Immunological and physiological observations in baboons with life-supporting genetically engineered pig kidney grafts.

BACKGROUND: Genetically engineered pigs could provide a source of kidneys for clinical transplantation. The two longest kidney graft survivals reported to date have been 136 and 310 days, but graft survival >30 days has been unusual until recently. METHODS: Donor pigs (n=4) were on an α1,3-galactosyltransferase gene-knockout (GTKO)/human complement regulatory protein (CD46) background (GTKO/CD46). In addition, the pigs were transgenic for at least one human coagulation regulatory protein. Two baboons received a kidney from a six-gene pig (GroupA) and two from a three-gene pig (GroupB). Immunosuppressive therapy was identical in all four cases and consisted of anti-thymoglobulin (ATG)+anti-CD20mAb (induction) and anti-CD40mAb+rapamycin+corticosteroids (maintenance). Anti-TNF-α and anti-IL-6R mAbs were administered to reduce the inflammatory response. Baboons were followed by clinical/laboratory monitoring of immune/coagulation/inflammatory/physiological parameters. At biopsy or euthanasia, the grafts were examined by microscopy. RESULTS: The two GroupA baboons remained healthy with normal renal function >7 and >8 months, respectively, but then developed infectious complications. However, no features of a consumptive coagulopathy, eg, thrombocytopenia and reduction of fibrinogen, or of a protein-losing nephropathy were observed. There was no evidence of an elicited anti-pig antibody response, and histology of biopsies taken at approximately 4, 6, and 7 months and at necropsy showed no significant abnormalities. In contrast, both GroupB baboons developed features of a consumptive coagulopathy and required euthanasia on day 12. CONCLUSIONS: The combination of (i) a graft from a specific six-gene genetically modified pig, (ii) an effective immunosuppressive regimen, and (iii) anti-inflammatory therapy prevented immune injury, a protein-losing nephropathy, and coagulation dysfunction for >7 months. Although the number of experiments is very limited, our impression is that expression of human endothelial protein C receptor (±CD55) in the graft is important if coagulation dysregulation is to be avoided.

Genome maintenance defects in cultured cells and mice following partial inactivation of the essential cell cycle checkpoint gene Hus1.

Cell cycle checkpoints are evolutionarily conserved signaling pathways that uphold genomic integrity. Complete inactivation of the mouse checkpoint gene Hus1 results in chromosomal instability, genotoxin hypersensitivity, and embryonic lethality. To determine the functional consequences of partial Hus1 impairment, we generated an allelic series in which Hus1 expression was incrementally reduced by combining a hypomorphic Hus1 allele, Hus1(neo), with either wild-type or null (Hus1(Delta1)) alleles. Primary Hus1(neo/Delta1) embryonic fibroblasts exhibited spontaneous chromosomal abnormalities and underwent premature senescence, while higher Hus1 expression in Hus1(neo/neo) cells allowed for normal proliferation. Antioxidant treatment almost fully suppressed premature senescence in Hus1(neo/Delta1) cultures, suggesting a critical role for Hus1 in oxidative stress responses. Treatment of Hus1(neo/neo) and Hus1(neo/Delta1) cells with the DNA adducting agent benzo(a)pyrene dihydrodriol epoxide resulted in a loss of cell viability that was associated with S-phase DNA damage checkpoint failure. Likewise, the DNA polymerase inhibitor aphidicolin triggered increased cell death, chromosomal aberrations, and H2AX phosphorylation, a marker for double-stranded DNA breaks, in Hus1(neo/neo) and Hus1(neo/Delta1) cultures compared to controls. Despite these pronounced genome maintenance defects in cultured Hus1(neo/Delta1) and Hus1(neo/neo) cells, mice of the same genotypes were born at expected frequencies and appeared grossly normal. A significant increase in micronucleus formation was observed in peripheral blood cells from Hus1(neo/Delta1) mice, but reduced Hus1 expression did not cause an elevated predisposition to spontaneous tumor development or accelerate tumorigenesis in p53-deficient mice. These results identify differential effects of altered Hus1 gene dosage on genome maintenance during in vitro culture, genotoxic stress responses, embryonic development, and adult homeostasis.

Anatomic, hematologic, and biochemical features of C57BL/6NCrl mice maintained on chronic oral corticosterone.

Metabolic syndrome is a condition that typically includes central obesity, insulin resistance, glucose intolerance, dyslipidemia, and hypertension. Disruption of the hypothalamic-pituitary-adrenal axis, a regulator of corticosterone secretion, occurs in some cases of metabolic syndrome and obesity, and Cushing hypercortisolemia is associated with obesity and metabolic disorders. We therefore assessed anatomic and clinical pathology in C57BL/6NCrl mice to evaluate the effects of chronic corticosterone in the drinking water at doses of 25, 50, and 100 µg/mL for 25 d. Treated mice developed obesity, glucose intolerance, electrolyte aberrations, and dyslipidemia that were dose-dependent and most severe in the 100-mu;g/mL treatment group. To evaluate return to normal function, additional C57BL/6NCrl mice received corticosterone-free water for 2 wk after the 25-d treatment period. According to results of gross examination, mice appeared to recover within days of exogenous corticosterone withdrawal; however, adrenal gland vacuolation and protein, lipid, and electrolyte abnormalities persisted. Together, these findings support chronic corticosterone exposure through the drinking water as a potentially useful, noninvasive method to induce some features of metabolic syndrome.