Liver allotransplantation after extracorporeal hepatic support with transgenic (hCD55/hCD59) porcine livers: clinical results and lack of pig-to-human transmission of the porcine endogenous retrovirus

BACKGROUND

Whole organ extracorporeal perfusion of a genetically modified humanized (transgenic) pig liver has been proposed as a technology that may sustain patients with severe liver failure while awaiting human liver transplantation.

METHODS

We report on two cases of successful extracorporeal perfusion of a transgenic pig liver in patients awaiting transplantation for fulminant hepatic failure. The pig livers used were transgenic for human CD55 (decay-accelerating factor) and human CD59. These transgenic modifications are designed to reduce or eliminate the hyperacute rejection inherent in pig-to-primate xenotransplants. We also report on the results of serial surveillance testing for presence of the porcine endogenous retrovirus (PoERV) in these two patients.

RESULTS

Extracorporeal perfusion in two patients was performed for 6.5 and 10 hr, respectively, followed by the successful transplantation of a human liver and resultant healthy patients (18 and 5 months later as of this writing). The porcine livers showed evidence of synthetic and secretory function (decreasing protime and bilirubin, bile production). Serial polymerase chain reaction analysis of these patients' peripheral blood mononuclear cells has failed to show presence of PoERV DNA sequences.

CONCLUSIONS

The CD55/CD59 transgenic porcine liver appears capable of safely "bridging" a patient to liver transplantation. Human PoERV infection from these livers has yet to be demonstrated.

Rapid reduction of MDCK cell cholesterol by methyl-beta-cyclodextrin alters steady state transepithelial electrical resistance

The role of plasma membrane lipids in regulating the passage of ions and other solutes through the paracellular pathway remains controversial. In this study we explore the contribution of cholesterol (CH) in maintaining the barrier function of an epithelial cell line using the CH-solubilizing agent methyl beta-cyclodextrin (MBCD) to stimulate CH efflux. Inclusion of 20 mM MBCD in both apical and basolateral media reduced CH levels by 70-80% with no significant effect on cell viability. Most of that decrease occurred during the first 30 min of incubation. Recovery of CH content to initial values was nearly complete 22 h after removal of MBCD. Within 30 min of adding MBCD to the culture medium, transepithelial electrical resistance (TER) increased, reaching maximum values 30-40% above controls. This early rise in TER occurred when MBCD was added to either side of the monolayer. The later rapid decline in TER was observed only when MBCD bathed the basolateral surface from which, coincidentally, CH efflux was most rapid. Freeze fracture replicas and transmission electron microscopy of monolayers exposed to MBCD for only 30 min revealed no increase in either the average tight junction (TJ) strand number or the dimensions of the lateral intercellular space. There was a statistically significant increase in the number of TJ particles associated with the E fracture face at this time. This raises the interesting possibility that during CH efflux there is a change in the interaction between TJ particles and underlying cytoskeletal elements. There was no change in staining for occludin and ZO-1. After exposing the basolateral surface to MBCD for 2 h, TER fell below control levels. The accompanying increase in mannitol flux suggests strongly that the decrease in TER resulted from an increase in the permeability of the paracellular and not the transcellular pathway. A decrease in immuno-staining for occludin and ZO-1 at TJs, a striking accumulation of actin at tri-cellular areas as well as a decline in the number of parallel strands, as seen in freeze fracture replicas, suggest that changes in cytoskeletal organization during long incubations with MBCD had physically disrupted the TJ network. Data are presented which suggest that the observed changes in paracellular permeability during CH efflux may be related to increased levels of lipid-derived second messengers, some of which may trigger changes in the phosphorylation status of TJ proteins.

Wringing out the costs. Preferred provider organizations are using technology to get the job done

The thin margins in the PPO business mean that these managed care plans must make sure they are deploying information technology in ways that improve efficiency. Information technology professionals at PPOs also are being called upon to develop initiatives that will give their organizations a competitive edge.

Group practices explore EDI options

Although physician groups have been relatively slow to take advantage of electronic commerce, more are discovering the benefits. Once group practice administrators get beyond their initial trepidation and realize that EDI is efficient, many are pleased with the results. And some are automating other transactions, including verifying patient eligibility for insurance coverage, gaining insurance authorization for referrals to specialists and checking the status of claims.

Dendritic cell precursors are enriched in the vascular compartment of the lung

The vast mucosal interface separating external from internal compartments of the lung is under the surveillance of a population of blood-borne, bone marrow-derived dendritic cells (DC) characterized by constant turnover. Because these sentinel cells process foreign antigens that have penetrated the epithelial barrier and transport them to local lymph nodes, they require continuous replenishment by blood-borne cells. In the present study, the phenotype and function of DC and their precursors isolated from the vascular compartment of the lung were examined and compared with those in vena cava blood. Intravascular leukocytes were retrieved by exhaustive perfusion of the lung vasculature. Leukocytes harvested from the subdiaphragmatic vena cava of the same animal served as a source of DC in prepulmonary blood. Typical, large, major histocompatibility class II+ antigen (MHC II+) DC constituted < 1% of leukocytes from either vascular compartment. These cells expressed intercellular adhesion molecule [ICAM]-1 and lymphocyte function-associated antigen [LFA]-1 and many were ED1(+) (lysosomal antigen in monocytes, macrophages, and some DC). No ED2(+) cells (macrophages) were identified. Very few of the circulating DC expressed the alpha-like subunit of integrin recognized by the OX62 monoclonal antibody. A striking difference appeared when neutrophil-depleted leukocytes were cultured with granulocyte macrophage colony-stimulating factor (GM-CSF) for 3 d; the number of MHC II+ DC generated from pulmonary vascular leukocytes was 76% greater than that from the vena cava population. After pulse-labeling with tritiated thymidine ([3H]TdR) followed by 3 d of culture with GM-CSF, DC from either source remained virtually unlabeled, as determined by autoradiography. On the day of harvest, DC and their precursors obtained from either vascular compartment were poor stimulators of the mixed leukocyte reaction and required GM-CSF for development of their full accessory cell capability. These data suggest that, relative to leukocytes in vena cava blood, those in the lung vascular compartment are enriched in a population of mononuclear cells that are capable of differentiating into MHC II+ DC when exposed to the appropriate growth factors, including GM-CSF. This enriched population of DC precursors could represent a source from which lung DC may be readily recruited not only to replenish the normally turning-over mucosal DC, but also to participate in inflammatory reactions occurring in the lung.

Improving the odds

Health care providers are using information systems to gather and analyze data that will help make entering capitated managed care contracts less of a gamble.