Single-cell transcriptional analysis of irradiated skin reveals changes in fibroblast subpopulations and variability in caveolin expression.

BACKGROUND: Radiation-induced fibrosis (RIF) is an important late complication of radiation therapy, and the resulting damaging effects of RIF can significantly impact reconstructive outcomes. There is currently a paucity of effective treatment options available, likely due to the continuing knowledge gap surrounding the cellular mechanisms involved. In this study, detailed analyses of irradiated and non-irradiated human skin samples were performed incorporating histological and single-cell transcriptional analysis to identify novel features guiding development of skin fibrosis following radiation injury. METHODS: Paired irradiated and contralateral non-irradiated skin samples were obtained from six female patients undergoing post-oncologic breast reconstruction. Skin samples underwent histological evaluation, immunohistochemistry, and biomechanical testing. Single-cell RNA sequencing was performed using the 10X single cell platform. Cells were separated into clusters using Seurat in R. The SingleR classifier was applied to ascribe cell type identities to each cluster. Differentially expressed genes characteristic to each cluster were then determined using non-parametric testing. RESULTS: Comparing irradiated and non-irradiated skin, epidermal atrophy, dermal thickening, and evidence of thick, disorganized collagen deposition within the extracellular matrix of irradiated skin were readily appreciated on histology. These histologic features were associated with stiffness that was higher in irradiated skin. Single-cell RNA sequencing revealed six predominant cell types. Focusing on fibroblasts/stromal lineage cells, five distinct transcriptional clusters (Clusters 0-4) were identified. Interestingly, while all clusters were noted to express Cav1, Cluster 2 was the only one to also express Cav2. Immunohistochemistry demonstrated increased expression of Cav2 in irradiated skin, whereas Cav1 was more readily identified in non-irradiated skin, suggesting Cav1 and Cav2 may act antagonistically to modulate fibrotic cellular responses. CONCLUSION: In response to radiation therapy, specific changes to fibroblast subpopulations and enhanced Cav2 expression may contribute to fibrosis. Altogether, this study introduces a novel pathway of caveolin involvement which may contribute to fibrotic development following radiation injury.

Understanding wound healing in obesity.

Obesity has become more prevalent in the global population. It is associated with the development of several diseases including diabetes mellitus, coronary heart disease, and metabolic syndrome. There are a multitude of factors impacted by obesity that may contribute to poor wound healing outcomes. With millions worldwide classified as obese, it is imperative to understand wound healing in these patients. Despite advances in the understanding of wound healing in both healthy and diabetic populations, much is unknown about wound healing in obese patients. This review examines the impact of obesity on wound healing and several animal models that may be used to broaden our understanding in this area. As a growing portion of the population identifies as obese, understanding the underlying mechanisms and how to overcome poor wound healing is of the utmost importance.

A Review of Radiation-Induced Vascular Injury and Clinical Impact.

ABSTRACT: The number of cancer survivors continues to increase because of advances in therapeutic modalities. Along with surgery and chemotherapy, radiotherapy is a commonly used treatment modality in roughly half of all cancer patients. It is particularly helpful in the oncologic treatment of patients with breast, head and neck, and prostate malignancies. Unfortunately, among patients receiving radiation therapy, long-term sequalae are often unavoidable, and there is accumulating clinical evidence suggesting significant radiation-related damage to the vascular endothelium. Ionizing radiation has been known to cause obliterative fibrosis and increased wall thickness in irradiated blood vessels. Clinically, these vascular changes induced by ionizing radiation can pose unique surgical challenges when operating in radiated fields. Here, we review the relevant literature on radiation-induced vascular damage focusing on mechanisms and signaling pathways involved and highlight microsurgical anastomotic outcomes after radiotherapy. In addition, we briefly comment on potential therapeutic strategies, which may have the ability to mitigate radiation injury to the vascular endothelium.

Investigating Immunomodulatory Biomaterials for Preventing the Foreign Body Response.

Implantable biomaterials represent the forefront of regenerative medicine, providing platforms and vessels for delivering a creative range of therapeutic benefits in diverse disease contexts. However, the chronic damage resulting from implant rejection tends to outweigh the intended healing benefits, presenting a considerable challenge when implementing treatment-based biomaterials. In response to implant rejection, proinflammatory macrophages and activated fibroblasts contribute to a synergistically destructive process of uncontrolled inflammation and excessive fibrosis. Understanding the complex biomaterial-host cell interactions that occur within the tissue microenvironment is crucial for the development of therapeutic biomaterials that promote tissue integration and minimize the foreign body response. Recent modifications of specific material properties enhance the immunomodulatory capabilities of the biomaterial and actively aid in taming the immune response by tuning interactions with the surrounding microenvironment either directly or indirectly. By incorporating modifications that amplify anti-inflammatory and pro-regenerative mechanisms, biomaterials can be optimized to maximize their healing benefits in harmony with the host immune system.

Operation Diversify Plastic Surgery: An Innovative Strategy to Increase Diversity in Plastic and Reconstructive Surgery.

Healthcare disparities remain a significant problem facing the US healthcare system with recent evidence of persistent racial and ethnic disparities especially among patients from minority backgrounds. Recent studies have documented advantages to a racially and ethnically diverse surgical workforce such as higher patient satisfaction scores, superior patient compliance with physician recommendations, and increased participation in clinical research studies by minority patients. In plastic and reconstructive surgery (PRS), there is a noted deficit among residents and faculty that come from ethnically underrepresented in medicine (URiM) backgrounds despite recent efforts to increase diversity in PRS surgeons. URiM medical students from three of the four historically Black medical universities organized to discuss pathways to PRS. Operation Diversify Plastic Surgery is a student-led organization that was developed to address the lack of diversity in PRS, challenges faced by students from institutions that lack PRS residency training programs, and unique factors that affect URiM students interested in PRS. Available studies note that mentoring relationships and research opportunities were instrumental in recruiting URiM students into PRS residency programs. Operation Diversify Plastic Surgery is an innovative solution to the insufficient URiM PRS residency candidate pool by increasing medical student exposure to PRS via educational lectures, virtual mentoring opportunities, and insights into research fellowships.

Understanding the Role of Adipocytes and Fibroblasts in Cancer.

ABSTRACT: Cancer is currently the second leading cause of death in the United States. There is increasing evidence that the tumor microenvironment (TME) is pivotal for tumorigenesis and metastasis. Recently, adipocytes and cancer-associated fibroblasts (CAFs) in the TME have been shown to play a major role in tumorigenesis of different cancers, specifically melanoma. Animal studies have shown that CAFs and adipocytes within the TME help tumors evade the immune system, for example, by releasing chemokines to blunt the effectiveness of the host defense. Although studies have identified that adipocytes and CAFs play a role in tumorigenesis, adipocyte transition to fibroblast within the TME is fairly unknown. This review intends to elucidate the potential that adipocytes may have to transition to fibroblasts and, as part of the TME, a critical role that CAFs may play in affecting the growth and invasion of tumor cells. Future studies that illuminate the function of adipocytes and CAFs in the TME may pave way for new antitumor therapies.

Attenuating Chronic Fibrosis: Decreasing Foreign Body Response with Acellular Dermal Matrix.

Surgical implants are increasingly used across multiple medical disciplines, with applications ranging from tissue reconstruction to improving compromised organ and limb function. Despite their significant potential for improving health and quality of life, biomaterial implant function is severely limited by the body's immune response to its presence: this is known as the foreign body response (FBR) and is characterized by chronic inflammation and fibrotic capsule formation. This response can result in life-threatening sequelae such as implant malfunction, superimposed infection, and associated vessel thrombosis, in addition to soft tissue disfigurement. Patients may require frequent medical visits, as well as repeated invasive procedures, increasing the burden on an already strained health care system. Currently, the FBR and the cells and molecular mechanisms that mediate it are poorly understood. With applications across a wide array of surgical specialties, acellular dermal matrix (ADM) has emerged as a potential solution to the fibrotic reaction seen with FBR. Although the mechanisms by which ADM decreases chronic fibrosis remain to be clearly characterized, animal studies across diverse surgical models point to its biomimetic properties that facilitate decreased periprosthetic inflammation and improved host cell incorporation. Impact Statement Foreign body response (FBR) is a significant limitation to the use of implantable biomaterials. Acellular dermal matrix (ADM) has been observed to decrease the fibrotic reaction seen with FBR, although its mechanistic details are poorly understood. This review is dedicated to summarizing the primary literature on the biology of FBR in the context of ADM use, using surgical models in breast reconstruction, abdominal and chest wall repair, and pelvic reconstruction. This article will provide readers with an overarching review of shared mechanisms for ADM across multiple surgical models and diverse anatomical applications.

Outcomes of Surgical Treatment of Migraines: A Systematic Review & Meta-Analysis.

Background: Migraine surgery at 1 of 6 identified "trigger sites" of a target cranial sensory nerve has rapidly grown in popularity since 2000. This study summarizes the effect of migraine surgery on headache severity, headache frequency, and the migraine headache index score which is derived by multiplying migraine severity, frequency, and duration. Materials and Methods: This is a PRISMA-compliant systematic review of 5 databases searched from inception through May 2020 and is registered under the PROSPERO ID: CRD42020197085. Clinical trials treating headaches with surgery were included. Risk of bias was assessed in randomized controlled trials. Meta-analyses were performed on outcomes using a random effects model to determine the pooled mean change from baseline and when possible, to compare treatment to control. Results: 18 studies met criteria including 6 randomized controlled trials, 1 controlled clinical trial, and 11 uncontrolled clinical trials treated 1143 patients with pathologies including migraine, occipital migraine, frontal migraine, occipital nerve triggered headache, frontal headache, occipital neuralgia, and cervicogenic headache. Migraine surgery reduced headache frequency at 1 year postoperative by 13.0 days per month as compared to baseline (I2 = 0%), reduced headache severity at 8 weeks to 5 years postoperative by 4.16 points on a 0 to 10 scale as compared to baseline (I2 = 53%), and reduced migraine headache index at 1 to 5 years postoperative by 83.1 points as compared to baseline (I2 = 2%). These meta-analyses are limited by a small number of studies that could be analyzed, including studies with high risk of bias. Conclusion: Migraine surgery provided a clinically and statistically significant reduction in headache frequency, severity, and migraine headache index scores. Additional studies, including randomized controlled trials with low risk-of-bias should be performed to improve the precision of the outcome improvements.

Historique: Le traitement de la migraine à l'une des six « zones gâchettes ¼ établies d'un nerf crânien sensoriel cible ont rapidement gagné en popularité depuis 2000. La présente étude résume l'effet du traitement chirurgical de la migraine sur la gravité et la fréquence des céphalées et sur le score de migraine obtenu par la multiplication de la gravité, de la fréquence et de la durée des migraines. Matériel et méthodologie: La présente analyse systématique de cinq bases de données fouillées depuis leur création jusqu'à mai 2020 respecte la liste PRISMA et est enregistrée sous le numéro d'identification CRD42020197085 de PROSPERO. Les chercheurs ont retenu les études cliniques sur le traitement des céphalées par des interventions chirurgicales. Ils ont évalué le risque de biais des études aléatoires et contrôlées. Ils ont également effectué des méta-analyses des résultats au moyen d'un modèle à effets aléatoires pour déterminer le changement moyen regroupé par rapport à l'état de référence et, dans la mesure du possible, pour comparer des sujets traités à des sujets témoins. Résultats: Au total, 18 études respectaient les critères, y compris six études aléatoires et contrôlées, une étude clinique contrôlée, et 11 études non contrôlées auprès de 1 143 patients ayant des pathologies incluant la migraine, la migraine occipitale, la migraine frontale, la céphalée occipitale, la céphalée frontale, la névralgie occipitale et la céphalée cervicogénique. Par rapport à l'état de départ, le traitement chirurgical de la migraine avait réduit la fréquence des céphalées de 13,0 jours par mois (I2 = 0%) un an après l'opération, la gravité des céphalées de 4,16 points sur une échelle de 0 à 10 de huit semaines à cinq ans après l'opération (I2 = 53%) et le score de migraine de 83,1 points de un à cinq ans après l'opération (I2 = 2%). Ces méta-analyses sont limitées par le petit nombre d'études pouvant être analysées, y compris des études comportant de forts risques de biais. Conclusion: Le traitement chirurgical de la migraine assure une diminution cliniquement et statistiquement significative de la fréquence et de la gravité des céphalées, ainsi que des scores de migraine. D'autres études, y compris des études aléatoires et contrôlées comportant un faible risque de biais, devront être exécutées pour mieux préciser les améliorations aux résultats cliniques.

Chelating the valley of death: Deferoxamine's path from bench to wound clinic.

There is undisputable benefit in translating basic science research concretely into clinical practice, and yet, the vast majority of therapies and treatments fail to achieve approval. The rift between basic research and approved treatment continues to grow, and in cases where a drug is granted approval, the average time from initiation of human trials to regulatory marketing authorization spans almost a decade. Albeit with these hurdles, recent research with deferoxamine (DFO) bodes significant promise as a potential treatment for chronic, radiation-induced soft tissue injury. DFO was originally approved by the Food and Drug Administration (FDA) in 1968 for the treatment of iron overload. However, investigators more recently have posited that its angiogenic and antioxidant properties could be beneficial in treating the hypovascular and reactive-oxygen species-rich tissues seen in chronic wounds and radiation-induced fibrosis (RIF). Small animal experiments of various chronic wound and RIF models confirmed that treatment with DFO improved blood flow and collagen ultrastructure. With a well-established safety profile, and now a strong foundation of basic scientific research that supports its potential use in chronic wounds and RIF, we believe that the next steps required for DFO to achieve FDA marketing approval will include large animal studies and, if those prove successful, human clinical trials. Though these milestones remain, the extensive research thus far leaves hope for DFO to bridge the gap between bench and wound clinic in the near future.

Adipose-Derived Stromal Cell-Based Therapies for Radiation-Induced Fibrosis.

Significance: Half of all cancer patients receive radiation therapy as a component of their treatment regimen, and the most common resulting complication is radiation-induced fibrosis (RIF) of the skin and soft tissue. This thickening of the dermis paired with decreased vascularity results in functional limitations and esthetic concerns and poses unique challenges when considering surgical exploration or reconstruction. Existing therapeutic options for RIF of the skin are limited both in scope and efficacy. Cell-based therapies have emerged as a promising means of utilizing regenerative cell populations to improve both functional and esthetic outcomes, and even as prophylaxis for RIF. Recent Advances: As one of the leading areas of cell-based therapy research, adipose-derived stromal cells (ADSCs) demonstrate significant therapeutic potential in the treatment of RIF. The introduction of the ADSC-augmented fat graft has shown clinical utility. Recent research dedicated to characterizing specific ADSC subpopulations points toward further granularity in understanding of the mechanisms driving the well-established clinical outcomes seen with fat grafting therapy. Critical Issues: Various animal models of RIF demonstrated improved clinical outcomes following treatment with cell-based therapies, but the cellular and molecular basis underlying these effects remains poorly understood. Future Directions: Recent literature has focused on improving the efficacy of cell-based therapies, most notably through (1) augmentation of fat grafts with platelet-rich plasma and (2) the modification of expressed RNA through epitranscriptomics. For the latter, new and promising gene targets continue to be identified which have the potential to reverse the effects of fibrosis by increasing angiogenesis, decreasing inflammation, and promoting adipogenesis.

Postamputation Residual Limb Pain Severity and Prevalence: A Systematic Review and Meta-Analysis.

Background: Individuals with an extremity amputation are predisposed to persistent pain that reduces their quality of life. Residual limb pain is defined as pain that is felt in the limb after amputation. Methods: A Preferred Reporting Items for Systematic Reviews and Meta-Analyses-compliant systematic review of 5 databases from inception to June 2020 was performed and is registered under the PROSPERO ID: CRD42020199297. Included studies were clinical trials with residual limb pain assessed at a minimum follow-up of 1 week. Meta-analyses of residual limb pain prevalence and severity were performed with subgroups of extremity and amputation etiology. Results: Twenty clinical trials met criteria and reported on a total of 1347 patients. Mean patient ages ranged from 38 to 77. Residual limb pain prevalence at 1 week, 1 month, 3 months, 6 months, 1 year, and 2 years, respectively, was 50%, 11%, 23%, 27%, 22%, and 24%. Mean residual limb pain severity at the 6 months or longer follow-up was 4.19 out of 10 for cancer amputations, 2.70 for traumatic amputations, 0.47 for vasculopathy amputations, 1.01 for lower extremity amputations, and 3.56 for upper extremity amputations. Conclusions: Residual limb pain severity varies according to the etiology of amputation and is more common after upper extremity amputation than lower extremity amputations. The most severe pain is reported by patients undergoing amputations due to cancer, followed by traumatic amputations, while vascular amputation patients report lower pain severity. Promising methods of reducing long-term pain are preoperative pain control, nerve or epidural blocks, use of memantine, calcitonin-containing blocks, and prophylactic nerve coaptations.

Contexte: Les personnes subissant une amputation d'un membre sont prédisposées à des douleurs persistantes réduisant leur qualité de vie. La douleur du membre résiduel est définie comme étant la douleur ressentie dans le membre après l'amputation. Méthodes: Une revue systématique conforme à PRISMA de 5 bases de données depuis leur création jusqu'en juin 2020 a été effectuée et enregistrée sous l'ID PROSPERO: CRD42020199297. Les études incluses étaient des essais cliniques avec douleur du membre résiduel évaluée à un suivi minimum de 1 semaine. Des méta-analyses sur la prévalence et la sévérité de la douleur du membre résiduel ont été réalisées avec des sous-groupes en fonction du membre et de la cause de l'amputation. Résultats: 20 essais cliniques satisfaisaient les critères et portaient sur un total de 1347 patients. Les âges moyens des patients étaient compris entre 38 et 77 ans. La prévalence de la douleur du membre résiduel à 1 semaine, 1 mois, 3 mois, 6 mois, 1 an et 2 ans était, respectivement, de 50%, 11%, 23%, 27%, 22%, et 24%. La sévérité moyenne de la douleur du membre résiduel aux suivis de 6 mois ou plus a été de 4,19 sur 10 pour les amputations pour cancer, 2,70 pour les amputations post traumatisme, 0,47 pour les amputations liées à une vasculopathie, 1,01 pour les amputations du membre inférieur et 3,56 pour les amputations du membre supérieur. Conclusions: La sévérité de la douleur du membre résiduel varie en fonction du motif de l'amputation, et elle est plus fréquente après une amputation du membre supérieur qu'après des amputations du membre inférieur. La douleur la plus sévère a été décrite par des patients subissant une amputation à cause d'un cancer, suivie des amputations traumatiques, alors que les patients ayant subi une amputation pour cause vasculaire signalent une sévérité plus faible. Des méthodes prometteuses de réduction de la douleur à long terme sont le contrôle préopératoire de la douleur, les blocs nerveux et épiduraux, l'utilisation de la mémantine, de blocs contenant de la calcitonine et la coaptation prophylactique des nerfs.