Protein and calorie restriction may improve outcomes in living kidney donors and kidney transplant recipients

Previously, we and others showed that dietary restriction protects against renal ischemia-reperfusion injury in animals. However, clinical translation of preoperative diets is scarce, and in the setting of kidney transplantation these data are lacking. In this pilot study, we investigated the effects of five days of a preoperative protein and caloric dietary restriction (PCR) diet in living kidney donors on the perioperative effects in donors, recipients and transplanted kidneys. Thirty-five kidney donors were randomized into either the PCR, 30% calorie and 80% protein reduction, or control group without restrictions. Adherence to the diet and kidney function in donors and their kidney recipients were analyzed. Perioperative kidney biopsies were taken in a selected group of transplanted kidneys for gene expression analysis. All donors adhered to the diet. From postoperative day 2 up until month 1, kidney function of donors was significantly better in the PCR-group. PCR-donor kidney recipients showed significantly improved kidney function and lower incidence of slow graft function and acute rejection. PCR inhibited cellular immune response pathways and activated stress-resistance signaling. These observations are the first to show that preoperative dietary restriction induces postoperative recovery benefits in humans and may be beneficial in clinical settings involving ischemia-reperfusion injury.

Whole chromosome aneuploidy in the brain of Bub1bH/H and Ercc1-/Δ7 mice

High levels of aneuploidy have been observed in disease-free tissues, including post-mitotic tissues such as the brain. Using a quantitative interphase-fluorescence in situ hybridization approach, we previously reported a chromosome-specific, age-related increase in aneuploidy in the mouse cerebral cortex. Increased aneuploidy has been associated with defects in DNA repair and the spindle assembly checkpoint, which in turn can lead to premature aging. Here, we quantified the frequency of aneuploidy of three autosomes in the cerebral cortex and cerebellum of adult and developing brain of Bub1b(H/H) mice, which have a faulty mitotic checkpoint, and Ercc1(-/Δ7) mice, defective in nucleotide excision repair and inter-strand cross-link repair. Surprisingly, the level of aneuploidy in the brain of these murine models of accelerated aging remains as low as in the young adult brains from control animals, i.e. <1% in the cerebral cortex and ∼0.1% in the cerebellum. Therefore, based on aneuploidy, these adult mice with reduced life span and accelerated progeroid features are indistinguishable from age-matched, normal controls. Yet, during embryonic development, we found that Bub1b(H/H), but not Ercc1(-/Δ7) mice, have a significantly higher frequency of aneuploid nuclei relative to wild-type controls in the cerebral cortex, reaching a frequency as high as 40.3% for each chromosome tested. Aneuploid cells in these mutant mice are likely eliminated early in development through apoptosis and/or immune-mediated clearance mechanisms, which would explain the low levels of aneuploidy during adulthood in the cerebral cortex of Bub1b(H/H) mice. These results shed light on the mechanisms of removal of aneuploidy cells in vivo.

An essential role for senescent cells in optimal wound healing through secretion of PDGF-AA

Cellular senescence suppresses cancer by halting the growth of premalignant cells, yet the accumulation of senescent cells is thought to drive age-related pathology through a senescence-associated secretory phenotype (SASP), the function of which is unclear. To understand the physiological role(s) of the complex senescent phenotype, we generated a mouse model in which senescent cells can be visualized and eliminated in living animals. We show that senescent fibroblasts and endothelial cells appear very early in response to a cutaneous wound, where they accelerate wound closure by inducing myofibroblast differentiation through the secretion of platelet-derived growth factor AA (PDGF-AA). In two mouse models, topical treatment of senescence-free wounds with recombinant PDGF-AA rescued the delayed wound closure and lack of myofibroblast differentiation. These findings define a beneficial role for the SASP in tissue repair and help to explain why the SASP evolved.

Abstract 2550: Expanded simple tandem repeat (ESTR) mutations in offspring of benzo(a)pyrene exposed DNA repair deficient male mice

Germ line mutations can be transmitted to the offspring and may thus affect an infinite number of generations thereafter. To study germ line mutations, expanded simple tandem repeats (ESTR) can be used as a sensitive tool, because they are known to be highly unstable and therefore exhibit high mutation rates. This facilitates the assessment of germ line mutations in a relatively small number of offspring following exposures that may pose a genetic risk to the germ line. We used two ESTR loci Ms6-hm and Hm-2 in families of benzo(a)pyrene (BaP) exposed and unexposed male mice, proficient or deficient for global genome repair (Xpc-/-). Male mice (C57BL/6) were exposed to BaP during 6 weeks (13 mg/kg bw, 3 times per week) and were crossed with female mice (Balb/C) 6 weeks after the last exposure to obtain offspring and to ensure the analysis of mutations originating from spermatogonial stem cells. The overall ESTR mutation rate at both ESTR loci, irrespective of the DNA repair capacity, was higher in offspring of benzo(a)pyrene exposed mice than in control mice (9.4% vs. 4.5%, P=0.054). This effect was predominantly seen in BaP exposed DNA repair deficient Xpc-/- mice; mutation frequencies were 12.5% in the exposed group (12 out of 96 offspring carried a mutant allele) and 3.4% in the unexposed group (3 out of 87), respectively (P=0.024). In DNA repair proficient mice, BaP was unable to increase the mutation frequency transmitted to the offspring (5.8% vs. 5.5% for offspring of exposed and unexposed fathers). These results indicate that analysis of tandem repetitive sequences is a sensitive method for the detection of germline mutations transmitted to the offspring and that the environmental mutagen BaP is able to induce germ line mutations in DNA repair deficient mice.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2550. doi:1538-7445.AM2012-2550