People's attitude toward xenotransplantation: affective reactions and the influence of the evaluation context.

BACKGROUND: One of the major issues in transplantation is to find a strategy to overcome the scarcity of human organs. One of the interventions under investigation is represented by xenotransplantation. The present study aimed to understand the role of psychological factors on people's perception of xenotransplantation. In particular, we tested a condition in which different alternatives (e.g., human vs. pig donors) are presented together allowing people to compare among them (joint evaluation) and two conditions in which people are presented with only one of the two alternatives and cannot compare them (separate evaluation). METHODS: The study was conducted with three different groups of participants: patients waiting for liver transplantation (N = 31 in joint evaluation and N = 30 in each of the two separate evaluation conditions); students (N = 30 in join evaluation and N = 30 in each of the two separate evaluation conditions); and healthy adults (N = 30 in joint evaluation and N = 30 in each of the two separate evaluation conditions). Participants were presented with hypothetical scenarios and asked how good (or bad) were their feelings toward one or two types of donor (e.g., human and pig). RESULTS: Patients showed a skeptical attitude toward xenotransplantation both when it was evaluated together with the human donor (P < 0.01) or when it was evaluated separately (P < 0.01). Differently, when asked to evaluate each donor separately healthy adults and students showed similar affective reactions toward the two alternatives (human organ and xenograft). CONCLUSIONS: The present study demonstrates that the evaluation context may increase the impact of affective reactions and reduce healthy people's ability to use information on the potential benefit of a novel biomedical technology. Regardless of the evaluation context, patients always rely on affective reactions and show an overall preference for the human organ.

Study of the microcirculation in hDAF transgenic rat livers xenoperfused with human blood.

BACKGROUND: The microcirculation was assessed in the livers of human decay accelerating factors (hDAF) and wild-type transgenic rats by fluorescent intravital microscopy, histology and histomorphology to determine the benefits of hDAF expression for the microcirculation of a rat liver xenograft perfused with human blood. METHODS: Male hDAF transgenic rats (group A; n = 20) and wild-type Sprague-Dawley rats (group B; n = 20) were xenoperfused with human blood, while other male wild-type Sprague-Dawley rats (group C; n = 10) were perfused with allogeneic blood. Following plasma and leukocyte staining with fluorescein sodium, and platelet staining with rhodamine, the right lobe of the liver was assessed by intravital microscopy, counting the numbers of perfused sinusoids and leukocytes adhering to the endothelium per mm(2), and calculating the acinar perfusion index (Pi). The liver underwent histological assessment at the end of each experiment. Mean +/- SEM values were calculated and the Mann-Whitney U-test was used for statistical analysis. RESULTS: The number of perfused sinusoids was higher in the group of hDAF rat livers (group A) and controls (group C) than in the group of non-transgenic rat livers perfused with human blood (group B) (P < 0.05), although only group C still had a significantly more perfused sinusoids than the other groups after 90 min of perfusion (P < 0.05). The acinar perfusion index was higher in groups A and C than in group B (P < 0.05); here again, only group C still had a significantly higher Pi than group B after 90 min of perfusion (P < 0.05). There was a massive accumulation of leukocytes that peaked after 5 min and persisted throughout the perfusion in all three groups. Histology showed portal and subendothelial hepatic vein hemorrhage, necrosis and inflammatory reaction, which were particularly evident in group B. CONCLUSION: In our study, rat livers transgenic for hDAF were better protected against early tissue damage by perfusion with human blood, but this did not result in a longer xenograft survival.

Strengthening acceptance for xenotransplantation: the case of attraction effect.

BACKGROUND: Despite being still at the experimental level, xenotransplantation may become an effective strategy to overcome the scarcity of human organs. However, at the present time there is considerable resistance to this kind of biomedical technology. The aim of the present study was to identify novel strategies to reduce patients' negative affective reactions towards xenotransplantation helping them to understand the advantages of xenotransplantation in a more analytical fashion and increase their acceptance for this approach. METHODS: The study was conducted in a group of patients with liver cirrhosis waiting for liver transplantation. They were presented with hypothetical scenarios and asked to choose among either two or three alternative types of donor defined by their species (e.g., livers from humans vs. other species) and availability (low for human donors and high for livers from non-human species). RESULTS: Patients were unwilling to accept xenotransplantation if they were presented with livers from humans (chosen by 97.5% of participants) vs. livers from genetically modified pigs (2.5%). On the other hand, a different group of patients was significantly more willing to accept xenotransplantation if they were presented with three different types of donors: respectively, human beings (74.4%), genetically modified pigs (25.6%) and genetically modified dogs. In addition, human livers were judged significantly more attractive than genetically modified livers from pigs, monkeys, dogs, or sheep and pig livers were rated as significantly more attractive than livers from monkeys, dogs, or sheep (for all comparisons P < 0.01). CONCLUSIONS: These results demonstrate that paradigms from other fields, like decision-making, might help to communicate more effectively the potential of xenotransplantation, modulating patients' affective reactions and allowing them to understand the potential strengths of this biomedical technology.

Metabolic activity of rat hepatocytes cultured on homologous acellular matrix and transplanted into Gunn rats.

The metabolic activity of hepatocytes cultured on homologous acellular matrix (HAM) and transplanted into rats genetically incapable of bilirubin conjugation (Gunn rats) has been investigated. Hepatocytes from Wistar male rats were seeded on HAM and cultured for 9 days, and the proliferation rate and albumin mRNA expression were assayed daily. HAM alone or HAM plus hepatocytes (cultured for 3 days) were implanted in a subcutaneous pocket of the dorsal region of Gunn rats. No immunosuppression therapy was used. Blood samples were collected weekly and rats were sacrificed 10 weeks after surgery. Hepatocytes cultured on HAM displayed a higher proliferation rate than those cultured on plastic, and albumin mRNA expression was detected in hepatocytes seeded on HAM, but not on plastic. Serum bilirubin concentrations did not differ from baseline values in both the sham-operated control and HAM transplanted rats. On the contrary, in rats transplanted with HAM plus hepatocytes, circulating bilirubin levels decreased from week 4-7, and then plateaued until week 10. Histology did not evidence signs of rejection, but only a mild degree of inflammation around the implanted patches. It is concluded that hepatocytes seeded on HAM and transplanted into Gunn rats are able to metabolize bilirubin for at least two months, without signs of rejection even in the absence of immunosuppressive therapy.

Acellular liver matrix improves the survival and functions of isolated rat hepatocytes cultured in vitro.

Alternative approaches to overcome the shortage of donors for liver transplantation may be the use of hepatocytes for bioartificial devices or transplantation. Therefore, the setting-up of new in vitro culture techniques allowing the long-term survival and functional maintenance of hepatocytes represents a formidable challenge. Aim of this study was to obtain a liver homologous acellular matrix (HAM) able to support viability and metabolic functions of rat hepatocytes in primary culture. HAMs were prepared by sequential incubation of rat liver slices in deoxycholic acid and DNase solutions. Dispersed rat hepatocytes were obtained by collagenase digestion and mechanical disaggregation. Isolated hepatocytes were seeded on uncoated and collagen- or HAM-coated tissue culture plastic wells. Cultures were examined by scanning electron microscopy (SEM), and the viability of hepatocytes and their ability to produce albumin and urea were assessed. The viability of freshly dispersed hepatocytes was about 98%. Hepatocytes seeded on HAM exhibited a significantly higher viability and a markedly lower apoptotic rate than those grown on plastic or collagen. Accordingly, albumin and urea nitrogen productions were significantly higher in HAM-cultured hepatocytes. SEM showed that hepatocytes seeded on HAM displayed a clustered organization, and were well anchored to the matrix and morphologically stable. Taken together, these findings indicate that HAM strongly improves viability and functional activity of rat hepatocytes cultured in vitro.