Engineering the migration and attachment behaviour of primary dermal fibroblasts

The availability of primary cells present in pathological conditions is often very limited due to stringent ethical regulation and patient consent. One such condition is chronic wounds, where dermal fibroblasts show a deficient migration. In vitro models with cellular tools that mimic the in vivo scenario would be advantageous to test new therapies for these challenging wounds. Since the availability of primary dermal fibroblasts present in chronic wounds is restricted and their “shelf-life” limited due to the increased senescence, our aim was to engineer human dermal fibroblasts with impaired migration using synthetic Arg-Gly-Asp (RGD) peptides. We studied fibroblast behaviour on three different two dimensional (2D) surfaces, representative of the dermal extracellular matrix and the materials used in the development of dermal scaffolds, in addition to commercially available, collagen-based 3D dermal scaffolds, demonstrating that the concentration of synthetic RGD peptides necessary to impair migration of dermal fibroblasts should be tailored to the particular surface/material and cell population used. The described technology could be translated to other cell types including established cell lines. A wide range of synthetic peptides exists, which differ in the amino acid sequence, thus increasing the possibilities of this technology.     

The Trypanosoma cruzi ribosomal P protein family: classification and antigenicity

The multi-copy ribosomal P proteins have been identified on the ribosomes of prokaryotic and eukaryotic cells, and their antigenicity is an important feature of human Trypanosoma cruzi infection. In this review, Mariano Levin, Martin Vazquez, Dan Kaplan and Alejandro Schijman give a rational basis for the classification of these proteins, and discuss their inter-relationship.     

Inhibition of cell migration by 24-kDa fibroblast growth factor-2 is dependent upon the estrogen receptor

The single-copy gene for fibroblast growth factor-2 (FGF-2) encodes for multiple forms of the protein with molecular masses of 24, 22.5, 22, and 18 kDa. We reported previously that the 24-22-kDa FGF-2 forms inhibit the migration of endothelial and MCF-7 cells by 50% and 70%, respectively. Here we show that this inhibition of migration is mediated by the estrogen receptor (ER). We have found that depletion of the receptor in either cell line abrogates the inhibitory activity of 24-kDa FGF-2 while re-introduction of the ER into deficient cells once again promotes the inhibitory response. To determine whether exposure to 24-kDa FGF-2 resulted in the activation of the estrogen receptor, 3T3 cells were cotransfected with estrogen receptor cDNA and an estrogen regulatory element-luciferase gene reporter construct and treated with 24- and 18-kDa FGF-2. The high molecular weight form stimulated luciferase activity 5-fold while 18-kDa FGF-2 at the same concentration had no effect. Treatment of ER-positive MCF-7 cells transfected with the reporter construct only showed the same results. Inclusion of the pure estrogen antagonist ICI 182,780 blocked the increase in luciferase activity by 24-kDa FGF-2, further indicating that the response was estrogen receptor dependent. Expression of dominant negative FGF receptor 1 inhibited ER activation, indicating that this was the cell surface receptor mediating the effect. Although growth factor-dependent activation of the ER was reported to require mitogen-activated protein kinase-induced phosphorylation at Ser(118) in COS and HeLa cells, this mechanism is not involved with the activation by 24-kDa FGF-2. These results suggest that the addition of 55 amino acids to the amino-terminal end of 18-kDa FGF-2 by alternative translation alters FGF-2 function and allows for the activation of a second signaling pathway involving the estrogen receptor.     

Rapid evolution in the Nebria gregaria group (Coleoptera: Carabidae) and the paleogeography of the Queen Charlotte Islands

Morphological differentiation in the ground beetles of the Nebria gregaria group, found on the Queen Charlotte Islands, has been used as support for the glacial refugium proposed for the northwest coast of North America. Two members of this species group, N. charlottae and N. louiseae, are restricted to cobble beaches in this archipelago. A third, N. haida, is found only in alpine regions of the archipelago and the adjacent mainland. The remaining two species of the gregaria group, N. lituyae and N. gregaria, show highly restricted distributions in the mountains of the Alaska panhandle and on the beaches of the Aleutian Islands, respectively. To determine the relationships of the five species, we conducted phylogenetic analyses on nucleotide sequence data obtained from five regions of the mitochondrial DNA. In total, 1835 bp were analyzed. The results suggest that one species, N. lituyae, does not belong in the gregaria group, and that only seven mutations separated the two most divergent of the four remaining species. We also conducted random amplified polymorphic DNA fingerprinting analyses on genomic DNA extracted from the five species. Analyses of genetic diversity revealed a lack of molecular differentiation among the Queen Charlotte species, suggesting that these populations may be postglacial in origin and that together N. gregaria, N. charlottae, N. louiseae, and N. haida might represent local variations of a single species. These results are consistent with conclusions derived for the morphological and genetical differentiation among Gasterosteus populations in the archipelago.     

Risk assessment for developing gliomas: a comparison of two cytogenetic approaches

Chromosome instability (CIN) measured as chromosome aberrations has long been suggested as a cancer susceptibility biomarker. Conventional cytogenetic end-points are now being improved by combining molecular methods, which increases the sensitivity, specificity, and precision of the assay. In this study we examined both spontaneous and gamma-ray induced CIN in lymphocyte cultures from 51 previously untreated glioma patients and 51 age-, sex- and ethnicity-matched controls. CIN was assessed using two parallel methods: (1) the mutagen sensitivity (MS) assay and (2) the multicolor fluorescence in situ hybridization (FISH) assay. The frequency of spontaneous breaks was significantly higher in glioma patients (mean+/-S.D., 2.12+/-1.07) than in controls (1.24+/-0.86, P<0.001) when using the FISH assay but not the MS assay (0.019+/-0.02 and 0.019+/-0.01, respectively; P=0.915). Similarly, the frequency of induced chromatid breaks was significantly higher using the FISH assay (3.39+/-1.72) but not the MS assay (0.42+/-0.16) in the patients versus controls (2.08+/-1.18 and 0.37+/-0.15, respectively; P<0.001 and P=0.10, respectively). By using the median number of breaks in the controls as the cutoff value, we observed an odds ratio (ORs) of 5.13 (95% CI=2.23-12.1) for spontaneous and 4.86 (95% CI=2.08-11.4) for induced CIN using the FISH assay, whereas the ORs were 1.32 (95% CI=0.49-3.58) and 1.28 (95% CI=0.59-2.80) for spontaneous and induced CIN using the MS assay. There was also a significant increase in the frequency of hyperdiploid cells in the glioma cases which could only be detected using the FISH assay (OR=4.0, 95% CL=0.9-17.0). By combining both methods an estimated risk of 7.0 (95% CI=1.7-25.6) was observed. There was no correlation between the breaks detected by the two methods suggesting that each method is a measure of a different event. The results indicate that using the multicolor FISH assay for detection of CIN in peripheral blood lymphocytes in glioma patients is a more useful marker for risk assessment.     

Molecular dynamics simulations of polypeptide conformations in water: A comparison of alpha, beta, and poly(pro)II conformations.

A significant fraction of the so-called "random coil" residues in globular proteins exists in the left-handed poly(Pro)II conformation. In order to compare the behavior of this secondary structure with that of the other regular secondary structures, molecular dynamics simulations, with the GROMOS suite of programs, of an alanine octapeptide in water, in alpha-helix, beta-strand, and left-handed poly(Pro)II conformations, have been performed. Our results indicate a limited flexibility for the alpha-helix conformation and a relatively larger flexibility for the beta-strand and poly(Pro)II conformations. The behavior of oligopeptides with a starting configuration of beta-strand and poly(Pro)II conformations, both lacking interchain hydrogen bonds, were similar. The (phi, psi) angles reflect a continuum of structures including both beta and P(II) conformations, but with a preference for local P(II) regions. Differences in the network of water molecules involved in hydrogen bonding with the backbone of the polypeptide were observed in local regions of beta and P(II) conformations. Such water bridges help stabilize the P(II) conformation relative to the beta conformation. Proteins 1999;36:400-406.     

Recombinant glycoproteins that inhibit complement activation and also bind the selectin adhesion molecules

Soluble human complement receptor type 1 (sCR1, TP10) has been expressed in Chinese hamster ovary (CHO) DUKX-B11 cells and shown to inhibit the classical and alternative complement pathways in vitro and in vivo. A truncated version of sCR1 lacking the long homologous repeat-A domain (LHR-A) containing the C4b binding site has similarly been expressed and designated sCR1[desLHR-A]. sCR1[desLHR-A] was shown to be a selective inhibitor of the alternative complement pathway in vitro and to function in vivo. In this study, sCR1 and sCR1[desLHR-A] were expressed in CHO LEC11 cells with an active alpha(1,3)-fucosyltransferase, which makes possible the biosynthesis of the sialyl-Lewisx (sLex) tetrasaccharide (NeuNAcalpha2-3Galbeta1-4(Fucalpha1-3)GlcNAc) during post-translational glycosylation. The resulting glycoproteins, designated sCR1sLex and sCR1[desLHR-A]sLex, respectively, retained the complement regulatory activities of their DUKX B11 counterparts, which lack alpha(1-3)-fucose. Carbohydrate analysis of purified sCR1sLex and sCR1[desLHR-A]sLex indicated an average incorporation of 10 and 8 mol of sLex/mol of glycoprotein, respectively. sLex is a carbohydrate ligand for the selectin adhesion molecules. sCR1sLex was shown to specifically bind CHO cells expressing cell surface E-selectin. sCR1[desLHR-A]sLex inhibited the binding of the monocytic cell line U937 to human aortic endothelial cells, which had been activated with tumor necrosis factor-alpha to up-regulate the expression of E-selectin. sCR1sLex inhibited the binding of U937 cells to surface-adsorbed P-selectin-IgG. sCR1sLex and sCR1[desLHR-A]sLex have thus demonstrated both complement regulatory activity and the capacity to bind selectins and to inhibit selectin-mediated cell adhesion in vitro.     

Reconstitution of proliferating cell nuclear antigen-dependent repair of apurinic/apyrimidinic sites with purified human proteins

An apurinic/apyrimidinic (AP) site is one of the most abundant lesions spontaneously generated in living cells and is also a reaction intermediate in base excision repair. In higher eukaryotes, there are two alternative pathways for base excision repair: a DNA polymerase beta-dependent pathway and a proliferating cell nuclear antigen (PCNA)-dependent pathway. Here we have reconstituted PCNA-dependent repair of AP sites with six purified human proteins: AP endonuclease, replication factor C, PCNA, flap endonuclease 1 (FEN1), DNA polymerase delta, and DNA ligase I. The length of nucleotides replaced during the repair reaction (patch size) was predominantly two nucleotides, although longer patches of up to seven nucleotides could be detected. Neither replication protein A nor Ku70/80 enhanced the repair activity in this system. Disruption of the PCNA-binding site of either FEN1 or DNA ligase I significantly reduced efficiency of AP site repair but did not affect repair patch size.