Immune modulation in transplant medicine: a comprehensive review of cell therapy applications and future directions.

Balancing the immune response after solid organ transplantation (SOT) and vascularized composite allotransplantation (VCA) remains an ongoing clinical challenge. While immunosuppressants can effectively reduce acute rejection rates following transplant surgery, some patients still experience recurrent acute rejection episodes, which in turn may progress to chronic rejection. Furthermore, these immunosuppressive regimens are associated with an increased risk of malignancies and metabolic disorders. Despite significant advancements in the field, these IS related side effects persist as clinical hurdles, emphasizing the need for innovative therapeutic strategies to improve transplant survival and longevity. Cellular therapy, a novel therapeutic approach, has emerged as a potential pathway to promote immune tolerance while minimizing systemic side-effects of standard IS regiments. Various cell types, including chimeric antigen receptor T cells (CAR-T), mesenchymal stromal cells (MSCs), regulatory myeloid cells (RMCs) and regulatory T cells (Tregs), offer unique immunomodulatory properties that may help achieve improved outcomes in transplant patients. This review aims to elucidate the role of cellular therapies, particularly MSCs, T cells, Tregs, RMCs, macrophages, and dendritic cells in SOT and VCA. We explore the immunological features of each cell type, their capacity for immune regulation, and the prospective advantages and obstacles linked to their application in transplant patients. An in-depth outline of the current state of the technology may help SOT and VCA providers refine their perioperative treatment strategies while laying the foundation for further trials that investigate cellular therapeutics in transplantation surgery.

Outcomes in patients with burns to the perineum, buttocks and genitalia: A retrospective cohort study.

BACKGROUND: Burns that involve the perineum, buttocks and genitals (PBG) have been associated with more challenging therapeutic needs and worse clinical outcomes. We aimed to investigate whether PBG burns are an independent predictor for mortality, morbidity and complications in a large, heterogenous patient collective and in comparison to patients without PBG burns. PATIENTS AND METHODS: Patients admitted to a level one burn center between August 2014 and July 2022 were included and stratified based on the presence of PBG burns on admission (PBG & control group = CTR). Demographic baseline data, burn aetiology, inhalation trauma (IHT), full-thickness burns (FT), number of operations (NOR), mortality, length of ICU stay (LOS-ICU), length of in-hospital stay (LOHS) and bacteraemia were assessed to compare key clinical characteristics and outcomes between the groups. Multivariate regression analyses and a 1:1 propensity score matching were conducted for key clinical outcomes. RESULTS: A total of 1024 patients were included in the analysis (PBG: n = 227; CTR: n = 797). PBG burns were older (median (IQR) 54 (34-72) vs. 44, (30-61) years, p < 0.0001), more frequently female (35% vs. 23%, p = 0.002) presented with larger total body surface area (TBSA) burns overall (27 (32-39) vs. 10 (13-15) %, p < 0.0001) and sustained FT burns more frequently (69% vs. 26% p < 0.0001). Scald burns were more frequently the cause of PBG burns (45% vs. 15%, p < 0.0001), PBG patients needed twice as many surgical procedures (Mean (SD) 2 (2.84) vs. 1 (1.6), p < 0.0001) as CTR. In multivariate analyses, a significant correlation was identified between length of ICU stay and presence of PBG burns. Following strict cohort matching to account for sex, age, cause of burn, TBSA %, presence of FT burn, inhalation trauma and bacteraemia, PBG burns were an independent predictor for mortality (p = 0.0003). CONCLUSION: PBG burns are at risk for prolonged intensive care, hospitalization and complications during treatment. Furthermore, the presence of PBG burns appears to be a risk factor for mortality, irrespective of patient age, TBSA affected and other relevant covariates.

Lymphedema-associated fibroblasts are a TGF-ß1 activated myofibroblast subpopulation related to fibrosis and stage progression in patients and a murine microsurgical model.

BACKGROUND: The driver of secondary lymphedema (SL) progression is chronic inflammation, which promotes fibrosis. Despite advances in preclinical research, a specific effector cell subpopulation as a biomarker for therapy response or stage progression is still missing for SL. METHODS: Whole skin samples of 35 murine subjects of a microsurgical-induced SL model and 12 patients with SL were collected and their fibroblasts were isolated. These lymphedema-derived fibroblasts (LAF) were cultured in a collagen I-poly-D-Lysine 3D hydrogel to mimic skin conditions. Fibroblasts from non-lymphedema skin were used as negative control and TGF-ß-stimulated fibroblasts were used to recreate profibrotic myofibroblasts. Quantitative immunocytofluorescence confocal microscopy analysis and invasion functional assays were performed in all subpopulations and statistically compared. RESULTS: In contrast to normal skin fibroblasts, LAF exhibit α-SMA-positive stress fibers and a reduced number of tight junctions in 3D hydrogel conditions. The switch from normal E-cadherin high phenotype to an N-cadherin high-E-cadherin low morphology suggests epithelial to mesenchymal transition for expansion and proliferation. This pathological behavior of LAF was confirmed by live cell imaging analysis of invasion assays. The significant activation of markers of the TGFBR2-Smad pathway and collagen synthesis (HSP-47) in LAF supports EMT phenotypic changes and previous findings relating to TGF-ß1 and fibrosis with lymphedema. CONCLUSIONS: A characteristic SL myofibroblast subpopulation was identified and translationally related to fibrosis and TGF-ß1-associated stage progression. This SL-related subpopulation was termed lymphedema-associated fibroblasts. A comprehensive stage-related characterization is required to validate LAF as a reliable biomarker for SL disease progression.

Hepatic Functional Pathophysiology and Morphological Damage Following Severe Burns: A Systematic Review and Meta-analysis.

Severe burns are devastating injuries affecting multiple organ systems. Little is known about the influence on the hepatic system and its physiology. This systematic review aimed to assess the current state of research on morphologic liver damage following severe burns. A search was conducted in PubMed, Web of Science, and Cochrane databases using PRISMA guidelines. Outcomes included serum levels of transaminases, fatty infiltration, and necrosis. Weighted individual study estimates were used to calculate pooled transaminase levels and necrosis/fatty infiltration rates using a random-effects approach. Risk ratios or odds ratios and 95% confidence intervals (CIs) were used to describe pooled estimates for risk factors. The literature search retrieved 2548 hits, of which 59 studies were included in qualitative synthesis, and finally 10 studies were included in the meta-analysis. Studies were divided into those reporting autopsies and those reporting changes of serum transaminase levels. The majority of liver autopsies showed fatty infiltration, 82% (95% CI 39-97%) or necrosis of the liver, 18% (95% CI 13-24%). Heterogeneity in studies on hepatic functional damage following severe burns was high. Only a few were well-designed and published in recent years. Many studies could not be included because of insufficient numerical data. There is a high number of patients dying from burns that present with fatty infiltration or necrosis of hepatic tissue. Transaminases were elevated during the initial days postburn. Further research on how severe burns affect the hepatic function and outcome, especially long-term, is necessary. Systematic review registration: PROSPERO:CRD42020206061.

The status quo of early burn wound excision: Insights from the German burn registry.

BACKGROUND: There is a common, well-known and established recommendation to excise burn wounds within 24-72 h in order to mitigate the systemic inflammatory and immunomodulatory response, shorten length of hospitalization through early grafting and optimize patient survival. Despite this apparent consensus, surprisingly few systematic studies have evaluated the actual adherence to this practice and its implications on patient outcomes. In this registry study, we sought to objectify the current status of early burn wound excision, its influencing factors and impact on patient outcomes for all German burn centers. METHODS: The German burn registry ('Deutsches Verbrennungsregister') was queried for 3 consecutive years for all patients, who received at least one surgical intervention. Patients were stratified based on whether the first surgical procedure was performed early (EE, within 72 h) or late (LE, after 72 h) post-burn. Descriptive statistics and univariate regressions were performed to quantify fraction of EE vs. LE and to evaluate factors which might favor one over the other (i.e. age, inhalation injury, burn severity by total body surface area (TBSA), scald vs. other burns, obesity, time of admission). Key patient outcomes were analyzed for each group (i.e. mortality, length of hospitalization, number of surgeries) and multifactorial regression analyses were carried out to model the impact of EE on mortality. Statistical significance was accepted at p < 0.05. RESULTS: After initial screening, 1494 complete records were included for final analysis and were stratified into EE and LE. Only 670 (44%) underwent EE within 72 h. Increasing TBSA burned (i.e. [TBSA > 30%]: 53.8% EE, [TBSA < 30%]: 43.5% EE, p < 0.01) and admission on a weekday between Sunday and Wednesday were associated with higher probability of EE (51.5% EE) versus Thursday to Sunday (37.3%, p < 0.001). Age, inhalation injury, cause of burn, and obesity had no effect on EE vs. LE. Patients with EE had significantly shorter median lengths of hospitalization (EE: 18 d, LE: 21 d, p < 0.01). The median number of operations was comparable for both groups. Gross mortality appeared higher in the EE group, but turned out to be comparable to LE after correction for age, TBSA and sex in multifactorial regression analysis. CONCLUSION: Despite apparent consensus among burn physicians, early excision of burn wounds is performed in less than 50% of cases in German burn centers. The relationship of EE to TBSA burned is expected and clinically sound, while a dependence on admission weekday raises administrative and infrastructural questions, especially when patients who receive EE have significantly shorter hospital stays. More analyses from other burn repositories are needed to compare and benchmark the international status quo of early burn wound excision.

Lymphatic Tissue Engineering: A Further Step for Successful Lymphedema Treatment.

BACKGROUND: Secondary lymphedema, caused by oncologic surgery, radiation, and chemotherapy, is one of the most relevant, nononcological complications affecting cancer survivors. Severe functional deficits can result in impairing quality of life and a societal burden related to increased treatment costs. Often, conservative treatments are not sufficient to alleviate lymphedema or to prevent stage progression of the disease, as they do not address the underlying etiology that is the disruption of lymphatic pathways. In recent years, lymphatic surgery approaches were revolutionized by advances in microsurgical technique. Currently, lymphedema can effectively be treated by procedures such as lymphovenous anastomosis (LVA) and lymph node transfer (LNT). However, not all patients have suitable lymphatic vessels, and lymph node harvesting is associated with risks. In addition, some data have revealed nonresponders to the microsurgical techniques. METHODS: A literature review was performed to evaluate the value of lymphatic tissue engineering for plastic surgeons and to give an overview of the achievements, challenges, and goals of the field. RESULTS: While certain challenges exist, including cell harvesting, nutrient supply, biocompatibility, and hydrostatic properties, it is possible and desirable to engineer lymph nodes and lymphatic vessels. The path toward clinical translation is considered more complex for LNTs secondary to the complex microarchitecture and pending final mechanistic clarification, while LVA is more straight forward. CONCLUSION: Lymphatic tissue engineering has the potential to be the next step for microsurgical treatment of secondary lymphedema. Current and future researches are necessary to optimize this clinical paradigm shift for improved surgical treatment of lymphedema.

Cell-specific ablation of Hsp47 defines the collagen-producing cells in the injured heart

Collagen production in the adult heart is thought to be regulated by the fibroblast, although cardiomyocytes and endothelial cells also express multiple collagen mRNAs. Molecular chaperones are required for procollagen biosynthesis, including heat shock protein 47 (Hsp47). To determine the cell types critically involved in cardiac injury­induced fibrosis theHsp47 gene was deleted in cardiomyocytes, endothelial cells, or myofibroblasts. Deletion ofHsp47 from cardiomyocytes during embryonic development or adult stages, or deletion from adult endothelial cells, did not affect cardiac fibrosis after pressure overload injury. However, myofibroblast-specific ablation of Hsp47; blocked fibrosis and deposition of collagens type I, III, and V following pressure overload as well as significantly reduced cardiac hypertrophy. Fibroblast-specific Hsp47-deleted mice showed lethality after myocardial infarction injury, with ineffective scar formation and ventricular wall rupture. Similarly, only myofibroblast-specific deletion of Hsp47reduced fibrosis and disease in skeletal muscle in a mouse model of muscular dystrophy. Mechanistically, deletion of Hsp47 from myofibroblasts reduced mRNA expression of fibrillar collagens and attenuated their proliferation in the heart without affecting paracrine secretory activity of these cells. The results show that myofibroblasts are the primary mediators of tissue fibrosis and scar formation in the injured adult heart, which unexpectedly affects cardiomyocyte hypertrophy.

Inactivation of Sox9 in fibroblasts reduces cardiac fibrosis and inflammation.

Fibrotic scarring drives the progression of heart failure after myocardial infarction (MI). Therefore, the development of specific treatment regimens to counteract fibrosis is of high clinical relevance. The transcription factor SOX9 functions as an important regulator during embryogenesis, but recent data point towards an additional causal role in organ fibrosis. We show here that SOX9 is upregulated in the scar after MI in mice. Fibroblast specific deletion of Sox9 ameliorated MI-induced left ventricular dysfunction, dilatation and myocardial scarring in vivo. Unexpectedly, deletion of Sox9 also potently eliminated persisting leukocyte infiltration of the scar in the chronic phase after MI. RNA-sequencing from the infarct scar revealed that Sox9 deletion in fibroblasts resulted in strongly downregulated expression of genes related to extracellular matrix, proteolysis and inflammation. Importantly, Sox9 deletion in isolated cardiac fibroblasts in vitro similarly affected gene expression as in the cardiac scar and reduced fibroblast proliferation, migration and contraction capacity. Together, our data demonstrate that fibroblast SOX9 functions as a master regulator of cardiac fibrosis and inflammation and might constitute a novel therapeutic target during MI.

Anti-androgenic therapy with finasteride improves cardiac function, attenuates remodeling and reverts pathologic gene-expression after myocardial infarction in mice.

Maladaptive cardiac remodeling after myocardial infarction (MI) is increasingly contributing to the prevalence of chronic heart failure. Women show less severe remodeling, a reduced mortality and a better systolic function after MI compared to men. Although sex hormones are being made responsible for these differences, it remains currently unknown how this could be translated into therapeutic strategies. Because we had recently demonstrated that inhibition of the conversion of testosterone to its highly active metabolite dihydrotestosterone (DHT) by finasteride effectively reduces cardiac hypertrophy and improves heart function during pressure overload, we asked here whether this strategy could be applied to post-MI remodeling. We found increased abundance of DHT and increased expression of androgen responsive genes in the mouse myocardium after experimental MI. Treatment of mice with finasteride for 21 days (starting 7 days after surgery), reduced myocardial DHT levels and markedly attenuated cardiac dysfunction as well as hypertrophic remodeling after MI. Histological and molecular analyses showed reduced MI triggered interstitial fibrosis, reduced cardiomyocyte hypertrophy and increased capillary density in the myocardium of finasteride treated mice. Mechanistically, this was associated with decreased activation of myocardial growth-signaling pathways, a comprehensive normalization of pathological myocardial gene-expression as revealed by RNA deep-sequencing and with direct effects of finasteride on cardiac fibroblasts and endothelial cells. In conclusion, we demonstrated a beneficial role of anti-androgenic treatment with finasteride in post-MI remodeling of mice. As finasteride is already approved for the treatment of benign prostate disease, it could potentially be evaluated as therapeutic strategy for heart failure after MI.