Long-Term Fluoride Release from Dental Resins Affects STRO-1+ Cell Behavior.

Fluoride-releasing restorative dental materials can be beneficial to remineralize dentin and help prevent secondary caries. However, the effects of fluoride release from dental materials on the activity of dental pulp stem cells are not known. Here we investigate whether different fluoride release kinetics from dental resins supplemented with modified hydrotalcite (RK-F10) or fluoride-glass filler (RK-FG10) could influence the behavior of a human dental pulp stem cell subpopulation (STRO-1(+) cells) known for its ability to differentiate toward an odontoblast-like phenotype. The 2 resins, characterized by similar physicochemical properties and fluoride content, exhibited different long-term fluoride release kinetics. Our data demonstrate that long-term exposure of STRO-1(+) cells to a continuous release of a low amount of fluoride by RK-F10 increases their migratory response to transforming growth factor ß1 (TGF-ß1) and stromal cell-derived factor 1 (SDF-1), both important promoters of pulp stem cell recruitment. Moreover, the expression patterns of dentin sialoprotein (dspp), dentin matrix protein 1 (dmp1), osteocalcin (ocn), and matrix extracellular phosphoglycoprotein (mepe) indicate a complete odontoblast-like cell differentiation only when STRO-1(+) cells were cultured on RK-F10. On the contrary, RK-FG10, characterized by an initial fluoride release burst and reduced lifetime of the delivery, did not elicit any significant effect on both STRO-1(+) cell migration and differentiation. Taken together, our results highlight the importance of taking into account fluoride release kinetics in addition to fluoride concentration when designing new fluoride-restorative materials.

Efficient cultivation of neural stem cells with controlled delivery of FGF-2.

Neural stem cells (NSCs) raised the hope for cell-based therapies in human neurodevelopmental and neurodegenerative diseases. Current research strategies aim to isolate, enrich, and propagate homogeneous populations of neural stem cells. Unfortunately, several concerns with NSC cultures currently may limit their therapeutic promise. Exhaustion of growth factors and/or their uncontrolled release with burst and fall in their concentration may greatly affect the in vitro behavior of NSCs. In this context, we investigate whether a device containing heparan sulfate (HS), which is a co-factor in growth factor-mediated cell proliferation and differentiation, could potentiate and prolong the delivery of fibroblast growth factor-2 (FGF-2) and thus improve in vitro NSC cultivation. We demonstrated that NSCs cultivated in media with a controlled release of FGF-2 from a polyelectrolyte polymer showed a higher proliferation rate, and reduced apoptosis and senescence. In these experimental conditions NSCs preserve their stemness properties for a longer period of time compared with controls. Also of interest is that cell fate properties are conserved as well. The controlled release of FGF-2 reduced the level of oxidative stress and this is associated with a lower level of damaged DNA. This result may explain the reduced level of senescence and apoptosis in NSCs cultivated in the presence of hydrogel-releasing FGF-2.

tBid induces alterations of mitochondrial fatty acid oxidation flux by malonyl-CoA-independent inhibition of carnitine palmitoyltransferase-1.

Recent studies suggest a close relationship between cell metabolism and apoptosis. We have evaluated changes in lipid metabolism on permeabilized hepatocytes treated with truncated Bid (tBid) in the presence of caspase inhibitors and exogenous cytochrome c. The measurement of beta-oxidation flux by labeled palmitate demonstrates that tBid inhibits beta-oxidation, thereby resulting in the accumulation of palmitoyl-coenzyme A (CoA) and depletion of acetyl-carnitine and acylcarnitines, which is pathognomonic for inhibition of carnitine palmitoyltransferase-1 (CPT-1). We also show that tBid decreases CPT-1 activity by a mechanism independent of both malonyl-CoA, the key inhibitory molecule of CPT-1, and Bak and/or Bax, but dependent on cardiolipin decrease. Overexpression of Bcl-2, which is able to interact with CPT-1, counteracts the effects exerted by tBid on beta-oxidation. The unexpected role of tBid in the regulation of lipid beta-oxidation suggests a model in which tBid-induced metabolic decline leads to the accumulation of toxic lipid metabolites such as palmitoyl-CoA, which might become participants in the apoptotic pathway.

Differential expression of multiple transglutaminases in human colon: impaired keratinocyte transglutaminase expression in ulcerative colitis.

BACKGROUND AND AIMS: Ulcerative colitis (UC) is characterised by refractory inflammatory ulceration and damage to the colon. The mechanisms underlying impaired healing have yet to be defined. As transglutaminase expression resulting in matrix protein cross linking is associated with increased wound healing in a rat model of colitis, we hypothesised that different types of transglutaminase might also play a role in UC. PATIENTS AND METHODS: Endoscopic and histological indices were studied in 26 patients with UC (10 active and 16 inactive) and in 20 normal controls undergoing colonoscopy. Transglutaminase activity was evaluated in plasma (factor XIIIa) by a radioenzymatic method. Factor XIIIa, tissue and keratinocyte transglutaminase protein content, and mRNA expression in the colon were evaluated by western blot analysis and semiquantitative reverse transcription-polymerase chain reaction (RT-PCR), respectively. Colonic location of transglutaminases and their reaction products, the epsilon-(gamma-glutamyl)lysine bonds, was evaluated by immunohistochemistry using specific monoclonal antibodies. RESULTS: Transglutaminase activity was significantly lower in the plasma of patients with active UC (4.2 (2.4) mU/ml; p<0.05 v controls) than in those with inactive UC and controls (10.6 (2.2) and 12.1 (1.7) mU/ml). As shown by western blot, protein levels of tissue transglutaminase and factor XIIIa were unchanged in active UC compared with inactive disease and controls, while the keratinocyte form was reduced in active UC. Tissue transglutaminase and factor XIIIa immunostaining was strongly present in damaged areas colocalising with isopeptide bonds. In contrast, the keratinocyte form was almost absent in active UC and localised in the upper part of the crypts in normal subjects. RT-PCR showed upregulation of tissue transglutaminase mRNA in active UC (320% compared with controls) while keratinocyte transglutaminase gene expression was downregulated in active UC. CONCLUSIONS: The results of the present study support the concept that, in the damaged colon, transglutaminases are needed in response to chronic injury and underline the key role of these enzymes in mucosal healing.

Hydrothane(R) interactions with biological components: a comparison with Chronoflex(R).

The interaction of a glycol-containing polyurethane, Hydrothane(R), was assessed with respect to protein adsorption and cell and bacterial adhesion. The results obtained were compared with those from a second polyurethane, Chronoflex(R). Dynamic contact angle (DCA) and protein adsorption studies indicated that the overall hydrophilic nature of Hydrothane in physiological environment was affected by the possible presence of hydrophobic domains still exposed at the surface after wetting. Indeed, despite the high degree of hydrophilicity in an aqueous environment, a stronger protein binding was evidenced on Hydrothane when the two serum- and urine-conditioned polyurethane surfaces were selectively washed by isopropanol/water mixtures of increasing concentrations. Furthermore, immunoblotting of the serum proteins adsorbed on Hydrothane demonstrated the presence on its surface of proteins able to establish hydrophobic interactions such as human serum albumin (HSA) and á 1-microglobulin ( á 1-m). The C3 fragment of complement showed an immunoblotting profile different from the control serum suggesting an activation of this fragment. The adhesion of fibroblasts and Pseudomonas aeruginosa on the surface of the two materials was evaluated and the data were related to protein adsorption. In both cases Hydrothane showed levels of adhesion of eukaryotic and prokaryotic cells significantly lower than Chronoflex. These data were related to the absence of a significant binding of proteins such as fibronectin bringing amino acid receptor sequences in their structure. (Journal of Applied Biomaterials & Biomechanics 2003; 1: 67-75).

17-beta estradiol elicits an autocrine leiomyoma cell proliferation: evidence for a stimulation of protein kinase-dependent pathway.

The mechanism by which estradiol (E2) acts on cell proliferation is still unclear. In this paper, we report the results of a series of experiments in an attempt to elucidate the effector pathway(s) involved in coupling the E2 receptors binding to cellular growth response in leiomyoma cells (LSMC). Under conditions of E2-dependent growth, E2 treatment of LSMC triggers rapid and transient activation of the MAP-kinase pathway. Interestingly, we demonstrate that the early downstream signal transduction events determined by E2-stimulation in quiescent LSMC, including the rapid protein tyrosine phosphorylation of a subset of intracellular proteins, such GAP, PI-3-K, and PLCgamma, and the concomitant activation of ancillary protein kinases, are related to E2-induced PDGF secretion. Moreover, we identify the PDGF, alone or in association with other growth factors, as the main growth factor involved in the proliferation response of LSMC to E2 stimulation. The addition of neutralizing antibodies anti-PDGF was able to inhibit the mitogenic activity present in LSMC conditioned media samples. On the other hand, E2 did not affect the constitutive expression as well as the ligand affinity of PDGF receptors on LSMC plasmamembrane. Cell treatment with the antiestrogen ICI 182780 correlate both with a perturbation of E2-induced transductional circuit and with the disappearance of the mitogenic factor, PDGF, in LSMC conditioned media; the latter therefore, represents the main autocrine mediator of cell growth modulation, upregulated by E2 and down-regulated by antiestrogenic compound. Our experiments suggest that growth factor secretion is an initial and integral part of the signaling events mediated by the estradiol receptors, not related, at least in part, to E2 transcriptional modulation.

Increased expression of IGF-binding protein-5 in Duchenne muscular dystrophy (DMD) fibroblasts correlates with the fibroblast-induced downregulation of DMD myoblast growth: an in vitro analysis.

In DMD the progressive loss of muscle ability and concomitant increasing fibrosis might originate from, besides other causes, the fibroblast paracrine inhibition of satellite cell "growth." In this study we report that in myoblast/fibroblast coculture experiments, the presence of DMD fibroblasts negatively interfered with DMD myoblast growth to an extent directly proportional to the percentage of DMD fibroblasts present in the mixed-cell cultures. Moreover, the observation that media conditioned with proliferating DMD fibroblasts inhibited the growth of DMD myoblasts more seriously than did control fibroblast-conditioned media suggested a paracrine effect by diffusible factors. IGF-binding proteins could act as such diffusible factors; in fact, IGFBP-5 transcript increased threefold in DMD fibroblasts proliferating in DMD muscle extracts, whereas IGFBP-3 mRNA decreased. In addition, high levels of IGFBP-5 protein were detected in DMD fibroblast-conditioned media. In neutralizing IGFBP-5 in DMD fibroblast-conditioned media by means of specific antibodies, or inhibiting IGFBP-5 gene expression in DMD fibroblasts by means of oligo antisense, the fibroblast-conditioned media lost inhibitory power over DMD myoblast proliferation.

Phenotypic features of alveolar monocytes/macrophages and IL-8 gene activation by IL-1 and TNF-alpha in asthmatic patients.

The alveolar macrophage (AM), a major defense cell in the lung, participates in immune and inflammatory reactions through the release of several regulatory and chemotactic cytokines. In particular, macrophages are considered to play a pivotal proinflammatory role in the production and maintenance of airway inflammation and bronchial hyperreactivity. To assess the phenotypic pattern of AM from asthmatic subjects, we performed the following experiments: 1) cytofluorometric analysis of specific phenotypic features (CD11b, CD14, CD16, CD45, HLA-DR, CD71, CD95, and CD44) 2) assessment of the production of tumor necrosis factor (TNF)-alpha, interleukin (IL)-1, and the chemotactic regulatory cytokine IL-8 by unstimulated and lipopolysaccharide-stimulated AM. In these patients, we phenotypically characterized the AM, showing their strong proinflammatory activity also in patients with mild asthma. Their activity has been clarified by our biomolecular data that showed a constitutive basal IL-8 production by AM, and also indicated that IL-1 and TNF-alpha were able to upregulate the ability of activated human AM to produce IL-8 at the protein and messenger ribonucleic acid (mRNA) levels.

Defective growth in vitro of Duchenne Muscular Dystrophy myoblasts: the molecular and biochemical basis.

As the molecular basis of Duchenne Muscular Dystrophy (DMD) was being discovered, increasing focus was placed on the mechanisms of progressive failure of myoregeneration. In this study, we propose a pathogenesis model for DMD, where an autocrine growth factor release of TGF-beta1-from necrotic myofibers-could contribute to the increasing loss of muscle regeneration. In fact, we report evidence that DMD myoblasts reduce their proliferation rate, in time and later cultures; in connection with this, we observed TGF-beta1 increase in conditioned media of DMD myoblasts, able to control the myoblast growth by reducing fusion and differentiation of DMD satellite cells.

Modulation of in vitro myogenesis induced by different polymer substrates.

The understanding of substrate dependence of cellular differentiation is important in the surface design of biocompatible artificial devices as well as cell-incorporated tissue engineered devices. In an attempt to understand some of the genetic and epigenetic aspects of the control of cell differentiation in the presence of two different materials, Chronoflex (CH) and plasma treated Chronoflex coated with Hyaluronan (CH-HA), we used primary cultures of human myogenic cells, a model that encompasses cell proliferation, migration, fusion, and differentiation dependent gene activation. By testing both the material samples on the growth of human myoblasts in primary cultures, we demonstrated that both CH and CH-HA substrates were able to support the cell growth since they did not affect cell count and DNA synthesis. On the contrary, the degree of myoblast differentiation, assessed as a function of creatine phosphokinase (CPK) activity on living cells, was completely different on the two biomaterials. Indeed, the amount of CPK increased on CH-HA cultured cells as a result of myotube formation, while CH grown myoblasts remained unfused and displayed no increase on the CPK activity even after 12 days culture. Moreover, the expression level of MyoD and myogenin mRNA, both related to myogenic cell differentiation, appeared extremely low in CH-grown cells, while they were rapidly induced in CH-HA cultured myoblasts.

Role of monocyte/macrophage population in immune response.

The central role of macrophages in host defence against infection and malignancy and processes such as atherosclerosis, makes macrophage biology a fascinating area for research in immunology and cell biology. The endocytic and phagocytic machinery of macrophages is particularly potent and their secretory potential is large and diverse. Studies of cell surface receptors and their role in antigen presentation, microbicidal and tumouricidal activity are actively researched and progress is now being made in defining receptors responsible for monocyte/macrophage cell adhesion within the immune system. This short-review highlights the recent advances in macrophage biology.

The differential effects of poly(2-hydroxyethyl methacrylate) and poly(2-hydroxyethyl methacrylate)/poly(caprolactone) polymers on cell proliferation and collagen synthesis by human lung fibroblasts.

Because of its chemical versatility and demonstrated biocompatibility, poly(2-hydroxyethyl methacrylate) (pHEMA) has been widely used as a polymer for biomedical applications. Since this hydrophilic material shows a poor interface with cells, blendings with other polymers were done to improve cytocompatibility. In our polymer, the presence of hydrophobic dominions on the material surface, due to the interpenetrating polymerization of pHEMA with poly(caprolactone) (PCL), seems to ameliorate the cytocompatibility in terms of cell adhesion and metabolism. For our experiments, we used IMR-90 human fibroblasts, as these cells strongly regulate DNA, RNA, and protein synthesis as anchorage-dependent variables. Cell attachment on a pHEMA/PCL interpenetrating polymer network was optimal, suggesting a strong adhesion between the cells and the polymer surface. Cell adhesion was weaker on pHEMA, as a significant fraction of the fibroblasts revealed a lack of spreading, with most cells remaining spherical. Moreover, only fibroblasts seeded on pHEMA significantly decreased mRNA synthesis; collagen production and cell shapes ranged from fully flat and proliferating, to minimally spread and nonproliferating. Finally, DNA synthesis, as a measure of cell proliferation, was markedly inhibited in cells cultured on pHEMA but not on pHEMA/PCL. In conclusion, our results suggest that control of cell growth and metabolism by biomedical polymers is based on physicochemical mechanism(s) in which the hydrophilicity/hydrophobicity ratio of the material surfaces may play an important role.

Modulation of cytokine production in activated human monocytes by somatostatin.

The immunosuppressor effects of the widely distributed neuropeptide somatostatin were examined on purified peripheral blood human monocytes. Somatostatin, at concentrations thought to be physiologic (10(-10)-10(-7) M), regulated monocyte/macrophage responses to (LPS) stimulation, as reflected by interleukin production. In particular, somatostatin had direct inhibitory effects on TNF-alpha, IL-1 beta, and IL-6 secretion by LPS-activated monocytes, while the decrease on IL-8 synthesis was modulated mainly by the action of somatostatin on TNF-alpha and IL-1 beta. In fact, the addition of these two inflammatory cytokines to the monocyte culture medium was able to induce IL-8 expression, as demonstrated by mRNA analysis, also in presence of the neuropeptide. Although somatostatin affected IL-8 production in an indirect way, it suppressed directly the chemotactic response of neutrophils to IL-8. Finally, somatostatin downregulation of monocyte activation was confirmed by the decrease of HLA-DR expression on cell plasma membranes (52% versus 33%). Our results confirm that somatostatin exerts preferential effects on the suppression of immunoreactions by modulating cytokine production and activity.

Chitosan-mediated stimulation of macrophage function.

According to the modern definition of biocompatibility, a biocompatible material need not be inert but be bioactive. A benign reactivity implies that the reactivity has to be appropriate for the intended use. Chitosan, a non-acetylated or partially deacetylated chitin (a linear homopolymer of beta (1-4)-linked N-acetylglucosamine) has been proposed as a biomaterial because of its apparent satisfactory biocompatibility. The present investigation demonstrates that chitosan has an in vitro stimulatory effect on both macrophage nitric oxide (NO) production and chemotaxis. The macrophage NO secretion is attributed to the N-acetylglucosamine unit of the chitosan molecule rather than to the glucosamine residue (28 and 15 microM NO respectively). Moreover, the immune stimulatory effect of chitosan was very specific since other glycosaminoglycans, such as N-acetyl-D-mannosamine and N-acetyl-D-galactosamine, had no effects on NO production (5 and 8 respectively). In vivo experiments strengthen this hypothesis. Transmission electron microscopy analysis identifies the presence of many leucocytes in the specimens after 14 d post-implantation, showing poor healing processes (i.e. fibroblast proliferation and collagen deposition) that characterize the tissue repair at this time in our animal model.

In vivo induction of macrophage Ia antigen (MHC class II) expression by biomedical polymers in the cage implant system.

Examination of the cellular components in the inflammatory exudate, which infiltrates subcutaneous cages, can be used to monitor the progress of an inflammatory response to an implanted material. Of particular interest is the study of monocyte/macrophage infiltration into the implanted cages containing biomaterials, as macrophages may initiate a wide spectrum of responses upon interaction with a foreign material. In this study, the authors propose a technique using subcutaneous tissue cages in conjunction with cytofluorimetric analysis of exudate leukocytes to evaluate the monocyte/macrophage cell activation in response to different materials. The studies reported here used several materials (thermoplastic and elastomeric polymers) as the challenging agent, to demonstrate whether polymers, chemically different from each other, could differentially activate macrophages to carry out their proinflammatory role more effectively. The materials tested included: poly(etherurethane ureas) (PEUU A'), poly(etherurethane ureas) with a surface active additive, Methacrol, (PEUU C'), polymethylsiloxane (PDMS), polyetherimide, (PEI), and polyetheretherketone, (PEEK). For all tested materials, the maximum numbers of exudate cells and of Ia-positive macrophages were found on day 7, although the entity of the cell increase was associated with the material used for the implant. Similarly, the percentage of Ia-positive macrophages varied according to the specific polymer present in the cages after 7 days. By day 14, the percentage of Ia-positive macrophages decreased with individual exudates showing 19-32% Ia-positive cells depending on the different type of material. Only in the case of PDMS did the percentage of Ia-positive macrophages remain the same as compared with control empty cage macrophages.