Recent Progress in Cell Therapy in Solid Organ Transplantation

There has been ample of preclinical and animal studies showing efficacy and safety of using various cells, such as stem cells or T regulatory cells, after transplantation for tissue repair, immunosuppression or tolerance induction. However, there has been a significant progress recently using cell therapy in solid organ transplantation in small clinical trials. Recent results have been promising and using cell therapy in solid organ transplantation seems feasible and safe. However, there are more hurdles to overcome such as dose and timing of the infusions. Current studies mainly focused on live donor kidney transplantation. Expansion of current regimes to other organs and deceased donor transplantation would be crucial.

Outcomes of Full-Right-Full-Left Split Liver Transplantation in Adults in the USA: A Propensity-Score Matched Analysis

BACKGROUND

Splitting a liver for utilization in adult/pediatric recipients has been shown to decrease mortality on the wait list without increasing the overall risk of long-term graft failure compared to a whole graft. However, splitting a single donor organ for two adult recipients, full-right-full-left split liver transplantation (FRFLSLT), to overcome organ shortage is still considered controversial.

OBJECTIVE

This study assessed the outcome of FRFLSLT comparing full-right (FR) and full-left (FL) with whole liver (WL) allografts in adults (1998-2010) using UNOS standard transplant analysis and research (STAR) file. Methods: Unadjusted allograft and patient survival were estimated using Kaplan-Meier survival curves. Adjusted analyses of survival were conducted controlling for propensity for WL allograft.

RESULTS

There were 83,313 cases of WL, 651 FR and 117 FL. Significant differences were evident in the unadjusted cohort between recipients who received FR and FL including donor, cold ischemic time, and days on transplant waiting list. Use of FL allograft resulted in a trend toward lower graft and patient survival compared to WL and FR, which was not statistically significant (p=0.07). In the matched cohort, FL hemiliver allograft had no detrimental effect on the allograft or patient survival after split liver transplantation when compared to FR and WL.

CONCLUSION

After adjusting for donor and recipient characteristics, there was no difference in allograft or patient survival with the use of FL, FR, or WL after liver transplantation in adults. FRFLSLT is a valuable and safe option to expand the donor pool.

Mesenchymal Stem Cells and Co-stimulation Blockade Enhance Bone Marrow Engraftment and Induce Immunological Tolerance

BACKGROUND

Organ transplantation currently requires long-term immunosuppression. This is associated with multiple complications including infection, malignancy and other toxicities. Immunologic tolerance is considered the optimal solution to these limitations.

OBJECTIVE

To develop a simple and non-toxic regimen to induce mixed chimerism and tolerance using mesenchymal stem cell (MSC) in a murine model.

METHODS

Wild type C57BL6 (H2D(k)) and Bal/C (H2D(d)) mice were used as donors and recipients, respectively. We studied to achieve tolerance to skin grafts (SG) through mixed chimerism (MC) by simultaneous skin graft and non-myeloablative donor bone marrow transplantation (DBMT) +/- MSC. All recipients received rapamycin and CTLA-4 Ig without radiation.

RESULTS

DBMT+MSC combined with co-stimulation blockage and rapamycin led to stable mixed chimerism, expansion of Tregs population and donor-specific skin graft tolerance. The flow cytometry analysis revealed that recipient mice developed 15%-85% chimerism. The skin allografts survived for a long time. Elimination of MSC failed to induce mixed chimerism and tolerance.

CONCLUSION

Our results demonstrate that donor-specific immune tolerance can be effectively induced by non-myeloablative DBMT-MSC combination without any additional cytoreductive treatment. This approach provides a promising and non-toxic allograft tolerance strategy.

Competitive Market Analysis of Transplant Centers and Discrepancy of Wait-Listing of Recipients for Kidney Transplantation

BACKGROUND

There are over 250 kidney transplant programs in the USA.

OBJECTIVE

To determine if highly competitive regions, defined as regions with a higher number of transplant centers, will approve and wait-list more end-stage renal disease (ESRD) candidates for transplant despite consistent incidence and prevalence of ESRD nationwide.

METHODS

ESRD Network and OPTN data completed in 2011 were obtained from all transplant centers including listing data, market saturation, market share, organs transplanted, and ESRD prevalence. Herfindahl-Hirschman Index (HHI) was used to measure the size of firms in relation to the industry to determine the amount of competition.

RESULTS

States were separated into 3 groups (HHI<1000 considered competitive; HHI 1000-1800 considered moderate competition; and HHI>1800 considered highly concentrated). The percentage of ESRD patients listed in competitive, moderate, and highly concentrated regions were 19.73%, 17.02%, and 13.75%, respectively. The ESRD listing difference between competitive versus highly concentrated was significant (p<0.05).

CONCLUSION

When there is strong competition without a dominant center as defined by the HHI, the entire state tends to list more patients for transplant to drive up their own center's market share. Our analysis of the available national data suggests a discrepancy in access for ESRD patient to transplantation due to transplant center competition.

Challenges of organ shortage for transplantation: solutions and opportunities

Organ shortage is the greatest challenge facing the field of organ transplantation today. A variety of approaches have been implemented to expand the organ donor pool including live donation, a national effort to expand deceased donor donation, split organ donation, paired donor exchange, national sharing models and greater utilization of expanded criteria donors. Increased public awareness, improved efficiency of the donation process, greater expectations for transplantation, expansion of the living donor pool and the development of standardized donor management protocols have led to unprecedented rates of organ procurement and transplantation. Although live donors and donation after brain death account for the majority of organ donors, in the recent years there has been a growing interest in donors who have severe and irreversible brain injuries but do not meet the criteria for brain death. If the physician and family agree that the patient has no chance of recovery to a meaningful life, life support can be discontinued and the patient can be allowed to progress to circulatory arrest and then still donate organs (donation after circulatory death). Increasing utilization of marginal organs has been advocated to address the organ shortage.

Outcomes of patients with portal vein thrombosis undergoing live donor liver transplantation

BACKGROUND

Live donor liver transplantation (LDLT) for patients with portal vein thrombosis (PVT) creates several technical challenges due to severe pre-operative condition and extensive collaterals. Although deceased donor liver transplantation in patients with PVT is now routinely performed at most centers, the impact of PVT on LDLT outcomes is still controversial.

OBJECTIVE

To determine the outcome of patients with PVT who underwent LDLT.

METHODS

We reviewed the outcome of adult patients with PVT who underwent LDLT in the USA from 1998 to 2009.

RESULTS

68 (2.9%) of 2402 patients who underwent LDLT had PVT. Comparing patients with and without PVT who underwent LDLT, those with PVT were older (53 vs 50 yrs), more likely to be male, had longer length of stay (25 vs 18 days) and higher retransplantation rate (19% vs 10.7%). The allograft and patient survival was lower in patients with PVT. In Cox regression analysis, PVT was associated with worse allograft survival (HR=1.7, 95% CI: 1.1-2.5, p<0.001) and patient survival (HR=1.6, 95% CI: 1.2-2.4, p<0.001) than patients without PVT.

CONCLUSIONS

Patients with PVT who underwent LDLT had a worse prognosis than those without PVT.

Clinical transplantation and tolerance: are we there yet?

Organ transplantation is not only considered as the last resort therapy but also as the treatment of choice for many patients with end-stage organ damage. Recipient-mediated acute or chronic immune response is the main challenge after transplant surgery. Nonspecific suppression of host immune system is currently the only method used to prevent organ rejection. Lifelong immunosuppression will cause significant side effects such as infections, malignancies, chronic kidney disease, hypertension and diabetes. This is more relevant in children who have a longer life expectancy so may receive longer period of immunosuppressive medications. Efforts to minimize or complete withdrawal of immunosuppression would improve the quality of life and long-term outcome of pediatric transplant recipients.

Living Donor Liver Transplantation for Hepatocellular Carcinoma: It Is All about Donors?

BACKGROUND

Live-donor liver transplantation (LDLT) is a valuable option for patients with hepatocellular carcinoma (HCC) as compared with deceased-donor liver transplantation (DDLT); the tumor could be eradicated early.

METHODS

Herein, we reviewed the outcome of adult patients with HCC who underwent LDLT from 1990 to 2009 in the USA, as reported to United Network for Organ Sharing.

RESULTS

Compared to DDLT (n=5858), patients who underwent LDLT for HCC (n=170) were more likely to be female (43.8% vs 23.8%), younger (mean age 48.6 vs 54.9 years) and have more tumors outside Milan criteria (30.7% vs 13.6%). However, the recipients of LDLT for HCC had a significantly shorter mean wait time before transplantation (173 vs 219 days; p=0.04). The overall allograft and patient survival were not different, though more patients in LDLT group were outside Milan criteria. Since implementation of the MELD exception for HCC, DDLT for HCC has increased form 337 (2.3%) cases in 2002 to 1142 (18.7%) in 2009 (p<0.001). However, LDLT for HCC has remained stable from 16 (5.7%) in 2002 to 14 (9.2%) in 2009 (p=0.1). Regions 1, 5 and 9 had the highest rate of LDLT for HCC compared to other regions.

CONCLUSIONS

LDLT can achieve the same long-term outcomes compared to DDLT in patients with HCC. The current MELD prioritization for HCC reduces the necessity of LDLT for HCC except in areas with severe organ shortage.

Improving Outcomes of Liver Transplantation for Polycystic Disease in MELD Era

BACKGROUND

Liver transplantation (LT) for polycystic liver disease (PLD) has evolved to be an option for treating these patients. Patients with PLD suffer from incapacitating symptoms because of very large liver volumes but liver function is preserved until a late stage.

OBJECTIVE/METHODS

Herein, we reviewed the outcome of adult patients with PLD who underwent LT in the US comparing pre-MELD (1990-2001) to MELD era (2002-2009).

RESULTS

During this period, only 309 patients underwent LT for PLD. The number of LT for PLD is very low comparing the two eras. The percentage of patients who had combined liver and kidney transplantation (CLKT) for this disease has not changed during MELD era (42.8% vs 38.6%). The waiting time for LT (337 vs 272 days) and CLKT (289 vs 220) has increased in MELD era (p<0.001). In MELD era, 53.4% of LT and 31.2% of CLKT were done as MELD exceptional cases. The allograft and patent survival have significantly improved in MELD era.

CONCLUSION

Patients with PLD had marked improvement of their outcomes after LT in MELD era.

Liver transplantation from hepatitis B surface antigen-positive donors

One possibility to increase the organ pool is to use grafts from hepatitis B virus (HBV) surface antigen (HBsAg)-positive donors, but few data are currently available in this setting. Herein, we reviewed the outcome of 92 liver transplantations using allografts from HBsAg-positive donors in the United States (1990-2009). They had experienced HBV-related (n = 68) or HBV-unrelated disease (n = 24). There was no difference between patients who received HBsAg-positive versus HBsAg-negative allografts based on age, Model for End-stage Liver Disease (MELD) score, length of stay, wait time, and donor risk index. HBsAg-positive allografts were more likely to be imported and used in MELD exceptional cases. Allograft and patient survival were comparable between the two groups. HBsAg-positive allografts deserve consideration when no other organ is available in a suitable waiting time in the present era of highly effective antiviral therapy.

Current status of pancreas and islet cell transplantation

Pancreas transplantation has emerged as an effective treatment for patients with diabetes mellitus, especially those with established end-stage renal disease. Surgical and immunosuppressive advances have significantly improved allograft survival. The procedure reduces mortality compared with diabetic kidney transplant recipients and wait listed patients. Improvements in diabetic nephropathy and retinopathy have also been demonstrated. Pancreas transplantation can improve cardiovascular risk profiles, improve cardiac function and decrease cardiovascular events. Lastly, improvements in diabetic neuropathy and quality of life can result from pancreas transplantation. Pancreas transplantation remains the most effective method to establish durable euglycemia for patients with diabetes mellitus.

Liver Transplantation in Patients with Portal Vein Thrombosis: Comparing Pre-MELD and MELD era

BACKGROUND

Portal vein thrombosis (PVT) used to be a relative contraindication for liver transplantation (LT). This obstacle has been dealt with following the improvement of LT-related techniques.

OBJECTIVE

To compare the outcome of adult patients with PVT who underwent LT before and after adopting MELD.

METHODS

We retrospectively searched our database for deceased donor LT recipients who had PVT, were operated between 1990 and 2009, and were 18 years old or more. The outcome of patients operated in pre-MELD era (1990-2001) was then compared with that of those operated in MELD era (2002-2009).

RESULTS

The incidence of patients undergoing LT with PVT has increased from 1.2% (491/40,730) in pre-MELD era to 6% (2540/42,601) in MELD era (p<0.01). Patients with PVT in MELD era were older (53.6 vs 50.5), had higher calculated MELD (21.3 vs 18.9), shorter length of hospital stay after LT (25 vs 21.7 days), more likely to develop HCC (14.8% vs 0), and more likely to receive DCD allograft (3.9% vs 0.8%). Donor risk indices were comparable in both groups (1.9 vs 1.9). The median waiting time before transplantation decreased during MELD era (71 vs 99 days). Allograft and patients survival was comparable between the two eras. However, allograft and patients survival rates were lower in patients with PVT compared to those without. In Cox regression analysis, PVT was associated with worse allograft (HR=1.3, 95% CI: 1.2-1.4, p<0.001) and patient survival (HR=1.3, 95% CI: 1.2-1.5, p<0.001) compared to non-PVT patients.

CONCLUSIONS

The incidence of patients with PVT has increased in MELD era without improvement in outcomes. Donor and recipients characteristics changed in MELD era. PVT is still associated with poor outcomes compared to patients without PVT.

Changing pattern of organ donation and utilization in the USA

BACKGROUND

Organ transplantation has proven highly effective in the treatment of various forms of end-stage organ failure. However, organ shortage is still the greatest challenge facing the field of organ transplantation.

OBJECTIVE

To assess the pattern of organ donation and utilization during the past decade in the USA.

METHODS

We studied OPTN/UNOS database for organ donation between January 2000 and December 2009. The retrieved records were then categorized into two time periods-from January 2000 to December 2004 (era 1), and from January 2005 to December 2009 (era 2).

RESULTS

There were 65,802 living and 71,401 deceased donors in the US from 2000 to 2009, including 66,518 (93.2%) brain-dead donors and 4,883 (6.8%) donation after cardiac death. Comparing two periods-from January 2000 to December 2004 (era 1) and from January 2005 to December 2009 (era 2), the number of deceased donors increased by 25% from 31,692 to 39,709 and living donors decreased by 7.6%. Donation after cardiac death increased from 3.5% to 9.3%. The portion of donors older than 64 years increased from 6.9% in era 1 to 11.3% in era 2 (p=0.03). The number of donors with a body mass index of >35 kg/m(2) was also increased from 6.8% to 11.2%. A significant increase in the incidence of cardiovascular/cerebrovascular as cause of death was also noted from 38.1% in era 1 to 56.1% in era 2 (p<0.001), as was a corresponding decrease in the incidence of death due to head trauma (34.9% vs. 48.8%). The overall discard rate also increased by 41% from 13,411 in era 1 to 19,516 in era 2. This increase in discards was especially more prominent in donation after cardiac death group which rose by 374% from 440 in era 1 to 2,089 in era 2. The discard rate for livers and kidneys increased by 31% and 68%, respectively, comparing era 1 and era 2. We noted a 78% increase for discarded donation after cardiac death livers and 1,210% for discarded donation after cardiac death kidneys.

CONCLUSION

We detected significant changes in the make-up of the donor pool over the past decade in the US. Over time, donor characteristics have changed with increased numbers of elderly donors and donors with comorbidities, especially donors who died of cardiovascular/cerebrovascular disease. The incidence of donation after cardiac death has increased significantly; brain-dead donors have only increased slightly and living donors have decreased. As the result, the discard rates have increased. The transplant community and policy makers should consider every precaution to safeguard the donor pool and prevent the decay of organ quality in favor of quantity.

Changing pattern of organ donation at a single center: are potential brain dead donors being lost to donation after cardiac death?

Donation after cardiac death (DCD) has proven effective at increasing the availability of organs for transplantation.We performed a retrospective examination of Massachusetts General Hospital (MGH) records of all 201 donors from 1/1/98 to the 11/2008, including 54 DCD, 115 DBD and 32 DCD candidates that did not progress to donation (DCD-dnp). Comparing three time periods, era 1 (01/98-12/02), era 2 (01/03-12/05) and era 3 (01/06-11/08), DCD’s comprised 14.8,48.4% and 60% of donors, respectively (p = 0.002). A significant increase in the incidence of cardiovascular/cerebrovascular as cause of death was evident in era 3 versus eras 1 and 2; 74% versus 57.1% (p<0.001),as was a corresponding decrease in the incidence of traumatic death. Interestingly, we noted an increase in utilization of aggressive neurological management over time, especially in the DCD group.We detected significant changes in the make-up of the donor pool over the past decade. That the changes in diagnosis over time did not differ between DCD and DBD groups suggests this difference is not responsible for the increase in DCD rates. Instead, we suggest that changes in clinical practice, especially in management of patients with severe brain injury may account for the increased proportion of DCD.

Live donor partial hepatectomy for liver transplantation: is there a learning curve?

BACKGROUND

Donor safety is the first priority in living donor liver transplantation (LDLT).

OBJECTIVE

To determine the characteristics and outcome of live liver donors who underwent donor hepatectomy from January, 1997 to May, 2007 at Massachusetts General Hospital.

METHODS

30 patients underwent LDLT between January, 1997 and May, 2007 at our institution.

RESULTS

The type of graft was the right lobe (segments 5-8) in 14, left lobe (segments 2-4) in 4, and left lateral sector (segments 2 and 3) in 12 patients. The mean donor age was 36 (range: 26-57) years. The mean follow-up was 48 (range: 18-120) months. No deaths occurred. Overall, 8 (26.6%) patients experienced a total of 14 post-operative complications. Donor complications based on graft type were as follows: left lateral sector (16.7%), left lobe (25%), and right lobe (35.7%). The experience was divided into two periods 1997-2001 (n=15) and 2002-2007 (n=15). Overall complications during 2 periods were 40% and 13.3%, respectively (p<0.001). The incidence of grade III complication also significantly decreased; 66.7% vs 33.3% (p<0.01).

CONCLUSION

Partial hepatectomy in living donors has a learning curve which appears to be approximately 15 cases. This learning curve is not restricted to the surgeons performing the procedure but involves all aspects of patient care.

Donor kidney recovery methods and the incidence of lymphatic complications in kidney transplant recipients

BACKGROUND

Lymphatic leak and lymphocele are well-known complications after kidney transplantation.

OBJECTIVE

To determine the incidence of lymphatic complications in recipients of living donor kidneys.

METHODS

Among 642 kidney transplants performed between 1999 and 2007, the incidence of lymphatic complications was retrospectively analyzed in recipients of living donor kidneys procured by laparoscopic nephrectomy (LP, n=218) or by open nephrectomy (OP, n=127) and deceased donor kidneys (DD, n=297). A Jackson-Pratt drain was placed in the retroperitoneal space in all recipients and was maintained until the output became less than 30 mL/day.

RESULTS

Although the incidence of symptomatic lymphocele, which required therapeutic intervention, was comparable in all groups, the duration of mean±SD drain placement was significantly longer in the LP group-8.6±2.7 days compared to 5.6±1.2 days in the OP group and 5.4±0.7 days in the DD group (p<0.001). Higher output of lymphatic drainage in recipients of LP kidneys could lead to a higher incidence of lymphocele if wound drainage is not provided.

CONCLUSION

More meticulous back table preparation may be required in LP kidneys to decrease lymphatic complications after kidney transplantation. These observations also support the suggestion that the major source of persistent lymphatic drainage following renal transplantation is severed lymphatics of the allograft rather than those of the recipient's iliac space.

Impact of donor kidney recovery method on lymphatic complications in kidney transplantation

INTRODUCTION

Prolonged lymphatic drainage and lymphocele are undesirable complications following kidney transplantation. We evaluated the impact of kidney recovery methods (deceased donor vs laparoscopic nephrectomy) on the lymphatic complications of the kidney transplant recipients.

METHOD

The incidence of lymphatic complications was retrospectively analyzed in recipients of deceased donor kidneys (DD, n = 62) versus laparoscopically procured kidneys from living donors (LP, n = 61). A drain was placed in the retroperitoneal space in all recipients. The drain was maintained until the output became less than 30 mL/d with no evidence of fluid collection by ultrasound examination.

RESULTS

There was no statistically significant difference in the patient demographics (age, gender, and original disease and procedure time) between two groups. The incidence of lymphocele that required therapeutic intervention was comparable in both groups (3.2%). However, the duration of drain placement was significantly longer in the LP group than in the DD group, 8.6 +/- 2.5 days versus 5.4 +/- 2.5 day, respectively (P < .05).

CONCLUSION

The recipients of laparoscopically removed kidneys had a higher incidence of prolonged lymphatic leakage. More meticulous back table preparation may be required in LP kidneys to prevent prolonged lymphatic drainage after kidney transplantation. These observations may indicate that the major source of persistent lymphatic leakage is lymphatics of the allograft rather than severed recipient lymphatics.

Outcome of kidney transplantation using expanded criteria donors and donation after cardiac death kidneys: realities and costs

Expanded criteria donors (ECDs) and donation after cardiac death (DCD) provide more kidneys in the donor pool. However, the financial impact and the long-term benefits of these kidneys have been questioned. From 1998 to 2005, we performed 271 deceased donor kidney transplants into adult recipients. There were 163 (60.1%) SCDs, 44 (16.2%) ECDs, 53 (19.6%) DCDs and 11 (4.1%) ECD/DCDs. The mean follow-up was 50 months. ECD and DCD kidneys had a significantly higher incidence of delayed graft function, longer time to reach serum creatinine below 3 (mg/dL), longer length of stay and more readmissions compared to SCDs. The hospital charge was also higher for ECD, ECD/DCD and DCD kidneys compared to SCDs, primarily due to the longer length of stay and increased requirement for dialysis (70,030 dollars, 72,438 dollars, 72,789 dollars and 47,462 dollars, respectively, p < 0.001). Early graft survival rates were comparable among all groups. However, after a mean follow-up of 50 months, graft survival was significantly less in the ECD group compared to other groups. Although our observations support the utilization of ECD and DCD kidneys, these transplants are associated with increased costs and resource utilization. Revised reimbursement guidelines will be required for centers that utilize these organs.

Arterial anastomosis disrupton in two kidney recipients of contaminated grafts from a donor with Gorham's syndrome

Transmission of donor infections to immunosuppressed recipients may produce serious complications. Here, we report two cases of ruptured renal artery pseudoaneurysm within a few months after renal transplantation from a donor with Gorham's syndrome, a rare disease characterized by proliferation of vascular and lymphatic channels associated with extensive bony destruction. The donor had died of respiratory failure, sepsis, and anoxic brain death due to difficult airway control secondary to a maxillofacial deformity.

Colorectal cancer after renal transplantation

BACKGROUND

The risk of developing malignancy is increased after transplantation, which is believed to be related to the use of immunosuppressive agents. Although the risk of hematological malignancies and skin cancer are clearly increased in this setting, the association with colorectal cancer is controversial.

METHODS

Retrospective analysis of patients with renal transplantation who developed colorectal cancer (1985-2001).

RESULTS

Over 17 years (1985-2002), 31 (5.5%) patients out of 556 renal transplant recipients developed cancer; 23 skin cancer and 8 non skin cancer. Three patients (0.5%) developed colorectal cancer. All were men of mean age 65 years. The mean elapsed time from transplantation to symptoms was 11 years. They were all treated with azathioprine, antilymphocyte globulin, prednisone, and additional immunosuppressive agents, such as mycophenolate mofetil, or cyclosporine. The patients with colorectal cancer underwent resection with primary anastomosis. They all experienced uneventful postoperative courses; no anastomotic leak occurred. Two patients were found to have liver metastases at the time of operation.

CONCLUSIONS

Our cases and a literature review suggest that there is no increase risk of colorectal cancer among transplant recipients compares to the general population. Whether colorectal cancer has a more aggressive course in transplant patients needs further evaluation.

Bacteroides fragilis toxin rearranges the actin cytoskeleton of HT29/C1 cells without direct proteolysis of actin or decrease in F-actin content

Enterotoxigenic strains of B. fragilis associated with childhood diarrhea produce a 20 kD zinc metalloprotease toxin (BFT). BFT is reported to cleave G-actin in vitro and also causes dramatic rounding and rearrangement of the F-actin cytoskeleton in human intestinal epithelial cell lines (HT29) and HT29/C1). To test the hypothesis that the proteolysis of cellular actin by BFT in vivo may contribute to these alterations in morphology and cytoskeletal architecture, we assessed the F-actin content and the arrangement of the F- and G-actin cytoskeleton in BFT-treated HT29/C1 cells by spectrofluorimetry, confocal microscopy, and immunoblotting. BFT-treated cells were compared to cells treated with C. difficile toxin A (CDA) or cytochalasin D. Using spectrofluorimetric quantification, the F-actin content of BFT- and cytochalasin D-treated cells was unchanged in contrast to a significant decrease in CDA-treated cells. By confocal microscopy, the arrangement of F- and G-actin in all treated cells was markedly different than control cells. There was no change in the immunoblotting pattern of actin in the Triton-soluble or -insoluble cellular fractions of BFT-treated HT29/C1 cells. We conclude that BFT alters the F- and G-actin cytoskeletal architecture of HT29/C1 cells without direct proteolysis of actin or decrease in F-actin content.

Bacteroides fragilis enterotoxin cleaves the zonula adherens protein, E-cadherin

Strains of Bacteroides fragilis associated with diarrheal disease (enterotoxigenic B. fragilis) produce a 20-kDa zinc-dependent metalloprotease toxin (B. fragilis enterotoxin; BFT) that reversibly stimulates chloride secretion and alters tight junctional function in polarized intestinal epithelial cells. BFT alters cellular morphology and physiology most potently and rapidly when placed on the basolateral membrane of epithelial cells, suggesting that the cellular substrate for BFT may be present on this membrane. Herein, we demonstrate that BFT specifically cleaves within 1 min the extracellular domain of the zonula adherens protein, E-cadherin. Cleavage of E-cadherin by BFT is ATP-independent and essential to the morphologic and physiologic activity of BFT. However, the morphologic changes occurring in response to BFT are dependent on target-cell ATP. E-cadherin is shown here to be a cellular substrate for a bacterial toxin and represents the identification of a mechanism of action, cell-surface proteolytic activity, for a bacterial toxin.

Nonthermal ablation of malignant esophageal strictures. Photodynamic therapy, endoscopic intratumoral injections, and novel modalities

Several novel nonthermal ablative modalities for the palliation of malignant esophageal stenoses have been developed over the past decade. In this article, the authors review techniques and clinical experience with photodynamic therapy as well as the intratumoral injection of alcohol, cytotoxins, and immunomodulators.

Bacteroides fragilis toxin exhibits polar activity on monolayers of human intestinal epithelial cells (T84 cells) in vitro

Strains of Bacteroides fragilis associated with diarrhea in children (termed enterotoxigenic B. fragilis, or ETBF) produce a heat-labile ca. 20-kDa protein toxin (BFT). The purpose of this study was to examine the activity of BFT on polarized monolayers of human intestinal epithelial cells (T84 cells). In Ussing chambers, BFT had two effects. First, BFT applied to either the apical or basolateral surfaces of T84 monolayers diminished monolayer resistance. However, the time course, magnitude, and concentration dependency differed when BFT was applied to the apical versus basolateral membranes. Second, only basolateral BFT stimulated a concentration-dependent and short-lived increase in short circuit current (Isc; indicative of C1- secretion). Time course experiments indicated that Isc returned to baseline as resistance continued to decrease, indicating that these two electrophysiologic responses to BFT are distinct. Light microscopic studies of BFT-treated monolayers revealed only localized cellular changes after apical BFT, whereas basolateral BFT rapidly altered the morphology of nearly every cell in the monolayer. Transmission and scanning electron microscopy after basolateral BFT confirmed a striking loss of cellular microvilli and complete dissolution of some tight junctions (zonula occludens) and zonula adherens without loss of desmosomes. The F-actin structure of BFT-treated monolayers (stained with rhodamine-phalloidin) revealed diminished and flocculated staining at the apical tight junctional ring and thickening of F-actin microfilaments in focal contacts at the basolateral monolayer surface compared to those in similarly stained control monolayers. BFT did not injure T84 monolayers, as assessed by lactic dehydrogenase release and protein synthesis assays. These studies indicate that BFT is a nonlethal toxin which acts in a polar manner on T84 monolayers to stimulate C1- secretion and to diminish monolayer resistance by altering the apical F-actin structure of these cells. BFT may contribute to diarrheal disease associated with ETBF infection by altering epithelial barrier function and stimulating C1- secretion.

Bacteroides fragilis toxin rapidly intoxicates human intestinal epithelial cells (HT29/C1) in vitro

Enterotoxigenic Bacteroides fragilis strains associated with childhood diarrhea produce a 20-kDa protein toxin (BFT). Purified BFT causes striking morphologic changes in subconfluent human colonic epithelial cells (HT29/C1). In a 3-h HT29/C1 cell assay, the estimated half-maximal effective concentration of BFT was 12.5 pM, and morphologic effects were detectable as early as 30 min and nearly complete by 1.5 h. Concentrations as low as 0.5 pM could also cause intoxication, but morphologic changes were detectable only when the assay was extended to 18 h. The onset of this intoxication was concentration dependent and rapid, occurring within minutes (<7 min at 0.25 nM, <2 min at 2.5 nM). Notably, the onset of intoxication at 37 degrees C became irreversible to washing within 2 min after exposure to BFT. Morphologic changes were completely inhibited by treatment of HT29/C1 cells with BFT at 4 degrees C but could be demonstrated by subsequent warming to temperatures of 15 degrees C or higher after washing. The time required for the association of BFT with HT29/C1 cells at 4 degrees C was inversely correlated with concentration. Inhibitors of endosomal and Golgi trafficking (NH4Cl and brefeldin A) prevented the intoxication of HT29/C1 cells by Clostridium difficile toxin A and cholera toxin, respectively, but not by BFT. Agents altering microtubule structure did not affect the cellular activity of BFT. These data indicate that a purified toxin from B. fragilis strains associated with diarrhea rapidly and irreversibly intoxicates human intestinal epithelial cells (HT29/C1) in a concentration- and temperature-dependent manner and that the process of intoxication may not involve internalization mechanisms utilizing microtubules or sensitive to pH or brefeldin A.