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Query: UNIPROT:P00750 (PLA)
 16,800 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Growth plate chondrocytes from both male and female rats have nuclear receptors for 17beta-estradiol (E(2)); however, recent studies indicate that an alternative pathway involving a membrane receptor may also be involved in the female cell response. E(2) directly affects the fluidity of chondrocyte membranes derived from female, but not male, rats. In addition, E(2) activates PKC in a nongenomic manner in female cells, and chelerythrine, a specific inhibitor of PKC, inhibits E(2)-dependent alkaline phosphatase activity in these cells, indicating PKC is involved in the signal transduction mechanism. The aims of this study were: (1) to examine if PKC mediates the effect of E(2) on chondrocyte proliferation, differentiation, and matrix synthesis; and (2) to determine the pathway that mediates the membrane effect of E(2) on PKC. Confluent, fourth passage resting zone (RC) and growth zone (GC) chondrocytes from female rat costochondral cartilage were treated with 10(-10) to 10(-7) M E(2) in the presence or absence of the PKC inhibitor chelerythrine, and changes in alkaline phosphatase specific activity, proteoglycan sulfation, and [3H]thymidine incorporation were measured. To examine the pathway of PKC activation, chondrocyte cultures were treated with E(2) in the presence or absence of genistein (an inhibitor of tyrosine kinases), U73122 or D609 (inhibitors of phospholipase C [PLC]), quinacrine (an inhibitor of phospholipase A(2) [PLA(2)]), and melittin (an activator of PLA(2)). Alkaline phosphatase specific activity and proteoglycan sulfation were increased and [3H]thymidine incorporation was decreased by E(2). The effects of E(2) on all parameters were blocked by chelerythrine. Treatment of the cultures with E(2) produced a significant dose-dependent increase in PKC. U73122 dose-dependently inhibited the activation of PKC in E(2)-stimulated female chondrocyte cultures. However, the classical receptor antagonist ICI 182780 was unable to block the stimulatory effect of E(2) on PKC. Moreover, the classical receptor agonist diethylstilbestrol (DES) had no effect on PKC, nor did it alter the stimulatory effect of E(2). Inhibition of tyrosine kinase and PLA(2) had no effect on the activation of PKC by E(2). The PLA(2) activator also had no effect on PKC activation by E(2). E(2) stimulated PKC activity in membranes isolated from the chondrocytes, demonstrating a direct membrane effect for this steroid hormone. These data indicate that the rapid nongenomic effect of E(2) on PKC activity in chondrocytes from female rats is sex-specific and dependent upon a G-protein-coupled phospholipase C.
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PMID:The membrane effects of 17beta-estradiol on chondrocyte phenotypic expression are mediated by activation of protein kinase C through phospholipase C and G-proteins. 1107 Mar 50

The ability to generate new bone for skeletal use is a major clinical need. Biomimetic scaffolds that interact and promote osteoblast differentiation and osteogenesis offer a promising approach to the generation of skeletal tissue to resolve this major health-care issue. In this study we examine the ability of surface-modified poly(lactic acid) (PLA) films and poly(lactic-co-/glycolic acid) (PLGA) (75:25) porous structures to promote human osteoprogenitor adhesion, spreading, growth, and differentiation. Cell spreading and adhesion were examined using Cell Tracker green fluorescence and confocal microscopy. Osteogenic differentiation was confirmed with alkaline phosphatase activity as well as immunocytochemistry for type I collagen, core binding factor-1 (Cbfa-1), and osteocalcin. Poor cell growth was observed on nonmodified PLA films and PLGA scaffolds. The polymers were then coupled with RGD peptides [using poly(L-lysine), or PLL] and physical adsorption as well as PLA films presenting adsorbed fibronectin (FN). Both modifications enhanced cell attachment and spreading. On PLA-FN and PLA-PLL-GRGDS films, the osteoblast response was dose dependent (20 pmol/L to 0.2 micromol/L FN and 30 nmol/L to 30 micromol/L PLL-GRGDS) and significant at concentrations as low as 2 nmol/L FN and 30 nmol/L PLL-GRGDS. With optimal concentrations of FN or RGD, adhesion and cell spreading were comparable to tissue culture plastic serum controls. In PLGA (75:25) biodegradable porous scaffolds, coated with FN, PLL-GRGDS, or fetal calf serum for 24 h in alpha MEM alone, prior to growth in dexamethasone and ascorbate-2-phosphate for 4-6 weeks, extensive osteoblast impregnation was observed by confocal and fluorescence microscopy. Cell viability in extended culture was maintained as analyzed by expression of Cell Tracker green and negligible ethidium homodimer-1 (a marker of cell necrosis) staining. Alkaline phosphatase activity, type I collagen, Cbfa-1, and osteocalcin expression were observed by immunocytochemistry. Mineralization of collagenous matrix took place after 4 weeks, which confirmed the expression of the mature osteogenic phenotype. These observations demonstrate successful adhesion and growth of human osteoprogenitors on protein- and peptide-coupled polymer films as well as migration, expansion, and differentiation on three-dimensional biodegradable PLGA scaffolds. The use of peptides/proteins and three-dimensional structures that provide positional and environmental information indicate the potential for biomimetic structures coupled with appropriate factors in the development of protocols for de novo bone formation.
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PMID:Human osteoprogenitor growth and differentiation on synthetic biodegradable structures after surface modification. 1172 22

Despite the widespread role of transforming growth factor-beta3 (TGFbeta3) in wound healing and tissue regeneration, its long-term controlled release has not been demonstrated. Here, we report microencapsulation of TGFbeta3 in poly-d-l-lactic-co-glycolic acid (PLGA) microspheres and determine its bioactivity. The release profiles of PLGA-encapsulated TGFbeta3 with 50:50 and 75:25 PLA:PGA ratios differed throughout the experimental period. To compare sterilization modalities of microspheres, bFGF was encapsulated in 50:50 PLGA microspheres and subjected to ethylene oxide (EO) gas, radio-frequency glow discharge (RFGD), or ultraviolet (UV) light. The release of bFGF was significantly attenuated by UV light, but not significantly altered by either EO or RFGD. To verify its bioactivity, TGFbeta3 (1.35 ng/mL) was control-released to the culture of human mesenchymal stem cells (hMSC) under induced osteogenic differentiation. Alkaline phosphatase staining intensity was markedly reduced 1 week after exposing hMSC-derived osteogenic cells to TGFbeta3. This was confirmed by lower alkaline phosphatase activity (2.25 +/- 0.57 mU/mL/ng DNA) than controls (TGFbeta3- free) at 5.8 +/- 0.9 mU/mL/ng DNA (p < 0.05). Control-released TGFbeta3 bioactivity was further confirmed by lack of significant differences in alkaline phosphatase upon direct addition of 1.35 ng/mL TGFbeta3 to cell culture (p > 0.05). These findings provide baseline data for potential uses of microencapsulated TGFbeta3 in wound healing and tissue-engineering applications.
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PMID:Sustained release of TGFbeta3 from PLGA microspheres and its effect on early osteogenic differentiation of human mesenchymal stem cells. 1657 87

Phospholipase A(2) (PLA(2)) not only plays a role in the membrane vesiculation system but also mediates membrane-raft budding and fission in artificial giant liposomes. This study aimed to demonstrate the same effects in living cells. Differentiated Caco-2 cells were cultured on filter membranes. MDCK cells were challenged with Influenza virus. The MDCK cultures were harvested for virus titration with a plaque assay. Alkaline phosphatase (ALP), a membrane-raft associated glycosylphosphatidylinositol (GPI)-anchored protein, was 70% released by adding 0.2 mmol/l lysophosphatidylcholine, which was abolished by treatment with a membrane-raft disrupter, methyl-beta-cyclodextrin. Activation of calcium-independent PLA(2) (iPLA(2)) by brefeldin A increased the apical release of ALP by approximately 1.5-fold (p<0.01), which was blocked by PLA(2) inhibitor bromoenol lactone (BEL). BEL also reduced Influenza virus production into the media (<10%) in the MDCK culture. These results suggest that cells utilize inverted corn-shaped lysophospholipids generated by PLA(2) to modulate plasma membrane structure and assist the budding of raft-associated plasma membrane particles, which virus utilizes for its budding. Brush borders are enriched with membrane-rafts and undergo rapid turnover; thus, PLA(2) may be involved in the regulatory mechanism in membrane dynamism. Further, iPLA(2) may provide a therapeutic target for viral infections.
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PMID:A possible role of lysophospholipids produced by calcium-independent phospholipase A(2) in membrane-raft budding and fission. 1964 79

This study was aimed at exploring the viability of osteoblasts on conductive tissue engineering material. Conductive biodegradable Polyprrole/Polylactide (PPy/PLA) was prepared by emulsion polymerization. Scanning electron microscope (SEM) and spectroscopy showed evenly dispersed PPy in PLA. PPy/PLA membrane was found being able to keep conductive stability for more than one month to provide electric circumstances (ECs) for osteoblasts. SEM displayed that osteoblasts adhered and spread well on PPy/PLA. ECs of 12.5, 25, 50, 75, 100, 125, 150, 175, 200 microA/cm2 were separately used to stimulate osteoblasts for 24h, 48h, 72h and 96h. Methyl-thiazole-tetrazolium (MTT) assay after 24h revealed that 50 microA/cm2 evidently accelerated osteoblasts proliferation. Alkaline phosphatase (ALP) activity assay revealed that, 48h later, 50 microA/cm2, and 75 microA/cm2 promoted osteoblasts differentiation. 50 microA/cm2 enhanced osteoblasts mineration. Conclusively, 50 microA/cm2 can strengthen osteoblasts' function and promote their viability.
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PMID:[Electrical stimulation enhances viability of osteoblasts on conductive biodegradable material]. 2084 48

Three-dimensional (3D) printing is a promising technology to fabricate the intricate biomimetic structure. The primary focus of this study was to develop the bioactive 3D-scaffolds to enhance bone regeneration. The 3D-poly (lactic acid) (PLA) scaffolds were extruded based on a computer-aided design (CAD) model and coated with gelatin (Gel) containing different concentrations of mucic acid (MA) and were investigated for their osteogenic potential. Coating the PLA scaffolds with Gel/MA improved their physicochemical properties, and the addition of MA did not alter these properties. The viability of mouse mesenchymal stem cells (mMSCs, C3H10T1/2) seeded onto the PLA/Gel/MA scaffolds remained unaffected both at metabolic and cell membrane integrity levels. Alkaline phosphatase and von Kossa staining indicated the promotion of osteoblast differentiation of mMSCs by MA in the PLA/Gel scaffolds. Inclusion of MA in PLA/Gel scaffolds also increased the expression of the master bone transcription factor, Runx2, and other osteoblastic differentiation marker genes in mMSCs. Thus, our results suggested that the 3D-printed PLA scaffolds coated with Gel/MA favor osteoblast differentiation and have potential applications in bone tissue engineering.
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PMID:3D-poly (lactic acid) scaffolds coated with gelatin and mucic acid for bone tissue engineering. 3256 92

A polylactide composite fracture fixator loaded with vancomycin cationic liposome (PLA@VL) was prepared by reverse evaporation method. The method of cationic liposome encapsulating vancomycin could effectively improve antibacterial property and achieve drug sustained release effect, so as to reduce toxicity of antibiotics in vivo. Scanning electron microscope (SEM) was used to observe morphology and Fourier transform infrared spectroscopy (FTIR) was used to detect the composition of the internal fixator. In vitro drug release model, in vitro degradation model and body fluid osteogenesis model were designed in this study. On the other hand, the experiments of inhibition zone and MC3T3-E1 osteoblasts in mice were conducted to explore antibacterial property, cell activity and adhesion of the PLA@VL composite internal fixator. Alkaline phosphatase (ALP) staining method and alizarin red assay were used to detect the osteogenic induction ability of the composite internal fixator. Finally, mice fracture models were established to verify osteogenic and anti-infection abilities of the composite internal fixator in vivo. The results showed that MC3T3-E1 cells had better adhesion and proliferation abilities on the PLA@VL composite internal fixator than on the PLA fixator, which indicated that the PLA@VL composite internal fixator possessed excellent osteogenic and anti-infection abilities both in vivo and in vitro. Therefore, the above experiments showed that the fracture internal fixator combined with vancomycin cationic liposome had better biocompatibility, antibacterial ability and osteogenic ability, which provides a promising anti-infection material for the clinical field of fracture.
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PMID:Study on the anti-infection ability of vancomycin cationic liposome combined with polylactide fracture internal fixator. 3318 Dec 11