Risk Factors and Innovations in Risk Assessment for Melanoma, Basal Cell Carcinoma, and Squamous Cell Carcinoma

Skin cancer is the most frequently diagnosed cancer globally and is preventable. Various risk factors contribute to different types of skin cancer, including melanoma, basal cell carcinoma, and squamous cell carcinoma. These risk factors encompass both extrinsic, such as UV exposure and behavioral components, and intrinsic factors, especially involving genetic predisposition. However, the specific risk factors vary among the skin cancer types, highlighting the importance of precise knowledge to facilitate appropriate early diagnosis and treatment for at-risk individuals. Better understanding of the individual risk factors has led to the development of risk scores, allowing the identification of individuals at particularly high risk. These advances contribute to improved prevention strategies, emphasizing the commitment to mitigating the impact of skin cancer.

A novel handheld fluorescent microarray reader for point-of-care diagnostic

A novel handheld optical sensor for quantification of fluorescent microarrays, the so-called portMD-113 has been developed. On the surface of a planar waveguide, the spots of different fluorescently labeled biological complexes are excited by the evanescent field of the guided light. The emitted fluorescence signals of the spots are independently and simultaneously detected applying our system, which consists of a pinehole array, a microlens array, an interference filter and a detector array. As it is demonstrated in comparative measurements, the detection limit of this sensor is close to that of commercial top microarray readers, e.g. of modern laser scanners, while it has remarkable and important advantages over them. Namely, the device comprises only a few low-cost, lightweight and small components without applying any moving or energy-intensive elements, which results in turn in a commercially competitive, handheld and compact design and in the possibility to be supplied simply by a battery or a personal computer. These advantageous properties open prospects e.g. for point-of-care medical checks, as well.

An enhanced expression of ABC 1 transporter in circulating leukocytes as a potential molecular marker for the diagnostics of glaucoma

OBJECTIVE

Glaucoma is a neurodegenerative disease. Since vascular dysregulation is supposed to be a risk factor for the development of glaucomatous damage, the preventive treatment might slow down the disease development. The efficiency of the therapeutic treatment depends particularly on a drug efflux pump regulated by ABC transporters. ABC 1 is also known to participate on the vascular regulation. This study was focused on the comparative analysis of ABC 1 expression levels in circulating leukocytes of non-glaucomatous individuals and glaucoma patients.

RESULTS AND CONCLUSIONS

The expression rates of ABC 1 were significantly increased in leukocytes of glaucoma patients compared to non-glaucomatous individuals. The expression level of ABC 1 was, furthermore, highly homogeneous in glaucoma patients. In contrast, these expression levels in non-glaucomatous individuals were extremely heterogeneous. This transporter acts as the energy-dependent unidirectional transmembrane cholesterol efflux pump and can export a wide range of hydrophobic drugs. Additionally an observed enhanced ABC 1 expression in circulating leukocytes may be implicated in the vascular regulation mechanisms of glaucoma. We proposed the enhanced expression of ABC 1 in leukocytes as a potential marker for the diagnostics and ex vivo molecular monitoring of glaucoma.

Increased DNA breaks and up-regulation of both G1 and G2 checkpoint genes p21WAF1/CIP1 and 14-3-3 ? in circulating leukocytes of glaucoma patients and vasospastic individuals

OBJECTIVE

Vascular disorder leading to local ischemia/reperfusion has been shown to play an important role in the glaucomatous damage. A decreased expression level of XPGC-gene has been found in circulating leukocytes of normal-tension glaucoma patients. Although decreased activity of XPGC-gene leads to insufficient DNA-repair, no leukopenia has been observed in glaucoma. Molecular mechanisms ensuring cell survival have not been elucidated yet for glaucoma with vascular disorder.

MATERIAL AND METHODS

Using the ex vivo optical imaging method of alkaline "comet assay" comparative quantification of DNA breaks was performed in circulating leukocytes of non-glaucomatous non-vasospastic and vasospastic individuals as well as both normal-tension and high-tension glaucoma patients. Relative expression levels of the anti-apoptotic factors P21(WAF1/CIP1) and 14-3-3 sigma were investigated in all groups tested.

RESULTS AND CONCLUSIONS

The quantification of P21(WAF1/CIP1) showed the highest expression rates in high-tension glaucoma patients which were significantly higher than those in all other groups tested. The highest expression rates of 14-3-3 sigma were found in both groups of glaucoma patients. These expression levels correlated well with DNA breaks measured. Since the expression of P21(WAF1/CIP1) in leukocytes was shown to be crucial for their survival under stress conditions, we suppose further that the up-regulation of this gene is the key event in the survival mechanisms of leukocytes in glaucoma accompanied with vascular disorder. The p21(WAF1/CIP1) gene should be further taken into consideration as a potential marker, the up-regulation of which in circulating leukocytes of vasospastic individuals may indicate an increased risk for the developing glaucoma.

Molecular imaging of perfusion disturbances in glaucoma

Ocular ischemia resulting from perfusion disturbances may play a major role in initiation of glaucoma. Possibly secondary to ischemia autoimmunogenic events are activated in glaucoma patients with increased prevalence of systemic autoimmune diseases. The determination of potential molecular markers in blood leukocytes could be useful for early noninvasive diagnostics of glaucoma. Our study using subtractive hybridization showed altered gene expression in leukocytes of glaucoma patients in comparison to age and sex matched healthy subjects. Subtracted genes encoding lymphocyte IgE receptor (Fc epsilon RII/CD23), T cell-specific tyrosine kinase, thromboxan A2 receptor, alkaline phosphatase and Na(+)/K(+)-ATPase are differentially expressed in circulating leukocytes of glaucoma patients. These genes show expression profiles characteristic for adherent leukocytes which could be an important contributor to blood-brain barrier breakdown which has been found in glaucoma patients.

Regulation of connective tissue growth factor gene expression in retinal vascular endothelial cells by angiogenic growth factors

BACKGROUND

Connective tissue growth factor (CTGF) is a novel, cysteine-rich secreted protein, which is implicated in fibrotic disorders and atherosclerosis. To elucidate the role of CTGF in fibrovascular proliferative retinopathy, we investigated the regulation of CTGF gene expression in a cell line of retinal vascular endothelial cells (RVEC) stimulated with fetal calf serum (FCS) and angiogenic growth factors, including vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), platelet-derived growth factor-BB (PDGF-BB), endothelial growth factor (EGF), transforming growth factor-beta 1 and -beta 3 (TGF-beta 1, TGF-beta 3), and insulin-like growth factor-I (IGF-I).

METHODS

RVEC derived from Macaca mulatta (CRL-1780; ATCC) were stimulated with 10% FCS as well as with VEGF, bFGF, PDGF-BB, TGF-beta 1, TGF-beta 3, EGF, or IGF-I. Time-dependent CTGF gene expression was assessed by northern blot analysis.

RESULTS

FCS, TGF-beta 1, TGF-beta 3, bFGF, and EGF induced an upregulation of CTGF gene expression in RVEC in a time-dependent manner. Highest expression was induced with TGF-beta 1. No response on CTGF gene expression could be detected to VEGF, PDGF-BB, or IGF-I.

CONCLUSION

The present study demonstrates for the first time that CTGF mRNA is expressed at high levels in RVEC, and that the level of the temporal pattern of its expression is differentially regulated by angiogenic growth factors, indicating a significant role of CTGF in the pathological course of uncontrolled retinal angiogenesis.

Connective tissue growth factor in retrocorneal membranes and corneal scars

We studied the localization and distribution of connective tissue growth factor (CTGF) in corneal scar tissue and membranes using in situ hybridization in 8 corneas from keratoplasty and 4 normal corneas. Identification of the cells was done with immunohistochemistry for SM-alpha-actin, vimentin, and Lu5. CTGF mRNA was found in activated corneal fibroblasts in 7 of 8 scars, 7 of 8 retrocorneal membranes and 2 subepithelial membranes, whereas the control corneas showed no CTGF mRNA expression. Vimentin was positive in all scars, retrocorneal and subepithelial membranes, SM-alpha-actin in 7 of 8 scars and 6 of 8 retrocorneal membranes. These results suggest that CTGF plays a crucial role in corneal wound healing and membrane formation.

Expression of connective tissue growth factor (CTGF) mRNA in plaques of human anterior subcapsular cataracts and membranes of posterior capsule opacification

PURPOSE

To investigate the correlation between connective tissue growth factor (CTGF) mRNA expression and immunohistochemical characteristics of anterior subcapsular cataract (ASC) formation as well as posterior capsule opacification (PCO) development (expression of type I collagen, alpha-smooth muscle actin and tenascin) under in vivo and under in vitro conditions in human and porcine lens epithelial cells.

METHODS

CTGF mRNA expression was investigated using in situ hybridization and RT-PCR. Expression of type I collagen, alpha-smooth muscle actin and tenascin was detected by immunohistochemical staining.

RESULTS

CTGF mRNA was expressed in human cataractous plaques of ASC and human PCO membranes, and appeared simultanously with the expression of type I collagen, alpha-smooth muscle actin and tenascin.

CONCLUSION

The predominant expression of CTGF mRNA in human ASC and human PCO membranes suggests a significant role of CTGF in the pathological course of these ocular disorders.

Amino acids of conserved kinase motifs of cytomegalovirus protein UL97 are essential for autophosphorylation

Thirteen point mutations targeting predicted domains conserved in homologous protein kinases were introduced into the UL97 coding region of the human cytomegalovirus. All mutagenized proteins were expressed in cells infected with recombinant vaccinia viruses (rVV). Several mutations drastically reduced ganciclovir (GCV) phosphorylation. Mutations at amino acids G340, A442, L446, and F523 resulted in a complete loss of pUL97 phosphorylation, which was strictly associated with a loss of GCV phosphorylation. Our results confirm that in rVV-infected cells pUL97 phosphorylation is due to autophosphorylation and show that several amino acids conserved within domains of protein kinases are essential for this pUL97 phosphorylation. GCV phosphorylation is dependent on pUL97 phosphorylation.

[Effect of lymphocyte-conditioned medium on expression of smooth muscle alpha-actin in lens epithelium cells in situ]

PURPOSE

Contraction of the capsule of the ocular lens is based upon proliferation and contraction of transformed lens epithelial cells. It is assumed that these processes can be assisted by postoperative intraocular inflammation. Previously, we reported that lens epithelial cell proliferation is enhanced by lymphocyte-conditioned medium (LCM). In this study we investigated the effect of LCM as well as of a culture medium conditioned by pigmented ciliary epitheilal cells (CBCM) on the expression of the smooth-muscle alpha-actin of the contractile cytoskeletal elements.

METHODS

Explants of the anterior lens capsule of freshly enucleated bovine eyes were cultured in serum-free LCM and CBCM for 3 days, followed by fixation. Smooth-muscle alpha-actin was identified by indirect immunoflorescence. Explants cultured in serum-free bFGF-containing and TGF-beta containing medium served as control.

RESULTS

Lens epithelial cells expressed smooth-muscle alpha-actin under the influence of LCM or TGF-beta. No smooth muscle alpha-actin could be detected under the influence of CBCM or bFGF.

CONCLUSION

Our results demonstrate that secreted molecules of activated lymphocytes are able to induce the transformation of lens epithelial cells into contractile myofibroblasts and may be involved in the post-operative contraction of lens capsules.

Functional regions of the human cytomegalovirus protein pUL97 involved in nuclear localization and phosphorylation of ganciclovir and pUL97 itself

In order to identify functional regions of the human cytomegalovirus protein pUL97 (i) different 5' fragments of the UL97 open reading frame (ORF) were fused to the coding region of the green fluorescent protein and (ii) recombinant vaccinia viruses (rVV) were generated carrying two full-length and 11 mutated UL97 ORFs. The results indicated the presence of an N-terminal region within pUL97 which changed the intracellular distribution of the fusion proteins. pUL97 was localized in the nucleus, but not in the nucleoli, and was detected in the nuclear matrix fraction. Expression of all pUL97 mutants could be confirmed by Western blot analysis. pUL97-associated ganciclovir (GCV) phosphorylation in rVV-infected cells, determined quantitatively by HPLC analysis, was abolished completely using individual UL97 deletion mutants. Phosphorylation of full-length and some of the mutated pUL97 was detected in cells infected with the rVVs. The UL97 constructs carrying point mutations from GCV-resistant HCMV isolates at positions 460M, 520H, 594V, and the 4 aa deletion 590AACR593, also resulted in decreased but not abolished phosphorylation of GCV in the rVV system, whereas the phosphorylation of pUL97 itself was not influenced. The rVV system is a suitable method for quantitatively testing the functional relevance of pUL97 mutations.

[Serum-free cultivation of bovine stromal fibroblasts]

The purpose of the present study was to conduct a comparative evaluation of the effect of several serum-free culture conditions on adhesion, population doubling, cryopreservation and PDGF-induced effects on cell proliferation of bovine stromal fibroblasts (BSF). Additionally, these effects were compared to serum-containing cultures.

METHODS

Only second-passage BSF were used. Cells were cultured using four different culture media (WM/F12, WM/F12 + FCS 1%, LR-1, DMEM). After 24 h, plating efficiency was determined using a cell-counter system. Subsequently, the cells were seeded at a density of 100 cells/mm2 and cultured for 10 days using the different culture media. Cell number was determined at day 2, 4, 7 and 10 after seeding. Furthermore, the effect of 50 ng/ml PDGF-BB on the proliferation of BSF was tested for these conditions. Cell vitality was determined after cryopreservation of two weeks for each culture medium.

RESULTS

The plating efficiency of BSF ranged from 50.2 to 55.5% for the serum-free culture media in contrast to serum-containing conditions, where plating efficiency was 94.8%. With WM/F12 + FCS 1%, a population doubling of 1.27 was observed after an incubation period of 10 days. In contrast, cultivation under serum-free conditions caused neither significant cell proliferation nor cell loss. The stimulation of cell proliferation with PDGF-BB was shown to be 28% (LR1), 40% (WM/F12 + FCS 1%) 76% (WM/F12) and 95% (DMEM) compared to the control. While cell vitality after cryo-preservation was found to be 62.7% using WM/F12 + FCS 1%, vitality using serum-free media was 12.6-22.8%.

CONCLUSIONS

The results of the present study demonstrate that with respect to optimal cell adhesion and cell vitality after cryo-preservation, serum-containing media should be used. BSF cultured under the serum-free conditions used in the present study can be maintained quiescent and vital for at least 10 days. Therefore, these serum-free media are useful for cell-culture studies (e.g., determination of proliferation and cytotoxicity).

Proliferative response of cultured human tenon's capsule fibroblasts to platelet-derived growth factor isoforms

BACKGROUND

Although platelet-derived growth factor (PDGF) has been thought to be critical in the wound-healing response of Tenon's capsule fibroblasts after glaucoma filtration surgery, no information is currently available concerning the proliferative effect of PDGF isoforms on this cell type. The aim of the present study was to evaluate the proliferative effect of PDGF-AB heterodimer and PDGF-AA and -BB homodimers on cultured human Tenon's capsule fibroblasts.

METHODS

Human Tenon's capsule fibroblasts, cultured under serum-free conditions, were stimulated with PDGF-AA, -AB and -BB isoforms in concentrations ranging from 1 to 100 ng/ml. Cell numbers were determined on days 1, 3, 5 and 7, using a cell counter.

RESULTS

Addition of PDGF-AB and -BB led to a dose-dependent increase in cell proliferation. A maximal response (79.9% over control) was obtained after 7 days with 30 ng/ml of PDGF-BB, with an EC50 of 8.9 ng/ml. The maximal increase in cell proliferation caused by PDGF-AB (30 ng/ml) was 54.9%, with an EC50 of 12.5 ng/ml. Stimulation with PDGF-AA revealed a significant effect only with concentrations higher than 30 ng/ml.

CONCLUSION

Our results indicate that PDGF-AB and -BB isoforms are potent stimulators of proliferation of human Tenon's capsule fibroblasts, suggesting that PDGF-AB and -BB isoforms play an important role in the wound-healing response after glaucoma filtration surgery.

The UL97 gene product of human cytomegalovirus is an early-late protein with a nuclear localization but is not a nucleoside kinase

The temporal expression of the UL97 gene product during human cytomegalovirus (HCMV) infection of human foreskin fibroblasts (HFF) and subcellular localization of this protein were analyzed by using a polyclonal antiserum raised against a truncated UL97 protein of 47 kDa. The UL97 protein was detectable 16 h after infection by Western blot (immunoblot) analysis. Since only reduced UL97 expression occurred in the presence of two inhibitors of DNA replication, phosphonoacetic acid and ganciclovir, we conclude that UL97 is an early-late gene, requiring DNA replication for maximum expression. By indirect immunofluorescence, the protein could be visualized in the nuclei of virus-infected HFF 22 h after infection. Nuclear localization of the UL97 protein was also detected in thymidine kinase-deficient 143B cells infected with a recombinant vaccinia virus containing the entire UL97 open reading frame (ORF), as well as in HFF transiently expressing the entire UL97 ORF under the control of HCMV major immediate-early promoter. However, transiently expressed 5'-terminal deletion mutants of the UL97 ORF in addition showed a cytoplasmic localization of the UL97 protein, confirming the presence of a nuclear localization site in the N-terminal region of the protein. Our high-pressure liquid chromatography analyses confirmed the ganciclovir phosphorylation by the UL97 protein, but no specific phosphorylation of natural nucleosides was observed, indicating that the UL97 protein is not a nucleoside kinase. During plaque purification of recombinant UL97-deficient HCMV, this virus was growth defective; hence, we presume that UL97 may be essential for the viral life cycle.

[Effect of heparin and ascorbic acid on growth behavior of cultivated corneal epithelial cells of the rabbit]

Although ascorbic acid and heparin are used for local therapy of corneal wounds that heal poorly (e.g., after chemical burns), little has been known up to now about the mechanisms underlying their effectiveness at the cellular level. The aim of the present study was therefore to evaluate the effect of heparin and ascorbic acid on the growth behaviour of corneal cells in vitro. For this purpose cell cultures from a corneal epithelial cell line were used. Stimulation of the cells with heparin at concentrations ranging from 10 to 200 micrograms/ml for 6 days led to a dose-dependent rise in growth rate (population doublings per day) of 0.48 +/- 0.50 to 2.19 +/- 1.65 (mean value +/- standard deviation, n = 10) with an EC50 of 132 micrograms/ml. In contrast, the addition of ascorbic acid at concentrations ranging from 0.5 to 3.0 mM led on average to a 40% dose-dependent inhibition of cell proliferation after 6 days, with an IC50 of 0.7 mM as-corbic acid. On the basis of these results, the use of heparin at concentrations of 180-200 micrograms/ml appears advantageous. In contrast, the local application of ascorbic acid for chemical burns with no stromal involvement should be subjected to a critical reassessment.

[PDGF-induced effect on cytosolic free calcium concentration of cultured retinal pericytes]

Although the selective loss of retinal pericytes has long been known to be one of the earliest histopathological findings in diabetic retinopathy, only limited information is available concerning their function and cell biology. Recently, it has been shown that the interaction of endothelial cells and pericytes plays an important role in the maintenance of vascular integrity. Additionally, it has been suggested that pericytes have a contractile function. Platelet-derived growth factor (PDGF), released from endothelial cells, has been shown to be a potent mitogen and vasoconstrictor. Cytosolic free calcium ([Ca2+]i) has been shown to play a key role as a second messenger for PDGF, involved in the regulation of various cellular functions, e.g. cell proliferation and vascular contractility. In order to characterize the effect of different PDGF homodimers on cultured bovine retinal pericytes, we investigated PDGF-AA- and -BB-dependent alterations in [Ca2+]i was determined with the Ca(2+)-sensitive fluorescent probe Quin-2. Basal levels were 118 +/- 30 nM. Stimulation with PDGF-BB in concentrations ranging from 5 to 20 ng/ml led to a dose-dependent increase of [Ca2+]i with an EC50 of 5.8 ng/ml. Maximum stimulation, to about 280% of basal levels, occurred after 3-4 min. In contrast, PDGF-AA was not effective. The results suggest that PDGF-BB may influence the integrity and contractility of the retinal microvasculature via modulation of the intracellular calcium homeostasis of pericytes. Additionally, it can be speculated that cultured retinal pericytes express mainly PDGF-beta-type receptors.

[Photodynamic activity of phthalocyanines in cultivated lens epithelial cells of the pig]

One of the most frequent complications of extracapsular cataract surgery is posterior capsule opacification (PCO), which is caused by proliferation and migration of retained lens epithelial cells on the posterior capsule surface. This complication leads to a reduction in visual acuity. Depending on the age of the patients, the incidence varies between 15 and 50%. Selective elimination of these cells would therefore prevent PCO. Phthalocyanines (Pc) are efficient photosensitizers of various carcinoma cell lines. Their attractive property is the strong absorption of visible light above 600 nm. Upon absorption of a photon, the sensitizer in its excited state can be either directly cytotoxic or produce reactive oxygen species type I (free radicals) or type II (singlet oxygen), which become the mediator of cellular injury by affecting membranes and subcellular organelles. Preconfluent cultures of porcine lens epithelial cells were incubated with aluminum phthalocyanine (AlPc) or aluminum phthalocyanine transulfonate (AlPcS4) in concentrations ranging from 0-20 microM for 1 h at 37 degrees C. Thereafter, cultures were exposed to red light for 5 min. A 300 W quartz halogen light bulb equipped with a cut-off filter that allowed transmission of the whole spectrum above 600 nm was used for activation of the sensitizers. To evaluate the effect of fluoride, 5 mM NaF was added to the dye-loaded cells immediately before light exposure. This treatment had no toxic effect. Subsequently, the treated cells were incubated in culture medium for 24 h. After trypsinization, the cell number was determined by a cell counter. Prior to light exposure neither AlPc nor AlPcS4 was toxic in corresponding controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Aluminium phthalocyanines-induced photolysis of human vascular wall cells in culture and the effect of fluoride on photodynamic action

BACKGROUND

Phthalocyanines, second-generation photosensitizers with several attractive properties for use in photodynamic therapy, have been shown to accumulate in malignant lesions and atherosclerotic plaques. After exposure of phthalocyanines-loaded tissues to visible light, the targeted cells become injured and eventually die. In vitro, when fluoride is added before exposure to the light, it can protect some cell types against photodynamic action sensitized by chloroaluminium phthalocyanine (AIPc) and its derivatives.

METHODS

The effect of 50 mumol/l chloroaluminium phthalocyanine tetrasulfonate (AIPcS4) and 5 mumol/l AIPc, with and without the addition of 5 mumol/l NaF, on the viability of cultured human endothelial cells (HuEC), human smooth muscle cells (HuSMC), and skin fibroblasts (HuSF) was examined. A 150 W quartz halogen light bulb equipped with a cut-off filter (lambda > 605 nm) was used to activate the phthalocyanines. Cell viability was examined 24 h after irradiation by staining of the cells with fluorescein diacetate/ethidiumbromide and by counting the number of attached cells with a cell counter.

RESULTS

In the case of AIPc, the viability of all cell types tested was reduced, in a dose-dependent manner, to about 50% of that of the corresponding controls for a maximum irradiation time of 600 s. When we used AIPcS4, both HuEC and HuSF were considerably less sensitive than HuSMC. The addition of fluoride to AIPc-loaded cells before exposure to light protected HuEC and HuSF, but not HuSMC. In the case of AIPcS4, with and without fluoride, only HuSMC were sensitive.

CONCLUSIONS

The addition of fluoride to AIPc or the use of AIPcS4 without fluoride could be a valuable approach, selectively destroying HuSMC without affecting HuEC and HuSF, for the reduction of restenosis rates after recanalization of stenosed or occluded arteries. Moreover, because neither type of phthalocyanines causes cutaneous phototoxicity, these second-generation photosensitizers seem to be best suited to the photodynamic treatment of atherosclerosis.

Serum-free cultivation of bovine lens epithelial cells

Mammalian cells in culture have individual nutritional requirements which are mainly fulfilled by the addition of fetal calf serum to the basic culture medium. Since many of the serum components are as yet poorly understood or even completely unknown, a number of difficulties arise in the evaluation of the effect of exogenously added factors or drugs on the growth of the cells. This paper presents data demonstrating the successful adaptation, routine cultivation and cryopreservation of bovine lens epithelial cells (BLEC) under serum-free culture conditions by use of the commercially available serum substitutes BMS, BM-86 Wissler and Ultroser G. Moreover, a culture medium especially designed for cell quiescence, named LR-1, is presented. Cells cultivated in culture medium containing 10% fetal calf serum served as controls. While BM-86 Wissler caused significantly reduced growth rates within 2 days and, finally, cell death after 12 days of incubation, the use of BMS resulted in growth rates which did not differ from the corresponding controls. Ultroser G resulted in a significant increase of proliferative activity of BLEC. LR-1 medium caused cell quiescence and kept the cells alive for a number of days. Thus, LR-1 allowed evaluation of the response of the cells to a mitogenic mixture from bovine brain mainly containing endothelial cell growth factor. The results demonstrate that cultivation of BLEC is possible under serum-free culture conditions. Moreover, the medium LR-1, which causes cell quiescence, is useful for the evaluation of growth factor-induced effects in vitro.

[Growth characteristics of bovine retinal pericytes in culture]

The loss of retinal pericytes is one of the earliest changes in diabetic retinopathy. In order to study this phenomenon in vitro, an optimal isolation and cultivation system has to be established. Therefore, pericytes from bovine retinae were isolated enzymatically with 0.4% collagenase in phosphate-buffered saline and identical immunologically by positive staining with antibodies against smooth muscle alpha-actin. Routine cultivation of pericytes was performed by using DMEM supplemented with 10% fetal calf serum. Dependent on the in vitro age of cells, the effect of the following reagents on proliferative activity was determined: fetal calf serum, heparin, ECGF, ECGF+heparin, and glucose. Increasing serum concentrations stimulated the proliferation of pericytes, although the degree of stimulation was reduced with increasing in vitro age. Heparin inhibited the growth in a dose-dependent manner; the achieving 50% inhibition was extrapolated to be 25 micrograms/ml. ECGF increased pericyte proliferation significantly, with a maximum at 10 microliters/ml. In addition, ECGF reversed the inhibitory effect of heparin. Furthermore, all tested glucose concentrations (5.5-27.75 mmol/l) did not show any influence on growth rates of pericytes. The results demonstrate that routine cultivation of retinal pericytes is possible. Moreover, they indicate that enhanced blood glucose concentrations, as observed in diabetic patients, are not the only important factor in the loss of retinal pericytes.

[Effect of platelet-derived growth factor PDGF on replication of cultivated bovine lens epithelial cells]

It has previously been reported that PDGF isoforms AB and BB induce an increase of cytosolic free calcium in cultured bovine lens epithelial cells in a dose-dependent manner. To evaluate the biological capacity of PDGF, we investigated the proliferative response of bovine lens epithelial cells to stimulation with PDGF-AA, -AB and -BB. Since various unspecific components of serum-containing media act as mitogenes and mask the effect of PDGF, serum-free culture conditions were a prerequisite for growth-factor-induced effects. Therefore, a basic medium (Waymouth's MB 752/1 with Ham F12 Nutrient Mixture 1:2, v/v; Gibco BRL) was supplemented with only 2 mM CaCl2, 10 micrograms/ml Transferrin, 10 micrograms/ml Thyroglobulin (both Sigma Chemie) and standard amounts of antibiotics. PDGF isoforms were obtained by separate expression of cloned genes in Escherichia coli, which has been previously described. Under these conditions the isoforms PDGF-AB and -BB caused an increase in proliferation in a dose-dependent manner. The maximum increase of the cell number was 21% for PDGF-AB with an EC5 of 5 ng/ml. PDGF-BB revealed a maximum increase of 33% with an EC5 of 1.5 ng/ml. PDGF-AA, when used in similar concentration was ineffective. These data show the involvement of PDGF isoforms AB and BB in the replicative action of BLEC.

[Expression of platelet derived growth factor receptors in cultivated lens epithelial cells]

It has been shown that PDGF plays a role in the regulation of lens growth and differentiation. PDGF occurs in vivo as a homodimer or heterodimer of the two polypeptide chains A and B. These isoforms bind with different affinities to two distinct receptor types, termed alpha and beta. In order to identify the different PDGF receptors on cultured bovine lens epithelial cells (BLEC), we performed receptor binding studies, using 125I-labelled PDGF isoforms. Analysis of our data revealed that BLEC expressed approximately 35,000 PDGF-BB binding sites (KD = 21 ng/ml) and 9000 PDGF-AB binding sites (KD = 11 ng/ml), but only 4800 PDGF-AA binding sites (KD = 7 ng/ml). This study represents the first demonstration that lens epithelial cells express PDGF receptors.

Lens epithelial cell response to isoforms of platelet-derived growth factor

It has been reported previously that platelet-derived growth factor (PDGF) may play an important role in the regulation of lens growth and differentiation. To evaluate PDGF-induced effects at the cellular level, we investigated the response of cultured bovine lens epithelial cells (BLEC) to PDGF-AB, -AA, and -BB isoforms at the cellular level. Stimulation of BLEC with PDGF isoforms showed no increase in cell proliferation under the culture conditions of this study. In contrast, measurement of cytosolic free calcium concentration ([Ca2+]i), which has been shown to be an important second messenger for controlling multiple cellular processes in the lens, revealed a dose-dependent rise in [Ca2+]i upon stimulation with PDGF-AB and -BB isoforms. PDGF-AA used in similar concentrations was not effective. Our data suggest that PDGF-AB and -BB may play a role in the regulation of cellular functions in BLEC via modulation of intracellular calcium homeostasis.

[Effect of heparin on proliferation of cultivated bovine lens epithelial cells]

The treatments proposed to date for the prevention of secondary cataract have shown limited efficacy or have not been satisfactory due to ocular toxicity. Since it has been demonstrated that heparin can inhibit the proliferative activity of smooth muscle cells and fibroblasts in vitro and in vivo, we examined the effect of heparin at concentrations ranging from 20 to 200 micrograms/ml on the proliferation of cultured bovine lens epithelial cells (BLEC) under various culture conditions: (1) serum-free medium (SFM); (2) SFM + aqueous humor 1:1; (3) SFM +1 and 10% fetal calf serum; (4) SFM +1% retinal extract; (5) SFM +50 micrograms/ml endothelial cell growth factor; (6) SFM +10 ng/ml epidermal growth factor; (7) SFM +10 ng/ml basic fibroblast growth factor. Heparin caused no cytotoxic effects in any of the experiments. With medium 2 and 3, heparin caused dose-dependent inhibition of cell proliferation at concentrations ranging from 10 to 50 micrograms/ml. Cells cultivated in medium 4-7 with the addition of 50 micrograms/ml heparin revealed increased proliferative activity when compared with the corresponding controls. The antiproliferative activity on BLEC in medium containing aqueous humor suggests that heparin is a valuable tool for the prevention of secondary cataract in vivo.

[Ascorbic acid. Cytotoxic effect on cultivated bovine lens epithelium cells]

Ascorbic acid is one of the main components (1.16 mM/l) of the aqueous humor. The molarity of this molecule is 25 times higher than in the plasma of the cow, man or horse. Now the question arises as to which function ascorbic acid has in this extremely high concentration referring to the proliferation of the lens epithelial cells. Thus, the effect of ascorbic acid was investigated upon bovine lens epithelial cells (BLEC) in the range of 0-3 mM/l. These cells were cultivated under various culture conditions (serum-free, serum-containing, aqueous-humor-containing medium) and also incubated with such mitogens as retinal extract (RE), crude endothelial cell growth factor (cECGF), basic fibroblast growth factor (bFGF) or with calcium. In each culture condition 1 mM/l ascorbic acid caused remarkable inhibition of the proliferation of BLEC. Higher concentrations (> 1.5 mM/l) revealed cytotoxic effects. These effects were independent of small variations in the pH value caused by ascorbic acid. In addition, the effect of 2 mM/l ascorbic acid in combination with catalase in a concentration of 500 Um/ml and 1000 Um/ml, respectively, was investigated. It could be shown that catalase is capable of preventing the cytotoxic effect of ascorbic acid. These results show the inhibitory effect of ascorbic acid in its physiological concentration in the proliferation of BLEC.