Attachment and proliferation of human osteoblast-like cells on guided bone regeneration (GBR) membranes in the absence or presence of nicotine: an in vitro study.

PURPOSE: To compare in vitro the attachment and proliferation of human osteoblast-like cells (MG63) on tissue culture plates and guided bone regeneration (GBR) membranes in the absence or presence of nicotine. MATERIALS AND METHODS: Membrane samples were fixed to wells and the cell number (CN) was counted after 24 hours (attachment assay) or 5 days (proliferation assay). The ratio of cell count (RCC) (CN at 5 days/CN at 24 hours) was calculated. The study had three parts: First, five different resorbable GBR membranes were compared (Resolut Adapt LT [RALT], Biocollagen [BC], Bio-Gide [BG], OsseoGuard [OG], and Demokritos Human Tissue Bank [DEM]). Next, cells were cultured on tissue culture plates with five different concentrations of nicotine. Finally, cells were cultured on the membrane that had demonstrated the highest RCC and CN in part 1 with four different concentrations of nicotine. RESULTS: At 24 hours, BG showed the highest CN and OG showed the lowest CN. At 5 days, BG showed the highest CN. The order of RCC was BG > OG > DEM > RALT ~ BC. At 24 hours, lower nicotine concentrations (0.3 and 3 µg/mL) showed higher CNs versus the control, whereas CNs for high nicotine concentrations (30 and 300 µg/mL) were lower than for the control. CN at 5 days and RCC were lowest with 300 µg/mL nicotine. At 24 hours and 5 days, all differences among wells with membrane were statistically insignificant. Nevertheless, CN at 5 days and RCC were highest with the lowest nicotine concentration (3 µg/mL) and lowest with high concentrations. CONCLUSIONS: Membrane materials influence attachment and proliferation of bone cells and, therefore, could affect the outcomes of GBR. On both tissue culture plates and membranes, there is a tendency toward a biphasic effect of nicotine, with stimulatory effects at low concentrations and inhibitory effects at high concentrations.

Glutamine, ornithine, citrulline and arginine levels in children with phenylketonuria: The diet effect.

BACKGROUND: Phenylketonuria (PKU) therapeutic diet is characterized by the great replacement of natural protein with a phenylalanine-free formula. AIM: To investigate the effect of diet on the amino acid serum levels in PKU patients and their total antioxidant status (TAS). METHODS: Thirty-seven poorly controlled patients (group A), 43 patients who strictly adhered to their diet (group B) and 50 controls were included in the study. In patients and controls blood chemistry, TAS and serum amino acid level determinations were performed. RESULTS: Phenylalanine levels significantly differed among the groups. Glutamine and ornithine levels were significantly higher in group A, while TAS (416±30 vs 228±23µmol/L, p<0.001), citrulline (39±15 vs 26±5µmol/L, p<0.001) and arginine levels (61±11 vs 80±12µmol/L, p<0.001) were higher in group B. The other determined amino acid serum levels did not differ among the groups of patients and controls. CONCLUSIONS: The high glutamine and ornithine levels in group A may reflect the high natural protein intake. High phenylalanine levels in these patients may locally affect the hepatocyte, enterocyte, and/or renal function resulting in low citrulline and arginine levels contributing to their low TAS.

Imatinib mesylate inhibits proliferation and exerts an antifibrotic effect in human breast stroma fibroblasts.

Tumor stroma plays an important role in cancer development. In a variety of tumors, such as breast carcinomas, a desmoplastic response, characterized by stromal fibroblast and collagen accumulation, is observed having synergistic effects on tumor progression. However, the effect of known anticancer drugs on stromal cells has not been thoroughly investigated. Imatinib mesylate is a selective inhibitor of several protein tyrosine kinases, including the receptor of platelet-derived growth factor, an important mediator of desmoplasia. Recently, we have shown that imatinib inhibits the growth and invasiveness of human epithelial breast cancer cells. Here, we studied the effect of imatinib on the proliferation and collagen accumulation in breast stromal fibroblasts. We have shown that it blocks the activation of the extracellular signal-regulated kinase and Akt signaling pathways and up-regulates cyclin-dependent kinase inhibitor p21(WAF1), leading to the inhibition of fibroblast proliferation, by arresting them at the G(0)/G(1) phase of the cell cycle. Imatinib inhibits more potently the platelet-derived growth factor-mediated stimulation of breast fibroblast proliferation. By using specific inhibitors, we have found that this is due to the inhibition of the Akt pathway. In addition, imatinib inhibits fibroblast-mediated collagen accumulation. Conventional and quantitative PCR analysis, as well as gelatin zymography, indicates that this is due to the down-regulation of mRNA synthesis of collagen I and collagen III-the main collagen types in breast stroma-and not to the up-regulation or activation of collagenases matrix metalloproteinase 2 and matrix metalloproteinase 9. These data indicate that imatinib has an antifibrotic effect on human breast stromal fibroblasts that may inhibit desmoplastic reaction and thus tumor progression.

Prior chronic in vivo glucocorticoid excess leads to an anabolic phenotype and an extension of cellular life span of skin fibroblasts in vitro.

Intense stress can be detrimental for tissue homeostasis and accelerates aging. On the other hand, repeated mild stresses can have beneficial and even life-prolonging effects. Hypersecretion of glucocorticoids (GCs) represents the major hormonal response to stress. However, besides its life-sustaining role, GC excess can promote a "catabolic" phenotype. Accordingly, we have studied the effect of long-lasting exposure to high GC levels in vivo on several parameters of tissue homeostasis, as well as cellular senescence, in cells removed from the high-GC milieu in vivo and then cultured in vitro. To this end, we have used human skin fibroblasts from (a) Cushing's syndrome patients that are characterized by chronic endogenous GC excess and (b) patients treated with exogenous GC administration. Interestingly, when Cushing's syndrome fibroblasts were cultured in vitro under standard conditions they express an "anabolic" phenotype, i.e., they restore their ability for collagen synthesis, secrete reduced levels of metalloproteases, and have an increased proliferative capacity and contractility. Furthermore, these cells exhibit a significant extension of their proliferative life span, while they respond better to exogenous stress by producing significantly higher levels of heat-shock protein-70 (HSP70). In addition, preliminary results with fibroblasts from patients subjected to chronic exogenous GC administration indicate that they express a similar behavior in vitro, at least with regard to the restoration of collagen expression. These data suggest that prior exposure to elevated GC concentrations is not associated with persisting adverse effects on fibroblasts and may also have a beneficial outcome in some aspects of cell physiology, including longevity in vitro.