TIMP-1 production in human retinal pigment epithelial cells after laser exposure

PURPOSE

To investigate changes in the production of tissue inhibitor of metalloproteinase type 1 (TIMP-1) by human retinal pigment epithelial (RPE) cells following argon laser exposure.

METHODS

Human cultured ARPE19 cells were exposed to argon green laser at four different energy levels ranging from 60mW to 360mW. After laser exposure, the culture media were sampled at 0, 24, 72 and 144 hours for TIMP-1 concentration produced by the RPE cells. The levels of TIMP-1 in the cells treated with different laser energy levels were compared with a control group not exposed to laser application. Immunocytochemistry for proliferating cell nuclear antigen (PCNA) was performed to detect any adverse effects on the RPE cells caused by laser exposure.

RESULTS

Immediately after laser exposure, the concentration of TIMP-1 was not detectable. At 24 hours after laser exposure, the concentration of TIMP-1 increased significantly in RPE cells treated with 120mW and 240mW at 24 hours (P=0.006 and P=0.001 respectively) compared with control cells. At 72 hours after treatment, RPE cells treated at 120mW, 240mW and 360mW demonstrated significantly increase in TIMP-1 production compared with control (P=0.003, P < 0.001 and P < 0.001, respectively). No significant reduction in cell viability was observed following laser application as detected by PCNA expression.

CONCLUSIONS

Our results demonstrated that early TIMP-1 production by RPE cells in cell cultures was enhanced following laser exposure.

Inhibition of glioma invasion by overexpression of pigment epithelium-derived factor

Pigment epithelium-derived factor (PEDF) is a potent inhibitor of angiogenesis and an inducer of neural differentiation. We previously reported the loss of PEDF expression in glioma progression. In this study, we investigated whether PEDF overexpression could suppress glioma growth and invasion. Glioma cell line U251 was stably transfected with a full-length human PEDF expression vector. The expression and release of various cytokines and angiogenic factors into the medium were analyzed by real-time reverse transcription-polymerase chain reaction, enzyme-linked immunosorbent assay, and gelatin zymography. Apoptosis was checked by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling. Growth inhibition was evaluated by using the in vitro Matrigel invasion. Tumorigenicity was examined in vivo by subcutaneous xenotransplantation into severe combined immunodeficient mice. In U251 cells overexpressing PEDF, thrombospondin-1 protein was upregulated (5.3-fold more), but the production of vascular endothelial growth factor (VEGF) (1.8-fold less) and basic fibroblast growth factor (2.5-fold less) was lower than in cells transfected with the vector only. PEDF also downregulated the production of matrix metalloproteinase-9. Conditioned medium collected from the PEDF-transfected U251 cells showed a significant reduction of VEGF expression. In vitro invasiveness was reduced by approximately 40%. PEDF expression prevented the growth of transfected cells and caused a significant increase in the percentage of cells undergoing apoptosis (50.4% in PEDF-transfected cells). Furthermore, the size of xenotransplants was significantly smaller. In conclusion, PEDF overexpression decreased malignancy, and this might be attributed to the promotion of apoptosis and the regulation of expression of angiogenic effectors. Thus, treatment with PEDF may be useful in patients with malignant gliomas. However, the mechanism of apoptosis induction needs to be investigated.

Effect of indocyanine green and illumination on gene expression in human retinal pigment epithelial cells

PURPOSE

To investigate the biological effects of indocyanine green (ICG) and acute illumination on human retinal pigment epithelial (RPE) cells.

METHODS

Three concentrations (0, 0.25, and 2.5 mg/mL) of ICG were applied to ARPE19 cells for 1 minute. After isotonic rinsing, the cells were irradiated with a light beam with a wavelength spectrum from 400 to 800 nm and an output of 1850 lumens for 15 minutes. The cells were collected at timed intervals for the investigation of cell death and expression of stress-response genes by reverse transcription-polymerase chain reaction, immunofluorescence, and Western blot analysis.

RESULTS

After ICG incubation, photoreactive changes were observed in the RPE cells. A reduction in cellular viability and considerable shrinkage of the cells were observed. The expressions of the apoptosis-related genes p53 and bax and the cell cycle arrest protein p21 were upregulated in cells treated with both ICG and light. Of the early-response genes, the expression of c-fos was specifically enhanced by light, with additive effects from the presence of ICG. Such stimulatory effects on these gene expressions were greater at 2.5 mg/mL than at 0.25 mg/mL ICG.

CONCLUSIONS

ICG in the presence of acute illumination can elicit cell-cycle arrest and even apoptosis in RPE cells. The establishment of a safety level in the application of ICG in the region of 0.25 mg/mL is recommended.

Changes of nuclear matrix in long-term culture of limbal epithelial cells

PURPOSE

This study was undertaken to investigate the changes of nuclear matrix in long-term culture of rabbit limbal epithelial cells.

METHODS

Epithelial cells outgrown from limbal basal epithelium were serially cultivated. Nuclear matrices of early and late passages were extracted for morphologic study and protein analysis by two-dimensional gel electrophoresis and immunoblotting.

RESULTS

Differential growth and changes in morphology were observed in limbal epithelial cells of early and late passages. Cytokeratin type 3 was expressed in cells of later passages, indicating corneal cell differentiation during the long-term culture. These cells also showed reduced density of nuclear matrix fibrils and thinning of nuclear lamina. They were shown by two-dimensional gel electrophoresis to have lost most nuclear matrix proteins, including lamin A/C and proliferating cell nuclear antigen. However, five new protein entities were also expressed.

CONCLUSION

The nuclear matrix appeared to change along with limbal epithelial cell differentiation in culture. Whether such changes may affect the growth and viability of limbal cells after transplantation requires in vivo tissue analysis.

Growth factor changes in ex vivo expansion of human limbal epithelial cells on human amniotic membrane

PURPOSE

Human limbal epithelial cells cultured on human amniotic membrane have been used for transplantation to treat corneal surface injuries. We determined whether the amniotic basement membrane affects the growth of human limbal epithelial cells through the production of growth factors.

METHODS

The epithelial cells grown out from limbal basal epithelium were placed on conventional culture plastic or on the epithelial side of denuded amniotic membrane under serum-free conditions. Culture supernatant was assayed for growth factor release at 24, 48, and 96 hours.

RESULTS

The cells grown on both substrata produced similar levels of epidermal growth factor (EGF). Cells grown on amniotic membrane showed enhanced secretion of tissue inhibitor of metalloproteinase type 1 (TIMP1) and reduced production of transforming growth factor beta1 and beta2. Depletion of EGF and TIMPI in cell culture slowed down cell growth and reduced EGF receptor expression, respectively.

CONCLUSION

Increased TIMPI influences the proteolytic system in the cell and extracellular matrix interaction, and decreased transforming growth factor beta1 and beta2 may stimulate corneal cell proliferation. We show that the amniotic membrane leads to differential expression of cytokines of limbal epithelial cells cultured on its surface. Such effects may be favorable to the growth and differentiation of the cells when used for ocular surface reconstruction.

Effects of all-trans-retinoic acid on human esophageal carcinoma cells and their nuclear matrices

Esophageal cancer is a common cancer among ethnic Chinese. The reported incidence of esophageal cancer has increased many fold in the past decades and is apparently still rising. Nuclear matrix forms the scaffold of the nucleus and participates in various nuclear functions. Cancer specific nuclear matrix proteins have been identified in several tumor systems. 2-D gel analysis shows the presence of novel nuclear matrix proteins in ATRA treated tumor cells and these proteins are cell line specific. Our preliminary study also shows ATRA altered the nuclear matrix density of tumor cells. The significance of these nuclear matrix proteins is discussed.

Effect of glucocorticoid hormone on nuclear matrix in cervical cancer cells in vitro

Human papillomavirus (HPV) is one of the crucial factors in cervical carcinogenesis. High risk HPV16 prototype has been demonstrated in association with the nuclear matrix in a cervical carcinoma cell line(1,2). Nuclear matrix (NM) has been established as playing an important role in various nuclear activities as well as carcinogenic processes. Dexamethasone (DEX) (glucocorticoid hormone) inhibited the growth of CC2/CUHK2 cervical carcinoma cells with concurrent induction of epithelial cell differentiation. 2D- PAGE (IEF and NEPHGE) revealed alternations in NM protein composition. Further demonstration of changes in NM was evidenced by NuMA (a novel NM protein) labelling. The HPV16 E7 oncoprotein was shown to be reduced in total cellular protein as well as in NM protein fractions in response to DEX treatment, and this suppressed expression was confirmed by RT-PCR. Thus, it is suggested that dexamethasone can down-regulate the growth of cervical cancer cells and its induced changes in NM may be a cause of this suppression.

Electrophoretic analysis of nuclear matrix proteins in human hepatocellular carcinoma

The nuclear matrix is the non-chromatin skeleton of the nucleus. This structure contributes to the shape of the nucleus and regulates various nuclear functions. In this study, nuclear matrix proteins of human normal liver, a liver cancer cell line, HepG2, and hepatocellular carcinomas (HCC) were investigated. Using high resolution two-dimensional polyacrylamide gel electrophoresis, the nuclear matrix proteins of 3 normal liver and 14 HCC were compared and contrasted. A high degree of similarity between normal liver, HepG2, and HCC nuclear matrix protein patterns was found. Two HCC specific nuclear matrix proteins were identified. Among these, one protein (HCC-1, Mr 62 kd, pI 5.3) appeared in all tumor samples and HCC-2 (Mr 33.25, pI 5.3-5.5) was present in 9/11 tumors, but absent in normal liver and HepG2. Our results indicate the presence of HCC specific nuclear matrix proteins. These matrix proteins may be used as markers for HCC.

Expression of nm23-H1 in human meningioma cells

The expression of nm23-H1 has been demonstrated to be highly correlated with the metastatic potential of various tumors. In the present investigation, meningiomas of different pathological grades were used to study on their nm23-H1 expression. Immunohistochemistry showed that nm23-H1 was expressed mainly in the cytoplasm especially in the perinuclear region in explants under short-term culture. Western-blotting demonstrated the specific expression of nm23 protein in all tumor samples. The expression was also found to be sex-dependent on tumor progression in female, but not in male patients. RT-PCR results confirmed nm23-H1 expression was higher in benign tumors than in their normal counterpart. Our observations thus suggest that nm23-H1 may play an important role in the progression of meningiomas in female patients.

The association of HPV 16 DNA with specific nuclear matrix proteins of normal and cervical carcinoma cell

Human papillomavirus type 16 (HPV 16) has been found to be integrated into the DNA of epithelial cells in most cervical cancers. The HPV16 DNA is bound to different nuclear matrix proteins in normal and cervical carcinoma cells. It has high affinity, for acidic proteins in cancer cells. The molecular weights of the acidic proteins are 200 kD, 186 kD and 67 kD. On the other hand, the viral DNA seemed to bind to higher molecular weight basic nuclear matrix proteins (250 kD, 150 kD) of normal cells. Further investigation of the functional roles of these nuclear matrix proteins may provide insight into the process of carcinogenesis of the cervix.

Microwave-enhanced immunohistochemical staining of a formalin-sensitive antigen-laminin receptor

Many potentially useful antigens have been difficult to detect in formalin-fixed, paraffin-embedded tissues. Recently a number of pathological and research laboratories have demonstrated that some antigens masked by formalin fixation could be restored to detectability by microwave heating. Previously, we were unable to demonstrate laminin receptor in cells processed by the routine fixation. Our results showed that microwave heating together with trypsin produced the best immunohistochemical staining for this receptor. Nevertheless, no significance was found in the levels of 67 kD LR in high and low metastatic tumor cell lines.

Fine structural observations on the human sperm nuclear matrix

The nucleus of the mammalian sperm is formed after a series of morphological and biochemical changes during spermatogenesis. The human sperm nucleus, after sequential extraction with detergents, nuclease and ammonium sulfate, consists of a fibroskeletal structure which maintains the original nuclear shape. The chromatin-depleted skeleton is formed by thick and thin fibers as well as electron-dense patches of different sizes. These highly branched matrix fibers had average diameters of 35 and 12 nm. Polarization of the fibroskeletal structure is apparent and can be used as a good model to study the function of nuclear matrix in nuclear compartmentation in germ cells.

An immuno-electron microscopic study on the relationship between nuclear matrix and DNA in rat spermatocytes

The nucleus of the mammalian spermatid undergoes a series of changes in its chromatin and nucleoprotein composition during transport from testis to epididymis. The sperm DNA is very tightly packaged by protamines instead of histones in somatic cells. However, the nuclear matrix and its association with DNA have not yet been definitively scrutinized with the electron microscope. The present study reveals that the protamine-depleted sperm nuclear matrix appears as a network of thick and thin filaments with glodular structures attached the these fibers. Monoclonal antibody to single- and doublestranded DNA was used to localize remnant DNA after extraction. By immunofluorescence microscopy, monoclonal antibody against DNA was localized outside the nucleus as a halo. Immuno-electron microscopy showed that gold particles were mainly associated with nuclear matrix surrounding the sperm head. Our results suggest a specific structural organization of sperm DNA with its matrix.

Electron microscopic analysis of the relationship between nuclear matrix stability and cell differentiation

Two cell lines, the less differentiated CC2/CUHK2 and the more differentiated CC3/CUHKE3, were used to study the difference in nuclear matrix stability against DNase 1 digestion. The nuclear matrix was almost totally extracted when the CC3/CUHK3 cells were digested with 100 micrograms/ml DNase 1, while that of the CC2/CUHK2 cells was still present even when 200 micrograms/ml DNase 1 was used. It is suggested that more differentiated cells have a less stable nuclear matrix while the less differentiated ones have a more stable nuclear matrix. The same phenomenon was also observed in normal human and rat cervical epithelia. The nuclear matrix of the poorly differentiated basal cells was more stable than that of the more differentiated superficial cells. This cell differentiation stage dependent stability of the nuclear matrix is probably related to the nuclear activity and gene expression.

Fine structural observation of a nucleolar-nuclear matrix-lamina-intermediate filament system in transformed cells

The nuclear matrix is a nonchromatin structure of the nucleus normally concealed by a much larger mass of chromatin. Several methods have been developed to remove chromatin from nucleus while preserving the underlying matrix architecture to some degree. The present study showed that after extraction of PtK2 cells and cervical carcinoma cells (CC3) with Triton X-100, ammonium sulfate and DNase, the nucleolar-nuclear matrix-intermediate filament (Nu-Nm-L-IF) network remained. The nucleolus was oval in shape and appeared as a fibrillar mass with an accentric dense fibrillar centre. This nucleolar skeleton was in direct connection with the nuclear matrix which in turn is connected with cytoplasmic intermediate filaments by lamins. It is concluded from these observations that the Nu-NM-L-IF system forms a continuous system which plays an important role in the maintenance of the nucleolar, nuclear and cytoplasmic integrity and cellular function.

Ultrastructural study on the development of the rat [correction of mouse] spermatocyte nuclear matrix during epididymal maturation

The rat sperm nucleus, after sequential extraction with detergents, nuclease and ammonium sulfate, consists of a skeletal structure that resembles the original nuclear shape. This chromatin-depleted skeleton is formed by thick and thin fibers as well as globular structures of different sizes. These fibers form anastomosis. The sperm nuclei obtained from testis and caput epididymis exhibits a loose fibrous network with thin fibers at the center. The entire nucleus of the sperm in the caudal epididymis is formed by a dense network of thick and thin fibers. These highly branched matrix fibers had diameters of 35 and 12 nm. It is concluded that the increase in density of the matrix fibers is related to the condensation of the chromatin in the maturation of the spermatozoa.

The growth and behaviour of pig retinal pigment epithelial cells in culture

The retinal pigment epithelium contains melanin and lipofuscin. It is believed that in the in vivo system, the incomplete degradation of phagocytosed outer segment discs leads to the formation of lipofuscin. Our results showed that pig RPE cells can be successfully cultured using standard culture techniques without addition of specific growth factors. In this system, the autofluorescent material is formed mainly from the degradation of pigment granules. This culture system may provide an excellent model for studying of diseases related to the retina.

Biological characteristics of a newly established human cervical carcinoma cell line

A new cell line, designated CC2/CUHK2, was established from a squamous carcinoma of the uterine cervix from a Chinese patient. The cell line grew well without interruption for over 12 months and over 90 passages. The doubling time of CC2/CUHK2 was 72 hours at passage 57. When seeded at a density of 1.5 x 10(3) cells per 25 cm2 tissues culture flask, the plating efficiency was 2.15%. Chromosome analysis showed a range of 30 to 130 with a modal number of 75. Immunoperoxidase staining of keratin showed positive reaction. Most of the CC2/CUHK2 cells showed weak nuclear staining of HPV capsid antigens with the ABC detection system. Analysis of the DNA samples extracted from the cervical cancer cells showed the presence of HPV type 16 DNA.

Establishment and characterization of two new cell lines derived from squamous cell carcinoma of the tongue in Chinese patients

Two new cell lines derived from squamous cell carcinoma of the tongue, T1/CUHK and T2/CUHK, have been established in culture. Analysis of the morphology, ultrastructure, chromosome number, spheroid formation and immunohistochemical properties of the two cell lines demonstrated that they are both well characterized. T1/CUHK cells grew relatively faster than T2/CUHK cells. Both cell lines were tumorigenic after inoculation into made mice and showed positive reactivity with HPV 16 DNA probe. The reactivity of both cell lines with HPV 18 DNA probe was weak.

Expression of a new surface membrane antigen (SQM1) in tumor cells cultured in media with different calcium ion levels

Terminal differentiation is usually achieved in normal as well as transformed squamous epithelial cells when cultured. On the other hand, tumor cells at various differentiation stages and with different biological characteristics comprise the heterogeneous properties of tumors which have been one of the barriers to effective treatments. Recently, a surface membrane protein has been reported in squamous cell carcinomas of the head and neck, which is recognized by a murine monoclonal antibody, SQM1. This glycoprotein was further suggested to be related to squamous cell differentiation and intercellular adhesion. In a recent study, the esophageal carcinoma cells of EC/CUHK2 cell line were induced to various differentiation stages as evidenced by the increasing amount of intracellular desmosomes and tonofilaments and greater binding ratios of cytokeratin and involucrin antibodies than in those cells that maintained lower calcium ion concentrations. The expression of SQM1 antigen was found to increase in intensity when the tumor cells were cultured in moderate to high calcium ion levels for 10 to 15 hours when the differentiation patterns were beginning to appear. The intensity declined gradually thereafter. Thus SQM1 protein might be related to the stage when the cells started committing with squamous differentiation.

Ultrastructural localization of a new surface membrane antigen (SQM1) related to squamous differentiation

Normal squamous epithelial cells readily undergo terminal differentiation in culture and are commonly used in differentiation studies. Several intracellular markers of squamous differentiation such as keratin, involucrin, transglutaminase and cholesterol sulfate have been well-studied and described by other workers. We have recently reported a surface membrane antigen in squamous carcinoma of the head and neck antigen in squamous carcinoma of the head and neck which is recognized by a murine monoclonal antibody SQMI. In this paper, we present our studies on the ultrastructural localization of SQMI antigen in cultured squamous epithelial cells using gold-labelled antibody. The cells studied included both normal and cancer cells at different degrees of differentiation. Under both transmission and scanning electron microscopy examination, the SQMI antigen was localized at the membrane surface of cultured cells, particularly at sites of cell-cell interdigitation. No association with desmosomal structure was observed in any of the specimens examined. There was however an association of SQMI antigen with microvilli of cell membrane. No non-specific cytoplasmic localization of SQMI antigen was observed. The intensity of SQM1 antigen revealed by gold-labelling appeared to have a positive correlation with the degree of differentiation of the cells in culture.