Recipient wound bed characteristics affect scarring and skin graft contraction

Adipose-derived stem cells transplantation improves survival and alleviates contraction of skin grafts via promoting macrophages M2 polarization

BACKGROUND

Full-thickness skin grafts are widely used in plastic and reconstructive surgery. The main limitation of skin grafting is the poor textural durability and associated contracture, which often needs further corrective surgery. Excessive inflammation is the main reason for skin graft contractions, which involve overactivation of myofibroblasts. These problems have prompted the development of new therapeutic approaches, including macrophage polarization modulation and stem cell-based therapies. Currently, adipose-derived stem cells (ASCs) have shown promise in promoting skin grafts survival and regulating macrophage phenotypes. However, the roles of ASCs on macrophages in decreasing skin grafts contraction remain unknown.

MATERIALS AND METHODS

Rat adipose-derived stem cells (rASCs) were isolated from rat inguinal adipose tissues. Full-thickness skin graft model was constructed on male rats divided into control group and rASCs treatment group. Skin graft was assessed for concentration, elasticity modulus and stiffness. Rat bone marrow-derived macrophages (rBMDMs) were isolated from rat femurs, and subsequent RT-qPCR and coculture assays were carried out to explore the cellular mechanisms. Immunohistochemical and immunofluorescence staining were used to verify mechanisms in vivo.

RESULTS

In vivo results showed that after injection of ASCs, improved texture, increased survival and inhibited contraction of skin grafts were seen. Vascularization was also improved as illustrated by laser perfusion image and vascular endothelial growth factor (VEGF) concentration. Histological analysis revealed that ASCs injection significantly reduced expression of pro-inflammatory cytokines (TNF-a, IL-1β) and increased expression of anti-inflammatory (IL-10) and pro-healing cytokines (IGF-1). At cellular level, after co-culturing with rASCs, rat bone marrow derived macrophages (rBMDMs) favored M2 polarization even under inflammatory stimulus.

CONCLUSION

ASCs treatment enhanced vascularization via angiogenic cytokines secretion and alleviated inflammatory environment in skin grafts by driving M2 macrophages polarization, which improved survival and decreased skin grafts contraction. Our work showed that ASCs transplantation can be harnessed to enhance therapeutic efficacy of skin grafting in cutaneous defects treatment.

Crafting Contours: A Comprehensive Guide to Scrotal Reconstruction

This review delves into reconstructive methods for scrotal defects arising from conditions like Fournier's gangrene, cancer, trauma, or hidradenitis suppurativa. The unique anatomy of the scrotum, vital for thermoregulation and spermatogenic function, necessitates reconstruction with thin and pliable tissue. When the scrotal defect area is less than half the scrotal surface area, scrotal advancement flap can be performed. However, for larger defects, some type of transplantation surgery is required. Various options are explored, including testicular transposition, tissue expanders, split-thickness skin grafts, local flaps, and free flaps, each with merits and demerits based on factors like tissue availability, defect size, and patient specifics. Also, physicians should consider how testicular transposition, despite its simplicity, often yields unsatisfactory outcomes and impairs spermatogenesis. This review underscores the individuality of aesthetic standards for scrotal reconstruction, urging surgeons to tailor techniques to patient needs, health, and defect size. Detailed preoperative counseling is crucial to inform patients about outcomes and limitations. Ongoing research focuses on advancing techniques, not only anatomically but also in enhancing post-reconstruction quality of life, emphasizing the commitment to continuous improvement in scrotal reconstruction.

In Vitro, Ex Vivo, and In Vivo Approaches for Investigation of Skin Scarring: Human and Animal Models

Significance: The cutaneous repair process naturally results in different types of scarring that are classified as normal or pathological. Affected individuals are often affected from an esthetic, physical (functional), and psychosocial perspective. The distinct nature of scarring in humans, particularly the formation of pathological scars, makes the study of skin scarring a challenge for researchers in this area. Several established experimental models exist for studying scar formation. However, the increasing development and validation of newly emerging models have made it possible to carry out studies focused on different variables that influence this unique process. Recent Advances: Experimental models such as in vitro, ex vivo, and in vivo models have obtained different degrees of success in the reproduction of the scar formation in its native milieu and true environment. These models also differ in their ability to elucidate the molecular, cellular, and structural mechanisms involved in scarring, as well as for testing new agents and approaches for therapies. The models reviewed here, including cells derived from human skin and in vivo animal models, have contributed to the advancement of skin scarring research. Critical Issues and Future Directions: The absence of experimental models that faithfully reproduce the typical characteristics of the different types of human skin scars makes the improvement of validated models and the establishment of new ones a critical unmet need. The fields of wound healing research combined with tissue engineering have offered newer alternatives for experimental studies with the potential to provide clinically useful knowledge about scar formation.

A Review of Laser Therapies for the Treatment of Scarring and Vascular Anomalies

Significance: Laser use has become part of the gold standard of treatment as an effective adjuvant in multimodal therapy for pathologic scarring caused by burns, trauma, acne, and surgery, as well as vascular anomalies. Understanding indications and applications for laser therapy is essential for physicians to improve patient outcomes. Recent Advances: Since the 1980s, the medical use of lasers has continuously evolved with improvements in technology. Novel lasers and fractionated technologies are currently being studied in the hopes to improve treatment efficacy, while reducing complications. Recent advancements include acne treatment with novel picosecond lasers, new hypertrophic scar therapies with simultaneous laser and intense pulsed light use, and novel systems such as lasers with intralesional optical fiber delivery devices. In addition, optimizing the timing of laser therapy and its use in multimodal treatments continue to advance the field of photothermolysis. Critical Issues: Selecting the correct laser for a given indication is the fundamental decision when choosing a laser balancing effective treatment with minimal complications. This article covers the principles of laser therapy, the preferred lasers used for the treatment of scarring and vascular anomalies, and discusses the current evidence behind these laser choices. Future Directions: To optimize laser therapy, larger randomized control trials and split scar studies are needed. Continued advancement through better randomized controlled studies will help to improve patient outcomes on a broader scale.

Disrupting mechanotransduction decreases fibrosis and contracture in split-thickness skin grafting

Burns and other traumatic injuries represent a substantial biomedical burden. The current standard of care for deep injuries is autologous split-thickness skin grafting (STSG), which frequently results in contractures, abnormal pigmentation, and loss of biomechanical function. Currently, there are no effective therapies that can prevent fibrosis and contracture after STSG. Here, we have developed a clinically relevant porcine model of STSG and comprehensively characterized porcine cell populations involved in healing with single-cell resolution. We identified an up-regulation of proinflammatory and mechanotransduction signaling pathways in standard STSGs. Blocking mechanotransduction with a small-molecule focal adhesion kinase (FAK) inhibitor promoted healing, reduced contracture, mitigated scar formation, restored collagen architecture, and ultimately improved graft biomechanical properties. Acute mechanotransduction blockade up-regulated myeloid CXCL10-mediated anti-inflammation with decreased CXCL14-mediated myeloid and fibroblast recruitment. At later time points, mechanical signaling shifted fibroblasts toward profibrotic differentiation fates, and disruption of mechanotransduction modulated mesenchymal fibroblast differentiation states to block those responses, instead driving fibroblasts toward proregenerative, adipogenic states similar to unwounded skin. We then confirmed these two diverging fibroblast transcriptional trajectories in human skin, human scar, and a three-dimensional organotypic model of human skin. Together, pharmacological blockade of mechanotransduction markedly improved large animal healing after STSG by promoting both early, anti-inflammatory and late, regenerative transcriptional programs, resulting in healed tissue similar to unwounded skin. FAK inhibition could therefore supplement the current standard of care for traumatic and burn injuries.

Reconstruction of Extensive Soft Tissue Defects of Lower Extremity With the Extended Anterolateral Thigh Flap

The anterolateral thigh flap is a classic flap used for various reconstruction defects. However, the flap viability of extended large skin paddles (ie, 240 cm²) was doubted by many surgeons. This study reports successful experience of reconstructing extensive soft tissue defects of lower extremity using extended large skin paddles. Twelve consecutive patients who had undergone reconstruction of defects using an extended anterolateral thigh flap were identified. Patient characteristics (age, sex, defect location, injured structures, and type of flap) and outcome data were analyzed retrospectively. One artery and 2 accompanying veins were anastomosed to vascularize each flap. Follow-up periods ranged from 10 to 91 months postoperatively. The average size of the flaps was 268.75 cm² (range = 220-391 cm²). All flaps were perforator flaps with one perforator except that 2 perforators were used in 3 patients. Two patients suffered partial flap necrosis of the distal portion with delayed healing. In conclusion, the extended anterolateral thigh flap is a considerable option for massive defects requiring composite tissue coverage. This flap is advantageous for reconstructing various complex defects in the lower extremities, providing a pliable and vascularized tissue to cover exposed extensive defects including tendons, nerves, and bones.

The Impact of Fibrin Sealant Volume on Skin Graft Contraction in a Full-Thickness Skin Graft Model

BACKGROUND

Fibrin sealant has been used for skin grafting in anatomically difficult facial areas. Although biodegradable, an excess of fibrin sealant may inhibit skin graft healing by inhibiting diffusion at the graft-recipient bed interface. The impact of fibrin sealant volume on graft healing was examined in a rat full-thickness skin graft model.

METHODS

Seventy-two full-thickness 2.5 × 2.5-cm skin grafts were used on the dorsum of male Sprague-Dawley rats. The grafts were treated with three different volumes of fibrin sealant placed onto the recipient bed: 0.0 mL or normal saline (group 1), 0.1 mL (group 2), and 0.4 mL (group 3). Graft healing and complications were assessed using digital photographs and necropsies on postoperative days 3, 7, and 21.

RESULTS

Group 3 showed the greatest graft contraction on days 3 and 21, while group 2 showed the least contraction on all 3 postoperative days (P = 0.002, 0.004, and <0.001, respectively). Histopathologic analysis showed inflammatory foreign body reactions in group 3 on days 3 and 7, and less vascular density on day 21 (P = 0.003). Group 1 showed the highest incidence of hematoma (P = 0.004).

CONCLUSION

An excess volume of fibrin sealant may produce pathologic wound contraction in skin grafting because a skin graft lacks a vascular pedicle and is highly dependent on diffusion from the host environment. Before using fibrin sealant for skin grafting in facial areas where the aesthetic outcome is important, the appropriate volume to use can be determined.

Factors associated with upper limb dysfunction in breast cancer survivors

OBJECTIVE

To analyze factors associated with upper limb dysfunction in women after breast cancer treatment.

METHODOLOGY

A cross-sectional study with 233 women over 18 years of age diagnosed with breast cancer and undergoing at least one cancer treatment (surgery and/or adjuvant treatment). Sociodemographic, anthropometric, and cancer treatment data were collected, as well as current physical and functional complications. Changes in breast tenderness and intercostobrachial nerve pathway, winged scapula, pain, cicatricial adherence, and lymphedema were evaluated by physical examination (inspection and palpation). Upper limb dysfunction was assessed using the DASH questionnaire. Chi-square test and logistic regression were used to verify possible associations between upper limb dysfunction and other variables.

RESULTS

The results showed that 55.4% of women had some level of upper limb dysfunction. Evaluating treatment conditions, lymphadenectomy, lymphedema, presence of pain, and intercostobrachial nerve injury were associated with some level of upper limb dysfunction in the crude analysis. The adjusted analysis showed that only upper limb dysfunction remained associated with intercostobrachial nerve injury, regardless of age and body mass index.

CONCLUSION

Upper limb dysfunction is frequent after breast cancer treatment and may be associated with neuropathies due to changes in the intercostobrachial nerve pathway.

Heterotopic Ossification and Hypertrophic Scars

Burns and trauma cause superficial and deep soft tissue wounds that cannot heal to the preinjury state. Healing requires cell proliferation and differentiation into the injured tissue type, laying down extracellular matrix, often as collagens. Heterotopic ossification causes severe pain, nonhealing wounds, and restricted range of motion. Treatment includes radiation therapy, nonsteroidal anti-inflammatory drugs, bisphosphonates, and possibly surgical excision and prophylactic measures. Hypertrophic scars, nonosseous lesions caused by excessive collagen deposition, are often painful, functionally limiting, and aesthetically displeasing. Treatment includes CO2 laser application, steroid injections, and excision with skin grafting. This article reviews the management of these pathologic wounds.

Ultrahigh dose gentamicin alters inflammation and angiogenesis in vivo and in vitro

Skin quality outcome after skin grafting is adversely affected by wound bed inflammation. Neomycin, gentamicin, and other aminoglycoside antibiotics are known to modulate inflammation, and topical application affords the use of higher doses than are possible to use systemically. Previous data suggest that clinically relevant doses of neomycin, but not gentamicin, may impair angiogenesis, which is critical to the durable survival of skin grafts. The role of gentamicin at ultrahigh doses compared with clinically relevant neomycin doses in regulating inflammatory expression and angiogenesis has been examined. In a porcine skin replacement excisional wound model, continuous exposure to gentamicin increased anti-angiogenic and inflammatory expression at 7 days postgrafting. In in vitro studies, gentamicin also impaired angiogenesis in a human umbilical vein endothelial cell (HUVEC) tube formation model, increased the expression of the anti-angiogenic gene C-X-C motif chemokine 10 (CXCL10) in HUVECs and macrophages, and increased pro-inflammatory cytokine expression of macrophages in a dose-dependent manner. Neomycin exerted similar effects in vitro at clinically relevant doses on HUVEC tube formation and macrophage pro-inflammatory expression. CXCL10 was upregulated in macrophages, but did not exhibit a change in HUVECs with neomycin treatment. Ultrahigh doses of gentamicin and clinically relevant doses of neomycin affect inflammation and angiogenesis in in vivo and in vitro models. These findings suggest that topical administration of aminoglycosides have the potential to adversely influence early skin graft survival.

Effectiveness of Autologous Fat Grafting in Adherent Scars: Results Obtained by a Comprehensive Scar Evaluation Protocol

BACKGROUND

Nowadays, patients normally survive severe traumas such as burn injuries and necrotizing fasciitis. Large skin defects can be closed but the scars remain. Scars may become adherent to underlying structures when the subcutical fat layer is damaged. Autologous fat grafting provides the possibility of reconstructing a functional sliding layer underneath the scar. Autologous fat grafting is becoming increasingly popular for scar treatment, although large studies using validated evaluation tools are lacking. The authors therefore objectified the effectiveness of single-treatment autologous fat grafting on scar pliability using validated scar measurement tools.

METHODS

Forty patients with adherent scars receiving single-treatment autologous fat grafting were measured preoperatively and at 3-month follow-up. The primary outcome parameter was scar pliability, measured using the Cutometer. Scar quality was also evaluated by the Patient and Observer Scar Assessment Scale and the DSM II ColorMeter. To prevent selection bias, measurements were performed following a standardized algorithm.

RESULTS

The Cutometer parameters elasticity and maximal extension improved 22.5 percent (p < 0.001) and 15.6 percent (p = 0.001), respectively. Total Patient and Observer Scar Assessment Scale scores improved from 3.6 to 2.9 on the observer scale, and from 5.1 to 3.8 on the patient scale (both p < 0.001). Color differences between the scar and normal skin remained unaltered.

CONCLUSIONS

For the first time, the effect of autologous fat grafting on functional scar parameters was ascertained using a comprehensive scar evaluation protocol. The improved scar pliability supports the authors' hypothesis that the function of the subcutis can be restored to a certain extent by single-treatment autologous fat grafting.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, IV.

Stem Cells and Tissue Engineering: Regeneration of the Skin and Its Contents

In this review, the authors discuss the stages of skin wound healing, the role of stem cells in accelerating skin wound healing, and the mechanism by which these stem cells may reconstitute the skin in the context of tissue engineering.

Pre-vascularization Enhances Therapeutic Effects of Human Mesenchymal Stem Cell Sheets in Full Thickness Skin Wound Repair

Split thickness skin graft (STSG) implantation is one of the standard therapies for full thickness wound repair when full thickness autologous skin grafts (FTG) or skin flap transplants are inapplicable. Combined transplantation of STSG with dermal substitute could enhance its therapeutic effects but the results remain unsatisfactory due to insufficient blood supply at early stages, which causes graft necrosis and fibrosis. Human mesenchymal stem cell (hMSC) sheets are capable of accelerating the wound healing process. We hypothesized that pre-vascularized hMSC sheets would further improve regeneration by providing more versatile angiogenic factors and pre-formed microvessels. In this work, in vitro cultured hMSC cell sheets (HCS) and pre-vascularized hMSC cell sheets (PHCS) were implanted in a rat full thickness skin wound model covered with an autologous STSG. Results demonstrated that the HCS and the PHCS implantations significantly reduced skin contraction and improved cosmetic appearance relative to the STSG control group. The PHCS group experienced the least hemorrhage and necrosis, and lowest inflammatory cell infiltration. It also induced the highest neovascularization in early stages, which established a robust blood micro-circulation to support grafts survival and tissue regeneration. Moreover, the PHCS grafts preserved the largest amount of skin appendages, including hair follicles and sebaceous glands, and developed the smallest epidermal thickness. The superior therapeutic effects seen in PHCS groups were attributed to the elevated presence of growth factors and cytokines in the pre-vascularized cell sheet, which exerted a beneficial paracrine signaling during wound repair. Hence, the strategy of combining STSG with PHCS implantation appears to be a promising approach in regenerative treatment of full thickness skin wounds.

Antecedent thermal injury worsens split-thickness skin graft quality: A clinically relevant porcine model of full-thickness burn, excision and grafting

Current standard of care for full-thickness burn is excision followed by autologous split-thickness skin graft placement. Skin grafts are also frequently used to cover surgical wounds not amenable to linear closure. While all grafts have potential to contract, clinical observation suggests that antecedent thermal injury worsens contraction and impairs functional and aesthetic outcomes. This study evaluates the impact of antecedent full-thickness burn on split-thickness skin graft scar outcomes and the potential mediating factors. Full-thickness contact burns (100°C, 30s) were created on the backs of anesthetized female Yorkshire Pigs. After seven days, burn eschar was tangentially excised and covered with 12/1000th inch (300μm) split-thickness skin graft. For comparison, unburned wounds were created by sharp excision to fat before graft application. From 7 to 120days post-grafting, planimetric measurements, digital imaging and biopsies for histology, immunohistochemistry and gene expression were obtained. At 120days post-grafting, the Observer Scar Assessment Scale, colorimetry, contour analysis and optical graft height assessments were performed. Twenty-nine porcine wounds were analyzed. All measured metrics of clinical skin quality were significantly worse (p<0.05) in burn injured wounds. Histological analysis supported objective clinical findings with marked scar-like collagen proliferation within the dermis, increased vascular density, and prolonged and increased cellular infiltration. Observed differences in contracture also correlated with earlier and more prominent myofibroblast differentiation as demonstrated by α-SMA staining. Antecedent thermal injury worsens split-thickness skin graft quality, likely by multiple mechanisms including burn-related inflammation, microscopically inadequate excision, and dysregulation of tissue remodeling. A valid, reliable, clinically relevant model of full-thickness burn, excision and skin replacement therapy has been demonstrated. Future research to enhance quality of skin replacement therapies should be directed toward modulation of inflammation and assessments for complete excision.

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.

Progress of clinical practice on the management of burn-associated pain: Lessons from animal models

Opioid-based analgesics provide the mainstay for attenuating burn pain, but they have a myriad of side effects including respiratory depression, nausea, impaired gastrointestinal motility, sedation, dependence, physiologic tolerance, and opioid-induced hyperalgesia. To test and develop novel analgesics, validated burn-relevant animal models of pain are indispensable. Herein we review such animal models, which are mostly limited to rodent models of burn-induced, inflammatory, and neuropathic pain. The latter two are pain syndromes that provide insight into the pain caused by systemic pro-inflammatory cytokines and direct injury to nerves (e.g., after severe burn), respectively. To date, no single animal model optimally mimics the complex pathophysiology and pain that a human burn patient experiences. No currently available burn-pain model examines effects of pharmacological intervention on wound healing. As cornerstones of pain and wound healing, pro-inflammatory mediators may be utilized for insight into both processes. Moreover, common clinical concerns such as systemic inflammatory response syndrome and multiple organ dysfunction remain unaddressed. For development of analgesics, these aberrations can significantly alter the potential efficacy and/or adverse effects of a prescribed analgesic following burn trauma. We therefore suggest that a multi-model strategy would be the most clinically relevant when evaluating novel analgesics for use in burn patients.