Intraluminal release of citrullinated histone 3 from various cellular origins coincides with microvascular thrombosis in burn wounds.

Loss of perfusion in the burn wound might cause wound deepening and impaired healing. We previously showed persistent microvascular thrombosis coinciding with intraluminal neutrophils extracellular traps in human burned skin. This study investigates the presence of intraluminal citrullinated histone 3 (H3cit) from different cellular origins (neutrophils, monocytes, and lymphocytes) in relation to microvascular thrombosis of burn wounds. Eschar was obtained from burn patients (n = 18) 6-40 days postburn with a mean total burned body surface area of 23%. Microvascular presence of tissue factor (TF), factor XII (FXII) and thrombi was assessed by immunohistochemistry. Intramicrovascular cell death was analyzed via immunofluorescent microscopy, combining antibodies for neutrophils (MPO), monocytes (CD14), and lymphocytes (CD45) with endothelial cell markers CD31 and H3cit. Significantly increased microvascular expression of TF, FXII, and thrombi (CD31+) was found in all eschar samples compared with control uninjured skin. Release of H3cit from different cellular origins was observed in the lumen of the dermal microvasculature in the eschar tissue 7-40 days postburn, with release from neutrophilic origin being 2.7 times more abundant. Intraluminal presence of extracellular H3cit colocalizing with either MPO, CD14, or CD45 is correlated to increased microvascular thrombosis in eschar of burn patients.

An in silico modeling approach to understanding the dynamics of the post-burn immune response.

Introduction: Burns are characterized by a massive and prolonged acute inflammation, which persists for up to months after the initial trauma. Due to the complexity of the inflammatory process, Predicting the dynamics of wound healing process can be challenging for burn injuries. The aim of this study was to develop simulation models for the post-burn immune response based on (pre)clinical data. Methods: The simulation domain was separated into blood and tissue compartments. Each of these compartments contained solutes and cell agents. Solutes comprise pro-inflammatory cytokines, anti-inflammatory cytokines and inflammation triggering factors. The solutes diffuse around the domain based on their concentration profiles. The cells include mast cells, neutrophils, and macrophages, and were modeled as independent agents. The cells are motile and exhibit chemotaxis based on concentrations gradients of the solutes. In addition, the cells secrete various solutes that in turn alter the dynamics and responses of the burn wound system. Results: We developed an Glazier-Graner-Hogeweg method-based model (GGH) to capture the complexities associated with the dynamics of inflammation after burn injuries, including changes in cell counts and cytokine levels. Through simulations from day 0 - 4 post-burn, we successfully identified key factors influencing the acute inflammatory response, i.e., the initial number of endothelial cells, the chemotaxis threshold, and the level of chemoattractants. Conclusion: Our findings highlight the pivotal role of the initial endothelial cell count as a key parameter for intensity of inflammation and progression of acute inflammation, 0 - 4 days post-burn.

THE THERAPEUTIC EFFECT OF ALLOPURINOL IN FATTY LIVER DISEASE IN RATS.

Background: Hyperuricemia is associated with non-alcoholic fatty liver disease (NAFLD). Aim: We therefore aimed at evaluating the influence of allopurinol on the course of NAFLD in rats. Study Design: We divided 21 mature albino Sprague Dawley rats into three groups: controls (n = 7, normal diet for 12 weeks); NAFLD rat models (by feeding water containing 30% fructose for first 8 weeks) treated with allopurinol subsequently for the next 4 weeks (n = 7); and similar case treated with placebo (saline) subsequently for the next 4 weeks (n = 7). Methods: We compared the histopathological scores, IL-1 and IL-2 immunoexpression levels across the groups. Liver histopathological score was determined by observing the steatosis (the percentage of liver cells containing fat): <25% = 1+, 25% - 50% = 2+, 51% - 75% = 3+, >75% = 4+; inflammation and necrosis: 1 focus per low-power field = 1+; and 2 or more foci = 2+. The number of liver IL-1 and IL-2 positive cells was measured by systematically scoring at least 100 hepatocyte cells per field in 10 fields of tissue sections by a magnification of 100. Results: Xanthine oxidase (XO) activity and lipid peroxidation was significantly different in the allopurinol group compared to the saline group (XO; 0.098 ± 0.006 mU/mg vs. 0.162 ± 0.008 mU/mg, p = 0.01, 0.116 ± 0.040 nmol malondialdehyde/mg versus 0.246 ± 0.040 nmol malondialdehyde /mg, p = 0.01). The allopurinol group had lower histopathological scores, IL-1 and IL-2 immunoexpression levels in the liver compared to the saline group (2.13 ± 0.35 against 5.45 ± 0.24, p = 0.003, IL-1; 5.76 ± 0.43 against 12.85 ± 3.26, p = 0.023, IL-2; 8.55 ± 1.14 against 56.23 ± 7.12, p = 0.002). Conclusions: Allopurinol has a therapeutic role against the progression of NAFLD of the rats.

The Complexity of the Post-Burn Immune Response: An Overview of the Associated Local and Systemic Complications.

Burn injury induces a complex inflammatory response, both locally and systemically, and is not yet completely unravelled and understood. In order to enable the development of accurate treatment options, it is of paramount importance to fully understand post-burn immunology. Research in the last decades describes insights into the prolonged and excessive inflammatory response that could exist after both severe and milder burn trauma and that this response differs from that of none-burn acute trauma. Persistent activity of complement, acute phase proteins and pro- and anti-inflammatory mediators, changes in lymphocyte activity, activation of the stress response and infiltration of immune cells have all been related to post-burn local and systemic pathology. This "narrative" review explores the current state of knowledge, focusing on both the local and systemic immunology post-burn, and further questions how it is linked to the clinical outcome. Moreover, it illustrates the complexity of post-burn immunology and the existing gaps in knowledge on underlying mechanisms of burn pathology.

Eye care in intensive care in COVID-19 era: a prospective observational study from Turkey.

OBJECTIVE: There has been an increase in intensive care applications due to respiratory failure of COVID-19 infection. Management of respiratory failure includes a range of additional interventions, including high-flow nasal oxygen, noninvasive and invasive ventilation and prone position. These interventions contain risk factors for the development of ocular complications. This study aimed to elucidate the ocular pathologies that occurred in COVID-19 patients hospitalized in the intensive care unit. PATIENTS AND METHODS: Patients who completed 24 hours in the intensive care unit were included in the study. Age, gender, duration of hospitalization before intensive care unit, comorbid diseases and APACHE 2 scores of COVID-19 patients admitted to intensive care unit were recorded. SOFA scores, presence of sedation and muscle relaxant, oxygen therapy (conventional oxygen therapy, high flow nasal oxygen therapy, noninvasive ventilation, invasive ventilation) and presence of prone position were recorded. All patients were evaluated daily for ocular findings. Routine eye care protocol was applied to all patients. RESULTS: Seventy patients were followed for a total of 596 days in the intensive care unit. Pathological ocular findings were observed during hospitalization in 59 of the patients followed. The incidence of chemosis in patients who underwent IMV was significantly higher compared to other methods (p<0.001). CONCLUSIONS: In this study, we observed that despite our routine eye care protocols, invasive mechanical ventilation applications predispose corneal surface damage in patients followed up in the intensive care unit with COVID-19 infection.

Scar formation from the perspective of complexity science: a new look at the biological system as a whole.

A burn wound is a complex systemic disease at multiple levels. Current knowledge of scar formation after burn injury has come from traditional biological and clinical studies. These are normally focused on just a small part of the entire process, which has limited our ability to sufficiently understand the underlying mechanisms and to predict systems behaviour. Scar formation after burn injury is a result of a complex biological system-wound healing. It is a part of a larger whole. In this self-organising system, many components form networks of interactions with each other. These networks of interactions are typically non-linear and change their states dynamically, responding to the environment and showing emergent long-term behaviour. How molecular and cellular data relate to clinical phenomena, especially regarding effective therapies of burn wounds to achieve minimal scarring, is difficult to unravel and comprehend. Complexity science can help bridge this gap by integrating small parts into a larger whole, such that relevant biological mechanisms and data are combined in a computational model to better understand the complexity of the entire biological system. A better understanding of the complex biological system of post-burn scar formation could bring research and treatment regimens to the next level. The aim of this review/position paper is to create more awareness of complexity in scar formation after burn injury by describing the basic principles of complexity science and its potential for burn care professionals.

Role of telocytes in the pathogenesis of ectopic pregnancy.

OBJECTIVE: The aim of this study is to investigate the effect of telocytes on tubal motility in ectopic pregnancies. PATIENTS AND METHODS: This study included patients with ectopic pregnancy (EP) (n=10) and control patients (n=10) (partial salpingectomy for contraception). Immunohistochemical staining for c-Kit, vimentin, CD34 and S100A was performed to quantify telocytes in the mucosa, muscular layer and serosa of fallopian tubes of control and EP group. Spontaneous and KCl- (80 mM) induced contraction and cumulative progesterone dose-relaxation (10-11-10-5 M) and cumulative oxytocin dose-contraction (10-10-10-4 M) responses were recorded. RESULTS: The groups were comparable in terms of age, gravida, parity, delivery type and gestational week (p>0.05). The homogenous distribution of telocytes in the mucosa and muscular layers of the control group, changed to heterogeneous localization the EP group. Immunohistochemical staining with vimentin, S100A, c-Kit and CD34, revealed increased telocyte counts in the muscular layer and serosa of the tubal tissues of EP. The frequency of the spontaneous contractions was higher in the control group (p<0.001); contrarily, the amplitude of the contractions was higher in ectopic pregnancies (p<0.001). Although the cumulative oxytocin dose-contraction curves were similar at all concentrations (p>0.05), the cumulative progesterone dose-relaxation curves exhibited higher relaxation response in the EP group at all concentrations (p<0.001). CONCLUSIONS: Increased telocyte count in the fallopian tube may decrease tubal motility and may affect the transfer of the blastocyst to the uterus and possibly contribute to the pathogenesis of EP.

[What is the stat of art in 3D bioprinting of cartilage? Challenges concerning the reconstruction of a burned ear]. / Hoe staat het met 3D-bioprinten van kraakbeen?

Five years ago in this journal we described our research into 3D bioprinting of ear cartilage for the purpose of making personalized cartilage implants for facial reconstruction. 3D bioprinting makes it possible to place living cells in a biodegradable scaffold to give a 3D structure to the tissue. We are able to develop a hybrid auricular cartilage implant model. However, Long term in vivo experiments are needed to test preclinical applicability. Nevertheless, the work presented in our studies provides a potential strategy for the use of biofabricated tissue constructs in the clinic. In short, 3D bioprinting is still in its infancy and has no direct clinical application yet. Before the step to the clinic can be made, the technique still has to go through a preclinical phase in which it is investigated how the 3D printed tissue would appear in vivo.

Salivary irisin: potential inflammatory biomarker in recurrent apthous stomatitis patients.

OBJECTIVE: Recurrent Aphthous Stomatitis (RAS) is the most common inflammatory condition of the oral mucosa characterised by recurrent onset of single or multiple painful ulcers mainly affecting the nonkeratinized oral mucosa. RAS mostly occurs in healthy individuals with no associated systemic diseases. Irisin is a newly identified adipomyokine and research has revealed that it has anti-inflammatory effects. The aim of this study was to investigate the significance of salivary irisin levels in patients with recurrent apthous stomatitis (RAS). PATIENTS AND METHODS: In this investigation, 80 individuals were evaluated. The patient group included 30 patients diagnosed with RAS and each control group consisted of 25 smoker and non-smoker healthy individuals. Saliva samples were collected and salivary irisin, interleukin-2 (IL-2) and interferon-É£ (IF-É£) levels were determined using enzyme-linked immunosorbent assay (ELISA). RESULTS: IL-2 and IF-É£ levels in RAS patients were significantly higher than control smoker and non-smoker groups (p=0.0001, p=0.0001, respectively). Irisin level was higher in RAS patients than smoker controls and non-smoker controls. The level of irisin was found as sensitive and specific as IL-2 and more sensitive and specific than IF-É£. The salivary levels of pro-inflammatory cytokines IL-2 and IF-É£ and irisin were higher in RAS group compared to controls. CONCLUSIONS: This is the first report evaluating the irisin an adipo-myokine as an inflammatory biomarker in RAS.

NOX2 Expression Is Increased in Keratinocytes After Burn Injury.

Reepithelialization is crucial for effective wound repair in burn wounds. Reactive oxygen species (ROS) have shown to be important in this. Recent studies suggest that NOX proteins produce ROS in keratinocytes. In the present study, we have studied NOX proteins in burn wounds, including the effect of C1-esterase inhibitor (C1inh) hereon, which is the endogenous inhibitor of complement activity whereof we have shown previously that it also increased the rate of reepithelialization in burn wounds. Skin tissue derived from healthy control Wistar rats (n = 6) were compared with burn-injured rats, with (n = 7) or without C1inh treatment (n = 7). After 14 days, rats were terminated. From the burn-injured rats, the entire wound and nonburned skin from the hind leg, that is, internal control was excised. From the control rats, dorsal skin was excised. In these skin samples, NOX2 and NOX4 were analyzed immunohistochemically. In nonburned rats, NOX2 was found in keratinocytes in both the basal layer and suprabasal layer of the epidermis; and the number of NOX2-positive keratinocytes was 367/mm2 (254-378). In burned rats, the number of NOX2-positive keratinocytes was significantly increased in the newly forming epidermis in the burned area to 1019/mm2 (649-1172), especially in the suprabasal layer, but significantly decreased in remote nonburned skin to 22/mm2 (6-89). C1inh treatment counteracted these changes in epidermal NOX2 expression in burned rats, both in the burned area as in remote nonburned skin. No NOX4 expression was found in the epidermis in none of the groups. NOX2 expression was increased in keratinocytes in newly forming epidermis after burn injury. C1inh, a drug that increases the rate of reepithelialization, counteracted this effect. These results suggest a role for NOX2 in the reepithelialization of burn wounds.

THE EFFECT OF ANTITHYROID DRUGS ON OSTEOPONTIN AND OXIDATIVE STRESS IN GRAVES' DISEASE.

OBJECTIVE: The aim of the present study is to evaluate the effects of methimazole (MTZ) and propylthiouracil (PTU) treatments on osteopontin (OPN) and oxidative stress in Graves' disease (GD). MATERIAL AND METHODS: The study included 60 cases with GD in hyperthyroid state and taking no antithyroid treatment, and 30 healthy volunteers. GD patients were randomly separated into two groups; 30 of them took PTU, and the other 30 took MTZ treatments. Blood samples were taken from the patients with GD before the treatment, and three months after the treatment was begun, when they were in the euthyroid state; blood samples of the healthy control subjects were also taken at these times. RESULTS: TAS and OSI levels before treatment were significantly higher in the GD group, when compared to the control group (p<0.001, for each). GD subjects taking PTU treatment had significantly higher TAS levels (p=0.001), and significantly lower TOS and OSI levels (p=0.008 and p=0.001, respectively). TAS levels significantly decreased in the patients taking MTZ treatment (p=0.029), but TOS and OSI levels did not change significantly (p>0.05). Pretreatment OPN levels were significantly higher in GD patients, when compared to the control group (p=0.014). OPN level significantly decreased in the GD group taking PTU treatment; however OPN levels in the group taking MTZ treatment did not change significantly when compared to the pretreatment value. CONCLUSION: PTU treatment is more effective in decreasing OPN and oxidative stress in GD patients, when compared to the MTZ treatment.

Impact of delayed and prolonged fixation on the evaluation of immunohistochemical staining on lung carcinoma resection specimen.

Pre-analytical factors, such as fixation time, influence morphology of diagnostic and predictive immunohistochemical staining, which are increasingly used in the evaluation of lung cancer. Our aim was to investigate if variations in fixation time influence the outcome of immunohistochemical staining in lung cancer. From lung resections, specimen with tumor size bigger than 4 cm, 10 samples were obtained: 2 were put through the standard fixation protocol, 5 through the delayed, and 3 through the prolonged fixation protocol. After paraffin embedding, tissue microarrays (TMAs) were made. They were stained with 20 antibodies and scored for quality and intensity of staining. Samples with delay in fixation showed loss of TMA cores on glass slides and deterioration of tissue quality leading to reduction in the expression of CK 7, Keratin MNF116, CAM 5.2, CK 5/6, TTF-1, C-MET, Napsin A, D2-40, and PD-L1. Prolonged fixation had no influence on the performance of immunohistochemical stains. Delay of fixation negatively affects the expression of different immunohistochemical markers, influencing diagnostic (cytokeratins) and predictive (PD-L1) testing. These results emphasize the need for adequate fixation of resection specimen.

Homocysteine-induced inverse expression of tissue factor and DPP4 in endothelial cells is related to NADPH oxidase activity.

PURPOSE: We previously found that homocysteine (Hcy)-induced apoptosis in endothelial cells coincided with increased NADPH oxidase (NOX) activity. In addition, in ischemic endothelial cells present in the heart, we showed that loss of serine protease dipeptidyl peptidase IV (DPP4) expression was correlated with induction of tissue factor (TF) expression. Since Hcy can initiate thrombosis through the induction of TF expression, in this study, we evaluated whether the inverse relation of TF and DPP4 is also Hcy-dependent and whether NOX-mediated reactive oxygen species (ROS) is playing a role herein. METHODS: Human umbilical vein endothelial cells (HUVECs) were incubated with 2.5 mM Hcy for 3 and 6 h. The effects of Hcy on DPP4 and TF expression and NOX2/p47phox-mediated nitrotyrosine (ROS) production were studied using digital-imaging microscopy. RESULTS: In HUVECs, high levels of Hcy showed a significant increase of TF expression and a concomitant loss of DPP4 expression after 6 h. In addition, NOX subunits NOX2 and p47phox were also significantly increased after 6 h of Hcy incubation and coincided with nitrotyrosine (ROS) expression. Interestingly, inhibition of NOX-mediated nitrotyrosine (ROS) with the use of apocynin not only reduced these effects, but also counteracted the effects of Hcy on TF and DPP4 expression. CONCLUSION: These results indicate that the inverse relation of TF and DPP4 in endothelial cells is also Hcy-dependent and related to NOX activity.

THE EFFECT OF GLUCOVANCE THERAPY ON BIOMECHANICAL DETERIORATION OF BONE IN STREPTOZOTOCIN-INDUCED DIABETIC RATS.

AIM: Is to evaluate the influence of glucovance therapy on biomechanical properties of bone in streptozotocin - induced diabetes mellitus (DM) in rats. MATERIALS AND METHODS: A total of 28 male Wistar-Albino rats (12-week-old; 210-300 g) were divided into 4 groups including control (C; no treatment; n=7), sham [Sh; distilled water (gavage, for 8 weeks); n=7], diabetes [DM; streptozotocin (45 mg/kg, single i.p injection); n=7] and diabetes+ Glucovance treatment [DM+G; streptozotocin (45 mg/kg, single i.p injection) + Glucovance (Glucovance, 500/5 mg/kg/day/rat, gavage, for 8 weeks); n=7] groups. Body weight, blood glucose levels (BGLs), bone mineral density (BMD) and geometric/mechanical properties of bone tissue were evaluated. BGLs in diabetic rats were significantly increased compared to non-diabetic rats, while the body weights were decreased (p<0.05). RESULTS: A significant difference was not detected between groups with regard to cross-sectional area of diaphyseal femur (p>0.05). Maximum load, energy absorption capacity, ultimate stress, ultimate strain, toughness and displacement were shown to decrease and stiffness was shown to increase in DM rats (p<0.05). Ultimate stress and maximum load were significantly increased in DM+G groups compared to DM groups (p<0.05). CONCLUSION: Glucovance treatment seems to be effective in restoration of biomechanical deterioration of bone specific to STZ-induced DM.

A RARE CAUSE OF PITUITARY APOPLEXY: CABERGOLINE THERAPY.

Pituitary apoplexy (PA) is a life-threatening clinical syndrome. Dopamine receptor agonists are the drugs of choice in the treatment of prolactinomas. The use of cabergoline is reported to cause an increased risk of PA, particularly in macroprolactinomas of cystic nature. In this report, we present a patient with a cystic macroprolactinoma who developed PA on the 16th week of cabergoline treatment.

SCREENING OF PROP-1, LHX2 AND POU1F1 MUTATIONS IN PATIENTS WITH ECTOPIC POSTERIOR PITUITARY GLAND.

OBJECTIVE: Ectopic posterior pituitary gland (EPP) is usually characterized by an abnormal pituitary stalk and hypoplasia of the anterior hypophysis. The genetic mechanisms involved in the development of EPP remain uncertain. The aim of this study is to determine whether mutations in the three genes, PROP-1, LHX2, and POU1F1, are associated with the risk for and the characteristics of EPP. METHODS: In the Endocrinology Outpatient Clinic of "Dr. Behcet Uz" Children's Hospital, 27 patients with EPP were submitted to sequencing analyses of the PROP-1, LHX2, and POU1F1 genes. RESULTS: Growth hormone, thyrotropin, corticotropin, gonadotropin, and vasopressin deficiency were observed in 22 (81.5%), 23 (85.2%), 17 (63%), 14 (51.9%), and two (7.4%) patients. Thirteen patients (48.1%) presented with hyperprolactinemia. Fourteen patients (51%) had a history of birth dystocia, and 12 cases (42.1%) had a history of breech presentation. Central nervous system abnormalities included five cases with corpus callosum agenesis, one case with schizencephaly, and one case with Chiari type 1 malformation. We identified a homozygous p.S109* mutation in exon 2 in one male patient with EPP and two different PROP1 gene polymorphisms (A142T or c.109+3 G>A polymorphism) in thirteen patients. CONCLUSIONS: Our results suggest that PROP1 gene abnormalities might explain the genetic mechanisms involved in the development of EPP.

Magnetic resonance enterography with oral mannitol solution: Diagnostic efficacy and image quality in Crohn disease.

PURPOSE: The aim of this study was to investigate the diagnostic efficacy and image quality of magnetic resonance enterography (MRE) using oral mannitol solution for the evaluation Crohn disease (CD). MATERIALS AND METHODS: We retrospectively evaluated MRE examinations of 153 patients with an assumed or definitive diagnosis of CD. There were 65 men and 88 women, with a mean age of 35.7 years (range: 6-73years). MRE findings of the patients were compared to histopathologic results obtained by surgery-fiberoptic endoscopy. The sensitivity, specificity and diagnostic efficacy rate were calculated. Additionally, image quality of MRE was evaluated using a four-point scale (1=excellent, 4=poor/non-diagnostic). RESULTS: Sensitivity, specificity and diagnostic efficacy were 92.5%, 93% and 92.8%, respectively. Six patients had false-positive and five patients had false-negative findings. Three falsely positive patients had ulcerative colitis and three had non-specific terminal ileitis. A total of 765 small bowel segments were analyzed; 475 (62%) had an image quality score of 1 and 15 (2%), an image quality score of 4. CONCLUSION: MRE using oral mannitol solution provides excellent image quality for MRE and has high degrees of diagnostic efficacy in CD patients.

Neutrophil extracellular traps coincide with a pro-coagulant status of microcirculatory endothelium in burn wounds.

Burn-induced tissue loss is partly related to secondary expansion of necrosis into vital dermis neighboring the initial burn injury. An important factor herein is the severe loss of perfusion of the burn wound, probably caused by microvascular damage induced by the intense local inflammatory responses as well as burn-induced hypercoagulation. We hypothesize that the formation of neutrophilic extracellular traps (NETs) play an important role in this. The purpose of this study was to investigate postburn intravascular thrombosis, NETs formation and the coagulant state in the microvasculature of burns in both animal models and patients. We used two in vivo burn wound models: rats and pigs. In rats, the entire wound was excised at day 14 postburn and in pigs burn wound biopsies were collected at different time points up to 60 days postburn. To confirm the data in patients, eschar from the burn wound was obtained from burn wound patients at different time points after wounding. The number of intravascular thrombi, the presence of intravascular NETs and the number of tissue factor (TF) positive blood vessels in the burn wound was determined. In rats, a significant increase in intravascular thrombi and TF expression was observed 14 days postburn, that in majority coincided with NETs. In pigs, a significant increase in intravascular thrombi and TF expression was found over time up to 60 days postburn, that in majority coincided with NETs too. Also in eschar of burn wound patients, a significant increase in intravascular thrombi was noted, that in majority coincided with NETs, already 0.5 days postburn and remained elevated up to 46 days postburn. This study shows the presence of NETosis in microcirculatory thrombosis of burn wounds and a switch in the microcirculatory endothelium toward a procoagulant phenotype.

Investigating histological aspects of scars in children.

OBJECTIVE: Very little is known about histological aspects of paediatric scars and the possible role of the immune system during their formation. In this study, the histology thoracic scars caused by the placement of an implantable central venous access device in children who underwent treatment for cancer was assessed. METHOD: The amount and type of collagen, the collagen orientation, the type of elastic fibres, the vascularsation, and the count of neutrophils, macrophages, and lymphocytes were analysed. The severity of scarring was assessed using the Vancouver scar scale (VSS). To evaluate the role of the immune system on scar severity and histology, the scars of children suffering from acute lymphoblastic leukaemia (ALL) were compared with the scars of children suffering from other types of childhood cancer. RESULTS: Our results showed an extremely random orientation of the collagen fibres of the paediatric scars with a mean collagen orientation index of 0.22 (standard deviation (SD) 0.10, zero indicating a perfectly random orientation and a perfectly parallel orientation). A lower collagen orientation index was seen in scars with a lower VSS score (VSS score <3: 0.19 versus VSS score ≥3 0.29, p=0.037). A higher total VSS score, resembling a worse scar, was assessed to the scars in the non-ALL group compared with the children with ALL (mean ALL: 0.91 (0-3) versus mean non-ALL: 2.50 (0-6), p=0.037). CONCLUSION: To our knowledge, this is the first study investigating a wide array of histological aspects in paediatric scars. Compared with adult scars, an extremely random collagen orientation was found (0.22 in children versus 0.41 and 0.46 adult normotrophic and hypertrophic scars, respectively). A lower collagen orientation index was found in scars with a lower VSS score. In addition, less severe scarring was measured in children suffering from ALL compared with children suffering from other types of childhood cancer. This suggests that the immune system could play a role in the development of aberrant scarring and should be a target for future research.

Lithocholic acid controls adaptive immune responses by inhibition of Th1 activation through the Vitamin D receptor.

Bile acids are established signaling molecules next to their role in the intestinal emulsification and uptake of lipids. We here aimed to identify a potential interaction between bile acids and CD4+ Th cells, which are central in adaptive immune responses. We screened distinct bile acid species for their potency to affect T cell function. Primary human and mouse CD4+ Th cells as well as Jurkat T cells were used to gain insight into the mechanism underlying these effects. We found that unconjugated lithocholic acid (LCA) impedes Th1 activation as measured by i) decreased production of the Th1 cytokines IFNγ and TNFαα, ii) decreased expression of the Th1 genes T-box protein expressed in T cells (T-bet), Stat-1 and Stat4, and iii) decreased STAT1α/ß phosphorylation. Importantly, we observed that LCA impairs Th1 activation at physiological relevant concentrations. Profiling of MAPK signaling pathways in Jurkat T cells uncovered an inhibition of ERK-1/2 phosphorylation upon LCA exposure, which could provide an explanation for the impaired Th1 activation. LCA induces these effects via Vitamin D receptor (VDR) signaling since VDR RNA silencing abrogated these effects. These data reveal for the first time that LCA controls adaptive immunity via inhibition of Th1 activation. Many factors influence LCA levels, including bile acid-based drugs and gut microbiota. Our data may suggest that these factors also impact on adaptive immunity via a yet unrecognized LCA-Th cell axis.