Hydrophobic surface induced pro-metastatic cancer cells for in vitro extravasation models

In vitro vascularized cancer models utilizing microfluidics have emerged as a promising tool for mechanism study and drug screening. However, the lack of consideration and preparation methods for cancer cellular sources that are capable of adequately replicating the metastatic features of circulating tumor cells contributed to low relevancy with in vivo experimental results. Here, we show that the properties of cancer cellular sources have a considerable impact on the validity of the in vitro metastasis model. Notably, with a hydrophobic surface, we can create highly metastatic spheroids equipped with aggressive invasion, endothelium adhesion capabilities, and activated metabolic features. Combining these metastatic spheroids with the well-constructed microfluidic-based extravasation model, we validate that these metastatic spheroids exhibited a distinct extravasation response to epidermal growth factor (EGF) and normal human lung fibroblasts compared to the 2D cultured cancer cells, which is consistent with the previously reported results of in vivo experiments. Furthermore, the applicability of the developed model as a therapeutic screening platform for cancer extravasation is validated through profiling and inhibition of cytokines. We believe this model incorporating hydrophobic surface-cultured 3D cancer cells provides reliable experimental data in a clear and concise manner, bridging the gap between the conventional in vitro models and in vivo experiments.

Albumin synthesis, catabolism and distribution in dialysis patients

Hypoalbuminemia predicts mortality in hemodialysis patients with end-stage renal disease (ESRD) and is assumed to result from malnutrition. We report here that plasma albumin levels are reduced significantly in both hemodialysis and peritoneal dialysis (PD) patients compared to normal subjects. Among hemodialysis patients with normal albumin levels (the upper quartile of albumin distribution), albumin synthesis rates, fractional catabolic rates, and distribution between the vascular and extravascular pool are normal, suggesting that ESRD per se does not derange albumin metabolism. Albumin synthesis is reduced in hemodialysis patients who are hypoalbuminemic, but the fractional albumin catabolic rate decreases normally, and albumin distribution between the vascular and extravascular space remains normal, suggesting that hypoalbuminemia results primarily from decreased synthesis. Using multiple linear regression analysis, the strongest correlates to plasma albumin concentration in 115 hemodialysis patients were the plasma level of the acute-phase C-reactive protein (CRP) and the normalized protein catabolic rate (PCRn). These two independent predictors of plasma albumin concentrations are markers of inflammation and of protein intake, respectively. CRP levels correlate more strongly with albumin concentration than does low PCRn. Activity of the acute-phase response is an important predictor of low plasma albumin concentration in hemodialysis patients independently of nutritional factors. External loss of albumin in the dialysate is an additional factor that contributes significantly to hypoalbuminemia in PD patients.

Long-term ouabain administration produces hypertension in rats

Ouabain has recently been identified as an endogenous Na(+)-K+ pump inhibitor. We administered ouabain chronically to normotensive rats with varying degrees of reduced renal mass (RRM) and to normal two-kidney rats to see whether hypertension could be produced. Normal male Wistar rats and rats with 25%, 60%, and 70% RRM received ouabain (13.9 micrograms/kg per day IP) in normal saline for 4 weeks followed by ouabain (27.8 micrograms/kg per day IP) for 3 to 4 more weeks. Respective control animals received vehicle only. Blood pressure was recorded weekly by tail plethysmography. Animals received tap water and standard rat chow, except for 70% RRM rats, which received distilled water and sodium-free chow. After 6 to 8 weeks of treatment, with rats under thiobutabarbital anesthesia, direct blood pressure was determined. Plasma, tissue, and urinary ouabain levels were measured with a specific radioimmunoassay. Animals receiving ouabain developed significant increases in mean blood pressure compared with control animals (70% RRM, 147 +/- 4 vs 116 +/- 4 mm Hg; 60% RRM, 140 +/- 4 vs 107 +/- 3 mm Hg; 25% RRM, 131 +/- 5 vs 100 +/- 2 mm Hg; no RRM, 116 +/- 4 vs 98 +/- 5 mm Hg). Plasma ouabain levels measured 24 hours after the last ouabain dose were not different in animals receiving ouabain vs those receiving vehicle. However, kidney tissue ouabain levels were significantly greater (6.39 +/- 1.17 vs 2.36 +/- 0.52 micrograms/kg, P < .05) in animals receiving ouabain. In conclusion, ouabain, given chronically, is associated with the development of hypertension in RRM rats as well as in normal rats. Blood pressure was greater in animals with greater degrees of RRM for a given ouabain dose.