Pterygial derived fibroblasts express functionally active histamine and epidermal growth factor receptors

High-throughput screening of transient receptor potential (TRP) channels in pterygium

PURPOSE

Pterygium is a hyaline degenerative disease of the conjunctiva characterized by the progression of fibrovascular connective tissue from the bulbar conjunctiva to the cornea. The mechanism of pterygium formation is still not fully understood. Transient receptor potential (TRP) channels are a group of ion channels with distinct characteristics. Recent indications suggest TRP channels may play a significant regulatory role in pterygium development, but previous studies have mainly focused on in silico analysis. Accordingly, in the present study, we aimed to decipher the expression signatures and role of TRP channels in pterygium development.

METHODS

The study encompassed a cohort of 45 patients matched for age and gender distribution, comprising 30 individuals with primary pterygium (PP) and 15 individuals with recurrent pterygium (RP). The control group consisted of unaffected conjunctival tissue obtained from the same set of patients. High-throughput screening of differentially expressed TRP channels in pterygium tissues was achieved with the help of Fluidigm 96.96 Dynamic Array Expression Chip and reactions were held in BioMark™ HD System Real-Time PCR platform.

RESULTS

Statistically significant increases were found in the expression of 21 genes, mainly TRPA1 (p = 0.021), TRPC2 (p = 0.001), and TRPM8 (p = 0.003), in patients with PP, and in TRPC5 (p = 0.05), TRPM2 (p = 0.029), TRPM4 (p = 0.03), TRPM6 (p = 0.045), TRPM8 (p = 0.038), TRPV1 (p = 0.01) and TRPV4 (p = 0.025) genes in RP tissues.

CONCLUSION

Collectively, TRP channel proteins appear to play pivotal roles in both the development and progression of pterygium, making them promising candidates for future therapeutic interventions in patients afflicted by this condition.

Histamine activates an intracellular Ca2+ signal in normal human lung fibroblast WI-38 cells

Histamine is an inflammatory mediator that can be released from mast cells to induce airway remodeling and cause persistent airflow limitation in asthma. In addition to stimulating airway smooth muscle cell constriction and hyperplasia, histamine promotes pulmonary remodeling by inducing fibroblast proliferation, contraction, and migration. It has long been known that histamine receptor 1 (H1R) mediates the effects of histamine on human pulmonary fibroblasts through an increase in intracellular Ca2+ concentration ([Ca2+]i), but the underlying signaling mechanisms are still unknown. Herein, we exploited single-cell Ca2+ imaging to assess the signal transduction pathways whereby histamine generates intracellular Ca2+ signals in the human fetal lung fibroblast cell line, WI-38. WI-38 fibroblasts were loaded with the Ca2+-sensitive fluorophore, FURA-2/AM, and challenged with histamine in the absence and presence of specific pharmacological inhibitors to dissect the Ca2+ release/entry pathways responsible for the onset of the Ca2+ response. Histamine elicited complex intracellular Ca2+ signatures in WI-38 fibroblasts throughout a concentration range spanning between 1 µM and 1 mM. In accord, the Ca2+ response to histamine adopted four main temporal patterns, which were, respectively, termed peak, peak-oscillations, peak-plateau-oscillations, and peak-plateau. Histamine-evoked intracellular Ca2+ signals were abolished by pyrilamine, which selectively blocks H1R, and significantly reduced by ranitidine, which selectively inhibits H2R. Conversely, the pharmacological blockade of H3R and H4R did not affect the complex increase in [Ca2+]i evoked by histamine in WI-38 fibroblasts. In agreement with these findings, histamine-induced intracellular Ca2+ signals were initiated by intracellular Ca2+ release from the endoplasmic reticulum through inositol-1,4,5-trisphosphate (InsP3) receptors (InsP3R) and sustained by store-operated Ca2+ channels (SOCs). Conversely, L-type voltage-operated Ca2+ channels did not support histamine-induced extracellular Ca2+ entry. A preliminary transcriptomic analysis confirmed that WI-38 human lung fibroblasts express all the three InsP3R isoforms as well as STIM2 and Orai3, which represent the molecular components of SOCs. The pharmacological blockade of InsP3 and SOC, therefore, could represent an alternative strategy to prevent the pernicious effects of histamine on lung fibroblasts in asthmatic patients.

Tyrosine Kinase Inhibitor, Vatalanib, Inhibits Proliferation and Migration of Human Pterygial Fibroblasts

PURPOSE

Vatalanib is a small-molecule tyrosine kinase inhibitor. We investigated the effects of vatalanib on the proliferation and migration of cultured human pterygial fibroblasts (HPFs).

METHODS

Pterygium tissues were obtained after pterygium excision surgery and subjected to primary culture. HPFs were treated with vatalanib at various concentrations. Mitomycin C (MMC) was used as a positive control. Cell proliferation and migration assays were used to investigate the effects of vatalanib. Cell death was measured using flow cytometry analysis. Western blot analysis was performed to identify signaling molecules associated with the response to vatalanib.

RESULTS

Vatalanib inhibited both proliferation and migration of HPFs in a dose-dependent manner. Cell proliferation was significantly suppressed by vatalanib (10 and 100 μM) and MMC (0.004% and 0.04%) treatments. Migration assays revealed significant HPF delay when treated with vatalanib (1, 10, and 100 μM) and MMC (0.004% and 0.04%) compared with that in a negative control. Cell death analysis showed that high concentrations of vatalanib (100 μM) and MMC (0.004% and 0.04%) decreased cell numbers. Western blot analysis of vatalanib-treated cells showed vascular endothelial growth factor and transforming growth factor-β significantly reduced, but there was no alteration in p53 protein levels in HPFs.

CONCLUSIONS

These results indicate that vatalanib significantly suppressed the proliferation and migration of HPFs by decreasing vascular endothelial growth factor and transforming growth factor-β. Vatalanib showed less toxicity than that of MMC. Based on these results, vatalanib may potentially serve as a new adjuvant treatment after pterygium excision surgery.

Squamous epithelium formation in the respiratory intestine of the bronze Corydoras Corydoras aeneus (Callichthyidae Teleostei)

Accessory respiratory organs in fish exhibit great diversity but share the presence of numerous capillaries covered by a simple squamous epithelium. The adoption of the intestine for respiratory function needs certain special modifications. In this study, we explored immunohistochemical and metabolic fingerprint features that could underlay this adaptation in bronze corydoras Corydoras aeneus. Immunohistochemical localization of the cytoplasmic domain of epidermal growth factor receptor (EGFR) in the respiratory part of intestine demonstrated a strong positive immunoreaction in epithelial cells and connective tissue. Fourier Transfer Infrared (FTIR) spectroscopy coupled with chemometrics discriminated between anterior and posterior region of intestine in terms of secondary structure of proteins and the abundance of p-cresol and other phenolics. The latter were reduced in the posterior part of intestine, indicating the cessation of digestive function in this region. It has been suggested that aquatic hypoxia via endocrine cells (hypoxia-sensitive) activate EGFR, which induce proliferation of squamous epithelial cells, thereby enabling gas diffusion in the posterior part of intestine. It seems that hypoxia and normoxia are opposed conditions adjusting the production of squamous epithelial cells in this intestine. The physiological role of EGFR in the respiratory intestine of bronze corydoras is of interest not only from an evolutionary aspect but also in terms of a potential model for observations process proliferation squamous epithelial cells. Future investigations on the molecular responses to different water oxygen levels in air-breathing bronze corydoras fish are required to clarify the mechanism responsible for squamous cell proliferation.

Proliferative Effects of Histamine on Primary Human Pterygium Fibroblasts

Purpose. It has been confirmed that inflammatory cytokines are involved in the progression of pterygium. Histamine can enhance proliferation and migration of many cells. Therefore, we intend to investigate the proliferative and migratory effects of histamine on primary culture of human pterygium fibroblasts (HPFs). Methods. Pterygium and conjunctiva samples were obtained from surgery, and toluidine blue staining was used to identify mast cells. 3-[4, 5-Dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) was performed to evaluate the proliferative rate of HPFs and human conjunctival fibroblasts (HCFs); ki67 expression was also measured by immunofluorescence analysis. Histamine receptor-1 (H1R) antagonist (Diphenhydramine Hydrochloride) and histamine receptor-2 (H2R) antagonist (Nizatidine) were added to figure out which receptor was involved. Wound healing model was used to evaluate the migratory ability of HPFs. Results. The numbers of total mast cells and degranulated mast cells were both higher in pterygium than in conjunctiva. Histamine had a proliferative effect on both HPFs and HCFs, the effective concentration (10 μmol/L) on HPFs was lower than on HCFs (100 μmol/L), and the effect could be blocked by H1R antagonist. Histamine showed no migratory effect on HPFs. Conclusion. Histamine may play an important role in the proliferation of HPFs and act through H1R.

Pterygium epithelium abnormal differentiation related to activation of extracellular signal-regulated kinase signaling pathway in vitro

AIM

To investigate whether the abnormal differentiation of the pterygium epithelium is related to the extracellular signal-regulated kinase (ERK) signaling pathway in vitro.

METHODS

The expression levels of phosphorylated ERK (P-ERK), keratin family members including K19 and K10 and the ocular master control gene Pax-6 were measured in 16 surgically excised pterygium tissues and 12 eye bank conjunctiva. In colony-forming cell assays, the differences in clone morphology and in K10, K19, P-ERK and Pax-6 expression between the head and body were investigated. When cocultured with the ERK signaling pathway inhibitor PD98059, the changes in clone morphology, colony-forming efficiency, differentiated marker K10, K19 and Pax-6 expression and P-ERK protein expression level were examined by immunoreactivity and Western blot analysis.

RESULTS

The expression of K19 and Pax-6 decreased in the pterygium, especially in the head. No staining of K10 was found in the normal conjunctiva epithelium, but it was found to be expressed in the superficial cells in the head of the pterygium. Characteristic upregulation of P-ERK was observed by immunohistochemistry. The clone from the head with more differentiated cells in the center expressed more K10, and the clone from the body expressed more K19. The P-ERK protein level increased in the pterygium epithelium compared with conjunctiva and decreased when cocultured with PD98059. The same medium with the ERK inhibitor PD98059 was more effective in promoting clonal growth than conventional medium with 3T3 murine feeder layers. It was observed that the epithelium clone co-cultured with the inhibitor had decreased K10 expression and increased K19 and Pax-6 expression.

CONCLUSION

We suggest ERK signaling pathway activation might play a role in the pterygium epithelium abnormal differentiation.

Comparison of gene expression profiles in primary and immortalized human pterygium fibroblast cells

PURPOSE

Pterygium is a fibrovascular growth on the ocular surface with corneal tissue destruction, matrix degradation and varying extents of chronic inflammation. To facilitate investigation of pterygium etiology, we immortalized pterygium fibroblast cells and profiled their global transcript levels compared to primary cultured cells.

METHODS

Fibroblast cells were cultured from surgically excised pterygium tissue using the explant method and propagated to passage number 2-4. We hypothesized that intervention with 3 critical molecular intermediates may be necessary to propage these cells. Primary fibroblast cells were immortalized sequentially by a retroviral construct containing the human telomerase reverse transcriptase gene and another retroviral expression vector expressing p53/p16 shRNAs. Primary and immortalized fibroblast cells were evaluated for differences in global gene transcript levels using an Agilent Genechip microarray.

RESULTS

Light microscopic morphology of immortalized cells was similar to primary pterygium fibroblast at passage 2-4. Telomerase reverse transcriptase was expressed, and p53 and p16 levels were reduced in immortalized pterygium fibroblast cells. There were 3308 significantly dysregulated genes showing at least 2 fold changes in transcript levels between immortalized and primary cultured cells (2005 genes were up-regulated and 1303 genes were down-regulated). Overall, 13.58% (95% CI: 13.08-14.10) of transcripts in immortalized cells were differentially expressed by at least 2 folds compared to primary cells.

CONCLUSION

Pterygium primary fibroblast cells were successfully immortalized to at least passage 11. Although a variety of genes are differentially expressed between immortalized and primary cells, only genes related to cell cycle are significantly changed, suggesting that the immortalized cells may be used as an in vitro model for pterygium pathology.

Immunohistochemical detection of Hsp90 and Ki-67 in pterygium

BACKGROUND

To examine the immunohistochemical expression of heat shock protein 90 (Hsp90) and Ki-67 protein in human pterygium.

MATERIALS AND METHODS

Tissues obtained during pterygium surgery of 15 patients who underwent the bare-sclera procedure and 10 normal conjunctivae were studied. All of these pterygia were primary ones. Recurrent pterygia were excluded. Normal bulbar conjunctivas (2 x 2 mm) were obtained from the nasal region close to the limbus from patients during their cataract and retina surgeries. Immunohistochemical detection of Hsp90 and Ki67 was done using the streptavidin-biotin method in paraffin embedded tissue sections.

RESULTS

The percentage of cells stained for Hsp90 was greater for pterygium epithelium (76 ± 10.8) than for normal conjunctiva (1.4 ± 0.8). In each pterygium sample more than 60% of cells were positive. The differences in positive cells between normal and pterygium epithelium were highly significant for Hsp90 (P < 0,001).Pterygium epithelium also showed a higher percentage of cells that stained for Ki67 (10.1 ± 9.5) than for normal conjunctiva (2.1 ± 1.9). The differences in positive cells were also statistically significant for Ki67 (P < 0.01). Although there were significant differences in the majority of samples observed. It was noted that in some samples there was no difference between normal and pterygium epithelium for Ki67.

CONCLUSION

Our results indicate an abnormal expression of Hsp90 and ki-67 in pterygium samples when compared to normal conjunctiva.The finding of abnormal expression of levels of Hsp90 in pterygium samples can stimulate new research into pterygium and its recurrence.

VIRTUAL SLIDES

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1128478792898812.

Transforming growth factor-β/Smad - signalling pathway and conjunctival remodelling in vernal keratoconjunctivitis

BACKGROUND

Vernal keratoconjunctivitis (VKC) is a chronic ocular allergic inflammation characterized by corneal complications and the formation of giant papillae. Sma- and Mad-related proteins (Smad) modulate extracellular matrix gene expression during wound healing, inflammation and tissue remodelling.

OBJECTIVE

To investigate the relationship between allergic inflammation and TGF-β/Smad signalling pathway, expression in VKC patients and in primary cultured conjunctival fibroblasts exposed to mediators found previously over-expressed in VKC.

METHODS

Smad-2, -3, -7, phospho-(p)Smads, TGF-β1 and -β2 were evaluated in the conjunctiva of normal subjects (CT) and VKC patients by immunohistochemistry. The expression of Smads, pro-collagen I (PIP), TGF-β1, -β2, mitogen-activated protein kinase (p38/MAPK), c-Jun N-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK1/2) were also determined in conjunctival fibroblast cultures exposed to histamine, IL-4, -13, TGF-β1, IFN-γ and TNF-α using immunostaining or RT-PCR.

RESULTS

Immunostaining for Smad-2, -3, pSmad-2, -3, TGF-β1, -β2 and PIP was significantly increased in VKC stroma compared with CT. In conjunctival fibroblast cultures, Smad-3 and PIP were stimulated by histamine, IL-4, -13 and TGF-β1 exposure, while PIP was reduced by IFN-γ, and TNF-α mRNA expression of Smad-3 was increased by histamine, while Smad-7 was reduced by IL-4. In addition, histamine, IL-4 and TNF-α increased JNK and ERK1/2 expression.

CONCLUSION AND CLINICAL RELEVANCE

The TGF-β/Smad signalling pathway is over-expressed in VKC tissues and modulated in conjunctival fibroblasts by histamine, IL-4, TGF-β1 and TNF-α. These mechanisms may be involved in fibrillar collagen production, giant papillae formation and tissue remodelling typical of VKC and might provide new therapeutic targets for its treatment.

Corneal and conjunctival findings after mitomycin C application in pterygium surgery: an in-vivo confocal microscopy study

PURPOSE

To perform a qualitative assessment of the topical side-effects of mitomycin C on cornea after pterygium surgery.

METHODS

In-vivo confocal microscopy (Heidelberg Retina Tomograph II in combination with the Rostock Cornea Module) was performed in 10 patients with unilateral primary pterygium. Mitomycin C 0.02% was applied topically to seven eyes for 5 min intraoperatively and twice daily for 5 days postoperatively. Three eyes underwent surgery without application of cytostatic agent. Patient follow-up was 1 month.

RESULTS

After application of mitomycin C, complete epithelialization of the operated zone was found 2 weeks after surgery. In-vivo confocal microscopy revealed signs of superficial punctate keratitis for 2 weeks in the central cornea only after application of mitomycin C. The presence of epithelial and stromal oedema in this group was noted for up to 2 weeks in the central cornea and for up to 4 weeks in the operated zone. In the control group, complete epithelialization was found after 1 week; there were no signs of oedema after 1 week in the central cornea or after 2 weeks in the operated zone. Leucocyte infiltration and increased Langerhans cell density were noted in both groups in the operated and central zones. Analysis of the conjunctiva revealed a decrease in goblet cell density following cytostatic application.

CONCLUSION

Local application of mitomycin C delays corneal epithelialization, and prolongs postoperative epithelial and stromal oedema in both the centre and periphery. Moreover, signs of punctate keratitis were noted 2 weeks after surgery in central intact cornea. Nevertheless, in-vivo confocal microscopy shows that these changes are reversible 4 weeks after application of mitomycin C 0.02%.

In Vivo Confocal Microscopy of the Ocular Surface

Over the past two decades, the applications of in vivo confocal microscopy to the investigation of ocular surface diseases in the living eye have been greatly extended. Confocal microscopy enables detailed investigation of tarsal and palpebral conjunctiva, central and peripheral cornea, tear film, and lids, and it allows evaluation of the ocular surface at the cellular level. High-quality imaging in both contact and noncontact modes has allowed new understanding of the functions of the ocular surface system, and in the coming years, such knowledge will become increasingly comprehensive and specific. Confocal microscopy may provide a link between well-established ex vivo histology and in vivo study of ocular pathology, not only in clinical science but also in clinical practice. The purpose of this review is to summarize the current knowledge about in vivo confocal microscopy of the ocular surface.

The involvement of adult stem cells originated from bone marrow in the pathogenesis of pterygia

Pterygium is a proliferative disease. Recent research has reported that stem cells are involved in the pathogenesis of various proliferative diseases, including solid tumors and diabetic proliferate vitreoretinopathy. In previous literature, we hypothesized that adult stem cells originated from bone marrow were involved in the pathogenesis of pterygium. We proved this by immunohistochemical staining with various stem cell markers. The staining showed adult stem cells in the pterygium. c-kit positive cells were observed primarily in the stroma, and some cells were also found in the basal epithelium. AC133 and CD34 positive cells were primarily found in the basal epithelium and were ovoid shaped, similar to the c-kit cells. However, some cells were found in vascular endothelium. STRO-1 positive cells were found mainly in the stroma and were spindle shaped. In recurrent pterygium, cells were more scattered and the expression pattern was denser. Therefore, we suggest a new theory of pterygium pathogenesis. Inflammation caused by environmental factors triggers the abnormal production of some growth factors and cytokines in order to recover from cellular damage. If these healing signals are excessive, limbal basal cells will be changed to abnormally-altered pterygial cells. The excessive wound healing process and remnant altered cells result in recurrence using the same mechanism.

Histamine receptors and the conjunctiva

PURPOSE OF REVIEW

The purpose of this review is to evaluate the effect of histamine on various receptors in the conjunctiva. A Medline search from 1980 was performed on the histamine receptor subtypes H1, H2 and H3 in the human conjunctiva.

RECENT FINDINGS

In the conjunctiva, histamine has been shown to induce various physiological and immunological changes through both H1 and H2 receptor stimulation. Histamine binding to conjunctival H1 receptors through the phospholipase C-dependent inositol phosphate pathway leads to the symptom of pruritus while histamine stimulation of the conjunctival H2 receptors has been indirectly shown to cause vasodilation.

SUMMARY

The effect of histamine on conjunctival H1 receptors appears to be the primary target for ocular allergy treatment as it is primarily involved in ocular pruritus. The exact interaction of the conjunctival H2 receptors appears to work in a complementary fashion to the H1 receptor in controlling other features of ocular allergy such as vasodilation and injection. Thus, oral and topical antihistamines with multiple histamine receptor binding activities may provide an improved treatment paradigm for the various signs and symptoms of ocular allergy. The histamine H1, H2 and H3 receptor affinities of ketotifen, pyrilamine, and epinastine appear to have the strongest H1 and H2 affinities.

Epidermal growth factor receptor signaling is partially responsible for the increased matrix metalloproteinase-1 expression in ocular epithelial cells after UVB radiation

Pterygia are inflammatory, invasive, and proliferative lesions of the human ocular surface in which the matrix metalloproteinase (MMP) collagenase-1 (MMP-1) is highly expressed. Pterygia development may involve MMP-1 activity against interstitial fibrillar collagen, an abundant extracellular matrix component of the cornea, and its induction by ultraviolet light (UVB). We examined the pathways responsible for enhanced expression of MMP-1 in pterygium epithelial cells after UVB exposure and/or treatment with chemical inhibitors of mitogen-activated protein kinases or epidermal growth factor receptor. The induction of MMP-1 by UVB was comparable to that mediated by heparin-binding epidermal growth factor-like growth factor and epidermal growth factor. The epidermal growth factor receptor inhibitor PD153035 partially blocked the UVB-mediated induction of MMP-1 and totally abrogated its production after stimulation with either heparin-binding epidermal growth factor-like growth factor or epidermal growth factor. UVB exposure enhanced the phosphorylated form of ERK1/2 in a time-dependent manner whereas the ERK1/2 inhibitor PD98059 decreased this induction by at least fivefold. Transcripts for c-jun and c-fos were detected as early as 2 hours after UVB exposure and were suppressed by PD98059. The identification of a specific intracellular signaling pathway responsible for the enhanced production of a key enzyme that denatures intact fibrillar collagen has important implications for understanding the pathophysiology and future therapy for pterygia.

Pathogenesis of pterygia: role of cytokines, growth factors, and matrix metalloproteinases

Pterygium is a common ocular surface disease apparently only observed in humans. Chronic UV exposure is a widely accepted aetiological factor in the pathogenesis of this disease and this concept is supported by epidemiological data, ray tracing models and histopathological changes that share common features with UV damaged skin. The mechanism(s) of pterygium formation is incompletely understood. Recent data have provided evidence implicating a genetic component, anti-apoptotic mechanisms, cytokines, growth factors, extracellular matrix remodelling (through the actions of matrix metalloproteinases), immunological mechanisms and viral infections in the pathogenesis of this disease. In this review, the current knowledge on pterygium pathogenesis is summarised, highlighting recent developments. In addition, we provide novel data further demonstrating the complexity of this intriguing disease.

The role of ultraviolet irradiation and heparin-binding epidermal growth factor-like growth factor in the pathogenesis of pterygium

Ultraviolet (UV) light is one of the major factors implicated in the pathogenesis of pterygium. The mechanism by which UV light induces this disease remains elusive. The aim of this study was to evaluate the effects of UVB irradiation on the expression of growth factors in cultured pterygium epithelial cells and to demonstrate their distribution within pterygium. We cultured pterygial epithelial cells from pterygium explants and these cells were exposed to 20 mJ/cm(2) of UVB. Total RNA was extracted at 0, 6, and 12 hours after irradiation. (32)P-labeled cDNA was synthesized and analyzed using microarray technology to determine the differential expression of 268 growth factor and cytokine related genes. Semiquantitative reverse transcriptase-polymerase chain reaction was used to corroborate this data. Conditioned media derived from cells exposed to UVB irradiation was analyzed for protein expression by enzyme-linked immunosorbent assay. Immunohistochemistry was used to evaluate the distribution of heparin-binding epidermal growth factor-like growth factor (HB-EGF) in pterygium tissue. Analysis of the hybridization signals revealed that the genes encoding HB-EGF, fibroblast growth factor 3, and cytotoxic trail ligand receptor were consistently elevated at 6 and 12 hours after UVB treatment. HB-EGF mRNA was elevated 6.8-fold at 6 hours after irradiation and was augmented in culture supernatants after the same treatment. Furthermore, HB-EGF reactivity was identified in the epithelium and vasculature of pterygium by immunohistochemistry. HB-EGF was present in normal limbal epithelium, although it was not induced in cultured limbal epithelial cells by UV irradiation. HB-EGF is a potent mitogen, localized in pterygium tissue, and significantly induced by UVB in pterygium-derived epithelial cells. We postulate that this growth factor is a major driving force in the development of pterygia and a means by which UV irradiation causes the pathogenesis of pterygium.