Sirolimus impairs wound healing

Risk factors for incisional hernia after liver transplantation in the era of mammalian target of rapamycin inhibitors use: a retrospective study of living donor liver transplantation dominant center in Korea

Purpose

Incisional hernia (IH) is a common complication after liver transplantation (LT) with an incidence rate of 5% to 46%. This retrospective study aimed to evaluate the risk factors for IH development after LT in the era of mammalian target of rapamycin (mTOR) inhibitors use.

Methods

Data on patients who underwent LT between 2015 and 2021 were retrospectively reviewed. The patients were divided into 2 groups (IH group and non-IH group) according to the postoperative occurrence of IH.

Results

We analyzed data from 878 patients during the study period, with 28 patients (3.2%) developing IH. According to multivariate analysis, body mass index exceeding 25 kg/m2 and the use of mTOR inhibitors within the first month after LT were the sole significant factors for both IH occurrence and the subsequent need for repair operations. Notably, a history of wound complications, a Model for End-stage Liver Disease score, and the timing of LT-whether conducted during regular hours or at night-did not emerge as significant risk factors for IH after LT.

Conclusion

Our study reveals a higher incidence of IH among obese patients following LT, often requiring surgical repair, particularly in cases involving mTOR inhibitor usage within the initial month after LT. Consequently, it is crucial to exercise increased vigilance, especially in obese patients, and exercise caution when considering early mTOR inhibitor administration after LT.

Drug suspending during wound healing effectively weakens immunosuppression-related complications by preserving CD8+ T cell function

Immunosuppressive medications, which interfere with the activation and proliferation of T and B cells, increase the risk of wound healing complications. To address it, this study aimed to validate the feasibility of drug suspending during wound healing, whilst exploring the mechanisms exerted by T cells, which are important in the wound healing process. For this, a mouse skin wound model was set up. Tacrolimus (FK506) and fingolimod (FTY720) were both administered intraperitoneally prior to wounding to inhibit the T cell activation and migration, respectively. Flow-cytometric analysis subsequently revealed the functional T cell subtypes detected during the healing process. A CD8a antibody was also administered to deplete CD8+ T cells in vivo to verify their specific function. It was found that FK506 or FTY720 administration delayed the early phase of wound healing by reducing collagen production, which was also supported by the downregulation of col1a1, col3a1 and tgfb1. However, there was no significant difference in the total healing period. Both spleen- and skin-derived CD8+ T cells were proliferated and activated after injury without intervention, whereas CD4+ T cells showed no significant changes. Furthermore, selectively depleting CD8+ T cells retarded the healing process by downregulating collagen production-associated genes (col1a1, col3a1, tgfβ1 and en1) and proteins (collagen type 1 and 3). In addition, the CD8a antibody decreased the expression of genes lta, tnfa, il13 and il13ra, and protein interleukin-13Rα. In conclusion, suspending immunosuppressive drugs during wound healing was shown to be feasible through restraining the migration of activated T cells. CD8+ T cells represented the primary functional subtype positively associated with wound healing.

Mammalian Target of Rapamycin Inhibitors and Wound Healing Complications in Kidney Transplantation: Old Myths and New Realities

Mammalian target of rapamycin inhibitors (mTOR-I) lacks nephrotoxicity, has antineoplastic effects, and reduces viral infections in kidney transplant recipients. Earlier studies reported a significant incidence of wound healing complications and lymphocele. This resulted in the uncomfortable willingness of transplant clinicians to use these agents in the immediate posttransplant period. As evidence and experience evolved over time, much useful information became available about the optimal use of these agents. Understandably, mTOR-I effects wound healing through their antiproliferative properties. However, there are a lot of other immunological and nonimmunological factors which can also contribute to wound healing complications. These risk factors include obesity, uremia, increasing age, diabetes, smoking, alcoholism, and protein-energy malnutrition. Except for age, the rest of all these risk factors are modifiable. At the same time, mycophenolic acid derivatives, steroids, and antithymocyte globulin (ATG) have also been implicated in wound healing complications. A lot has been learnt about the optimal dose of mTOR-I and their trough levels, its combinations with other immunosuppressive medications, and patients' profile, enabling clinicians to use these agents appropriately for maximum benefits. Recent randomized control trials have further increased the confidence of clinicians to use these agents in immediate posttransplant periods.

EYE DISEASE IN KIDNEY TRANSPLANTATION: CLINICAL CHALLENGES IN A UNIQUE PATIENT POPULATION

Eye disease is common among kidney transplant recipients and their management is challenging. Chronic kidney disease is associated with ocular complications, both independently and in the context of various systemic disorders. In addition, chronic immunosuppression predisposes kidney transplant recipients to an array of long-term ocular issues. This may be broadly categorized into infections, malignancies, and other immunosuppression-specific side effects. The interdependence of kidney disease, transplant pharmacotherapy and ocular health therefore requires a multispecialty approach. Although the kidney transplant population has grown along with the burden of associated oculopathies, systematic guidelines targeting this patient group are lacking. This evidenced-based narrative review summarizes the pertinent issues that may present in the ophthalmic and optometric clinical settings, with emphasis on collaborative management and directions for future research.

Curcumin represses mTORC1 signaling in Caco-2 cells by a two-sided mechanism involving the loss of IRS-1 and activation of AMPK

The mechanistic target of rapamycin complex 1 (mTORC1) is a central modulator of inflammation and tumorigenesis in the gastrointestinal tract. Growth factors upregulate mTORC1 via the PI3K/AKT and/or Ras/MAPK signal pathways. Curcumin (CUR), a polyphenol found in turmeric roots (Curcuma longa) can repress mTORC1 kinase activity in colon cancer cell lines; however, key aspects of CUR mechanism of action remain to be elucidated including its primary cellular target. We investigated the molecular effects of physiologically attainable concentration of CUR (20 μM) in the intestinal lumen on mTORC1 signaling in Caco-2 cells. CUR markedly inhibited mTORC1 kinase activity as determined by the decreased phosphorylation of p70S6K (Thr389, -99%, P < 0.0001) and S6 (Ser235/236, -92%, P < 0.0001). Mechanistically, CUR decreased IRS-1 protein abundance (-80%, P < 0.0001) thereby downregulating AKT phosphorylation (Ser473, -94%, P < 0.0001) and in turn PRAS40 phosphorylation (Thr246, -99%, P < 0.0001) while total PRAS40 abundance was unchanged. The use of proteasome inhibitor MG132 showed that CUR-mediated loss of IRS-1 involved proteasomal degradation. CUR lowered Raptor protein abundance, which combined with PRAS40 hypophosphorylation, suggests CUR repressed mTORC1 activity by inducing compositional changes that hinder the complex assembly. In addition, CUR activated AMPK (Thr172 phosphorylation, P < 0.0001), a recognized repressor of mTORC1, and AMPK upstream regulator LKB1. Although cargo adapter protein p62 was decreased by CUR (-49%, P < 0.004), CUR did not significantly induce autophagy. Inhibition of AKT/mTORC1 signaling by CUR may have lifted the cross-inhibition onto MAPK signaling, which became induced; p-ERK1/2 (+670%, P < 0.0001), p-p38 (+1433%, P < 0.0001). By concomitantly targeting IRS-1 and AMPK, CUR's mechanism of mTORC1 inhibition is distinct from that of rapamycin.

Bone Health Management After Hematopoietic Cell Transplantation: An Expert Panel Opinion from the American Society for Transplantation and Cellular Therapy

Bone health disturbances commonly occur after hematopoietic cell transplantation (HCT) with loss of bone mineral density (BMD) and avascular necrosis (AVN) foremost among them. BMD loss is related to pretransplantation chemotherapy and radiation exposure and immunosuppressive therapy for graft-versus-host-disease (GVHD) and results from deficiencies in growth or gonadal hormones, disturbances in calcium and vitamin D homeostasis, as well as osteoblast and osteoclast dysfunction. Although the pathophysiology of AVN remains unclear, high-dose glucocorticoid exposure is the most frequent association. Various societal treatment guidelines for osteoporosis exist, but the focus is mainly on menopausal-associated osteoporosis. HCT survivors comprise a distinct population with unique comorbidities, making general approaches to bone health management inappropriate in some cases. To address a core set of 16 frequently asked questions (FAQs) relevant to bone health in HCT, the American Society of Transplant and Cellular Therapy Committee on Practice Guidelines convened a panel of experts in HCT, adult and pediatric endocrinology, orthopedics, and oral medicine. Owing to a lack of relevant prospective controlled clinical trials that specifically address bone health in HCT, the answers to the FAQs rely on evidence derived from retrospective HCT studies, results extrapolated from prospective studies in non-HCT settings, relevant societal guidelines, and expert panel opinion. Given the heterogenous comorbidities and needs of individual HCT recipients, answers to FAQs in this article should be considered general recommendations, with good medical practice and judgment ultimately dictating care of individual patients. Readers are referred to the Supplementary Material for answers to additional FAQs that did not make the core set.

Costimulation Blockade in Vascularized Composite Allotransplantation

Vascular composite allotransplantation (VCA) is a field under research and has emerged as an alternative option for the repair of severe disfiguring defects that result from infections or traumatic amputation in a selected group of patients. VCA is performed in centers with appropriate expertise, experience and adequate resources to effectively manage the complexity and complications of this treatment. Lifelong immunosuppressive therapy, immunosuppression associated complications, and the effects of the host immune response in the graft are major concerns in VCA. VCA is considered a quality of life transplant and the risk-benefit ratio is dissimilar to life saving transplants. Belatacept seems a promising drug that prolongs patient and graft survival in kidney transplantation and it could also be an alternative approach to VCA immunosuppression. In this review, we are summarizing current literature about the role of costimulation blockade, with a focus on belatacept in VCA.

mTORC2 deficiency in cutaneous dendritic cells potentiates CD8+ effector T cell responses and accelerates skin graft rejection

Mechanistic target of rapamycin (mTOR) complex (mTORC)1 and mTORC2 regulate the differentiation and function of immune cells. While inhibition of mTORC1 antagonizes dendritic cell (DC) differentiation and suppresses graft rejection, the role of mTORC2 in DCs in determining host responses to transplanted tissue remains undefined. Using a mouse model in which mTORC2 was deleted specifically in CD11c⁺ DCs (TORC2^DC-/- ), we show that the transplant of minor histocompatibility Ag (HY)-mismatched skin grafts from TORC2^DC-/- donors into wild-type recipients results in accelerated rejection characterized by enhanced CD8⁺ T cell responses in the graft and regional lymphoid tissue [Correction added on January 9, 2019, after first online publication: in the previous sentence, major was changed to minor]. Similar enhancement of CD8⁺ effector T cell responses was observed in MHC-mismatched recipients of TORC2^DC-/- grafts. Augmented CD8⁺ T cell responses were also observed in a delayed-type hypersensitivity model in which mTORC2 was absent in cutaneous DCs. These elevated responses could be ascribed to an increased T cell stimulatory phenotype of TORC2^DC-/- and not to enhanced lymph node homing of the cells. In contrast, rejection of ovalbumin transgenic skin grafts in TORC2^DC-/- recipients was unaffected. These findings suggest that mTORC2 in skin DCs restrains effector CD8⁺ T cell responses and have implications for understanding of the influence of mTOR inhibitors that target mTORC2 in transplant.

Cyclodextrin Polymer Preserves Sirolimus Activity and Local Persistence for Antifibrotic Delivery over the Time Course of Wound Healing

Fibrosis and dysphagic stricture of the esophagus is a major unaddressed problem often accompanying endoscopic removal of esophageal cancers and precancerous lesions. While weekly injections of antiproliferative agents show potential for improved healing, repeated injections are unlikely clinically and may alternatively be replaced by creating an esophageal drug delivery system. Affinity-based polymers have previously shown success for continuous delivery of small molecules for weeks to months. Herein, we explored the potential of an affinity-based microparticle to provide long-term release of an antiproliferative drug, sirolimus. In molecular docking simulations and surface plasmon resonance experiments, sirolimus was found to have suitable affinity for beta-cyclodextrin, while dextran, as a low affinity control, was validated. Polymerized beta-cyclodextrin microparticles exhibited 30 consecutive days of delivery of sirolimus during in vitro release studies. In total, the polymerized beta-cyclodextrin microparticles released 36.9 mg of sirolimus per milligram of polymer after one month of incubation in vitro. Taking daily drug release aliquots and applying them to PT-K75 porcine mucosal fibroblasts, we observed that cyclodextrin microparticle delivery preserved bioactivity of sirolimus inhibiting proliferation by 27-67% and migration of fibroblasts by 28-100% of buffer treated controls in vitro. Testing for esophageal injection site losses, no significant loss was incurred under simulated saliva flow for 10 min, and 16.7% of fluorescently labeled polymerized cyclodextrin microparticle signal was retained at 28 days after submucosal injection in esophageal tissue ex vivo versus only 4% of the initial amount remaining for free dye molecules injected alone. By combining affinity-based drug delivery for continuous long-term release with a microparticle platform that is injectable yet remains localized in tissue interstitium, this combination platform demonstrates promise for preventing esophageal fibrosis and stricture.

Laparoscopic Repair of Boundary Incisional Hernia in a Kidney Transplant Patient: A Safe Tacks-Fibrin Glue Combined Mesh Fixation Technique

BACKGROUND

Incisional hernia in renal transplant patients is a complication that negatively affects the global outcome of transplant and quality of life. The repair of this condition was classically made by open repair with mesh. Increasing evidence suggests that laparoscopic repair could be advocated as the technique of choice in these patients with optimal results. However, the fixation of mesh should be performed by a mixed combination of fibrin sealant (lateral margin of wall defect) and tacks (medial margin). The tacks fixation of the mesh along the lateral margin of the wall defect, close to the graft, is generally difficult for the small size of the remaining aponeurotic plane and dangerous for the underlying presence of the graft.

MATERIALS AND METHODS

A case of incisional hernia in a kidney transplant recipient was repaired by laparoscopic mesh technique. The polypropylene-polyglycolic acid composite mesh was fastened with a mixed technique of absorbable tacks for medial margin of the defect and fibrin sealant for the lateral side in contiguity with graft surface.

RESULTS

The patient was discharged after 4 days. The 6-month follow-up did not show mesh displacement or recurrence of hernia.

CONCLUSIONS

The laparoscopic mesh repair may become the criterion standard for kidney transplant patients affected by incisional hernia. The difficulties of mesh fixation close to the graft can be overcome by the combination of fibrin sealant glue and absorbable tacks at different margins of the wall defect. This technique may offer advantages for this population of patients.

[Effects of rapamycin and deferoxamin on wound healing after ischemia and hypoxia]

Objective

To explore the effect and mechanism of rapamycin and deferoxamin on wound healing after ischemia and hypoxia.

Methods

The model of ischemia and hypoxia wound was made on the back of 40 SPF male adult Sprague Dawley rats, weight (300±20) g; they were randomly divided into 4 groups ( n=10): the control group (group A), deferoxamine intervention group (group B), rapamycin intervention group (group C), and deferoxamine+rapamycin intervention group (group D). At 3, 6, and 9 days after model preparation, rats of groups A, B, C, and D were intra-peritoneally injected with normal saline, deferoxamin (10 mg/kg), rapamycin (3 mg/kg), deferoxamin (10 mg/kg)+rapamycin (3 mg/kg) respectively. The wound healing was observed and the healing time was recorded in each group; the wound healing tissue was harvested to test the mRNA and protein expressions of mammalian target of rapamycin (mTOR), hypoxia inducible factor 1α (HIF-1α), and vascular endothelial growth factor (VEGF) by real-time fluorescence quantitative PCR and Western blot at 2 days after wound healing.

Results

All rats survived to the end of the experiment, and wounds healed; the healing time of groups A, B, and D was significantly shorter than that of group C ( P<0.05), but there was no significant difference between groups A, B, and D ( P>0.05). Real-time fluorescence quantitative PCR showed that the expression of mTOR mRNA in groups C and D was significantly decreased when compared with the expressions in groups A and B ( P<0.05); there was significant difference between groups A and B ( P<0.05), but no significant difference between groups C and D ( P>0.05). The expressions of HIF-1α mRNA and VEGF mRNA were signi-ficantly higher in groups B and D than groups A and C, and in group A than group C ( P<0.05), but there was no signifi-cant difference between groups B and D ( P>0.05). Western blot showed that the relative expressions of mTOR protein in groups C and D were significantly decreased when compared with the expressions in groups A and B ( P<0.05), but there was no significant difference between groups C and D ( P>0.05). The relative expressions of HIF-1α protein in groups A, B, and C were significantly increased when compared with expression in group D ( P<0.05), but there was no significant difference between groups A, B, and C ( P>0.05). The relative expression of VEGF protein were significantly lower in groups B, C, and D than group A, in group D than groups B and C, and in group C than group B ( P<0.05).

Conclusion

Defe-roxamin can promote the wound healing of rats after ischemia and hypoxia, and the effect of rapamycin is opposite. It may be related to the existence of mTOR and HIF-1 signaling pathway in chronic ischemia-hypoxia wound.

AGEs Induced Autophagy Impairs Cutaneous Wound Healing via Stimulating Macrophage Polarization to M1 in Diabetes

Autophagy is essential in physiological and pathological processes, however, the role of autophagy in cutaneous wound healing and the underlying molecular mechanism remain elusive. We hypothesized that autophagy plays an important role in regulating wound healing. Here, we show that enhanced autophagy negatively impacts on normal cutaneous healing process and is related to chronic wounds as demonstrated by the increased LC3 in diabetic mice skin or patients' chronic wounds. In addition, inhibition of autophagy by 3-MA restores delayed healing in C57BL/6 or db/db mice, demonstrating that autophagy is involved in regulating wound healing. Furthermore, we identify that macrophage is a major cell type underwent autophagy in wounds and increased autophagy induces macrophages polarization into M1 with elevated CD11c population and gene expressions of proinflammatory cytokines. To explore the mechanism underlying autophagy-impaired wound healing, we tested the role of IRF8, a regulator of autophagy, in autophagy-modulated macrophages polarization. IRF8 activation is up-regulating autophagy and M1 polarization of macrophages after AGEs (advanced glycation endproducts) treatment, blocking the IRF8 with shIRF8 inhibits autophagic activity and M1 polarization. In summary, this study elucidates that AGEs induces autophagy and modulates macrophage polarization to M1 via IRF8 activation in impairment of cutaneous wound healing.

Growth hormone abolishes the negative effects of everolimus on intestinal wound healing

AIM: To investigate whether the simultaneous treatment with human growth hormone (hGH) abolishes the negative effects of everolimus on anastomotic healing.

METHODS: Forty-eight male Sprague-Dawley-rats were randomized to three groups of 16 animals each (I: vehicle; II: everolimus 3 mg/kg po; III: everolimus 3 mg/kg po + hGH 2.5 mg/kg sc). Animals were pre-treated with hGH and/or everolimus daily for seven days. Then a standard anastomosis was created in the descending colon and treatment was continued for another seven days. The anastomosis was resected in toto and the bursting pressure was assessed as a mechanical parameter of intestinal healing. Moreover, biochemical (Hydroxyproline, PCNA, MPO, MMP-2 and MMP-9) and histological (cell density, angiogenesis, amount of granulation tissue) parameters of intestinal healing were assessed.

RESULTS: Anastomotic bursting pressure was significantly reduced by everolimus and a simultaneous treatment with hGH resulted in considerably higher values (I: 134 ± 19 mmHg, II: 85 ± 25 mmHg, III: 114 ± 25 mmHg; P < 0.05, I vs II; P = 0.09, I vs III and II vs III) Hydroxyproline concentration was significantly increased by hGH compared to everolimus alone (I: 14.9 ± 2.5 μg/mg, II: 8.9 ± 3.6 μg/mg, III: 11.9 ± 2.8 μg/mg; P < 0.05, I vs II/III and II vs III). The number of MPO-positive cells was reduced significantly by hGH compared to everolimus alone (I: 10 ± 1 n/mm², II: 15 ± 3 n/mm², III: 9 ± 2 n/mm²; P < 0.05, I vs II and II vs III), while the number of PCNA-positive cells were increased by hGH (I: 28 ± 3 /mm², II: 12 ± 3 /mm², III: 26 ± 12 /mm²; P < 0.05, I vs II and II vs III). Corresponding to these biochemical findings, HE-histology revealed significantly increased amount of granulation tissue in hGH-treated animals.

CONCLUSION: Inhibition of intestinal wound healing by everolimus is partially neutralized by simultaeous treatment with hGH. Both inflammation as well as collagen deposition is influenced by hGH.

Sirolimus conversion efficacy for graft function improvement and histopathology in renal recipients with mild to moderate renal insufficiency

This study was designed to evaluate whether sirolimus (SRL) conversion effectively improves renal function and histopathology in calcineurin inhibitor (CNI)-treated renal recipients with mild to moderate renal insufficiency. SRL conversion from CNI was performed in patients who underwent kidney transplantation from 6 months to 5 yr prior to screening. Forty-five patients were enrolled. The effect of SRL conversion on graft function was evaluated, and protocol biopsies were performed preconversion and 1 yr after conversion. Overall graft function after SRL conversion gradually improved, and the improvement in renal function was closely associated with the shorter duration of CNI exposure. When we divided the patients by the duration of CNI exposure, the patients with less than 1 yr of CNI exposure demonstrated significant improvement, but patients with a greater than 1 yr CNI exposure did not exhibit significant improvement. In contrast, protocol biopsies demonstrated no significant improvements in the modified "ah" score or other Banff scores after SRL conversion. Furthermore, the duration of CNI treatment prior to SRL conversion was not associated with histological findings 1 yr after SRL conversion. SRL conversion improved graft function in renal recipients with mild to moderate renal insufficiency, but this effect is not accompanied by histological improvement.

[Multimodal oncological therapy concepts, chemotherapy and immunosuppressive drugs: effects on surgical morbidity and mortality]

Systemic chemotherapy, targeted therapies and radiotherapy for patients with malignant tumors lead to unfavorable surgical conditions with increased risks of postoperative complications. For gastric cancer and cancer of the esophagogastric junction, surgery after neoadjuvant treatment is associated with a mortality of approximately 5 %. Given the increase in metastatic surgery for colorectal carcinoma, surgeons should be aware of the specific side effects of therapeutic drugs to ensure an optimal course of treatment. The impact of chemotherapy-induced hepatic lesions on postoperative development is unclear. Bevacizumab treatment should be stopped at least 5 weeks before surgery to reduce the risk of thromboembolic events, bleeding and wound healing complications. Immunosuppressive and immunomodulating agents alter wound healing and preoperative alterations should be carefully evaluated. For patients with chronic corticosteroid therapy, perioperative supplementation should be considered when planning surgery as well as routine dosages.

Topical tacrolimus does not negatively impact acute skin wound healing

Despite the increasing use of topical tacrolimus, there is little information about its effect on skin wound healing. To determine effects on acute cutaneous wound healing, two full-thickness skin wounds were imparted on the backs of 45 hairless mice, which were then divided into vehicle-, topical tacrolimus- and topical steroid-treated group. Each drug was topically applied once daily. The wound area was assessed by using dermoscopic images every two days after wounding. At 3, 7 and 11 days after wounding, 10 wounds in each group were collected for semi-quantitative analysis of histological features including re-epithelialization, polymorphonuclear leucocytes, fibroblasts and collagen. We also checked the mRNA expression levels of EGF, TGF-β, TNF-α and IL-1α. While topical application of clobetasol propionate was found to delay re-epithelialization and infiltration of polymorphonuclear leucocyte, topical treatment with tacrolimus showed patterns similar to that of the vehicle. In the tacrolimus-treated group, mRNA expression levels of IL-1α and TGF-β were slightly decreased, while the others were similar with the vehicle-treated group. Unlike steroid, topical tacrolimus, therefore, did not disturb the wound healing process in a murine skin wound model.

Refractory autoimmune hemolytic anemia after intestinal transplant responding to conversion from a calcineurin to mTOR inhibitor

AIHA is a rare and serious complication of solid organ transplantation. Herein, we report four cases of warm or mixed AIHA in pediatric patients following combined liver, small bowel and pancreas transplant. The hemolysis was refractory to multiple treatment modalities including steroids, rituximab, IVIG, plasmapheresis, cytoxan, discontinuation of prophylactic penicillin, and a change in immunosuppression from tacrolimus to cyclosporine. All patients had resolution or marked improvement of hemolysis after discontinuation of maintenance of CNI and initiation of sirolimus immunosuppression. One patient developed nephrotic syndrome but responded to a change in immunosuppression to everolimus. Three of the four patients continue on immunosuppression with sirolimus or everolimus without further hemolysis, evidence of rejection or medication side effects. Based on our experience and review of similar cases in the literature, we have proposed a treatment algorithm for AIHA in the pediatric intestinal transplant patient population that recommends an early change in immunosuppressive regimen from CNIs to sirolimus therapy.

Immunomodulation at epithelial sites by obesity and metabolic disease

Obesity and related type 2 diabetes are increasing at epidemic proportions globally. It is now recognized that inflammatory responses mediated within the adipose tissue in obesity are central to the development of disease. Once initiated, chronic inflammation associated with obesity leads to the modulation of immune cell function. This review will focus specifically on the impact of obesity on γδ T cells, a T-cell subset that is found in high concentrations in epithelial tissues such as the skin, intestine, and lung. Epithelial γδ T cell function is of particular concern in obesity as they are the guardians of the epithelial barrier and mediate repair. A breakdown in their function, and subsequently the deterioration of the epithelium can result in dire consequences for the host. Obese patients are more prone to non-healing injuries, infection, and disease. The resulting inflammation from these pathologies further perpetuates the disease condition already present in obese hosts. Here we will provide insight into the immunomodulation of γδ T cells that occurs in the epithelial barrier during obesity and discuss current therapeutic options.

Free tissue transfer for head and neck reconstruction in solid organ transplant patients

BACKGROUND

Patients with head and neck malignancies who have had solid organ transplant and require free tissue transfer are a unique population. This study was performed to evaluate the effect of immunosuppression on the rate of perioperative complications and the success of free tissue transfer in the head and neck.

METHODS

Complications in solid organ transplant patients undergoing free tissue transfer for reconstruction of head and neck malignancies from 1998 to 2010 were evaluated.

RESULTS

A total of 22 flaps in 17 patients were performed. Eight patients (11 of 22 flaps) had complications. The median hospital stay was 6 days (range, 4-26 days). The median length of follow-up was 13.5 months (range, 3.5-49.9 months).

CONCLUSIONS

Solid organ transplant patients are at an increased risk of de novo malignancies due to chronic immunosuppression. This study demonstrates that free tissue transfer is a viable option in transplant patients with morbidity similar to nontransplant patients.

Experience of laparoscopic incisional hernia repair in kidney and/or pancreas transplant recipients

Despite the wide popularity of laparoscopic incisional hernia repair (LIHR) in the nontransplant population, there are very few reports of LIHR available in abdominal organ transplant patients and none exclusively on kidney and/or pancreas (KP) transplant patients. We retrospectively reviewed a consecutive series of LIHR in KP transplant recipients performed over a period of 4 years and compared the results with LIHR in non-transplant patients during the same period. A total of 36 transplant patients were compared with 62 nontransplant patients. There were five patients converted to the open procedure in the transplant and four in nontransplant patients (p-NS). There were three seromas and one patient had a bowel perforation in the transplant group versus eight seromas, one bowel perforation and one small bowel obstruction noted in the nontransplant group. One patient in each group had a mesh infection requiring explant. Patients were followed up for a mean period of 2.2 years in the transplant group and 3 years in the nontransplant group. Overall there were five recurrences in the transplant group and four in the nontransplant group (p = NS). These results suggest that that LIHR is a safe and effective alternative to open repair.

Protective measures against ultrafiltration failure in peritoneal dialysis patients

Ultrafiltration failure in patients undergoing peritoneal dialysis is a condition with an incidence that increases over time. It is related to increased cardiovascular morbidity and mortality and is a major cause of the abandonment of the treatment technique. Because the number of patients undergoing renal replacement therapy is increasing with society aging and because approximately 10% of this population is treated with peritoneal dialysis, this matter is becoming more common in everyday practice for clinicians involved in the care of patients with chronic renal failure. In this review, we summarize the available measures used to prevent and treat ultrafiltration failure and the current state of research in the field, both in the experimental and clinical settings, focusing on the possible clinical applications of recent findings.

Angiogenesis in cutaneous disease: part I

Angiogenesis is an important process in normal physiology and disease pathogenesis. Angiogenesis is controlled in a healthy body by a system of angiogenic growth factors and angiogenesis inhibitors. When angiogenic growth factors are predominantly expressed, blood vessel growth occurs and disease may result. Successful therapies have been developed that target growth factors, their receptors, or the cascade pathways that are activated by growth factor/receptor interactions. There is good evidence that angiogenesis plays an important role in a wide range of cutaneous maladies, and angiogenesis-targeting therapies are playing an increasing role in the management of dermatologic disease. Cutaneous angiogenesis offers an exciting new arena for targeted dermatologic therapeutics.

LEARNING OBJECTIVES

After completing this learning activity, participants should be able to distinguish angiogenic growth factors and inhibitors, recognize angiogenic mediating agents and compare their mechanisms of action, and apply the use of angiogenic mediating agents in clinical and research situations.

Consequences of surgical stress on the kinetics of skin wound healing: partial hepatectomy delays and functionally alters dermal repair

The objective was to determine the significance of surgical trauma in dermal wound healing. Using intravital microscopy, we analyzed the healing kinetics of full-thickness dermal wounds in the ears of SKH1 mice. Partial hepatectomy (pHx) simulated major surgical trauma, while laparotomy only served as a sham operation (sham). Animals without abdominal surgery served as controls (control). Laparotomy wounds were analyzed for biomechanical qualities and collagen deposition. Morphological characterization of skin repair was performed by histology/immunohistochemistry. In vitro cell assays assessed the paracrine effects of surgical stress. PHx caused a transient increase in tumor necrosis factor-alpha (TNF-alpha) and interleukin (IL)-6 levels and led to weight loss, reflecting the host's overall response to surgery. Wound closure in pHx animals was delayed vs. control and sham animals, as indicated by significantly lower values of epithelialization and neovascularization over 10 days. Ear wound histology further revealed a provisional wound matrix with a reduced microvessel density. Moreover, pHx-laparotomy wounds showed a reduced bursting strength coexisting with significantly decreased collagen content. PHx and sham serum caused a significant alteration in in vitro fibroblast viability. Skin healing is dependent on the extent of surgery and is influenced by its paracrine effects. Therefore, considerable effort should be focused on the development of strategies limiting surgery-associated perturbations of dermal repair.

Everolimus interferes with the inflammatory phase of healing in experimental colonic anastomoses

BACKGROUND

Delayed wound healing is a serious side effect of mTOR inhibitor-based immunosuppression after solid organ transplantation. The aim of this study was to test the hypothesis that the mTOR inhibitor everolimus interferes with the inflammatory phase of healing in experimental colonic anastomoses.

MATERIALS AND METHODS

Thirty male Sprague-Dawley rats received a colonic anastomosis. Then, animals were randomized to three groups of daily treatment with either vehicle or everolimus in two different dosages (1.0mg/kg or 3.0mg/kg). After 7 d, rats were sacrificed, and mechanical, histologic, and biochemical parameters of intestinal healing were assessed.

RESULTS

Anastomotic bursting pressure was significantly decreased by everolimus in both dosages, whereas hydroxyproline content was reduced only by the high everolimus dosage. Everolimus diminished cellular proliferation and new vessel growth. Furthermore, both quantity as well as quality of newly synthesized collagen fibers in the anastomotic granulation tissue was reduced. On the other hand, myeloperoxidase-positive (MPO) cells and interleukin-6 (IL-6) concentrations were increased, as was the activity of matrix-metalloproteinases MMP-2 and MMP-9.

CONCLUSION

Everolimus interferes with the inflammatory phase of healing. However, it remains unclear whether this phenomenon is involved in everolimus impairment of experimental anastomotic repair.

Impaired lower extremity wound healing secondary to sirolimus after kidney transplantation

PURPOSE

Sirolimus is an immunosuppressive drug used as part of the drug regimen after kidney, liver, and heart transplantation. There have been numerous reports of transplant surgical wound healing complications secondary to sirolimus. The authors present a case of impaired wound healing in the lower extremity after kidney transplantation for a patient on sirolimus. This is one of the few reported cases that we are aware of that demonstrates the effects of sirolimus on wound healing at a nontransplant site.

METHODS

A case highlighting aggressive limb-salvage modalities for a kidney transplant patient on sirolimus is presented. The subject was informed that data concerning the case would be submitted for publication. A brief review of the literature shows the wound healing problems previously associated with sirolimus.

RESULTS

Despite all salvage techniques employed, including aggressive early debridement, forefoot offloading, IV antibiotics, negative pressure wound therapy, and hyperbaric oxygen therapy, the patient eventually went on to failure and a transtibial amputation.

CONCLUSION

Physicians specializing in wound care and limb salvage must be aware of the effects of sirolimus on wound healing and should consider modifications to these patients' immunosuppressive regimens.

A systematic approach to minimizing wound problems for de novo sirolimus-treated kidney transplant recipients

BACKGROUND

Wound healing problems and lymphoceles have been reported with greater frequency in kidney recipients given de novo sirolimus. This problem has led to increased patient morbidity and cost; and has been an impediment to the completion of randomized controlled trials in which wound problems have necessitated premature discontinuation of mammalian target of rapamycin inhibitors.

METHODS

We developed a systematic program to reduce these problems based on patient selection (body mass index [BMI] <32 kg/m2), the use of closed suction drains, modifications of surgical technique, and avoidance of a loading dose of sirolimus. Consecutive series of adult kidney-only recipients given antibody induction followed by de novo sirolimus, mycophenolate mofetil, and steroids were compared; group 1: 204 patients transplanted with few restrictions and group 2: 103 patients transplanted using the above program.

RESULTS

This approach resulted in a significant reduction (group 2 vs. group 1) in cumulative wound complications (7.8% vs. 19.6%, P=0.007), and nonoperative wound complications (2.9% vs. 14.2%, P=0.001). In addition, the incidence of lymphoceles detected (22.3% vs. 47.1%, P<0.0001), treated (4.8% vs. 24.5%, P<0.0001), or needing surgical intervention (1.9% vs. 14.2%, P=0.001) was significantly reduced. Multivariate analysis demonstrated that a BMI more than 30 to 32 kg/m2 was the most significant variable related to delayed wound healing (odds ratio [OR] 3.01, 0.02) or surgical repair (OR 8.05, P=0.0001), whereas BMI (OR 1.54, P=0.038) and acute rejections (OR 1.34, P=0.03) were most associated with lymphocele treatment.

CONCLUSIONS

A systematic program of wound care using de novo sirolimus can produce wound healing complications comparable with that reported with other agents.

Defects in skin gamma delta T cell function contribute to delayed wound repair in rapamycin-treated mice

Disruptions in the normal program of tissue repair can result in poor wound healing, which perturbs the integrity of barrier tissues such as the skin. Such defects in wound repair occur in transplant recipients treated with the immunosuppressant drug rapamycin (sirolimus). Intraepithelial lymphocytes, such as gammadelta T cells in the skin, mediate tissue repair through the production of cytokines and growth factors. The capacity of skin-resident T cells to function during rapamycin treatment was analyzed in a mouse model of wound repair. Rapamycin treatment renders skin gammadelta T cells unable to proliferate, migrate, and produce normal levels of growth factors. The observed impairment of skin gammadelta T cell function is directly related to the inhibitory action of rapamycin on mammalian target of rapamycin. Skin gammadelta T cells treated with rapamycin are refractory to IL-2 stimulation and attempt to survive in the absence of cytokine and growth factor signaling by undergoing autophagy. Normal wound closure can be restored in rapamycin-treated mice by addition of the skin gammadelta T cell-produced factor, insulin-like growth factor-1. These studies not only reveal that mammalian target of rapamycin is a master regulator of gammadelta T cell function but also provide a novel mechanism for the increased susceptibility to nonhealing wounds that occurs during rapamycin administration.

Rapamycin affects early fracture healing in mice

BACKGROUND AND PURPOSE

The immunosuppressive drug rapamycin (RAPA) prevents rejection in organ transplantation by inhibiting interleukin-2-stimulated T-cell division. Rapamycin has also been suggested to possess strong anti-angiogenic activities linked to a decrease in production of vascular endothelial growth factor (VEGF). Angiogenesis and VEGF are thought to play a crucial role in fracture healing and as osteoporotic and traumatic fractures are common complications in immunosuppressed, organ transplantation patients, we conducted this study to analyze the effect of rapamycin treatment on bone repair.

EXPERIMENTAL APPROACH

We investigated the effect of rapamycin treatment on bone repair in a murine closed femur fracture model using radiological, histomorphometric, immunohistochemical, biomechanical and protein biochemical analyses.

KEY RESULTS

X-ray analyses demonstrated that rapamycin treatment inhibits callus formation after two weeks of fracture healing. The radiologically observed lack of callus formation was confirmed by histomorphometric analyses, which revealed a significantly diminished callus size and a reduced amount of bone formation when compared with vehicle-treated controls. Biomechanical testing further demonstrated that rapamycin significantly reduces torsional stiffness of the callus. Interestingly, this effect was associated with decreased vessel formation; a diminished proliferation of osteoblasts, endothelial cells and periosteal cells; and a reduced VEGF expression in hypertrophic chondrocytes. After five weeks treatment, however, the negative impact of rapamycin on fracture healing was overcome.

CONCLUSIONS AND IMPLICATIONS

Thus, rapamycin initially delays fracture healing, most probably by inhibiting cell proliferation and neovascularization in the callus. These undesirable effects should be considered when rapamycin is administered to patients sustaining bone fractures.

In human endothelial cells rapamycin causes mTORC2 inhibition and impairs cell viability and function

AIM

Drug-eluting stents are widely used to prevent restenosis but are associated with late endothelial damage. To understand the basis for this effect, we have studied the consequences of a prolonged incubation with rapamycin on the viability and functions of endothelial cells.

METHODS AND RESULTS

Human umbilical vein or aorta endothelial cells were exposed to rapamycin in the absence or in the presence of tumour necrosis factor alpha (TNFalpha). After a 24 h-incubation, rapamycin (100 nM) caused a significant cell loss associated with the increase of both apoptosis and necrosis, as quantified by propidium iodide staining, caspase 3 activity, and lactate dehydrogenase release. Rapamycin also impaired cell mobility, as assessed by a wound test, and promoted the formation of actin stress fibres, as determined with confocal microscopy. Moreover, the inhibitor prolonged TNFalpha-dependent E-selectin induction, inhibited endothelial nitric oxide synthase expression at both mRNA (quantitative real-time polymerase chain reaction) and protein level (enzyme-linked immunosorbent assay and western blot), and lowered bioactive nitric oxide output (RFL-6 reporter cell assay). Under the conditions adopted, rapamycin inhibited both mammalian target-of-rapamycin complexes (mTORC1 and mTORC2), as indicated by the reduced amount of raptor and rictor bound to mTOR in immunoprecipitates and by the marked hypophosphorylation of protein S6 kinase I (p70S6K) and Akt, determined by western blotting. The selective inhibition of mTORC1 by AICAR did not affect endothelial viability.

CONCLUSION

A prolonged treatment with rapamycin impairs endothelial function and hinders cell viability. Endothelial damage seems dependent on mTORC2 inhibition.

Healing time, long-term result and effects of stem cell treatment in acute tympanic membrane perforation

OBJECTIVE

The incidence of otitis media in children between the age of 2 and 6 years is well documented. Repeated attacks may cause acute and chronic perforations. The surgical treatment for repairing chronic perforation is quite uncomfortable for the patients of this age group because of the invasiveness of this treatment. The aim of this study was to determine the long-term influence of embryonic stem cells on acute perforations and the effect of gelatin as a vehicle for applied stem cells. The possibility of teratogenic effects of the stem cells was also observed.

METHODS

Bilateral laser myringotomy was performed in 17 adult Sprague-Dawley rats, divided into two groups. Gelatin, a substance suitable as vehicle for bioactive material was used bilaterally around the perforation in group A, to serve as a scaffold for repairing tissue. The stem cells were used in the right tympanic membrane perforation leaving the left tympanic membrane as a control. The animals in group B received the same treatment except for the use of gelatin and in addition received an immuno-suppressive agent. After half a year of observation the mechanical stiffness of the tympanic membrane was measured by moiré interferometry for group B and the morphological study was performed by light microscopy for both groups A and B and electron microscopy for group A.

RESULTS

Stem cell treated ears did not show any enhanced healing of the perforation although a marked thickening of the lamina propria was observed compared with control group. After half a year the strength and the stiffness of the tympanic membrane was almost the same for both treated and untreated ears. No evidence of teratoma was found after half a year.

CONCLUSION

This study suggests that the stem cells stimulate the proliferation of connective tissue and fibers in the lamina propria, possibly mediated by secreted substances, although the stiffness properties do not seem to be altered. The use of gelatin does not seem to enhance the healing process of the tympanic membrane perforation.