Increased cellular senescence and vascular rarefaction exacerbate the progression of kidney fibrosis in aged mice following transient ischemic injury.

Recent findings indicate that elderly patients with acute kidney injury (AKI) have an increased incidence of progression to chronic kidney disease (CKD) due to incomplete recovery from an acute insult. In the current study, a co-morbid model of AKI was developed to better mimic the patient population and to investigate whether age exacerbates the fibrosis and inflammation that develop in the sequelae of progressive kidney disease following acute injury. Young (8-10 weeks) and aged (46-49 weeks) C57BL/6 mice were subjected to 30 min bilateral renal ischemia-reperfusion (I/R) to induce AKI. The aged animals have greater mortality and prolonged elevation of plasma creatinine correlating with less tubular epithelial cell proliferation compared to the young. Six weeks post-reperfusion, interstitial fibrosis is greater in aged kidneys based on picrosirius red staining and immunolocalization of cellular fibronectin, collagen III and collagen IV. Aged kidneys 6 weeks post-reperfusion also express higher levels of p53 and p21 compared to the young, correlating with greater increases in senescence associated (SA) ß-galactosidase, a known marker of cellular senescence. A higher influx of F4/80(+) macrophages and CD4(+) T lymphocytes is measured and is accompanied by increases in mRNA of monocyte chemoattractant protein-1 (MCP-1) and tumor necrosis factor-α (TNF-α). Importantly, microvascular density is significantly less, correlating with an increase in nitro-tyrosine, a marker of oxidative stress. Collectively, these data demonstrate that prolonged acute injury in the aged animals results in an accelerated progression of kidney disease in a chronic state.

A spatially and temporally restricted mouse model of soft tissue sarcoma.

Soft tissue sarcomas are mesenchymal tumors that are fatal in approximately one-third of patients. To explore mechanisms of sarcoma pathogenesis, we have generated a mouse model of soft tissue sarcoma. Intramuscular delivery of an adenovirus expressing Cre recombinase in mice with conditional mutations in Kras and Trp53 was sufficient to initiate high-grade sarcomas with myofibroblastic differentiation. Like human sarcomas, these tumors show a predilection for lung rather than lymph node metastasis. Using this model, we showed that a prototype handheld imaging device can identify residual tumor during intraoperative molecular imaging. Deletion of the Ink4a-Arf locus (Cdkn2a), but not Bak1 and Bax, could substitute for mutation of Trp53 in this model. Deletion of Bak1 and Bax, however, was able to substitute for mutation of Trp53 in the development of sinonasal adenocarcinoma. Therefore, the intrinsic pathway of apoptosis seems sufficient to mediate p53 tumor suppression in an epithelial cancer, but not in this model of soft tissue sarcoma.