Biomedical subjects

Yvonne Kapila

Publications and source records attributed to Yvonne Kapila.

3 recordsLinked to original sources

PubMed2006

Dexamethasone's enhancement of osteoblastic markers in human periodontal ligament cells is associated with inhibition of collagenase expression.

Although dexamethasone (Dex) substantially enhances the osteoblastic phenotype in osteogenic cells, including human periodontal ligament (PDL) cells, the basis for this response remains poorly understood. Since the accretion of a collagenous matrix is important for an osteoblastic response and dexamethasone is known to decrease collagenase expression, we examined whether osteoblastic differentiation mediated by Dex is linked to a decrease in collagenase expression in PDL cells. Early passage human PDL cells were exposed to Dex, or ascorbic acid (AA) or beta-glycerophosphate (betaGP) alone, or in various combinations in serum-free media for 3 or 5 days. Cells exposed to Dex alone or any combinations of treatments that included Dex demonstrated increased core binding factor alpha 1 (Cbfa1), alkaline phosphatase (AP), osteonectin (ON), osteopontin (OP), bone sialoprotein (BSP) and collagen I (alpha1) expression when compared to control cells or those exposed to AA or betaGP. The induction of these osteoblastic markers was accompanied by a decrease in collagenase-1 expression. Collagenase activity showed a statistically significant strong negative relationship to Cbfa1 (Pearson's r=-0.97), AP (r=-0.87), OP (r=-0.95) and BSP (r=-0.82) in 5-day cultures, and moderately strong relationship to ON (r=-0.74) from 3 days culture. Dex also produced a dose-dependent increase in AP that was paralleled by a decrease in collagenase activity (r=-0.98). Addition of collagenase inhibitors increased AP expression while concomitantly suppressing collagenase activity. Conversely, addition of exogenous collagenase decreased the AP phenotype of the cells, which was more marked in the absence then in the presence of Dex. The findings indicate that Dex enhances specific markers of osteoblastic differentiation in PDL cells by decreasing collagenase expression, and suggest that endogenous collagenase may regulate osteoblastic differentiation of these cells.

Alkaline Phosphatase↗

PubMed2004

Squamous cell carcinoma cell aggregates escape suspension-induced, p53-mediated anoikis: fibronectin and integrin alphav mediate survival signals through focal adhesion kinase.

Resistance to anoikis, or apoptosis triggered by detachment from the extracellular matrix (ECM), lengthens the survival of malignant cells, facilitating reattachment and colonization of secondary sites. To examine the molecular mechanisms underlying resistance to anoikis in human oral squamous cell carcinoma (SCC) cells, we cultured human squamous carcinoma (HSC-3) cells in suspension on plates coated with poly-2-hydroxyethyl methacrylate, which blocks access to the ECM. Cells in suspension that formed multicellular aggregates had significantly lower levels of apoptosis than single cells. Aggregates, but not single cells, had high levels of fibronectin. Preincubation with a cyclic arginine-glycine-aspartic acid peptide or fibronectin-blocking antibody significantly increased anoikis. Single cells had markedly lower expression of the integrin alpha(v) receptor than aggregates. Blocking alpha(v) function with a blocking antibody or by transfection with an antisense oligonucleotide increased apoptosis and inhibited aggregation. In single cells but not aggregates, phosphorylation of the integrin-associated focal adhesion kinase (FAK) at tyrosine 397 was reduced, and p53 levels were increased. Apoptosis was increased by blocking FAK with an antisense oligonucleotide and reduced by blocking p53. These findings show that SCC cells escape suspension-induced anoikis by forming multicellular aggregates that avail themselves of fibronectin survival signals mediated by integrin alpha(v). Single cells in suspension that do not form aggregates undergo anoikis because of decreased FAK phosphorylation and increased p53 levels. Thus, SCC cells appear to use neighboring cells and the ECM molecule FN to promote the metastatic phenotype.

Animals↗

PubMed2004

Functional differences between integrin alpha4 and integrins alpha5/alphav in modulating the motility of human oral squamous carcinoma cells in response to the V region and heparin-binding domain of fibronectin.

The high-affinity heparin-binding domain and the V region of fibronectin (FN) mediate invasion and migration of human oral squamous cell carcinoma (SCC) cells. We investigated the role of the alpha4, alpha5, and alphav integrin receptors--which are central to mediating interactions with these domains of FN--in regulating SCC cell migration. SCC cells expressed the alpha4, alpha5, and alphav integrin subunits on their surface, although alpha4 expression was low. Treatment with recombinant FN proteins containing an alternatively spliced V region (V+) and either an unmutated (H+) or a mutated, nonfunctional high-affinity heparin-binding domain (H-) increased expression of alpha5 and alphav and cell motility. Antisense alpha5 or alphav oligonucleotides inhibited cell motility stimulated by FN proteins, as did blocking antibodies to alpha5 or alphav. Blocking antibodies to alpha5 increased alphav and alpha4 levels, and blocking antibodies to alphav increased the levels of alpha5 and alpha4, without increasing cell motility. In contrast, an antisense alpha4 oligonucleotide and alpha4-blocking antibodies increased cell motility, especially migration stimulated by V+H+ and V+H- FN proteins. alpha4-Blocking antibodies alone increased motility, probably by inducing alpha5 and alphav expression. Transfection with alpha4 cDNA decreased cell motility and alpha5 and alphav expression. Thus, the increased motility induced by the FN protein is probably mediated by alphav and alpha5, whereas alpha4 downregulates this process in a transdominant fashion.

Base Sequence↗