Modulation of angiogenic functions in human macrophages by biomaterials.

We examined the ability of polyvinylchloride (PVC), polytetrafluorethylene (PTFE) and tissue culture polystyrene (TCPS) to affect angiogenic functions in human monocyte-derived macrophages by measuring the mRNA expression of genes encoding angiogenic and anti-angiogenic molecules including basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF), angiopoietin-1 (Ang-1) and thrombospondin-1 (Tsp-1). The angiogenic activity of the corresponding macrophage conditioned media (CM) was measured by the proliferation of endothelial cells and the sprouting of new capillaries from fragments of human placental blood vessels. We determined that bFGF was not expressed in macrophages while VEGF and Tsp-1 mRNAs were expressed constitutively. Ang-1 was expressed in macrophages cultured up to 7 days on PTFE and TCPS independent of the culture stage. In contrast, macrophages cultured on PVC did not produce detectable amounts of Ang-1 mRNA after 7 days. CM from macrophages cultured either on PTFE or TCPS stimulated angiogenesis whereas CM from macrophages cultured on PVC inhibited it. The results demonstrate that polymers can cause differential expression of the angiogenic molecule Ang-1 in macrophages. They also induce different phenotypes of macrophages, which can either stimulate or inhibit angiogenesis suggesting a material-dependent influence on neovascularization.

Active influx transport is mediated by members of the organic anion transporting polypeptide family in human epidermal keratinocytes.

Normal human epidermal keratinocytes have been shown to express a cell-type-specific pattern of extrahepatic cytochrome P450 enzymes and efflux transport proteins showing that these cells metabolize and excrete a variety of xenobiotics. Recently transport proteins involved in the uptake of xenobiotics have been detected and here we analyzed the mRNA and protein expression profiles and functional activities of these proteins in human keratinocytes in comparison to primary liver cells. The transporters studied included the subtypes A, B, C, D, and E of the organic anion transporting polypeptide (OATP) family, which are responsible for the uptake of various anionic and neutral molecules and especially organic cations - including drugs. Constitutive expression of OATP-B, OATP-D, and OATP-E was shown for the first time in normal human epidermal keratinocytes on a molecular level using reverse transcription polymerase chain reaction and northern blot analysis, as well as in human skin tissue shown by tissue blot hybridization and immunohistochemistry. Expression of OATP-A and OATP-C was not detected in any of the keratinocyte samples. In contrast, liver tissue showed a significant expression of OATP-A and OATP-B as well as OATP-C, a weak expression of OATP-D, and no expression of OATP-E. These data revealed that normal human epidermal keratinocytes express a specific profile of transporters involved in drug influx. Using a newly developed uptake-transport assay, uptake of known and well-characterized OATP substrates like estradiol-17beta-glucuronide and estrone sulfate was inhibited in normal human epidermal keratinocytes by specific inhibitors such as taurocholate, verifying the functional capacity of the expressed OATPs. Human dermal fibroblasts seem to have a lower influx transport activity for estradiol-17beta-glucuronide, which correlates with the immunohistologic data. Even though the substrate specificity of the OATP isoforms is only partially known until now, our findings support the concept that uptake of large organic cations like drugs in keratinocytes is an active transport process mediated by members of the OATP family.