Physiological oxygen and co-culture with human fibroblasts facilitate in vivo-like properties in human renal proximal tubular epithelial cells.

Reliable prediction of compound mediated nephrotoxicity in humans is still unsatisfactory irrespective of the recent advancements in in silico, in vitro and in vivo models. Therefore, current in vitro approaches need refinement to better match the human in vivo situation, specifically with regard to the potential influence of other cell types (e.g. fibroblasts) and to the potential biases introduced by the excessive 21% O2 (AtmOx) as employed in routine cell culturing. We used a transwell co-culture model combining human renal proximal tubule epithelial cells (RPTEC/TERT1) and human fibroblasts (fHDF/TERT166) to compare the functional properties and expression of selected marker proteins at 21% O2 and at the physiologically normal 10% O2 tension (PhysOx) commensurate with in vivo conditions. Culturing at PhysOx and co-culturing with fibroblasts significantly improved epithelial barrier integrity, expression of transporters (e.g. aquaporin 2; OCT-MATE; MRP-OAT) and metabolism. Moreover, beyond culturing these human cells in co-culture for up to 41 days, we were able to demonstrate increased functionality of cation transport, as shown via ASP+ (OCT-MATE axis), and anion transport, as shown via LY (MRP-OAT axis). Thus, adjusting the in vitro system to near physiological conditions had a major impact on functionality and provides the basis for the future development of true flow-through microfluidic renal testing systems with better predictability of human renal proximal toxicity.

Characterization of Novel Collagenolytic Proteases.

Collagenolytic proteases have many potential applications in different areas of science, industry, and medicine. The determination of the activity of such proteins is paramount to their application. Here, we describe methods which can be applied to determine the activity and some basic characteristics of potential collagenases.

Networks of protein kinases and phosphatases in the individual phases of contextual fear conditioning in the C57BL/6J mouse.

Although protein kinases and phosphatases have been reported to be involved in fear memory, information about these signalling molecules in the individual phases of contextual fear conditioning (cFC) is limited. C57BL/6J mice were tested in cFC, sacrificed and hippocampi were used for screening of approximately 800 protein kinases and phosphatases by protein microarrays with subsequent Western blot confirmation of threefold higher or lower hippocampal levels as compared to foot shock controls. Immunoblotting of the protein kinases and phosphatases screened out was carried out by Western blotting. A network of protein kinases and phosphatases was generated (STRING 9.1). Animals learned the task in the paradigm and protein kinase and phosphatase levels were determined in the individual phases acquisition, consolidation and retrieval and compared to foot shock controls. Protein kinases discoidin containing receptor 2 (DDR2), mitogen activated protein kinase kinase kinase 7 (TAK1), protein phosphatases dual specificity protein phosphatase (PTEN) and protein phosphatase 2a (PP2A) were modulated in the individual phases of cFC. Phosphatidyl-inositol-3,4,5-triphosphate 3-phosphatase and phosphatidylinositol-3 kinase (PI3K) that is interacting with PTEN were modulated as well. Freezing time was correlating with PP2A levels in the retrieval phase of cFC. The abovementioned protein kinases, phosphatases and inositol-signalling enzymes were not reported so far in cFC and the results are relevant for interpretation of previous and design of future studies in cFC or fear memory. Protein phosphatase PP2A was, however, the only signalling compound tested that was directly linked to retrieval in the cFC.