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]

Histological spectrum of mycophenolate mofetil-related colitis: association with apoptosis

AIMS

The main purpose of this study was to define diagnostic histological characteristics of mycophenolate mofetil (MMF)-related colitis in association with crypt epithelial cell turnover.

METHODS AND RESULTS

The examined material included 43 colonic biopsies from renal transplant recipients with MMF administration and persistent diarrhoea. Thirty-three cases showed MMF-related colitis, while 10 showed no significant changes. The histological findings were scored and correlated with the apoptotic index (AI) and with the proliferation rate (PR) of the crypt epithelium examined by TUNEL assay and Ki-67 immunoexpression. Ten cases of Crohn disease and 10 of ulcerative colitis were used as comparative groups. Crypt distortion and loss as well as increased apoptosis constituted the main features, their degree and combination leading either to an inflammatory bowel disease (IBD)-like (82%) or to a graft-versus-host disease-like pattern (18%). A high AI was associated more frequently with moderate and severe crypt distortion, while the values were significantly higher compared with the control groups (P < 0.01). High PR was noted in 18 of 29 (62.1%) of the cases.

CONCLUSIONS

The diagnostic hallmark of MMF-related colitis is an IBD-like histological pattern in association with increased epithelial apoptosis, while apoptotic cell death seems to be a potential pathogenetic factor of mucosa injury.

Histopathological Changes in the Gastrointestinal Tract Due to Medications

In keeping with the stated goal of providing the surgical pathologist with tools to recognize abnormalities of the gastrointestinal (GI) tract due to drugs (AGIDS), in part II of this review we embark in a more organ-based description of AGIDS. Adequate space is given to the numerous adverse gastrointestinal effects of nonsteroidal anti-inflammatory drugs. Pill esophagitis, esophagitis dissecans, proton pump inhibitors’ effects, diaphragm disease, and the recently described effects of drugs such as olmesartan, mycophenolate, and of compounds such as yttrium-90 are highlighted among several others. The inclusion of drug effects in the differential diagnosis of “conventional” diseases (such as gastric antral vascular ectasia, graft-versus-host disease, ischemic colitis, acute colitis, collagenous enteritis, inflammatory bowel disease) is underscored to avoid sometimes significant diagnostic pitfalls. We reiterate the message of the necessary collaboration between pathologist and clinician in the recognition of these entities to provide the best patient care.

Mycophenolic acid glucuronide is transported by multidrug resistance-associated protein 2 and this transport is not inhibited by cyclosporine, tacrolimus or sirolimus

1. The purpose of this study was to investigate the contribution of MRP2 to the efflux of mycophenolic acid (MPA), and its phenyl glucuronide (MPAG) and acyl glucuronide (AcMPAG) metabolites, using Madin-Darby canine kidney II cells stably transfected with human MRP2 gene (MDCKII/MRP2 cells). 2. Compared to parental MDCKII cells, MPAG was significantly translocated from basolateral (BL) to apical (AP) side in MDCKII/MRP2 cells, indicating MPAG is a substrate for MRP2. AcMPAG is highly translocated from BL to AP side in both cells, suggesting that AcMPAG is actively secreted possibly through an efflux transporter other than MRP2. Appreciable translocation of MPA was not observed in MDCKII/MRP2 cells. 3. Furthermore, using MRP2-expressing Sf9 membrane vesicles, the Michaelis-Menten constant (Km) value for MRP2-mediated MPAG transport was calculated at 224.2 ± 42.7 µM. In the vesicle system, cyclosporine, tacrolimus and sirolimus did not inhibit the uptake of MPAG via MRP2. 4. These findings indicate that only MPAG not MPA and AcMPAG is a substrate for MRP2 and that the interaction between MPAG and concomitantly administered immunosuppressive agents does not occur at MRP2 level.

Crypt apoptotic count reproducibility in small bowel allograft biopsies

Enumeration of crypt apoptotic bodies (AB) is used in the diagnosis of acute cellular rejection (ACR) in small bowel allografts. Due to differing definitions, there is a potential for variation in AB numbers between pathologists that may affect diagnosis. Thirty biopsies from allografts were obtained: 10 negative for ACR, 10 indeterminate, and 10 with mild ACR. Three pathologists blindly reviewed each case twice and counted the maximal AB number per 10 crypts. Intraobserver kappa ranged from 0.423 to 0.913 and interobserver kappa from 0.478 to 0.686 depending on AB definition. Intraobserver diagnosis agreement based on classical AB number occurred in 81 of 90 instances (90%) and in 77 of 90 using the liberal definition (85%), P < .01). There was substantial intraobserver and moderate to substantial interobserver agreement in crypt AB counts. However, both intraobserver and interobserver variability would have led to diagnostic discrepancies in a small subset of cases.

Enhanced apoptosis in post-liver transplant hepatitis C: Effects of virus and immunosuppressants

Hepatitis C (HCV)-infected patients have a poorer survival post-liver transplantation compared to patients transplanted for other indications, since HCV recurrence post-transplant is universal and commonly follows an aggressive course. There is increasing evidence that in the non-transplant setting, induction of hepatocyte apoptosis is one of the main mechanisms by which HCV drives liver inflammation and fibrosis, and that HCV proteins directly promote apoptosis. Recent studies have shown that post-liver transplant, there is a link between high levels of HCV replication, enhanced hepatocyte apoptosis and the subsequent development of rapidly progressive liver fibrosis. Although the responsible mechanisms remain unclear, it is likely that immunosuppressive drugs play an important role. It is well known that immunosuppressants impair immune control of HCV, thereby allowing increased viral replication. However there is also evidence that immunosuppressants may directly induce apoptosis and this may be facilitated by the presence of high levels of HCV replication. Thus HCV and immunosuppressants may synergistically interact to further enhance apoptosis and drive more rapid fibrosis. These findings suggest that modulation of apoptosis within the liver either by changing immunosuppressive therapy or the use of apoptosis inhibitors may help prevent fibrosis progression in patients with post-transplant HCV disease.

Lymphocyte counts in kidney allograft recipients are associated with IMPDH2 3757T>C gene polymorphism

Inosine monophosphate dehydrogenase (IMPDH), the rate-limiting enzyme for de novo synthesis of guanine nucleotides, is required for lymphocyte proliferation. Inhibition of IMPDH by mycophenolic acid (MPA) constitutes part of an immunosuppressive therapy in kidney allograft recipients. The 3757T>C polymorphic variant (rs11706052) of the IMPDH2 gene, which encodes 1 of 2 IMPDH isoenzymes, has been associated with increased IMPDH activity and reduced ability of MPA to exert antiproliferative effects on lymphocytes. The association of IMPDH2 3757T>C SNP with posttransplant courses of kidney allograft recipients remains unclear. Therefore, the aim of the present study was to evaluate associations between this single nucleotide polymorphism and common posttransplant complications among Polish kidney allotransplant recipients. We observed that the frequency of IMPDH2 3757C allele in this group (n=177) did not differ significantly from a control cohort representing the background population of Poland (n=550). There were no significant differences between patients carrying the IMPDH2 3757CT and TT genotypes with respect to acute rejection risk, neutropenia, or incidences of serious infections or gastrointestinal side effects. However, we noted that the 3757C allele was associated with higher lymphocyte counts and a reduced incidence of lymphopenia among kidney allograft recipients. Our findings may be of practical significance to tailor immunosuppressive regimens in kidney transplant recipients.

Duodenal villous atrophy: a cause of chronic diarrhea after solid-organ transplantation

Persistent diarrhea is commonly observed after solid organ transplantation (SOT). A few cases of mycophenolate mofetil (MMF)-induced duodenal villous atrophy (DVA) have been previously reported in kidney-transplant patients with chronic diarrhea. Herein, we report on the incidence and characteristics of DVA in SOT patients with chronic diarrhea. One hundred thirty-two SOT patients with chronic diarrhea underwent an oesophago-gastroduodenoscopy (OGD) and a duodenal biopsy after classical causes of diarrhea have been ruled out. DVA was diagnosed in 21 patients (15.9%). It was attributed to mycophenolic acid (MPA) therapy in 18 patients (85.7%) (MMF [n = 14] and enteric-coated mycophenolate sodium [n = 4]). MPA withdrawal or dose reduction resulted in diarrhea cessation. The incidence of DVA was significantly higher in patients with chronic diarrhea receiving MPA compared to those who did not (24.6% vs. 5.1%, p = 0.003). DVA was attributed to a Giardia lamblia parasitic infection in two patients (9.5%) and the remaining case was attributed to azathioprine. In these three patients, diarrhea ceased after metronidazole therapy or azathioprine dose reduction. In conclusion, DVA is a frequent cause of chronic diarrhea in SOT recipients. MPA therapy is the most frequent cause of DVA. An OGD should be proposed to all transplant recipients who present with persistent diarrhea.

Characterization of Epithelial Apoptosis in Biopsies of Small-Bowel Allografts Using Cleaved Caspase 3 Immunostaining

Background. The diagnosis of acute cellular rejection (ACR) in small-bowel allograft biopsies depends in part on quantification of crypt apoptotic bodies (ABs). The definition of ABs varies between authors. Recently, immunoperoxidase stains specific for apoptotic material have been used in paraffin-embedded tissue. The aim was to characterize AB morphology and quantify ABs using immunoperoxidase and hematoxylin and eosin (H&E) staining. Methods. Allograft biopsies with diagnoses of negative for ACR, indeterminate for ACR, and mild ACR were selected. Sections were stained for cleaved caspase 3 (CC3). The number of ABs per 10 crypt epithelial cells was compared by H&E and CC3 staining. Results. A total of 39 cases (15 negative, 12 indeterminate, 12 mild ACR) were obtained. CC3 staining revealed that ABs varied from well-developed “classical” exploding crypt cells to intraepithelial clusters of basophilic material. In 61%, the number detected by CC3 was higher than on H&E stains (mean 4.30 and 3.56; P < .002), with good overall correlation. With the latter definition, AB numbers by H&E were significantly higher in most cases (72%), with the diagnosis of mild ACR being downgraded in 50% if only classical ABs were counted. Conclusions. ABs have a range of morphology in biopsies of intestinal allografts, and H&E identifies the majority. The results suggest that AB counts should include basophilic clusters.

The impact of histopathologic examination of graft-versus-host disease in the era of reduced-intensity conditioning regimen: a study from the Gruppo Italiano Trapianto di Midollo Osseo

Reduced-intensity conditioning regimens have reshaped the clinical presentation of graft-versus-host disease after hematopoietic stem cell transplants. However, histopathologic features of graft-versus-host disease following reduced-intensity conditioning regimens have not been fully characterized. In a series of 112 biopsies (skin, n = 60; gastrointestinal [GI] tract, n = 44; liver, n = 8), we described the morphologic profile of graft-versus-host disease following reduced-intensity conditioning and investigated whether histopathologic changes of graft-versus-host disease following reduced-intensity conditioning have a diagnostic and/or prognostic value. Forty-four patients (49.5%) experienced acute graft-versus-host disease, 2 (2.2%) late-onset acute graft-versus-host disease (grade I, n = 13; grade II-IV, n = 33), 24 (27.0%) chronic graft-versus-host disease (de novo n = 12, progressive n = 12) and 19 (21.3%) overlap syndrome. In the skin, we observed: (i) phase-nonspecific changes, such as acute graft-versus-host disease features in chronic graft-versus-host disease patients (n = 4/24; 16.6%), (ii) subtle alterations such as superficial fibrosis in widened dermal papillae (n = 8), in acute graft-versus-host disease/late-onset graft-versus-host disease (n = 6/46; 13.0%) or chronic graft-versus-host disease (n = 2/24, 8.3%) patients, and (iii) features of chronic and acute graft-versus-host disease coexisting in the same specimen in overlap syndrome (n = 3/19; 15.7%). In the GI tract, we did not demonstrate peculiar features differing from those commonly observed in the myeloablative setting. By univariate analysis, a reduced overall survival was associated with graft-versus-host disease type (chronic graft-versus-host disease P = .006, acute graft-versus-host disease P = .03), older age (P = .04), and histopathologic diagnosis of "consistent with" + definite graft-versus-host disease (P = .02). Histopathologic diagnosis retained an independent prognostic value by multivariate analysis (P = .01). The present study indicates that pathologists should be aware of the peculiar morphologic changes of cutaneous graft-versus-host disease following reduced-intensity conditioning and further recommends histopathology in the diagnostic workup of graft-versus-host disease in patients undergoing reduced-intensity conditioning regimen.