluorouracil, bleomycin, and mitomycin C. Although further clinical investigation is required for newer treatments, initial results are promising.

Clinical applications of basic research that shows reducing skin tension could prevent and treat abnormal scarring: the importance of fascial/subcutaneous tensile reduction sutures and flap surgery for keloid and hypertrophic scar reconstruction

We use evidence-based algorithms to treat abnormal scarring, including keloids and hypertrophic scars (HSs). This involves a multimodal approach that employs traditional methods such as surgical removal, postoperative radiotherapy, corticosteroid injection, laser, and silicone gel sheets. As a result, the rate of abnormal scarring recurrence has decreased dramatically over the past 10 years. However, several problems remain to be solved. First, despite the optimization of a radiotherapy protocol, over 10% of cases who are treated with surgery and postoperative radiotherapy still recur in our facility. Second, the treatment options for cases with huge keloids are very limited. To address these problems, we performed basic research on the mechanisms that drive the formation of keloids and HSs. Extrapolation of these research observations to the clinic has led to the development of two treatment strategies that have reduced the rate of abnormal scar recurrence further and provided a means to remove large scars. Our finite element analysis of the mechanical force distribution around keloids revealed high skin tension at the keloid edges and lower tension in the keloid center. Moreover, when a sophisticated servo-controlled device was used to stretch wounded murine dorsal skin, it was observed that the stretched samples exhibited upregulated epidermal proliferation and angiogenesis, which are also observed in keloids and HSs. Real-time RT-PCR also revealed that growth factors and neuropeptides are more strongly expressed in cyclically stretched skin than in statically stretched skin. These findings support the well-established notion that mechanical forces on the skin strongly influence the cellular behavior that leads to scarring. These observations led us to focus on the importance of reducing skin tension when keloids/HSs are surgically removed to prevent their recurrence. Clinical trials revealed that subcutaneous/fascial tensile reduction sutures, which apply minimal tension on the dermis, are more effective in reducing recurrence than the three-layered sutures used by plastic surgeons. Moreover, we have found that by using skin flaps (e.g., perforator flaps and propeller flaps), which release tension on the wound, in combination with postoperative radiotherapy, huge keloids can be successfully treated.

A conditional gating mechanism assures the integrity of the molecular force-sensor titin kinase

As more and more recent investigations point out, force plays an important role in cellular regulation mechanisms. Biological responses to mechanical stress are often based on force-induced conformational changes of single molecules. The force sensor, titin kinase, is involved in a signaling complex that regulates protein turnover and transcriptional adaptation in striated muscle. The structural architecture of such a force sensor determines its response to force and must assure both activity and mechanical integrity, which are prerequisites for its function. Here, we use single-molecule force-clamp spectroscopy to show that titin kinase is organized in such a way that the regulatory domains have to unfold before secondary structure elements that determine the overall fold and catalytic function. The stepwise unfolding over many barriers with a topologically determined sequence assures that the protein can react to force by conformational changes while maintaining its structural integrity.