Mycophenolic acid (cellcept and myofortic) induced injury of the upper GI tract. Am J Surg Pathol. 2009;33:1355-1363. [PMID: 19542873 DOI: 10.1097/pas.0b013e3181a755bd]

Gut mucosa alterations after kidney transplantation: a cross sectional study

BACKGROUND

Kidney transplant recipients (KTRs) rely on immunosuppressants like mycophenolate to prevent organ rejection. However, mycophenolate often causes intestinal symptoms and inflammation in various organs, including the skin and the colon. While KTRs have an increased risk for skin cancer, the risk of colorectal cancer is not increased. Elucidating the histological alterations in the colon of KTRs and comparing these changes with known skin alterations would help understand how immunosuppressants influence cancer development and progression.

METHODS

Whole slide images from gut biopsies (Non-transplanted subjects n = 35, KTRs n = 49) were analyzed using the ImageJ and R programming environment. A total of 22,035 epithelial cells, 38,870 interstitial cells, 3465 epithelial cell mitoses, and 7477 endothelial cells, each characterized by multiple microscopy parameters, from a total of 1788 glands were analyzed. The large database was subsequently analyzed to verify the changes of inflammatory milieu in KTRs and in cancer.

RESULTS

KTRs without colon-cancer showed a significantly higher density of interstitial cells in the colon compared to non-transplanted patients. Moreover, the increase in interstitial cell number was accompanied by subtle modifications in the architecture of the colon glands, without altering the epithelial cell density. We could not identify significant structural modifications in cancer samples between KTRs and non-transplanted patients.

CONCLUSIONS

Our findings demonstrate an increased number of resident interstitial cells in the colon of KTRs, as in other patients treated with mycophenolate. These changes are associated with subtle alterations in the architecture of colon glands.

Clinical Features of Gastroduodenal Ulcers in Kidney Transplant Patients

Objective The risk of developing peptic ulcers and gastrointestinal bleeding is high in patients with chronic kidney disease (CKD). Whether or not kidney transplant patients, who are treated with multiple medications, including immunosuppressive drugs, are at an increased risk of developing peptic ulcers is unclear. Methods In this retrospective study, we compared the clinical and endoscopic features of gastroduodenal ulcers between kidney transplant patients and CKD patients. The subjects underwent upper gastrointestinal endoscopy between January 2015 and March 2021. Results Gastroduodenal ulcers were observed more frequently (6.5%) in kidney transplant patients than in CKD patients (2.1%) (p=0.026). Due in part to the lower median age in the kidney transplant ulcer group than in the CKD ulcer group (59 vs. 70 years old, p=0.016), the rates of atrophic gastritis and Helicobacter pylori infection were also lower in the kidney transplant ulcer group than in the CKD ulcer group. Significantly more kidney transplant patients were treated with acid secretion inhibitors than CKD ulcer patients (100% vs. 34.8%, p=0.0005). Peptic ulcers were observed frequently in kidney transplant patients, even though common risk factors for gastroduodenal ulcers other than immunosuppressive drugs were few. All kidney transplant patients were taking immunosuppressive medications, and tacrolimus, mycophenolate mofetil, and methylprednisolone were taken more frequently than others. Conclusion Kidney transplant patients have a high risk of developing gastroduodenal ulcers. All kidney transplant patients take immunosuppressive medications, so there may be an association between immunosuppressive medications and gastroduodenal ulcer development.

Gastrointestinal Biopsies in the Patient Post-Stem Cell Transplant: An Approach to Diagnosis

Graft-versus-host disease (GVHD) is a major complication of hematopoietic stem cell transplantation (SCT), leading to a significant morbidity and mortality. Histologically, gastrointestinal GVHD is characterized by crypt apoptosis and dropout. However, similar histologic features can also be seen in drug-induced injury and opportunistic infection. Knowledge of the timing of biopsy, patient medications, evidence of infection, and presence of GVHD at other organ sites can aid in the correct diagnosis and subsequent management of these patients. This review focuses on the pathologic differential diagnosis of apoptosis in gastrointestinal biopsies obtained from SCT patients.

Drug-induced digestive tract injury: decoding some invisible offenders

There is an ever-growing list of pharmacological agents, several of which are attributed to cause clinically significant gastrointestinal (GI) injury. Many patients present with significant but nonspecific symptoms, that in conjunction with the absence of relevant drug history on the requisition slip can make the histopathologic diagnosis challenging. To complicate this, although some drugs have relatively characteristic histopathologic features (such as doxycycline), there exist many other drugs that exhibit wide and varying spectra of histopathologic findings (such as immune checkpoint inhibitors or olmesartan) and have histomorphologic overlap with many other commonly encountered disease entities. This review discusses the histopathologic features of some relatively recently described drugs causing GI tract injury, namely doxycycline, tacrolimus, mycophenolate, immune checkpoint inhibitors, and olmesartan. We also discuss the common mimics in histopathologic differential and some pearls that can help distinguish GI tract injury induced by the aforementioned drugs from its mimics. Awareness of the wide spectra of histopathologic changes associated with these drugs is crucial for practicing pathologists, to avoid misdiagnosis and guiding the clinician for an optimal patient management, which usually involves modifying or discontinuing the offending drug. Needless to say, once a diagnosis of drug-induced injury is suspected, clinicopathologic correlation including corroboration with the drug history is of utmost importance as is the exclusion of dual pathology in these patients.

Host and immunosuppression-related factors influencing fibrosis occurrence post liver transplantation

Post liver transplantation (LT) fibrosis has a negative impact on graft function. Cytokine production in the host immune response after LT may contribute to the variable CYP3A-dependent immunosuppressive drug disposition, with subsequent impact on liver fibrogenesis, together with host-related factors. We aimed to investigate whether the cytochrome P4503A5*3 (CYP3A5*3) or TBX21 genotypes impact post-LT liver fibrogenesis. Furthermore, the impact of immunosuppressants on cellular apoptosis has been evaluated using human hepatocytes harvested from cirrhotic explanted livers. We have enrolled 98 LT recipients that were followed for occurrence of liver fibrosis for at least 12 months. There was a statistically significant higher trough level of TAC in patients with homozygous CC-TBX21 genotype (7.83 ± 2.84 ng/ml) vs. 5.66 ± 2.16 ng/ml in patients without this genotype (p = 0.009). The following variables were identified as risk factors for fibrosis ≥2: donor age (p = 0.02), neutrophil to lymphocyte ratio (p = 0.04) and TBX21 genotype CC (p = 0.009). In the cell culture model cytometry analysis has indicated the lowest apoptotic cells percentage in human cirrhotic hepatocytes cultures treated with mycophenolate mofetil (MMF) (5%) and TAC + MMF (2%) whereas the highest apoptosis percentage was registered for the TAC alone (11%). The gene expression results are concordant to cytometry study results, indicating the lowest apoptotic effect for MMF and MMF + TAC immunosuppressive regimens. The allele 1993C of the SNP rs4794067 may predispose to the development of late significant fibrosis of the liver graft. MMF-based regimens have a favourable anti-apoptotic profile in vitro, supporting its use in case of LT recipients at high risk for liver graft fibrosis.

Mycophenolic Acid Induces the Intestinal Epithelial Barrier Damage through Mitochondrial ROS

Mycophenolic acid (MPA) may cause gastrointestinal adverse effects by damaging the intestinal epithelial barrier, the underlying mechanisms remain elusive. Studies have demonstrated that oxidative stress caused by reactive oxygen species (ROS) is linked to tight junction (TJ) proteins and apoptosis, both of which cause abnormalities in intestinal barrier function. Mitochondria, one of the main sources of ROS and abnormally high levels of ROS are linked to mitochondrial dysfunction. The aim of this study was to investigate whether MPA induces intestinal barrier dysfunction through regulation of the mitochondrial ROS. MPA-induced intestinal injury model in Kunming mice and Caco-2 cells. The effect of MPA on Caco-2 cell viability was measured by MTT; tissue diamine oxidase and endotoxin expression were determined by ELISA; expression of total proteins of ZO-1, occludin, Bax, Bcl-2, and mitochondrial proteins of Cytochrome C and Bax was measured by Western blot; and the localization of Cytochrome C with MitoTraker was observed by immunofluorescence staining. Caco-2 cell apoptosis, ROS levels, and mitochondrial membrane potential were detected by flow cytometry, while intramitochondrial ROS levels were observed by MitoSOX fluorescence staining. The results showed that MPA increased intracellular and mitochondrial ROS production to promote oxidative stress and the antioxidant NAC effectively restored ZO-1 and occludin expressions, reduced apoptosis in intestinal epithelial cells. Furthermore, we found that low concentrations of MPA caused mitochondrial damage, induced hyperpolarization of the mitochondrial membrane potential and the translocation of Cytochrome C and Bax proteins from the cytoplasm to the mitochondria. The mitochondrial protectant SS-31 reduces intracellular and intramitochondrial ROS, upregulates TJ, and reduces apoptosis. Our studies suggest that MPA-induced intestinal barrier dysfunction in vivo and in vitro is mediated, at least in part, by impairing mitochondrial function and promoting oxidative stress.

Metagenomics combined with activity-based proteomics point to gut bacterial enzymes that reactivate mycophenolate

Mycophenolate mofetil (MMF) is an important immunosuppressant prodrug prescribed to prevent organ transplant rejection and to treat autoimmune diseases. MMF usage, however, is limited by severe gastrointestinal toxicity that is observed in approximately 45% of MMF recipients. The active form of the drug, mycophenolic acid (MPA), undergoes extensive enterohepatic recirculation by bacterial β-glucuronidase (GUS) enzymes, which reactivate MPA from mycophenolate glucuronide (MPAG) within the gastrointestinal tract. GUS enzymes demonstrate distinct substrate preferences based on their structural features, and gut microbial GUS enzymes that reactivate MPA have not been identified. Here, we compare the fecal microbiomes of transplant recipients receiving MMF to healthy individuals using shotgun metagenomic sequencing. We find that neither microbial composition nor the presence of specific structural classes of GUS genes are sufficient to explain the differences in MPA reactivation measured between fecal samples from the two cohorts. We next employed a GUS-specific activity-based chemical probe and targeted metaproteomics to identify and quantify the GUS proteins present in the human fecal samples. The identification of specific GUS enzymes was improved by using the metagenomics data collected from the fecal samples. We found that the presence of GUS enzymes that bind the flavin mononucleotide (FMN) is significantly correlated with efficient MPA reactivation. Furthermore, structural analysis identified motifs unique to these FMN-binding GUS enzymes that provide molecular support for their ability to process this drug glucuronide. These results indicate that FMN-binding GUS enzymes may be responsible for reactivation of MPA and could be a driving force behind MPA-induced GI toxicity.

Cardiovascular events in adult polymyositis and dermatomyositis: a meta-analysis of observational studies

OBJECTIVES

We aimed to review whether polymyositis (PM) and dermatomyositis (DM) patients have an increased cardiovascular (CV) risk, including ischaemic heart disease (IHD), cerebrovascular accidents (CVA), and venous thromboembolism (VTE).

METHODS

We searched PubMed, Embase, and the Cochrane database for relevant studies from inception to February 2021.

RESULTS

Twenty-two studies comprising 25,433 patients were included. With PM/DM versus general populations, the risk was significantly increased for CV events (relative risk (RR)=2.37, 95%CI:1.86-3.02). The RR of CV events for males with PM/DM was higher than for females (RR = 1.43; 95%CI:1.17-1.74). PM/DM patients followed for one to five years had a significantly higher CV risk than those followed for five to ten years (RR = 3.51, 95%CI:1.95-6.32). The risk was increased for North Americans (RR = 4.28, 95%CI:2.57-7.11), Europeans (RR = 2.29, 95%CI:1.58-3.31), and Asians (RR = 2.03, 95%CI:1.41-2.90). Our meta-analysis found that the elevated CV event risk was related to PM (RR = 2.35, 95%CI:1.51-3.66) and DM (RR = 2.55, 95%CI:1.66-3.93). Subgroup analyses showed that the risk was significantly increased for IHD (RR = 1.76, 95%CI:1.40-2.21), CVA morbidity (RR = 1.31, 95%CI:1.03-1.67), and ischaemic stroke (IS) (RR = 1.47, 95%CI:1.26-1.73), with no statistically significant increased risk of haemorrhagic stroke mortality (RR = 1.43, 95%CI:0.92-2.21). The CV event risk was increased for VTE (RR = 4.60, 95%CI:3.17-6.66), deep venous thrombosis (DVT) (RR = 5.53, 95%CI:3.25-9.39), and pulmonary embolism (PE) (RR = 5.26, 95%CI:2.62-10.55).

CONCLUSION

This meta-analysis found that PM/DM patients had a ∼2.37 times increased CV risk, particularly males diagnosed in the previous five years. PM/DM may be an independent risk factor for developing IHD, IS, DVT, and PE.

Pediatric autoimmune gastritis: clinical correlates and histologic features

Autoimmune gastritis is a well-known pathologic entity, but there are few studies that examine its clinical and histologic presentation in children. This is a single institution, retrospective study performed on patients diagnosed from 2011 through 2019. Patients were identified by their pathologic diagnosis within the laboratory information system. The electronic medical record and archived slides were reviewed. Twenty-two children (3 months to 18 years; median, 10.9 years) with autoimmune gastritis were diagnosed of a total of 14,257 nonconsultation gastric biopsies from unique patients (0.15% prevalence). Patients with autoimmune gastritis were diagnosed at an average age of 10.9 years and were mostly female (68.2% women, 31.8% men). The majority had extragastric immune disorders (13/22; 59.1%). All patients in the study had gastric body mucosa with enterochromaffin-like cell hyperplasia, atrophy, and histologic features of chronic injury. Most biopsies showed gastric body metaplasia (n = 19) or active gastric inflammation. However, antral atrophy was also observed in 12 patients, and antral metaplasia was identified in one patient; four patients had active chronic antral gastritis. All biopsies were negative for Helicobacter pylori. Pediatric autoimmune gastritis is a rare disorder that should be recognized because of its systemic effects with long-term morbidity. In addition, the possibility of tandem extragastric immune disorders should be considered when a diagnosis of pediatric autoimmune gastritis is established.

Recalcitrant Esophageal Stricture Secondary to Mycophenolate Mofetil

Mycophenolate mofetil (MMF) is associated with various gastrointestinal toxicities. However, limited literature studies exist reporting MMF-related gastrointestinal toxicity manifesting as esophageal strictures. We report a case of a 62-year-old male with kidney transplant on MMF, tacrolimus, and prednisone, presenting with progressive dysphagia and odynophagia. Esophagogastroduodenoscopy revealed severe esophageal stricturing with near food bolus impaction, requiring dilations, esophageal stent, and ultimately gastrostomy tube. Biopsies revealed nonspecific inflammation with no evidence of infectious/neoplastic process; thus, our multidisciplinary esophageal group determined that the process was secondary to MMF. This case demonstrates that, though rare, MMF can result in severe esophageal strictures causing significant morbidity.

Orthotopic Heart Transplant Recipient with Enteric-coated Mycophenolate Sodium (Myfortic) Induced Colitis

Patient: Male, 66-year-old

Final Diagnosis: Drug-induced colitis

Symptoms: Abdominal discomfort • anorexia • diarrhea • weight loss

Medication: Enteric-coated mycophenolate sodium (Myfortic)

Clinical Procedure: Colonoscopy • colon biopsy

Specialty: Cardiology • Infectious Disease

Sirolimus vs mycophenolate mofetil (MMF) in primary combined pancreas and kidney transplantation. Results of a long-term prospective randomized study

The study was intended to compare pancreas graft survival rates in two groups of pancreas and kidney transplant recipients prospectively randomized to treatment either with sirolimus or MMF. From 2002 to 2013, 238 type 1 diabetic recipients with end-stage kidney disease were randomized 1:1 to sirolimus or MMF treatment. Noncensored pancreas survival at 5 years was 76.4 and 71.6% for sirolimus and MMF groups, respectively (P > .05). Death-censored pancreas survival was better in the sirolimus group (P = .037). After removal of early graft losses pancreas survival did not differ between groups (MMF 83.1% vs sirolimus 91.6%, P = .11). Nonsignificantly more grafts were lost due to rejection in the MMF group (10 vs 5; P = .19). Cumulative patient 5-year survival was 96% in the MMF group and 91% in the sirolimus group (P > .05). Five-year cumulative noncensored kidney graft survival rates did not statistically differ (85.6% in the sirolimus group and 88.8% in MMF group). Recipients treated with MMF had significantly more episodes of gastrointestinal bleeding (7 vs 0, P = .007). More recipients in the sirolimus group required corrective surgery due to incisional hernias (21 vs 12, P = .019). ClinicalTrials No.: NCT03582878.

Giant Gastric Ulcers: An Unusual Culprit

Mycophenolate Mofetil (MMF) is routinely used immunosuppressant in solid organ transplantation is commonly associated with several gastrointestinal (GI) side effects. Here we present a case of giant gastric ulcer of 5 cm from MMF use post cardiac transplant. CASE DESCRIPTION: A 56-year-old male with history of severe ischemic cardiomyopathy post heart transplant was on immunosuppression with MMF, tacrolimus and prednisone for 5 months. He presented with severe epigastric pain and intermittent episodes of melena for 1 month. His pain radiated to back that is worsened with eating. Associated with loss of appetite, vomiting and 16-pound weight loss in 3 months. He never smoked, drank alcohol or used over the counter pain medications. He was profoundly anemic requiring blood transfusions. EGD performed demonstrated very large clean-based ulcer of 5 cm diameter in the body, smaller ulcer of 8 mm diameter in pre-pyloric region and 5-10 small aphthous ulcers in the gastric body and fundus. Gastric biopsies taken from the ulcer were negative for Helicobacter pylori, cytomegalovirus and malignancy. Flexible sigmoidoscopy revealed non-bleeding inflamed internal hemorrhoids. Consequently, MMF was discontinued and switched to azathioprine. He was treated with twice daily proton pump inhibitor therapy with resolution of abdominal pain, improved appetite and weight gain. DISCUSSION: MMF is well known for common GI side-effects such as nausea, diarrhea, vomiting, ulcers, abdominal pain and rarely gastrointestinal bleeding. Few studies reported 3 to 8% incidence of ulcer perforation and GI bleeding within 6 months. Risk of gastroduodenal erosions is nearly 1.83 times for MMF, with the highest lesions associated with MMF-tacrolimus-corticosteroid combination treatment as seen in our patient. Hypothesis is that GI tract is vulnerable because of dependence of enterocytes on de novo synthesis of purines, which is disrupted by MMF. Typically, upper GI mucosal injuries of mucosal irritation leading to esophagitis, gastritis and/or ulcers are seen. Endoscopy is both diagnostic and therapeutic if bleeding gastric ulcers are noted. Minor complications improve with reduction of drug dose or use of enteric coated preparation if feasible. Discontinuation of the drug is main stay in the management of MMF related ulcer disease. Simple medical treatment with either H2-receptor antagonists, proton-pump inhibitors, coating agents, prostaglandins or combination has proven effective in most cases. Considering excellent results with medical management of ulcer, role of surgery is limited.

IMP dehydrogenase-2 drives aberrant nucleolar activity and promotes tumorigenesis in glioblastoma

In many cancers, high proliferation rates correlate with elevation of rRNA and tRNA levels, and nucleolar hypertrophy. However, the underlying mechanisms linking increased nucleolar transcription and tumorigenesis are only minimally understood. Here we show that IMP dehydrogenase-2 (IMPDH2), the rate-limiting enzyme for de novo guanine nucleotide biosynthesis, is overexpressed in the highly lethal brain cancer glioblastoma. This leads to increased rRNA and tRNA synthesis, stabilization of the nucleolar GTP-binding protein nucleostemin, and enlarged, malformed nucleoli. Pharmacological or genetic inactivation of IMPDH2 in glioblastoma reverses these effects and inhibits cell proliferation, whereas untransformed glia cells are unaffected by similar IMPDH2 perturbations. Impairment of IMPDH2 activity triggers nucleolar stress and growth arrest of glioblastoma cells even in the absence of functional p53. Our results reveal that upregulation of IMPDH2 is a prerequisite for the occurance of aberrant nucleolar function and increased anabolic processes in glioblastoma, which constitutes a primary event in gliomagenesis.

Esophagitis in patients without gastroesophageal reflux disease or eosinophilic esophagitis: diagnostic considerations

PURPOSE OF REVIEW

A multitude of inflammatory diseases other than gastroesophageal reflux disease (GERD) and eosinophilic esophagitis can affect the esophagus. Despite the deceptively simple organization of squamous mucosa and its limited number of inflammatory responses, a wide array of histologic patterns can be seen in inflammatory disorders involving the esophagus. Each such histologic pattern is associated with a limited number of underlying conditions, and the clinician can use this information to narrow the differential diagnosis. The purpose of this review is to review and discuss the pathologic diagnosis of esophagitis caused by conditions other than GERD or eosinophilic esophagitis, with an emphasis on recent developments in the field.

RECENT FINDINGS

Recent studies suggest that lymphocytic esophagitis may be a histologic manifestation of esophageal motility disorders. Immunophenotypic features of infiltrating lymphocytes may be helpful in this scenario. immunoglobulin G4-related disease has been implicated as a cause of esophageal inflammation with ulceration, strictures, and mass-forming fibrosis, whereas epidermoid metaplasia has been linked molecularly to the squamous cell neoplasia pathway.

SUMMARY

Improved knowledge and appreciation of the pathology of esophageal inflammation are needed to better understand the pathogenesis of various types of esophagitis, and to inform new approaches to the therapy and management of inflammatory esophageal diseases.

Review of Drug-induced Injury in Mucosal Biopsies From the Tubular Gastrointestinal Tract

The use of prescription and over-the-counter medications is on the rise in the US population, especially among those aged 65 and over, with over 46% of the population taking at least 1 prescription medication. Given the frequency of medication use, and that the majority of these medications are taken orally, it has become increasingly relevant for pathologist examining endoscopically obtained gastrointestinal tract mucosal biopsies to consider and recognize patterns of mucosal injury associated with various drugs. Reports on injuries associated with certain classes of drugs can be scattered among different sources, making a comprehensive view of various injury patterns and the drugs known to cause them difficult to obtain. Herein, we provide a comprehensive overview of the drugs known to cause mucosal injuries in the tubular gastrointestinal tract organized by the organ involved and the prominent pattern of injury.

Pathology of Gastrointestinal and Liver Complications of Hematopoietic Stem Cell Transplantation

CONTEXT.—

Despite advances in therapeutic and preventive measures, hematopoietic stem cell transplant recipients remain at risk for a variety of gastrointestinal and liver complications.

OBJECTIVE.—

To detail the pathologic features of the various gastrointestinal and liver complications occurring after hematopoietic stem cell transplantation in relation to their clinical context. The specific complications covered include graft-versus-host disease, mycophenolate mofetil-induced injury, timeline of infections, neutropenic enterocolitis, gastrointestinal thrombotic microangiopathy, sinusoidal obstruction syndrome, hepatic iron overload, and the controversy around cord colitis syndrome.

DATA SOURCES.—

The content of this article is based on pertinent peer-reviewed articles in PubMed, relevant textbooks, and on the authors' personal experiences.

CONCLUSIONS.—

The final histopathologic diagnosis requires the integration of clinical and histologic findings and the exclusion of other competing causes of injury. Review of the clinical data, including the original disease pretransplant, the type of transplant, the timing of the gastrointestinal and/or liver manifestations, the timing of the biopsy after transplant, the presence of graft-versus-host disease in other organs and sites, the list of drug regimens, and the clinical and laboratory evidence of infection, is the key to reaching the proper histologic diagnosis.

Celiac-like Enteropathy Associated With Mycophenolate Sodium in Renal Transplant Recipients

Background

Although colonic injury is a well-known complication of mycophenolic acid (MPA), the involvement of the upper gastrointestinal tract is less extensively documented. We present the occurrence of celiac-like duodenopathy manifested as a severe diarrhea syndrome in 2 renal transplant recipients on enteric-coated mycophenolate sodium.

Methods

The patients belong to a setting of 16 renal transplant recipients under MPA suffering from chronic diarrhea in the absence of MPA-related colitis.

Results

Both patients had a history of persistent diarrhea with significant weight loss. Colonic mucosa was unremarkable, whereas duodenal biopsies revealed celiac-like changes with increased epithelial cell apoptosis. Clinical symptoms completely resolved, and follow-up biopsies demonstrated normalization of histology after enteric-coated mycophenolate sodium withdrawal and switching to azathioprine.

Conclusions

Celiac-like enteropathy seems to represent a rare side effect of MPA-associated immunosuppressive therapy and should be taken into account in the differential diagnosis of diarrhea in transplant recipients treated with MPA particularly in the absence of MPA-related colitis. As macroscopic lesions are usually missing, blind duodenal biopsies are necessary to establish the diagnosis.

Heart transplant recipient with mycophenolate mofetil-induced colitis: the great imitator

In this article, we report a case of a 55-year-old male heart transplant recipient who presented with diarrhoea. An extensive workup for infectious diseases was negative. The patient had a colonoscopy with biopsies showing colitis that mimicked graft-versus-host disease on histopathology. After excluding other potential causes and excluding acute cellular rejection, mycophenolate mofetil was discontinued, and the patient had significant clinical improvement with increased appetite and weight gain.

An intact microbiota is required for the gastrointestinal toxicity of the immunosuppressant mycophenolate mofetil

BACKGROUND

Mycophenolate mofetil (MMF) is commonly prescribed after transplantation and has major advantages over other immunosuppressive drugs, but frequent gastrointestinal (GI) side-effects limit its use. The mechanism(s) underlying MMF-related GI toxicity have yet to be elucidated.

METHODS

To investigate MMF-related GI toxicity, experimental mice were fed chow containing MMF (0.563%) and multiple indices of toxicity, including weight loss and colonic inflammation, were measured. Changes in intestinal microbial composition were detected using 16S rRNA Illumina sequencing, and downstream PICRUSt analysis was used to predict metagenomic pathways involved. Germ-free (GF) mice and mice treated with orally administered broad-spectrum antibiotics (ABX) were utilized to interrogate the importance of the microbiota in MMF-induced GI toxicity.

RESULTS

Mice treated with MMF exhibited significant weight loss, related to loss of body fat and muscle, and marked colonic inflammation. MMF exposure was associated with changes in gut microbial composition, as demonstrated by a loss of overall diversity, expansion of Proteobacteria (specifically Escherichia/Shigella), and enrichment of genes involved in lipopolysaccharide (LPS) biosynthesis, which paralleled increased levels of LPS in the feces and serum. MMF-related GI toxicity was dependent on the intestinal microbiota, as MMF did not induce weight loss or colonic inflammation in GF mice. Furthermore, ABX prevented and reversed MMF-induced weight loss and colonic inflammation.

CONCLUSIONS

An intact intestinal microbiota is required to initiate and sustain the GI toxicity of MMF. MMF treatment causes dynamic changes in the composition of the intestinal microbiota that may be a targetable driver of the GI side-effects of MMF.

Unique causes of esophageal inflammation: a histopathologic perspective

Gastroenterologists frequently perform endoscopic esophageal mucosal biopsies for pathologic diagnosis in patients experiencing symptoms of esophagitis. The more common causes of esophagitis diagnosed on esophageal mucosal biopsy include reflux esophagitis, eosinophilic esophagitis, and infectious esophagitis caused by Candida albicans, herpes simplex virus, and/or cytomegalovirus. However, there are several causes of esophagitis seen less frequently by pathologists that are very important to recognize. We discuss unique types of esophageal inflammation, including acute bacterial esophagitis, esophageal manifestations of dermatologic diseases, medication-induced esophageal injury, and sloughing esophagitis; and we review their clinical and histopathologic features.

Use of the National Institutes of Health Consensus Guidelines Improves the Diagnostic Sensitivity of Gastrointestinal Graft-Versus-Host Disease

CONTEXT

- Graft-versus-host disease of the gastrointestinal tract is a common complication of hematopoietic stem cell transplant associated with significant morbidity and mortality. Accurate diagnosis can be difficult and is a truly clinicopathologic endeavor.

OBJECTIVES

- To assess the diagnostic sensitivity of gastrointestinal graft-versus-host disease using the 2015 National Institutes of Health (NIH) histology consensus guidelines and to analyze histologic findings that support the guidelines.

DESIGN

- Patients with allogeneic hematopoietic stem cell transplants were identified via a retrospective search of our electronic medical records from January 1, 2005, to January 1, 2011. Endoscopies with available histology were reviewed by 2 pathologists using the 2015 NIH guidelines. The clinical diagnosis was used as the gold standard. A nontransplant set of endoscopic biopsies was used as a control.

RESULTS

- Of the 250 total endoscopies, 217 (87%) had a clinical diagnosis of gastrointestinal graft-versus-host disease. Use of the NIH consensus guidelines showed a sensitivity of 86% and a specificity of 65%. Thirty-seven of 58 (64%) cases with an initial false-negative histopathologic diagnosis were diagnosed as graft-versus-host disease on our review.

CONCLUSIONS

- Use of the NIH histology consensus guidelines results in a high sensitivity and specificity, thereby decreasing false-negatives. Additionally, use of the NIH guidelines aids in creating uniformity and diagnostic clarity. Correlation with clinical and laboratory findings is critical in evaluating the differential diagnosis and to avoid false-positives. As expected, increased apoptosis with decreased inflammation was associated with a pathologic diagnosis of graft-versus-host disease and supports the NIH guidelines.

Exploration of Fecal Microbiota Transplantation in the Treatment of Refractory Diarrhea After Renal Transplantation

OBJECTIVE

Exploration of fecal microbiota transplantation in the treatment of refractory diarrhea after renal transplantation.

METHODS

Summarize the etiology of 120 cases with diarrhea after renal transplantation from 2014 to 2017 in our hospital. There were 4 recipients of refractory diarrhea who accepted fecal microbiota transplantation with informed consent, and we collected clinical data of stool and bacterial culture, gut microbiota analysis, graft function, electrolytes, immunosuppressant concentrations of prognostic evaluation of patients with fecal transplantation.

RESULTS

The absorption of electrolyte is slightly higher and concentration of tacrolimus and creatinine were not significantly changed compared with before.

CONCLUSION

Fecal microbiota transplantation provides a new choice to refractory diarrhea after renal transplantation as an innovative treatment, but the effectiveness of fecal microbiota transplantation needs long-term observation and further evaluation through large sample data.

The Many Faces of Medication-Related Injury in the Gastrointestinal Tract

Every year many new medications are approved for clinical use, several of which can cause clinically significant gastrointestinal tract toxicity. This article emphasizes the histologic features and differential diagnosis of drug-induced injury to the gastrointestinal mucosa. Ultimately, clinical correlation and cessation of a drug with resolution of symptoms are needed to definitively confirm a drug as a causative factor in mucosal injury. Recognizing histologic features in gastrointestinal biopsies, however, can allow surgical pathologists to play a key role in establishing a diagnosis of drug-induced gastrointestinal toxicity.

The Apoptotic Crypt Abscess: An Underappreciated Histologic Finding in Gastrointestinal Pathology

OBJECTIVES

To differentiate apoptotic crypt abscesses (ACAs) from neutrophilic crypt abscesses (NCAs).

METHODS

Cases with crypt abscesses were classified as containing ACAs, NCAs, or mixed crypt abscesses (MCAs) by H&E staining. Sections were stained with cleaved caspase 3 and myeloperoxidase and recategorized.

RESULTS

Fifty-nine cases were reviewed: inflammatory bowel disease (IBD; n = 33), acute cellular rejection (n = 5), graft vs host disease (GVHD; n = 14), cytomegalovirus (n = 5), and drug reaction (n = 2). Concordance was seen in 59%, with most reclassifications resulting from a change of ACAs to MCAs. When cases were classified as having NCA vs those with apoptosis (ACA and MCA), there was 85% agreement (P < .01). NCAs were present in IBD (96%) and not in GVHD or drug injury. Crypt abscesses with apoptosis were seen in 18% of IBD and 96% of non-IBD cases.

CONCLUSIONS

ACAs and MCAs can be distinguished from NCAs and may be a diagnostically useful finding.

Mucosal Biopsy After Bone Marrow Transplantation

Gastrointestinal mucosal biopsies in the hematopoietic stem cell transplantation setting are challenging because histologic features of graft-versus-host disease (GVHD), which is treated by increasing immunosuppression, overlap with those of other conditions, such as infection, which can get worse with GVHD treatment. More than one condition can occur at the same time. It is important to understand the histologic features of GVHD, drug toxicity, infection, and clinical factors surrounding patients, including timing of biopsy in relation to transplantation, medication history, and laboratory data. Rendering a correct diagnosis and generating a pathology report with standard language that can direct clinical management ensure proper management.

Mycophenolate mofetil toxicity mimicking acute cellular rejection in a small intestinal transplant

Mycophenolate mofetil (MMF) is an important medication used for maintenance immunosuppression in solid organ transplants. A common gastrointestinal (GI) side effect of MMF is enterocolitis, which has been associated with multiple histological features. There is little data in the literature describing the histological effects of MMF in small intestinal transplant (SIT) recipients. We present a case of MMF toxicity in a SIT recipient, with histological changes in the donor ileum mimicking persistent acute cellular rejection (ACR). Concurrent biopsies of the patient’s native colon showed similar changes to those from the donor small bowel, suggesting a non-graft specific process, raising suspicion for MMF toxicity. The MMF was discontinued and complete resolution of these changes occurred over three weeks. MMF toxicity should therefore be considered as a differential diagnosis for ACR and graft-versus-host disease in SITs.

Medication-associated gastrointestinal tract injury

Medication-associated gastrointestinal (GI) tract injury has been known for centuries for some medications. The more recently introduced biologicals are a class of drugs that constantly increases, and as such, the spectrum of GI tract side effects is steadily growing. This review covers not only long-known GI tract side effects of drugs but also those more recently described. A comprehensive but concise list of medications used in daily practice and associated with GI tract injury is presented.

Allograft biopsy findings in patients with small bowel transplantation

In this study, we sought to determine the incidence of post-transplant complications including acute cellular rejection (ACR), infection, and post-transplant lymphoproliferative disease (PTLD) in mucosal allograft biopsies in patients with small bowel transplant at our institution. We retrospectively reviewed pathology reports from 5675 small bowel allograft biopsies from 99 patients and analyzed the following: indications for biopsy, frequency and grade of ACR, the presence of infectious agents, results of workup for potential PTLD, results of C4d immunohistochemistry (IHC), features of chronic mucosal injury, and findings in concurrent native bowel biopsies. Findings from 42 allograft resection specimens were also correlated with prior biopsy findings. Indeterminate, mild, moderate, and severe ACR were seen in 276 (4.9%), 409 (7.2%), 100 (1.8%), and 207 (3.6%) of biopsies, respectively. Although ACR may show histologic overlap with mycophenolate mofetil toxicity, we found the analysis of concurrent native bowel biopsies to be helpful in this distinction. Adenovirus was the most common infectious agent seen (11%), and we routinely performed adenovirus IHC on biopsies. Eighteen patients (18%) developed PTLD, 83% of which were EBV associated, but only 28% of PTLD cases were diagnosed on mucosal allograft biopsies. C4d IHC did not correlate with the presence of donor-specific antibodies in limited cases.

Hepatitis C-induced hepatocyte apoptosis following liver transplantation is enhanced by immunosuppressive agents

In recurrent hepatitis C (HCV) post-liver transplantation (OLT), the combination of immunosuppressants and HCV is postulated to increase hepatocyte apoptosis and liver fibrosis. We evaluated hepatocyte apoptosis within the liver tissue of patients with postOLT HCV recurrence compared to HCV-negative individuals and correlated these findings with the effects of immunosuppressants on HCV-induced cell death and its inhibition in primary mouse hepatocytes (PMoH). Liver biopsies from patients with and without HCV were evaluated by immunohistochemistry for markers of apoptosis M30 CytoDEATH (M30) and cleaved PARP (clPARP). PMoH from C57BL/6 mice were infected with recombinant adenoviruses (rAdHCV) that expressed HCV proteins in hepatocytes. Infected cells were treated with cyclosporine, tacrolimus, sirolimus and/or MMF with or without pan-caspase inhibitor Q-VD-Oph. Cell viability and apoptosis were evaluated using crystal violet assays and Western immunoblots probed for cleaved caspase-3 (clCas3) and clPARP. Both M30 and clPARP were increased in the liver biopsies of patients with postOLT HCV recurrence compared to HCV-negative individuals. Treatment of rAdHCV-infected PMoH with cyclosporine, tacrolimus or sirolimus reduced cell viability and increased clCas3 and clPARP compared to rAdHCV infection alone. Addition of MMF to cyclosporine, tacrolimus or sirolimus further reduced cell viability and increased clCas3 and clPARP. Q-VD-Oph improved cell viability in HCV-infected PMoH treated with immunosuppressants alone and in combination and reduced clCas3 and clPARP by approximately 90%. Immunosuppressive agents, especially in combination, enhanced apoptosis in HCV-infected hepatocytes. The finding that Q-VD-Oph reversed hepatocyte death suggests that treatments utilizing apoptosis inhibition might reduce liver injury in postOLT HCV recurrence.

A four-drug combination therapy consisting of low-dose tacrolimus, low-dose mycophenolate mofetil, corticosteroids, and mizoribine in living donor renal transplantation: A randomized study

OBJECTIVE

We compared a three-drug combination therapy (control group) consisting of tacrolimus, mycophenolate mofetil, and corticosteroids in living donor renal transplantation with a four-drug combination therapy (study group), in which the doses of tacrolimus and mycophenolate mofetil were halved and the immunosuppressive drug mizoribine was added, in order to determine whether the incidence rates of acute rejection after transplantation between the study group and the control group are similar, whether the study group regimen prevents the occurrence of calcineurin inhibitor-induced renal damage, and whether the study group regimen prevents adverse effects such as diarrhea caused by mycophenolate mofetil.

METHODS

We investigated the incidence of acute rejection, serum creatinine levels, and estimated glomerular filtration rate and the incidence of adverse effects such as diarrhea.

RESULTS

There was no significant difference between the two groups in the incidence of acute rejection. Renal function (estimated glomerular filtration rate and serum creatinine) was maintained in the control group whereas in the study group renal function gradually improved, with a statistical difference observed at 12 months. The incidence of gastrointestinal symptoms including diarrhea was significantly higher in the control group than in the study group. There was no significant difference in the incidence of cytomegalovirus infection and other adverse effects.

CONCLUSION

These results suggest the study group therapy is an effective regimen in preventing acute rejection and the deterioration of renal function. These results also show this therapy can reduce the incidence of adverse effects such as gastrointestinal symptoms.

Olmesartan-associated sprue-like enteropathy: a systematic review with emphasis on histopathology

Sprue-like enteropathy associated with the angiotensin II receptor blocker (ARB) olmesartan was first described in 2012, and a number of cases have since been reported. This syndrome is characterized by severe diarrhea and sprue-like histopathologic findings in the intestine, often with increased subepithelial collagen. The incidence of this adverse drug reaction is not entirely clear, although it is thought to be rare. It is also not well established if other ARBs cause such a syndrome, although case reports suggest they can. The histopathologic features of olmesartan-related injury have only been described in a limited number of cases, and there are no guidelines regarding the histopathologic distinction of olmesartan-associated enteropathy from other causes of sprue (eg, celiac disease, tropical sprue). Herein, we review the histopathologic changes and clinical observations described in recent reports of olmesartan-associated sprue-like enteropathy comprising case series and isolated reports, other relevant literature, and our experience at a referral center specializing in small intestinal disorders. We will review recent literature suggesting other ARBs can be associated with a similar phenotype. Lastly, we will discuss the histopathologic differential diagnosis and provide clues to distinguish this entity from other entities which can cause sprue-like histopathology.

Effect of Immunosuppressive Agents on Hepatocyte Apoptosis Post-Liver Transplantation

INTRODUCTION

Immunosuppressants are used ubiquitously post-liver transplantation to prevent allograft rejection. However their effects on hepatocytes are unknown. Experimental data from non-liver cells indicate that immunosuppressants may promote cell death thereby driving an inflammatory response that promotes fibrosis and raises concerns that a similar effect may occur within the liver. We evaluated apoptosis within the liver tissue of post-liver transplant patients and correlated these findings with in vitro experiments investigating the effects of immunosuppressants on apoptosis in primary hepatocytes.

METHODS

Hepatocyte apoptosis was assessed using immunohistochemistry for M30 CytoDEATH and cleaved PARP in human liver tissue. Primary mouse hepatocytes were treated with various combinations of cyclosporine, tacrolimus, sirolimus, or MMF. Cell viability and apoptosis were evaluated using crystal violet assays and Western immunoblots probed for cleaved PARP and cleaved caspase 3.

RESULTS

Post-liver transplant patients had a 4.9-fold and 1.7-fold increase in M30 CytoDEATH and cleaved PARP compared to normal subjects. Cyclosporine and tacrolimus at therapeutic concentrations did not affect hepatocyte apoptosis, however when they were combined with MMF, cell death was significantly enhanced. Cell viability was reduced by 46% and 41%, cleaved PARP was increased 2.6-fold and 2.2-fold, and cleaved caspase 3 increased 2.2-fold and 1.8-fold following treatment with Cyclosporine/MMF and Tacrolimus/MMF respectively. By contrast, the sirolimus/MMF combination did not significantly reduce hepatocyte viability or promote apoptosis.

CONCLUSION

Commonly used immunosuppressive drug regimens employed after liver transplantation enhance hepatocyte cell death and may thus contribute to the increased liver fibrosis that occurs in a proportion of liver transplant recipients.

NIH Consensus development project on criteria for clinical trials in chronic graft-versus-host disease: II. The 2014 Pathology Working Group Report

The 2005 National Institute of Health (NIH) Consensus Conference outlined histopathological diagnostic criteria for the major organ systems affected by both acute and chronic graft-versus-host disease (GVHD). The 2014 Consensus Conference led to this updated document with new information from histopathological studies of GVHD in the gut, liver, skin, and oral mucosa and an expanded discussion of GVHD in the lungs and kidneys. The recommendations for final histological diagnostic categories have been simplified from 4 categories to 3: no GVHD, possible GVHD, and likely GVHD, based on better reproducibility achieved by combining the previous categories of "consistent with GVHD" and "definite GVHD" into the single category of "likely GVHD." Issues remain in the histopathological characterization of GVHD, particularly with respect to the threshold of histological changes required for diagnostic certainty. Guidance is provided for the incorporation of biopsy information into prospective clinical studies of GVHD, particularly with respect to biomarker validation.

Coeliac-like duodenal pathology in orthotopic liver transplant patients on mycophenolic acid therapy

AIMS

Diarrhoea following orthotopic liver transplantation (OLT) is a significant clinical problem associated with mycophenolic acid (MPA). The histological injury pattern associated with MPA in the large bowel is well documented in the literature; however, that in the duodenum is less extensively documented. The aim of this study was to investigate the histological spectrum of duodenal injury specifically in symptomatic OLT patients on MPA, and to compare this with the spectrum in patients with coeliac disease and in normal controls.

METHODS AND RESULTS

We reviewed our pathology database for all duodenal biopsies from patients on the OLT list over a period of 19 years. Medical records, anti-tissue transglutaminase IgA serology and histology were reviewed. Of the 667 patients who underwent endoscopy, 127 had duodenal biopsies (152 biopsies). Of these, 87.5% were normal. Sixteen showed abnormal histology, and seven (43.8%) of these were on MPA at the time of biopsy. Significant features included coeliac-like changes (shortened villi and increased intraepithelial lymphocyte counts), and novel findings included increased endocrine cell counts, apoptotic counts and lamina propria eosinophil counts in comparison with normal duodenal biopsies.

CONCLUSIONS

Pathologists should be aware of the features of MPA-associated duodenal injury, including coeliac-like changes and increased apoptotic counts. In those with abnormal histology, discontinuation or a reduction in the dose of MPA should be discussed.

Gastrointestinal pathology in transplant patients

The assessment of gastrointestinal (GI) specimens from transplant patients is complicated by the wide range of potentially rare pathologies that may be found in this clinical setting. Acute GI graft-versus-host disease (GvHD) is characterized by epithelial cell apoptosis, although there is increasing recognition that acute and/or chronic inflammation may also be present. By contrast, thus far there are no histological features known to be specific to chronic GI GvHD. Mycophenolate mofetil colitis may mimic both GvHD and inflammatory bowel disease, whereas both cytomegalovirus (CMV) and adenovirus infections can cause gland apoptosis. Post-transplant lymphoproliferative disorder should be considered if a Crohn's-like histological picture is seen, and granulomas in biopsies from umbilical cord blood recipients should raise a suspicion of cord colitis syndrome. Finally, the GI tract may be involved directly or indirectly by the disease that originally required haematopoietic stem cell or liver transplantation.

Recipient pretransplant inosine monophosphate dehydrogenase activity in nonmyeloablative hematopoietic cell transplantation

Mycophenolic acid, the active metabolite of mycophenolate mofetil (MMF), inhibits inosine monophosphate dehydrogenase (IMPDH) activity. IMPDH is the rate-limiting enzyme involved in de novo synthesis of guanosine nucleotides and catalyzes the oxidation of inosine 5'-monophosphate to xanthosine 5'-monophosphate (XMP). We developed a highly sensitive liquid chromatography-mass spectrometry method to quantitate XMP concentrations in peripheral blood mononuclear cells (PMNCs) isolated from the recipient pretransplant and used this method to determine IMPDH activity in 86 nonmyeloablative allogeneic hematopoietic cell transplantation (HCT) patients. The incubation procedure and analytical method yielded acceptable within-sample and within-individual variability. Considerable between-individual variability was observed (12.2-fold). Low recipient pretransplant IMPDH activity was associated with increased day +28 donor T cell chimerism, more acute graft-versus-host disease (GVHD), lower neutrophil nadirs, and more cytomegalovirus reactivation but not with chronic GVHD, relapse, nonrelapse mortality, or overall mortality. We conclude that quantitation of the recipient's pretransplant IMPDH activity in PMNC lysate could provide a useful biomarker to evaluate a recipient's sensitivity to MMF. Further trials should be conducted to confirm our findings and to optimize postgrafting immunosuppression in nonmyeloablative HCT recipients.

The challenging diagnosis of Cronkhite-Canada syndrome in the upper gastrointestinal tract: a series of 7 cases with clinical follow-up

Cronkhite-Canada syndrome is a rare protein-losing enteropathy, classically characterized by ectodermal changes and gastrointestinal polyposis. The etiology remains obscure but immune dysregulation may be important. The diagnosis of Cronkhite-Canada syndrome in the upper gastrointestinal tract is challenging, frequently resulting in delayed patient management. In this study, we described the initial clinical presentations, upper gastrointestinal endoscopic appearances, clinical follow-up, and histologic diagnoses in 7 patients who were subsequently diagnosed with Cronkhite-Canada syndrome. Histology slides were reviewed, and IgG4 immunohistochemical analysis was performed. The most common initial endoscopic impressions were antral malignancy and gastric infection, but gastroduodenal polyposis was not described. On histologic review, the main findings in the gastric mucosa were a prominent mucosal edema, a mixed inflammatory infiltrate rich in eosinophils, and architectural changes with gland dilatation and withering. In the duodenal mucosa, total or subtotal duodenal villous atrophy, inflammation, crypt distortion, and increased apoptotic bodies were the most common features. Three patients died of the disease, and 4 patients were asymptomatic at a mean follow-up of 3.5 years. No intestinal malignancy had been diagnosed. In 2 patients foci of dysplasia in colonic polyps were identified. In only 1 patient, a significant increase in IgG4-positive plasma cells was observed in a colonic polyp. In summary, we found that patients with Cronkhite-Canada syndrome have histologic features commonly found in other immune disorders of the gastrointestinal tract that may help in establishing the diagnosis and further supports the hypothesis that Cronkhite-Canada syndrome may represent an immune dysregulation syndrome, different from IgG4-related disease.

Non-reflux esophagitis: a review of inflammatory diseases of the esophagus exclusive of reflux esophagitis

Esophagitis is a frequent cause of clinical symptoms and is often an indication for upper endoscopy. Mucosal biopsies are procured for diagnostic purposes and may be used to assess the efficacy of treatment, as in patients with eosinophilic esophagitis. This article outlines salient clinical and pathologic features of diseases that cause esophagitis exclusive of reflux esophagitis.

A practical approach to small bowel biopsy interpretation: celiac disease and its mimics

While celiac disease is the most common cause of villous remodeling and intraepithelial lymphocytosis in the proximal small bowel, there are many entities that can mimic its histologic appearance. The purpose of this review is to discuss normal small bowel histology and the differential diagnosis of celiac disease. Approaches to evaluate increased intraepithelial lymphocytes are presented, followed by a detailed discussion of the pathology of celiac disease. Particular emphasis is given to those conditions that cause intraepithelial lymphocytosis in the setting of preserved villous architecture, although other important entities, such as peptic injury, idiopathic inflammatory bowel disease, medication injury, eosinophilic (allergic) gastroenteritis, autoimmune enteropathy, common variable immunodeficiency, and infections are also reviewed.

Mycophenolic acid mediated disruption of the intestinal epithelial tight junctions

Gastrointestinal toxicity is a common adverse effect of mycophenolic acid (MPA) treatment in organ transplant patients, through poorly understood mechanisms. Phosphorylation of myosin light chain 2 (MLC2) is associated with epithelial tight junction (TJ) modulation which leads to defective epithelial barrier function, and has been implicated in GI diseases. The aim of this study was to investigate whether MPA could induce epithelial barrier permeability via MLC2 regulation. Caco-2 monolayers were exposed to therapeutic concentrations of MPA, and MLC2 and myosin light chain kinase (MLCK) expression were analyzed using PCR and immunoblotting. Epithelial cell permeability was assessed by measuring transepithelial resistance (TER) and the flux of paracellular permeability marker FITC-dextran across the epithelial monolayers. MPA increased the expression of MLC2 and MLCK at both the transcriptional and translational levels. In addition, the amount of phosphorylated MLC2 was increased after MPA treatment. Confocal immunofluorescence analysis showed redistribution of TJ proteins (ZO-1 and occludin) after MPA treatment. This MPA mediated TJ disruption was not due to apoptosis or cell death. Additionally ML-7, a specific inhibitor of MLCK was able to reverse both the MPA mediated decrease in TER and the increase in FITC-dextran influx, suggesting a modulating role of MPA on epithelial barrier permeability via MLCK activity. These results suggest that MPA induced alterations in MLC2 phosphorylation and may have a role in the patho-physiology of intestinal epithelial barrier disruption and may be responsible for the adverse effects (GI toxicity) of MPA on the intestine.

A four-year pathology review of the near total face transplant

In December of 2008, our institution performed a near total face transplant. The patient was monitored for signs of rejection assessed by paired skin and mucosa biopsies. The results of histological review of 120 biopsies collected during the first 4 years posttransplant are discussed. All biopsies were stained with hematoxylin and eosin, periodic acid-Schiff, immunohistochemical and TUNEL assays and graded using the Banff 2007 classification. Grade III rejection was diagnosed clinically at weeks 45 and 66, posttransplant; week 45 was determined as folliculitis while the erythema episode at week 66 confirmed an acute rejection (AR) that required hospitalization. The mucosa frequently showed interface inflammation without clinical signs of rejection and was not present in skin biopsies. In all, 34 of the 45 mucosal biopsies (75%) showed these interface changes. Clinical symptoms concurred with skin pathology in two grade III rejections. The mucosa showed histologic signs of rejection more frequently, which may indicate: increased mucosal sensitivity to rejection, a different type or subtype of AR that is specific to the mucosa, or a nonspecific process such as a drug effect. With more data and world experience, the diagnosis of face transplant rejection will be better defined and the Banff classification enhanced.