Role of wild-type estrogen receptor-beta in mitochondrial cytoprotection of cultured normal male and female human lens epithelial cells

The influence of sexual category as a modifier of cellular function is underinvestigated. Whether sex differences affect estrogen-mediated mitochondrial cytoprotection was determined using cell cultures of normal human lens epithelia (nHLE) from postmortem male and female donors. Experimental indicators assessed included differences in estrogen receptor-beta (ERbeta) isoform expression, receptor localization in mitochondria, and estrogen-mediated prevention of loss of mitochondrial membrane potential using the potentiometric fluorescent compound JC-1 after nHLE were exposed to peroxide. The impact of wild-type ERbeta (wtERbeta1) was also assessed using wtERbeta1 siRNA to suppress expression. A triple-primer PCR assay was employed to determine the proportional distribution of the receptor isoforms (wtERbeta1, -beta2, and -beta5) from the total ERbeta message pool in male and female cell cultures. Irrespective of sex, nHLE express wtERbeta1 and the ERbeta2 and ERbeta5 splice variants in similar ratios. Confocal microscopy and immunofluorescence revealed localization of the wild-type receptor in peripheral mitochondrial arrays and perinuclear mitochondria as well as nuclear staining in both cell populations. The ERbeta2 and ERbeta5 isoforms were distributed primarily in the nucleus and cytosol, respectively; no association with the mitochondria was detected. Both male and female nHLE treated with E(2) (1 muM) displayed similar levels of protection against peroxide-induced oxidative stress. In conjunction with acute oxidative insult, RNA suppression of wtERbeta1 elicited the collapse of mitochondrial membrane potential and markedly diminished the otherwise protective effects of E(2). Thus, whereas the estrogen-mediated prevention of mitochondrial membrane permeability transition is sex independent, the mechanism of estrogen-induced mitochondrial cytoprotection is wtERbeta1 dependent.

The influence of stromal contraction in a wound model system on corneal epithelial stratification

PURPOSE

The healing process of some corneal wounds involves closure by stromal contraction and the renewal of the stratified epithelium. In wound gape injury such stromal contraction occurs with epithelial stratification. In previous in vitro studies of noncontracted and contracted corneal fibroblast-seeded collagen gels (FSCGs) it was shown that initiation of wound contraction by the myofibroblast phenotype (present within the wounded stroma) was dependent on vitronectin and/or fibronectin. This study considers one aspect of the epithelial-stromal interaction that occurs during wounding. The stratification of corneal epithelial cells on noncontracted and contracted corneal FSCGs was compared.

METHODS

Dissociated bovine corneal epithelial cells were seeded on noncontracted and contracted corneal FSCGs, and these assemblies were cultured for 7 days. The epithelium that formed was evaluated using laser confocal microscopy and immunohistochemical markers directed against cytokeratin 3, desmoplakin I and II, integrin alpha-6 subunit, laminin, and collagen VII. The characteristics of the epithelium were compared with stromal carriers comprised of dissociated bovine corneal epithelial cells seeded on intact stroma and basement membrane (stromal carrier biopsies).

RESULTS

The stratified epithelium that developed on contracted corneal fibroblast-seeded collagen gels was similar to that formed on stromal carriers, whereas nonstratified epithelium formed on noncontracted FSCGs.

CONCLUSIONS

These studies showed that the contracted state of fibroblast-seeded gels enhanced the development of well-organized, stratified corneal epithelium.

Vitronectin or fibronectin is required for corneal fibroblast-seeded collagen gel contraction

PURPOSE

The wound healing process in the corneal stroma involves the activation of corneal keratocytes and the expression of associated phenotypes (fibroblasts and myofibroblasts). One of these phenotypes, the myofibroblasts, synthesizes alpha-smooth muscle actin in order to affect wound closure by contracting the surrounding matrix. Excessive contraction results in the formation of unresolvable scars that are undesirable in the corneal stroma. The authors tested the effect of vitronectin and fibronectin on the contraction process associated with corneal wound healing.

METHODS

Collagen gels were prepared and were exposed to different treatments of fetal calf serum (FCS). The FCS used was either depleted of fibronectin and vitronectin or contained a known concentration of fibronectin, vitronectin, or both at 50 microg/ml. Contraction was measured using image analysis and cross sections of contracted gels were examined for alpha-smooth muscle actin expression using laser confocal microscopy.

RESULTS

Fibroblasts seeded in collagen gels paralleled the morphologic characteristics and cell distribution of keratocytes in unwounded cornea. Matrix contraction was dependent on the presence of fibronectin and/or vitronectin where myofibroblasts were present. The cell-mediated contraction process was maximal at 0.5 x 10(5) fibroblasts/ml.

CONCLUSIONS

These studies showed that vitronectin or fibronectin is required for the myofibroblast-associated contraction to occur in this in vitro model of stromal wound healing. This model system shows a distinct potential for further studies relating to the corneal wound healing process.

Effect of hyperbaric oxygen on human skin cells in culture and in human dermal and skin equivalents

A critical stage of cutaneous wound healing is the development and maturation of the epidermis. In the aged, and in certain pathologies, this repair process is compromised due to a variety of deficiencies, one of which is tissue oxygenation. Several phases of wound healing are dependent on adequate tissue oxygen levels, and hyperbaric oxygenation has been shown to transiently elevate these levels. The use of human cell monolayers, dermal equivalents and human skin equivalents provide excellent opportunities for studying wound healing using in vivo relevant models. The goal of this study was to examine the effect of hyperbaric oxygen on cell proliferation, differentiation, and matrix biosynthesis in monolayer cultures and epidermopoiesis in the developing skin equivalent. Normal human dermal fibroblasts, keratinocytes and melanocytes, dermal equivalents and skin equivalents were exposed to hyperbaric oxygen at pressures up to three atmospheres, for up to 10 consecutive daily treatments lasting 90 minutes each. Increase in fibroblast proliferation (cf., 30% at 1 atmosphere after 10 days treatment), was observed without a significant effect on proliferation of normal human melanocytes and glycosaminoglycan synthesis. Stimulation of collagen synthesis after two days of treatment was only significant at 1 atmosphere (about 20% increase) but this differential was not observed after 5 days of treatment. Hyperbaric oxygenation above 2 atmospheres, inhibited proliferation of fibroblasts and keratinocytes in cell monolayer cultures (e.g., a 10 day treatment at 3 atmospheres appeared cytostatic to keratinocytes). In contrast, hyperbaric treatment up to 3 atmospheres dramatically enhanced keratinocyte differentiation, and epidermopoiesis in the complete human skin equivalent. These results support the importance of hyperbaric oxygen therapy in wound healing, and should provide an insight into oxygen utilization during repair of peripheral human tissue. The results also show the utility of the human skin equivalent as a model for evaluation of parameters involved in wound healing.

Secretion of proinflammatory cytokines by human conjunctival epithelial cells

The production of cytokines by human conjunctival epithelial cells following stimulation was investigated. Primary cultures of human conjunctival epithelial cells were characterized by morphology and keratin expression. Cultured epithelial cells were treated with varying concentrations of lipopolysaccharide, interleukin (IL)-1 beta, calcium ionophore A23187, or phorbol myristate acetate, and cytokine secretion was determined over specified intervals. Culture supernatants and cell lysates were analyzed by ELISA for IL-1 beta, IL-3, IL-4, IL-5, IL-6, IL-8, IL-11, IL-1 receptor antagonist (IL-1ra), tumor necrosis factor-alpha (TNF-alpha), and granulocyte-macrophage colony stimulating factor (GM-CSF). With the exception of IL-1ra, unstimulated conjunctival epithelial cells produced cytokines at relatively low or undetectable levels. IL-1ra was detected in both culture supernatants and cell lysates under basal conditions. In response to stimuli, conjunctival epithelial cells secreted the proinflammatory cytokines TNF-alpha, IL-6, IL-8, and GM-CSF in a dose- and time-dependent fashion. After stimulation, the intracellular levels of IL-1ra increased in these cells but the supernatant-associated levels remained unchanged. None of the other cytokines evaluated (IL-1 beta, IL-3, IL-4, IL-5, and IL-11) were detected in supernatants or lysates of resting or stimulated cells. These findings suggest that conjunctival epithelial cells may contribute to the pathogenesis of human ocular diseases by production of proinflammatory cytokines. Further evaluation of these cells as targets of therapy is warranted.

Stem cells of the corneal epithelium lack connexins and metabolite transfer capacity

The stem cells of the corneal epithelial lineage are confined to the basal cell layer of the limbus, a vascularized outer corneal rim. These slow cycling cells of great proliferative potential maintain the corneal epithelial mass. Since cell-cell communication plays an important role in development and differentiation, we conducted a comparative examination of the expression of two corneal connexins, C x 43 and C x 50, and the tracer transfer capacity of the limbal and corneal epithelia using the scrape loading technique. C x 43 is abundantly expressed in the basal cell layer of the epithelium covering the cornea, but is essentially absent from the mouse, human, neonatal rabbit, and chicken limbal epithelium. In the adult rabbit the limbal epithelium displays an overall weak C x 43 immunoreactivity, but C x 43-free isolated basal cells can be distinguished. C x 50 is expressed throughout the corneal epithelium of the three mammalian corneas, but is not detectable in the limbus. Scrape loading experiments in the rabbit yielded results which were consistent with the immunohistological findings; limbal epithelium lacked tracer (lucifer yellow) transfer capacity, strongly suggesting the absence of functional gap junctions. Altogether, our results demonstrate the incompetence of stem cells for gap junction-mediated cell-to-cell communication. This property may reflect the need of these unique cells to maintain a distinct intracellular environment.

Effects of amiprilose hydrochloride on the components of human skin equivalents

Amiprilose hydrochloride has been shown to inhibit the proliferation of a number of hyperproliferative cell types including psoriatic skin cells. In the present study, the effects of amiprilose hydrochloride on human tissue equivalents were examined by incubating a) dermal equivalents, b) skin equivalents in the process of epidermalization, and c) mature skin equivalents, with varying concentrations of the drug. In all three models amiprilose hydrochloride concentrations of 0.1% (wt/vol) and lower were not toxic to fibroblasts and keratinocytes and did not interfere with the differentiation of the skin equivalent and the developing skin equivalent. When tested in dermal equivalents, concentrations of amiprilose hydrochloride between 0.1 and 0.5% resulted in changes in fibroblast morphology with development of large intracellular vacuoles, and concentrations greater than 5% were toxic. In mature skin equivalents, in addition to changes in fibroblast morphology, amiprilose hydrochloride in concentrations of 1 to 10% affected the epidermis. When 0.5% amiprilose hydrochloride was present in the developing skin equivalent during differentiation, the epidermal keratinocytes were also affected. Thus the morphology of basal keratinocytes was modified, the differentiation was incomplete, and the dermal-epidermal attachment was compromised. These studies suggest the possibility of an extracellular mechanism of action of amiprilose hydrochloride and delineate acceptable dosage ranges for the potential drug.

Cellular models and tissue equivalent systems for evaluating the structures and significance of age-modified proteins

The accumulation of modified proteins in aging is well documented in many aging models. For example, the deamidated isoforms of triosephosphate isomerase accumulate in: (a) old erythrocytes, (b) fibroblasts from old donors, (c) fibroblasts aged in vitro, (d) premature-aging syndromes and (e) old cells in the eye lens. However, a fundamental remaining question is: 'Do such modified proteins interfere with cellular function?' It has been difficult to assess this question at the molecular level using whole-organism models and equally frustrating to evaluate the physiological significance of such changes using classical cellular models. Tissue equivalent systems (TES) provide an opportunity for examining the molecular basis and physiological consequences of modified proteins during aging. TES are composed of differentiating and proliferating heterogeneous cell types with symbiotic cell-cell and cell-matrix interactions. They closely resemble, both morphologically and functionally, the tissues from which they were derived. Aging studies utilizing TES can provide information on modifications of protein structures, isozyme patterns, enzymes of the cellular environmental protection system and metabolic parameters which may regulate protein synthesis and degradation.

Inhibition of psoriatic cell proliferation in in vitro skin models by amiprilose hydrochloride

Amiprilose hydrochloride, a 3-substituted glucose derivative, was found to inhibit the proliferation of human fibroblasts and keratinocytes originating from psoriatic lesions. Fibroblasts and keratinocytes were obtained from skin biopsies of normal donors, and from the biopsies of active/involved and uninvolved sites of psoriatic donors. The cells were cultured as monolayers or as components of tissue equivalent models. Keratinocytes and fibroblasts originating from biopsies of psoriatically involved areas were shown to proliferate at a significantly higher rate than those derived from uninvolved areas. The antiproliferative effect of amiprilose hydrochloride was not observed with normal keratinocytes or fibroblasts from the skin of healthy donors or from uninvolved areas of psoriatic donors. Amiprilose hydrochloride was not cytotoxic to any of these cells at levels below 0.1%. The combination of the low cytotoxicity and the selective antiproliferative effect indicates that this compound may be a useful antipsoriatic agent. The use of monolayer cultures and tissue equivalent models in this study illustrates the utility of such a progressive strategy in the evaluation of potential topical pharmaceuticals.

In vivo degradation of oxidized, regenerated cellulose

Oxidized, regenerated cellulose (ORC) was surgically implanted on the uterine horns of rabbits, and its biodegradation was studied in vivo. Samples of peritoneal lavages, serum, and urine were collected during the degradation process and analyzed for carbohydrate components utilizing high-performance liquid chromatography with pulsed amperometric detection (h.p.l.c.-p.a.d.). Degradation was rapid, and oligomeric products were evident primarily in the peritoneal fluid from the implantation site, with no apparent accumulation in either the serum or the urine. The size distribution and the amount of the oligomeric products decreased after day one, and by day four peritoneal lavages were essentially free of oligomers. The structure of the products formed was consistent with the lability of the polymer in solution, and the kinetics of degradation paralleled the results of the previously reported in vitro studies. Rabbit peritoneal macrophages, when incubated with ORC in vitro were observed to readily ingest and hydrolyze the polymeric material. A mechanism of degradation consisting of chemical depolymerization, followed by enzymatic hydrolysis mediated by glycosidases endogenous to peritoneal macrophages, is proposed.

Biodegradation of oxidized regenerated cellulose

The in vitro solubilization and degradation of regenerated cellulose was studied under conditions which approximate those found in vivo, when the material is used as an adhesion barrier to assist normal wound repair. Factors affecting solubilization which were examined included the effects of serum or plasma, and the presence of hydrolytic enzymes. Products of the solubilization and degradation processes were examined by high performance liquid chromatography coupled with pulsed amperometric detection. The oxidized polymer readily undergoes chain shortening to give oligomers which, in the presence of plasma or serum, are further hydrolyzed to smaller fragments, including glucuronic acid and glucose. Proposed mechanisms of degradation are discussed.

Simultaneous assay for plasmin and DNase using radiolabeled human fibroblasts on microcarriers

A critical step in tissue and wound repair is the removal of eschar--accumulation of denatured cellular and extracellular macromolecules. Enzymatic debridement using a combination of plasmin (fibrinolysin) and DNase has been successfully utilized on a variety of types of wounds. Monitoring the activity of these enzymes by measuring the rate of fibrinolysis, or by viscometric changes due to DNA hydrolysis, is exceedingly cumbersome, time consuming, and, at best, only semiquantitative. Although spectrophotometric assays using synthetic substrates offer several advantages, they do not allow extrapolation of the data to the more complex natural substrates encountered in vivo. We have, therefore, developed an in vitro radioisotopic assay for the simultaneous and quantitative measurement of the hydrolytic activity of both plasmin and DNase. Double labeled ([3H]thymidine, [14C]leucine) human dermal fibroblasts grown on microcarrier beads are utilized as sources of nucleic acid and protein substrates. The assay meets all the criteria of analytical validity, is sensitive and rapid, and is amenable to adaptation for analysis of other hydrolytic enzymes. The method offers a direct evaluation of the enzymatic debridement of wounds using actual human cellular substrates. Moreover, the microcarriers provide a greatly increased surface area for cell attachment and growth, are amenable to rapid separation from the cells by simple mechanical methods, and are ideally suited to analytical manipulations.

A simple method of drying virus on inanimate objects for virucidal testing

A simple method for drying virus on inanimate objects (cover slips) under vacuum in the cold is described. Following this procedure virus maintains high titers (10(6-7)) for periods of 1-3 wk at -70 degrees C depending on the virus. For virucidal assay of disinfectants, cover slips are exposed to medium simulating the disinfectant (virus control) or disinfectant in an upright position in an Ultra-Vu cuvette. Cover slips are readily removed and placed in tissue culture medium for dilution of virus and determination of virus titer. Cytotoxicity of disinfectant is determined by exposing cover slip without virus to disinfectant, then placing it in medium, diluting the medium and incubating with the indicator cells. The use of this technique results in high titers of virus on cover slips, which are inanimate objects requiring minimal manipulation. The titration of virus or cytotoxicity in microplates is cell, medium, serum, and labware economical.

Synthesis of certain 4'-substituted nucleosides

We have developed general methods for the synthesis of 4'-fluoro- and 4'-methoxynucleosides by addition of iodinemonofluoride or iodine and methanol across the double bond of suitably protected 4',5'-unsaturated pyrimidine and purine nucleosides. The structures of these adducts have been determined by a combination of chemical, spectroscopic, and electrophoretic methods. The 4'-methoxy- and the uridine analogs of nucleocidin have been synthesized from the corresponding 4'-fluorouridine and 4'-methoxyadenosine derivatives.