Preexisting venous calcification prior to dialysis vascular access surgery.

Vascular calcification is present in arterial vessels used for dialysis vascular access creation prior to surgical creation. Calcification in the veins used to create a new vascular access has not previously been documented. The objective of this study was to describe the prevalence of venous calcification in samples collected at the time of vascular access creation. Sixty-seven vein samples were studied. A von Kossa stain was performed to quantify calcification. A semi-quantitative scoring system from 0 to 4+ was used to quantify the percentage positive area for calcification as a fraction of total area (0: 0; 1+: 1-10%; 2+: 11-25%; 3+: 26-50%; 4+: >50% positive). Twenty-two of 67 (33%) samples showed evidence of venous calcification. Histologic examination showed varying degrees of calcification within each cell layer. Among the subset of patients with calcification, 4/22 (18%), 19/22 (86%), 22/22 (100%), and 7/22 (32%) had calcification present within the endothelium, intima, media, and adventitia, respectively. The mean semi-quantitative scores of the 22 samples with calcification were 0.18 ± 0.08, 1.2 ± 0.14, 1.6 ± 0.13, and 0.36 ± 0.12 for the endothelium, intima, media, and adventitia, respectively. Our results demonstrate that vascular calcification is present within veins used to create new dialysis vascular access, and located predominately within the neointimal and medial layers.

Severe venous neointimal hyperplasia prior to dialysis access surgery.

BACKGROUND: Venous neointimal hyperplasia is the most common cause of arteriovenous (AV) fistula and graft dysfunction following dialysis access surgery. However, the pathogenetic impact of pre-existing venous neointimal hyperplasia at the time of AV access creation on final clinical success is currently unknown in the setting of advanced chronic kidney disease (CKD) and end-stage renal disease (ESRD) patients. The aim of this study was to perform a detailed histological, morphometric, and immunohistochemical analysis of vein specimens in advanced CKD and ESRD patients collected at the time of new vascular access placement. METHODS: Vein samples from 12 patients were collected at the time of AV access creation near the site of AV anastomosis. Histological, immunohistochemistry and morphometric studies were performed on these vein samples. RESULTS: Examination of the tissue specimens obtained at the time of surgery showed neointimal hyperplasia in 10 of 12 specimens, ranging from minimal to very severe. The majority of cells within the neointima were myofibroblasts with a minority of contractile smooth muscle cells present. CONCLUSION: Our work represents a detailed description of the morphometric and cellular phenotypic lesions present in the veins of CKD and ESRD patients, prior to dialysis access placement. These studies (i) suggest the future possibility of a new predictive marker (pre-existing venous neointimal hyperplasia) for AV dialysis access dysfunction and (ii) open the door for the future development of novel local therapies for optimization of the venous substrate on which the dialysis access is created.

Retinoblastoma function is essential for establishing lung epithelial quiescence after injury.

The retinoblastoma gene product (RB) regulates cell cycle, quiescence, and survival in a cell type-dependent and environment-dependent manner. RB function is critical in the pulmonary epithelium, as evidenced by nearly universal RB inactivation in lung cancer and increased lung cancer risk in persons with germline RB gene mutations. Lung carcinomas occur in the context of epithelial remodeling induced by cytotoxic damage. Whereas the role of RB in development and normal organ homeostasis has been extensively studied, RB function in the context of cellular injury and repair has remained largely unexplored. In the current studies, the RB gene was selectively deleted in the respiratory epithelium of the mouse. Although RB was not required for establishing or maintaining quiescence during lung homeostasis, RB was essential for establishing quiescence during epithelial repair after injury. Notably, aberrant cell cycle progression was sustained for 9 months after injury in RB-deficient lungs. Prenatal and postnatal RB ablation had similar effects, providing evidence that timing of RB loss was not critical to the outcome and that the injury-induced phenotype was not secondary to compensatory alterations occurring during development. These data show that RB is essential for repair of the respiratory epithelium after cytotoxic damage and support a critical unique role for RB in the context of epithelial remodeling after injury. Because human cancers are associated with chronic cellular damage, these findings have important new implications for RB-mediated tumor suppression.

Two tandemly linked interferon-gamma-activated sequence elements in the promoter of glycosylation-dependent cell adhesion molecule 1 gene synergistically respond to prolactin in mouse mammary epithelial cells.

Previously, we reported that glycosylation-dependent cell adhesion molecule 1 (GlyCAM 1) was a novel target for prolactin (PRL) in the mouse mammary gland. However, the signaling pathway by which PRL regulates GlyCAM 1 expression has not been specified. In the present study, we showed that PRL induced GlyCAM 1 expression in primary mammary epithelial cells of mice through the Janus kinase 2/signal transducer and activator of transcription 5 (Stat5) pathway. Deletion and site-directed mutagenesis analyses of the GlyCAM 1 promoter demonstrated that the two tandemly linked Stat5 binding sites [interferon-gamma-activated sequence 1 and -2 (GAS1 and GAS2)] in the proximal promoter region were crucial and synergistically responded to PRL. GAS2, a consensus GAS site, was essential and, by itself, weakly responded to PRL, whereas GAS1, a nonconsensus site, failed to respond to PRL but was indispensable for the maximal activity of the GlyCAM 1 promoter. Gel shift assays showed that probe containing GAS1 and GAS2 bound two Stat5 complexes, which represent Stat5 dimer and tetramer, respectively, while GAS2, by itself, bound Stat5 as a dimer only, and GAS1 showed no apparent binding activity. Interruption of tetramer formation by mutation of a tryptophan to alanine (W37A), and a leucine to serine (L83S) in the N terminus of Stat5A attenuated the synergistic effect between the two tandemly linked GAS sites. Overexpression of W37A and L83S mutants in primary mammary epithelial cells suppressed endogenous GlyCAM 1 expression.