Subtypes of melanocytes and melanoma cells distinguished by their intercellular contacts: heterotypic adherens junctions,adhesive associations,and dispersed desmoglein 2 glycoproteins

In the tissue integration of melanocytes and melanoma cells, an important role is attributed to cell adhesion molecules, notably the cadherins. In cultured melanoma cells, we have previously described a more heterogeneous repertoire of cadherins than normal, including some melanoma subtypes synthesizing the desmosomal cadherin, desmoglein 2, out of the desmosomal context. Using biochemical and immunological characterization of junctional molecules, confocal laser scanning, and electron and immunoelectron microscopy, we now demonstrate homo- and heterotypic cell-cell adhesions of normal epidermal melanocytes. In human epidermis, both in situ and in cell culture, melanocytes and keratinocytes are connected by closely aligned membranes that are interspersed by small puncta adhaerentia containing heterotypic complexes of E- and P-cadherin. Moreover, melanocytes growing in culture often begin to synthesize desmoglein 2, which is dispersed over extended areas of intimate adhesive cell-cell associations. As desmoglein 2 is not found in melanocytes in situ, we hypothesize that its synthesis is correlated with cell proliferation. Indeed, in tissue microarrays, desmoglein 2 has been demonstrated in a sizable subset of nevi and primary melanomas. The biological meanings of these cell-cell adhesion molecule arrangements, the possible diagnostic and prognostic significance of these findings, and the implications of the heterogeneity types of melanomas are discussed. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. This work was supported in parts by grants from the Deutsche Forschungsgemeinschaft to W. K. Peitsch (project PE 896/1) and the Deutsche Krebshilfe to W. W. Franke (project 10-2049).     

In vitro cultivation of Dipetalonema viteae third-stage larvae: evaluation of culture media, serum, and other supplements

Third-stage larvae of Dipetalonema viteae obtained from the tick vector developed to the fourth stage in several cell-free culture systems. Survival and development of larvae in a number of commercially available cell culture media, supplemented with serum and other defined and undefined components, were compared. All cultures were gassed with 5% carbon dioxide in nitrogen. Best survival, growth and development were obtained in stationary cultures containing 1:1 (v/v) mixtures of NCTC 135, either RPMI 1640 or Iscove's Modified Dulbecco's Medium, and a supplement of 20% non-heat-inactivated fetal bovine serum. The importance of the medium composition and physical environment of the culture system, for the survival, growth and development of D. viteae was demonstrated.     

High Affinity Peptide Inhibitors of the Hepatitis C Virus NS3-4A Protease Refractory to Common Resistant Mutants

Hepatitis C virus (HCV) NS3-4A protease is essential for viral replication. All current small molecular weight drugs against NS3-4A are substrate peptidomimetics that have a similar binding and resistance profile. We developed inhibitory peptides (IPs) capping the active site and binding via a novel “tyrosine” finger at an alternative NS3-4A site that is of particular interest for further HCV drug development. The peptides are not cleaved due to a combination of geometrical constraints and impairment of the oxyanion hole function. Selection and optimization through combinatorial phagemid display, protein crystallography, and further modifications resulted in a 32-amino acid peptide with a K_i of 0.53 nm. Inhibition of viral replication in cell culture was demonstrated by fusion to a cell-penetrating peptide. Negligible susceptibility to known (A156V and R155K) resistance mutations of the NS3-4A protease was observed. This work shows for the first time that antiviral peptides can target an intracellular site and reveals a novel druggable site on the HCV protease.     

Expression of simple epithelial type cytokeratins in stratified epithelia as detected by immunolocalization and hybridization in situ

Multi-layered ("stratified") epithelia differ from one-layered ("simple") polar epithelia by various architectural and functional properties as well as by their cytoskeletal complements, notably a set of cytokeratins characteristic of stratified tissue. The simple epithelial cytokeratins 8 and 18 have so far not been detected in any stratified epithelium. Using specific monoclonal antibodies we have noted, in several but not all samples of stratified epithelia, including esophagus, tongue, exocervix, and vagina, positive immunocytochemical reactions for cytokeratins 8, 18, and 19 which in some regions were selective for the basal cell layer(s) but extended into suprabasal layers in others. In situ hybridization with different probes (riboprobes, synthetic oligonucleotides) for mRNAs of cytokeratin 8 on esophageal epithelium has shown, in extended regions, relatively strong reactivity for cytokeratin 8 mRNA in the basal cell layer. In contrast, probes to cytokeratin 18 have shown much weaker hybridization which, however, was rather evenly spread over basal and suprabasal strata. These results, which emphasize the importance of in situ hybridization in studies of gene expression in complex tissues, show that the genes encoding simple epithelial cytokeratins can be expressed in stratified epithelia. This suggests that continual expression of genes coding for simple epithelial cytokeratins is compatible with the formation of squamous stratified tissues and can occur, at least in basal cell layers, simultaneously with the synthesis of certain stratification-related cytokeratins. We also emphasize differences of expression and immunoreactivity of these cytokeratins between different samples and in different regions of the same stratified epithelium and discuss the results in relation to changes of cytokeratin expression during fetal development of stratified epithelia, in response to environmental factors and during the formation of squamous cell carcinomas.     

First results of the investigation of the stability and tissue integration of a degradable, elastomeric copolymer in an animal model]

The stability and tight integration into adjacent tissue of a novel, degradable, elastic copolymer were examined in an animal model. The biomaterial was used for the reconstruction of a gastric wall defect in Sprague-Dawley rats (n=42) to test the polymeric material under the extreme chemical, enzymatical and mechanical conditions of the stomach. In the control group (n=21) the same defect of the gastric wall was primarily closed without biomaterial implantation. In the baseline group (n=21) the animals were kept under standard conditions without any surgical procedure. The implantation periods were 1 week, 4 weeks and 6 months. The animals' weight was determined preoperatively and before explantation. After explantation, air was pumped into the stomach and the pressure was measured by using a pressure-gauge in order to test whether the surgically produced union of the stomach wall and the polymer patch was gas-tight. After 1 week of implantation time a statistically significant increase of the body weight of the animals was found only in the baseline group. Four weeks and 6 months after the abdominal surgical procedure, a statistically significant increase of the animals' weight was found in the implantation group, the control and the baseline group. Gastrointestinal complications like fistula, perforation or peritonitis did not occur in any of the animals. The measurement of the stomach pressure after maximal gas insufflation did not show significant differences between the implantation group, the control and the baseline group in any of the time periods investigated. Despite very high strains of the gastric wall, no gas leakage was detected. There was a tight connection between the polymer and the adjacent stomach wall in all animals investigated. An adequate mechanical stability of the biomaterial was detectable under the extreme pathophysiological conditions of the stomach milieu. A fast and unfavourable degradation of the degradable polymer was not found in any of the animals. Further investigations are needed to analyse the mechanisms of the tissue integration of the biomaterial as well as the degradation kinetic of the polymer and the process of the tissue remodeling. The knowledge of these processes is necessary to adapt the novel biomaterial and thus prepare it for the use and implantation in different body locations and to develop novel therapeutical options in medicine.     

Accumulation of uridine diphosphoglucose pyrophosphorylase in Dictyostelium discoideum via preferential synthesis

At the end of the exponential growth phase, the enzyme UDP-glueose pyrophosphorylase is present in the vegetative cells of Dictyostelium discoideum NC4 (haploid) at a low level (about 0.05% of total protein). During the initial stages of fruiting body construction, while the cells are entering into multicellular aggregates, the enzyme level remains constant, but increases dramatically thereafter reaching a peak (about 0.5% of total protein) at the end of fruiting body construction, and then partially decreasing. Previous studies have shown that both the accumulation and disappearance are keyed to the flow of morphogenetic events.In this study, cells were labeled with amino acids for different periods throughout the sequence. The enzyme was quantitatively immune-precipitated from crude cell extracts, the precipitate was washed and redissolved, and the enzyme protein separated by acrylamide gel electrophoresis in order to estimate the differential incorporation ratio, i.e. $\text{disints}\text{min in enzyme protein per 10}{}^8\text{cells}\text{disints}\text{min in total protein per 10}{}^8\text{cells}\text{× 100}$ for each labeling period. During the initial stages, when the enzyme level remained relatively constant, this ratio was about 0.03 to 0.04%. As the enzyme began to accumulate it rose progressively, attaining levels of 0.6 to 0.8% toward the end of fruiting body construction before declining. The data are not consistent with the theory of Gustafson and Wright (1973) that differential turnover controls the level of this enzyme during the development of D. discoideum. They are consistent with the conclusion that directed changes in the differential rate of synthesis of UDP-glucose pyrophosphorylase is the controlling element.The estimates of enzyme content are based on a value for the specific enzyme activity of 100,000 units/mg enzyme, which had been determined previously using samples of the enzyme purified to apparent physical homogeneity. This figure has been confirmed in the present study by quantitative immuneprecipitation of the enzyme from crude extracts of homogeneously labeled cells. The method can be generally used to determine if a specific biological activity estimate obtained with a purified protein is consistent with its activity when measured before or during purification.     

Cell proliferation and cellular activity of primary cell cultures of the oral cavity after cell seeding on the surface of a degradable, thermoplastic block copolymer]

Using standard cell biological and biochemical methods we were able to test the ability of a degradable, thermoplastic block copolymer to support the adhesion, proliferation, and the cellular activity of primary cell cultures of the oral cavity in vitro. The delicate balance between a group of endogenous enzymes, Matrix Metalloproteinases (MMPs), and their inhibitors (Tissue Inhibitor of MMPs, TIMPs) have a decisive function in the remodeling of the extracellular matrix during processes like wound healing or the integration of biomaterials in surrounding tissues after implantation. Recently developed, biodegradable thermoplastic elastomers with shape-memory properties may be the key to develop new therapeutical options in head and neck surgery. Primary cell cultures of the oral cavity of Sprague-Dawley rats were seeded on the surface of a thermoplastic block copolymer and on a polystyrene surface as control. Conditioned media of the primary cells were analyzed for MMPs and TIMPs after different periods of cell growth. The MMP and TIMP expression was analysed by zymography and a radiometric enzyme assay. No statistically significant differences in the appearance and the kinetic of MMP-1, MMP-2, MMP-9 and TIMPs were detected between cells grown on the polymer surface compared to the control. An appropriate understanding of the molecular processes that regulate cellular growth and integration of a biomaterial in surrounding tissue is the requirement for an optimal adaptation of biodegradable, polymeric biomaterials to the physiological, anatomical, and surgical conditions in vivo to develop new therapeutic options in otolaryngology and head and neck surgery.     

Unraveling ferulate role in suberin and periderm biology by reverse genetics

Plant cell walls are dramatically affected by suberin deposition, becoming an impermeable barrier to water and pathogens. Suberin is a complex layered heteropolymer that comprises both a poly(aliphatic) and a poly(aromatic) lignin-like domain. Current structural models for suberin attribute the crosslinking of aliphatic and aromatic domains within the typical lamellar ultrastructure of the polymer to esterified ferulate. BAHD feruloyl transferases involved in suberin biosynthesis have been recently characterized in Arabidopsis and potato (Solanum tuberosum). In defective mutants, suberin, even lacks most of the esterified ferulate, but maintains the typical lamellar ultrastructure. However, suberized tissues display increased water permeability, in spite of exhibiting a similar lipid load to wild type. Therefore, the role of ferulate in suberin needs to be reconsidered. Moreover, silencing the feruloyl transferase in potato turns the typical smooth skin of cv. Desirée into a rough scabbed skin distinctive of Russet varieties and impairs the normal skin maturation that confers resistance to skinning. Concomitantly to these changes, the skin of silenced potatoes shows an altered profile of soluble phenolics with the emergence of conjugated polyamines.Key words: BAHD feruloyl acyltransferases, ferulate, periderm, potato tuber skin, suberin, suberized tissues, waxRecently published reverse genetic studies in Arabidopsis and potato identified two orthologous genes that encode a BAHD feruloyl transferase acting on aliphatics and showed that deficiency in these enzymes produces a decrease in suberin-associated ferulic acid. These results, here discussed, signify an important advance in suberin biochemistry and ultrastructure, providing a valuable new insight into the organization of the suberized tissues and their role in the control of water vapour loss.