Mitogenic activity of sulfated chitosan and cellulose derivatives is related to protection of FGF-2 from proteolytic cleavage.

Novel chitosan (CHS) and cellulose sulfates (CSs) are studied regarding their mitogenic activity and their protective effect against proteolytic digestion of FGF-2. An intermediate degree of sulfation (DS(S) ) and lower concentration of CHS have superior effect on 3T3 cell growth while the mitogenic activity of CS increases with DS(S) and concentration. Experiments with trypsin as model proteinase show that protection of FGF-2 from proteolytic digestion depends on DS(S) and the concentration of derivatives in the same manner as cell growth. Studies on stability of FGF-2 added to cultures of 3T3 cells show that the FGF-2 concentration remains higher in the presence of derivatives. Results indicate that the mitogenic activity of CHS and CS is due to protection of FGF-2 from proteolytic cleavage.

Controlling fibroblast adhesion with pH modified polyelectrolyte multilayers.

Tissue cells need to adhere to a biomaterial surface to promote their growth and differentiation and, thus, foster the integration of implants. As a result, surface features and their modification play an important role in biomedical applications. In this study, the layer-by-layer (LbL) technique was used to design self-assembled polyelectrolyte multilayer (PEM) coatings of polyethyleneimine (PEI) and heparin (HEP) on glass, which will control the adhesion of primary human dermal fibroblasts in a model system. The study showed that, among other surface features, the wettability of surfaces can be controlled by changing the conditions during multilayer self-assembly. Here, the pH value of the HEP solution was adjusted to acidic or alkaline values for terminal layers, which also led to a change in multilayer growth. Further, the study revealed that plain terminal layers were rather cytophobic. Upon pre-adsorption of fibronectin (FN), a clear effect on cell adhesion and morphology in dependence on the pH setup was evident. Proliferation studies clearly showed that terminal layers, which impaired cell adhesion, also inhibited growth of human fibroblasts under serum-conditions. On the other hand, on layers with pronounced cell adhesion an elevated cell growth was also observed. As a result, HEP terminated multilayers are interesting for applications requiring cell repellent properties, whereas PEI terminated multilayers could be used to promote cell adhesion and growth on implant surfaces.

Immobilization of poly (ethylene imine) on poly (L-lactide) promotes MG63 cell proliferation and function.

Poly (ethylene imine) (PEI) is a polycation widely used for DNA transfection to cells but also applied as primary polycation for layer-by-layer (LBL) assembly of polyelectrolytes. The aim of the present study was to investigate the effect of modification with PEI on the biocompatibility of poly (L-lactide) (PLLA) films. PEI with different molecular weight was immobilized on PLLA by either adsorption or covalent binding. Cell morphologies, immuno-fluorescence staining, cell proliferation by lactate dehydrogenase assay and cell differentiation by alkaline phosphatase assay were utilized to assess the biocompatibility of the modified PLLA using osteoblast cell line MG63. Results revealed that PEI modification remarkably improved cell adhesion, viability, proliferation and function compared with plain PLLA. Hence, PEI-modified PLLA is acceptable as transfection vehicle for engineering of bone and other tissues, or as primary layer to allow LBL assembly to generate biomimetic surface coatings.

pH-dependent modulation of fibroblast adhesion on multilayers composed of poly(ethylene imine) and heparin.

Adhesion of tissue cells is a prerequisite for their growth and differentiation but prevents also apoptosis. Here the layer-by-layer technique (LbL) was used to design multilayer structures of poly(ethylene imine) (PEI) and heparin (HEP) on glass as model biomaterial to control the adhesion of primary human dermal fibroblasts. Distinct surface features like wettability, charge and lateral structures were controlled by changing the pH value of the HEP solution during multilayer assembly to acidic, neutral or alkaline values. While plain terminal layers were rather cytophobic, the pre-adsorption of serum or fibronectin (FN) caused a distinct change in cell morphology in dependence on the pH setup. The effect of serum was more prominent on PEI layers probably due to their positive surface charge, whereas the effect of FN was more pronounced on HEP terminated multilayers possibly due to its ability to bind FN specifically. Those layers which hampered cell adhesion also inhibited growth of human fibroblasts under serum conditions. Conversely, on layers where cell adhesion was increased also an elevated growth and, thus, metabolic activity was observed.

Curcumin induces changes in expression of genes involved in cholesterol homeostasis.

Curcuminoids, the yellow pigments of curcuma, exhibit anticarcinogenic, antioxidative and hypocholesterolemic activities. To understand the molecular basis for the hypocholesterolemic effects, we examined the effects of curcumin on hepatic gene expression, using the human hepatoma cell line HepG2 as a model system. Curcumin treatment caused an up to sevenfold, concentration-dependent increase in LDL-receptor mRNA, whereas mRNAs of the genes encoding the sterol biosynthetic enzymes HMG CoA reductase and farnesyl diphosphate synthase were only slightly increased at high curcumin concentrations where cell viability was reduced. Expression of the regulatory SREBP genes was moderately increased, whereas mRNAs of the PPARalpha target genes CD36/fatty acid translocase and fatty acid binding protein 1 were down-regulated. LXRalpha expression and accumulation of mRNA of the LXRalpha target gene ABCg1 were increased at low curcumin concentrations. Although curcumin strongly inhibited alkaline phosphatase activity, an activation of a retinoic acid response element reporter employing secreted alkaline phosphatase was observed. These changes in gene expression are consistent with the proposed hypocholesterolemic effect of curcumin.