TGF-beta1, -beta2, and -beta3 in vitro: biphasic effects on Tenon's fibroblast contraction, proliferation, and migration

PURPOSE: To compare the effects of the three human transforming growth factor-beta (TGF-beta) isoforms and different concentrations of TGF-beta on human Tenon's capsule fibroblasts (HTF), with a view to delineating the role of this growth factor in the subconjunctival scarring response after glaucoma filtration surgery. METHODS: Application of recombinant human TGF-beta1, -beta2, and -beta3 (range 0-10(-8) M) was assessed using several assays of HTF function: fibroblast-mediated collagen contraction, proliferation, and migration. RESULTS: All three isoforms of TGF-beta behaved in a similar manner in vitro. They each stimulated HTF-mediated collagen contraction, proliferation, and migration with a characteristic concentration-dependent response, with peak activities at 10(-9), 10(-12), and 10(-9) M, respectively, that were significantly different from control (P<0.05). At concentrations above and below peak activities, HTF activity was reduced, demonstrating biphasic effects of TGF-beta. CONCLUSIONS: TGF-beta1, -beta2, and -beta3 have similar actions in vitro; this is demonstrated by their effects on several HTF-mediated functions. TGF-beta induces a response in HTF that is concentration-dependent, with different functions being maximally stimulated at different concentrations. This biphasic response highlights the significance of the concentration profile of TGF-beta at the wound site. These findings are important in filtration surgery, where constant changes in the local environment occur due to the passage of aqueous and the wound healing process. The varying levels of TGF-beta in the aqueous and subconjunctival tissues may thus significantly modify the conjunctival scarring response.     

Involvement of CTGF in TGF-beta1-stimulation of myofibroblast differentiation and collagen matrix contraction in the presence of mechanical stress

PURPOSE: This study was undertaken to investigate the role of connective tissue growth factor (CTGF) in fibroblast-to-myofibroblast differentiation and fibroblast-mediated collagen matrix contraction in the presence of mechanical stress. METHODS: An in vitro three-dimensional contraction model of human corneal-fibroblast-seeded collagen lattices (FSCLs) in the presence of mechanical stress generated by attaching the lattices to the culture well was used to measure FSCL contraction. FSCLs were treated with CTGF; TGF-beta1; serum-free (SF) control medium; or TGF-beta1 plus antisense oligodeoxynucleotides to CTGF; TGF-beta1 plus scrambled-sequence oligodeoxynucleotide to CTGF; or TGF-beta antibody. Expression of alpha-smooth muscle actin (alpha-SMA) by fibroblasts in FSCLs was detected by immunostaining and confocal microscopy, whereas ELISA was used for the fibroblasts cultured on plastic. The conditioned media were analyzed by ELISA for CTGF production. RESULTS: Exogenous CTGF stimulated significantly less collagen matrix contraction and myofibroblast differentiation than TGF-beta1, but similar to that stimulated by SF. TGF-beta1 stimulated fibroblasts to express CTGF. CTGF antisense oligodeoxynucleotide inhibited TGF-beta1-stimulated myofibroblast differentiation and FSCL contraction. Exogenous CTGF circumvented the inhibitory effects of CTGF antisense on FSCL contraction. TGF-beta antibody significantly inhibited FSCL contraction and myofibroblast differentiation under mechanical stress and SF control conditions. CONCLUSIONS: In the presence of mechanical stress, CTGF is necessary for TGF-beta1-stimulation of myofibroblast differentiation and subsequent collagen matrix contraction, but CTGF alone is not sufficient to induce myofibroblast differentiation and collagen matrix contraction. Thus, TGF-beta1 appears to regulate multiple genes that are essential for fibroblast-mediated contraction of stressed matrix, one of which is CTGF.     

The effects of single doses of beta radiation on the wound healing behaviour of human Tenon's capsule fibroblasts

Aim: To determine the effects of single doses of beta radiation on the wound healing functions of human Tenon's capsule fibroblasts (hTf). METHODS: hTf were grown in tissue culture and irradiated with beta radiation using a strontium 90 source. The effects of beta radiation on fibroblast migration was studied using microporous transwell membranes. The effects of radiation on fibroblast contraction was investigated using a fibroblast populated collagen gels model. Production of extracellular matrix molecules (collagen I, collagen III, and fibronectin) by monolayers of irradiated fibroblasts was quantified for 14 days following single doses of beta radiation. RESULTS: Growth inhibiting doses of beta radiation did not inhibit fibroblast migration or contraction at any time point. Levels of soluble fibronectin from irradiated populations were significantly reduced after >500 cGy beta radiation. Collagen I and III levels were not reduced after any dose of radiation, and increased following treatment with 1000 cGy beta radiation. CONCLUSIONS: Growth arresting doses of beta radiation have unique effects on the wound healing behaviour of human Tenon's capsule fibroblasts. There was no significant effect on cellular migration or contraction, but ECM production was altered. Fibronectin production was inhibited following higher radiation doses, and collagen I and III production increased after 1000 cGy. The effects of single doses of beta radiation on ocular fibroblast wound healing behaviour are very different from those of 5-fluorouracil and mitomycin C, and these differences may be exploited clinically in the regulation of wound healing after glaucoma filtration surgery.     

The Rho-kinase inhibitor H-1152P suppresses the wound-healing activities of human Tenon's capsule fibroblasts in vitro

PURPOSE: To analyze the role of Rho-kinase signaling in the wound-healing activities of human Tenon's capsule fibroblasts by using H-1152P, a potent inhibitor of this kinase, in vitro. METHODS: The optimal concentration of H-1152P was determined by MTT test. Cell proliferation was measured by BrdU incorporation and Ki-67 immunostaining, whereas cell viability was investigated by ethidium homodimer-1 dye exclusion. The actin cytoskeleton organization was demonstrated by alpha-smooth muscle actin (SMA) immunostaining and Alexa 488-phalloidin staining. Cell migration was studied on restrained collagen gels and in a scratch-wound assay followed by Ki-67 and fibronectin immunostaining. The effect of H-1152P on contraction was analyzed in floating collagen gels populated with fibroblasts, which were subsequently processed for fibronectin immunostaining. The levels of adducin and the protein kinase A (PKA)-dependent phosphorylation of this protein were detected by immunoblot analysis, to rule out interference with PKA. RESULTS: Incorporation of BrdU and upregulation of Ki-67 were reduced by 80% to 90% in cells incubated with 10 microM of this inhibitor for 4 days (P < 0.01). H-1152P caused the disassembly of stress fibers in a dose-dependent manner without exerting toxic effects and without a considerable interference with the PKA-pathway. H-1152P also significantly suppressed cell migration 3- to 3.5-fold and the contraction of collagen lattices fivefold with a dose-dependent impairment in the assembly of the fibronectin network. CONCLUSIONS: These findings imply a role for Rho-kinase in the wound-healing activities of human Tenon's capsule fibroblasts and show the potential of H-1152P as a safe and specific means to suppress these events.     

Expression of bone morphogenetic proteins (BMPs), their receptors, and activins in normal and scarred conjunctiva: role of BMP-6 and activin-A in conjunctival scarring?

Bone morphogenetic proteins (BMPs) and activins are multifunctional growth factors, which also affect wound healing and tissue fibrosis. To determine their putative role in conjunctival wound healing and scarring, we investigated the expression of various BMPs, BMP receptors, and activins in normal and scarred human conjunctival tissue and in cultured human Tenon's capsule fibroblasts on the mRNA and protein level. Messenger RNA expression of BMP-2, BMP-3, BMP-4, BMP-5, BMP-6, BMP-7, the BMP receptors type I (BMPR-IA, BMPR-IB) and II (BMPR-II), and of activin A and B was investigated by semi-quantitative RT-PCR in normal conjunctival specimens and in scarred filtering blebs as well as in cultured Tenon's capsule fibroblasts obtained from patients with primary open-angle glaucoma (POAG), pseudoexfoliation (PEX) glaucoma and cataract. Immunohistochemistry was used to study the protein expression of BMP-2, BMP-4, BMP-6, BMP-7, and activin A in normal and scarred conjunctival tissue as well as in cultured Tenon's capsule fibroblasts. BMP-2, BMP-3, BMP-4, BMP-6, BMP-7, all BMP receptors, and activin A were expressed on the mRNA and protein level in conjunctival biopsies without showing any differences between groups of patients. The mRNA and protein expression of both BMP-6 and activin A was found to be significantly increased in scar tissue compared with normal conjunctiva and could be immunolocalized to epithelial cells, vascular endothelia, stromal fibroblasts, and macrophage-like cells. However, no significant increase in receptor gene expression was observed in scar tissue. With the exception of BMP-7, all growth factors and receptors were also expressed in cultured Tenon's fibroblasts without showing any differences between cultures derived from normal and scarred conjunctival specimens. These findings suggest various BMPs and activin A as components of the conjunctival cytokine meshwork regulating tissue homeostasis and wound healing and provide evidence that alterations in the expression of BMP-6 and activin A, in particular, are associated with conjunctival scarring. Modulation of BMP/activin activities may, therefore, be explored as new approaches for managing postoperative conjunctival scarring responses in glaucoma patients.     

An in vitro model of posterior capsular opacity: SPARC and TGF-beta2 minimize epithelial-to-mesenchymal transition in lens epithelium

PURPOSE: This report presents a novel model for studies of extracellular matrix (ECM) in posterior capsular opacification (PCO) in vitro. Lens epithelial cells (LEC) were cultured with an intraocular lens (IOL) on a surface of type IV collagen in an evaluation of the importance of the ECM-cell interaction in formation of PCO. Abnormal migration, proliferation, and expression of proteins associated with the epithelial-to-mesenchymal transition (EMT) that characterizes PCO were observed in the presence and absence of the matricellular protein SPARC (secreted protein, acidic and rich in cysteine), which regulates matrix-cell interactions. METHODS: The model for PCO in vitro consisted of an IOL placed on a membrane coated with collagen IV, a major constituent of the lens capsule. LECs from the lenses of wild-type (WT) and SPARC-null (SP-null) mice were cultured in the presence or absence of 10 ng/mL TGF-beta2 and 20 mug/mL recombinant human SPARC (rhSP) for up to 6 days. The migration of LECs was quantified. Labeling with BrdU and the measurement of DNA synthesis were assays for cell proliferation. Expression of the EMT markers, collagen type I, fibronectin, and alpha-smooth muscle actin were assessed using immunocytochemistry or Western immunoblots. RESULTS: LEC migration, proliferation, and the synthesis of EMT markers were enhanced in SP-null compared with WT LECs. TGF-beta2 inhibited the migration and proliferation of both WT and SP-null LECs in the presence of rhSP. TGF-beta2 increased the production of collagen type I, fibronectin, and alpha-SMA. The responses of SP-null LECs were rescued by the addition of recombinant human (rh)SP. CONCLUSIONS: A simple IOL culture system was useful for the evaluation of the effects of SPARC and TGF-beta2 on PCO in vitro. The action of TGF-beta2 on LEC migration and proliferation is influenced by SPARC, a regulator of matrix-cell interactions. The results indicate a functional intersection between pathways activated by TGF-beta2 and SPARC in the formation of PCO.     

Role of transforming growth factor-beta1 and its latent form binding protein in pseudoexfoliation syndrome

Pseudoexfoliation (PEX) syndrome is a common and clinically important systemic condition characterized by the pathologic production and accumulation of an abnormal fibrillar extracellular material in many intra- and extraocular tissues. Recent evidence suggests that it is a type of elastosis associated with the excess synthesis of elastic microfibrillar components such as fibrillin-1. Since transforming growth factor (TGF)-beta is a major modulator of extracellular matrix formation, the potential involvement of TGF-beta and its latent form binding protein (LTBP) in this aberrant matrix process was investigated.The expression of various isoforms of TGF-beta and LTBP was investigated in the anterior segment tissues of PEX and control eyes on the protein and mRNA level by light and electron microscopic immunohistochemistry, in situ hybridization, and semiquantitative RT-PCR. TGF-beta1 and TGF-beta2 levels were measured in aqueous humor and serum of PEX and control patients by ELISA. Cultures of Tenon's capsule fibroblasts were established to study the effect of TGF-beta1 on fibrillin-1 mRNA expression by Northern blot analysis.Significantly increased concentrations of both total and active TGF-beta1 were measured in the aqueous humor of PEX eyes without and with glaucoma as compared to control eyes, whereas levels of TGF-beta2 were not significantly different. The expression of TGF-beta1, LTBP-1, and LTBP-2, but not TGF-beta2, was markedly increased in anterior segment tissues of PEX eyes, particularly in the non-pigmented epithelium of the ciliary body, on both the mRNA and the protein level. Latent TGF-beta1 staining was consistently associated with PEX material deposits and could be released by proteolytic processing. Double immunolabeling revealed clear co-localization of LTBP-1 and -2 with latent TGF-beta1 and with fibrillin-1 on PEX fibrils. The expression of mRNA coding for fibrillin-1 was up-regulated in vitro by TGF-beta1.This study provides evidence for a significant role of TGF-beta1 and the LTBPs 1 and 2 in PEX syndrome. The results suggest that increased levels of latent and active TGF-beta1 in the aqueous humor of PEX patients, derived from enhanced local synthesis and activation, promote the buildup of the abnormal extracellular elastic material characteristic of PEX syndrome. They further support a dual role for LTBPs, both as integral structural components of PEX fibers and as a means of matrix anchorage of latent TGF-beta1, representing one possible mechanism for the regulation of TGF-beta1 activity in PEX eyes. Future therapeutic strategies might focus on TGF-beta1 antagonistic approaches.     

精氨酸-甘氨酸-天门冬氨酸-丝氨酸肽对人Tenon囊成纤维细胞的贴壁抑制试验观察

目的：研究精氨酸-甘氨酸-天门冬氨酸-丝氨酸（Arg-Gly-Asp-Ser，RGDS）肽对人Tenon囊成纤维细胞与纤维连接蛋白（FN）粘附、增殖的影响。方法：在传代培养的人Tenon囊成纤维细胞中加入不同浓度的RGDS（1、0.1、0.001g/L），用未贴壁细胞记数法及MTT法测定RGDS肽对人Tenon囊成纤维细胞粘附、增殖的影响。结果：RGDS肽能抑制成纤维细胞在FN上的粘附，呈浓度效应特点，能抑制成纤维细胞的增殖，呈浓度及时间效应特点。结论：在细胞水平上证实RGDS肽可阻止人Tenon囊成纤维细胞对FN的粘附和增殖，具有避免青光眼滤过术后瘢痕化形成的应用前景。     

Effect of growth factors on the activation of human Tenon's capsule fibroblasts

PURPOSE: To investigate stimulatory effects of PDGF-AA, PDGF-AB, PDGF-BB, bFGF, IL-1beta, TGF-beta1 and TGF-beta2 on the proliferation and myofibroblast transformation of cultured human Tenon's capsule fibroblasts and to characterize expression of PDGF- and TGF-beta-receptors in these cells. METHODS: To determine cell proliferation, cell number of 2nd passage cultured human Tenon's capsule fibroblasts was measured before and after addition of growth factors using a computer-based cell counter system. Immunoblotting was used to detect and quantitate alpha-smooth-muscle actin (alpha-SMA) expression. Expression of PDGF- and TGF-beta-receptor mRNA was detected by RT-PCR, expression of the corresponding protein was demonstrated using Western blot. RESULTS: A significant increase in proliferation (p < or = 0.05) was detected after exogenous stimulation with PDGF-AA (10 ng/ml and 100 ng/ml), PDGF-AB (10 ng/ml and 100 ng/ml), PDGF-BB (10 ng/ml and 100 ng/ml), bFGF (100 ng/ml), IL-1beta (1 ng/ml and 10 ng/ml), TGF-beta1 (0.5 ng/ml) and TGF-beta2 (0.5 ng/ml). Both TGF-beta1 and TGF-beta2 stimulated expression of alpha-SMA in a dose dependent manner with peak activity at a concentration of 50 ng/ml (TGF-beta1) and 500 ng/ml (TGF-beta2). Protein and mRNA of PDGF-receptor type alpha and type beta and TGF-beta-receptors type I, II and III are expressed in cultured human Tenon's capsule fibroblasts. CONCLUSIONS: The present investigation strongly supports the hypothesis that PDGF-isoforms are major stimulators of proliferation of Tenon's capsule fibroblasts after glaucoma filtering surgery while TGF-beta-isoforms are essential for the transformation of Tenon's capsule fibroblasts into myofibroblasts.     

Differences in the histopathology and matrix metalloproteinase expression in Tenon's tissue of primary open-angle glaucoma and primary angle-closure glaucoma

PURPOSE: To investigate the differences in the histopathology and matrix metalloproteinase (MMP) expression in the Tenon's tissue of primary open-angle glaucoma (POAG) patients, primary angle-closure glaucoma (PACG) patients, and non-glaucomatous patients. METHODS: POAG and PACG patients, who underwent a trabeculectomy and had no history of ocular disease except glaucoma, were enrolled. The number and instillation period of topical eye drops were reviewed. For the controls, which were patients without glaucoma or a history of ocular surgery, the Tenon's tissue was obtained in the course of retinal detachment surgery. For glaucoma patients, the Tenon's tissue was obtained during the trabeculectomy. H&E and Masson's trichrome staining and immunohistochemistry for MMP-1, MMP-2, and MMP-9 were performed. A total of six eyes of POAG, six eyes of PACG, and four control eyes were evaluated. RESULTS: The duration of topical anti-glaucoma medication and the mean number of anti-glaucoma medications were similar in the POAG and PACG groups. The levels of MMP-1 and 2 were elevated in the POAG and PACG groups compared to the control group (p=0.03, 0.01, respectively). Compared with the control group, the MMP-2 level was higher in the POAG patients (p=0.01), whereas the MMP-1 was higher in the PACG patients (p=0.04). The levels of MMP-9 in the POAG and PACG patients were not significantly different from that of the control patients (p=0.48, 0.26). The levels of MMP-2 were significantly lower in the PACG patients than in the POAG patients (p=0.02). CONCLUSIONS: The MMP expression was altered in the Tenon's tissue of glaucoma patients compared to the control group. The levels of MMP-2 were lower in the PACG patients than in the POAG patients. These results suggest that there may be histopathological differences in the Tenon's tissue of POAG and PACG patients.     

Matrix metalloproteinases and their inhibitors in aqueous humor of patients with pseudoexfoliation syndrome/glaucoma and primary open-angle glaucoma

PURPOSE: To determine the presence, activity, and quantitative differences of matrix metalloproteinases (MMPs) and their endogenous inhibitors (TIMPs) in aqueous humor and serum samples of patients with pseudoexfoliation (PEX) syndrome, PEX glaucoma (PEXG), primary open-angle glaucoma (POAG), and cataract. METHODS: Aqueous humor and serum samples were collected from 100 patients with PEX syndrome, PEX glaucoma (PEXG), POAG, and cataract, respectively. Levels of MMP-1, -2, -3, -7, -9, and -12 and TIMP-1 and -2 were determined by zymography, Western blot analysis, and specific immunoassays. Activity assay kits were used to quantitate levels of endogenously activated MMP-2 and -9. RESULTS: MMP-2, -3, -7, -9, and -12 and TIMP-1 and -2 were identified in human aqueous humor samples from all groups of patients with a six to sevenfold molar excess of TIMPs over MMPs. Whereas serum samples showed no significant differences, total MMP-2 and -3 and TIMP-1 and -2 were detected at significantly higher concentrations in aqueous samples from PEX eyes with and without glaucoma compared with cataractous eyes. MMP-2 and -3 and TIMP-1 were also detected in higher, but not significantly different, amounts in aqueous samples of POAG eyes. However, levels of endogenously activated MMP-2 were significantly decreased in both PEX and POAG samples. The ratio of MMP-2 to its principal inhibitor TIMP-2 was balanced in cataract samples, but was decreased in samples from patients with PEXG, resulting in an excess of TIMP-2 over MMP-2. CONCLUSIONS: The findings suggest that complex changes in the local MMP-TIMP balance and reduced MMP activity in aqueous humor may promote the abnormal matrix accumulation characteristic of PEX syndrome and may be causally involved in the pathogenesis of both PEX glaucoma and POAG.     

纤维连接蛋白对原发性开角型青光眼小梁网细胞增殖、黏附和迁移的影响

目的通过研究纤维连接蛋白（FN）对体外培养的原发性开角型青光眼（POAG）患者小梁网细胞增殖、黏附、迁移的影响,探讨FN与POAG发病机制的关系。方法取临床确诊的POAG患者小梁网切除术中的深层巩膜组织块,进行小梁网细胞体外原代和传代培养．并对其进行免疫细胞化学和电镜鉴定。取第3代小梁网细胞,实验组分别加入浓度为5、10、20、40、100μg／ml的FN（含无血清DMEM／F12培养液）培养,对照组不加FN。培养24h后,采用CCK-8比色法和Transwell试剂盒检测各组光密度值,分析FN对POAG小梁网细胞增殖、黏附、迁移的影响。采用SPSS17．0统计软件,组间比较采用One-Way ANOVA分析,两两比较采用SNK检验。结果经过免疫细胞化学和电镜鉴定后,确定培养的细胞为POAG小梁网细胞。不同浓度FN对小梁网细胞均有影响。FN对POAG小梁网细胞有促增殖作用,在FN为5～10μg／ml浓度范围,小梁网细胞增殖相对缓慢,10μg／ml以后呈现上调趋势,在40μg／ml时达到增殖高峰,100μg／ml仍促进增殖,但是相对缓慢。各实验组光密度值分别与阴性对照组比较,差异均有统计学意义（P〈0．01）;各实验组不同浓度组间比较,差异有统计学意义（F=81．778,P〈0．05）。FN浓度为5、10、20、40、100μg／ml时．小梁网细胞的增殖率分别为18．6％、54．7％、67．9％、98．7％和121．5％。同样,FN对POAG小梁网细胞有明显的促黏附、迁移作用。小梁网细胞的黏附、迁移能力随FN浓度的增加而增强,基本呈现曲线上升趋势,与阴性对照组比较,差异均有统计学意义（P〈0．05）。结论FN能促进POAG患者小梁网细胞增殖、黏附和迁移,其在POAG发病机制中的作用可能为通过影响POAG小梁网细胞的增殖、黏附、迁移功能参与房水流出的调节过程。     

Gamma-interferon effects on human fibroblasts from Tenon's capsule

Gamma-interferon (G-IFN) exhibits antiproliferative effects, inhibits collagen synthesis by fibroblasts, and may help to regulate the turnover of fibrous tissue. Fibroblasts from Tenon's capsule are cellular components that contribute to unsuccessful glaucoma filtration surgery. Therefore, the authors studied the effects of G-IFN on growth, wound closure, collagen synthesis, and extracellular matrix in cultured human Tenon's capsule fibroblasts (HTCF). HTCF incubated with G-IFN at doses of 1 to 1000 U/ml showed cellular heterogeneity, with some cells showing morphologic changes characteristic of senescence, and a dose-dependent inhibition of wound closure. At 1000 U/ml, G-IFN reduced collagen synthesis by 57%, reduced immunofluorescent staining of collagen type I and fibronectin network, and altered the organization of actin microfilaments into large cable-like structures. Cell proliferation and viability were not affected at any concentration of G-IFN. These results suggest that G-IFN may be useful to modulate wound healing after filtration surgery.     

Immunohistochemical evaluation of the extracellular matrix in trabecular meshwork in steroid-induced glaucoma

BACKGROUND: To immunohistochemically examine the localization of the extracellular matrix (ECM) in the trabecular meshwork (TM) in steroid-induced glaucoma (SG) specimens. METHODS: We morphologically and immunohistochemically examined six trabecular tissues from three eyes with SG, two with primary open angle glaucoma (POAG), and one without glaucoma. For the morphological study, the ultra-microtome sections were observed using an electron microscope. For the light microscopic immunohistochemical analyses, frozen sections were stained by the avidin-biotin complex method using anti-type IV collagen, anti-type VI collagen, anti-heparan sulfate proteoglycan (HSPG), anti-fibronectin or anti-myocilin (MYOC) antibody. RESULTS: The morphological examinations revealed accumulations of basement membrane-like and fine fibrillar-like materials in the outer TM of SG specimen. Type IV collagen, HSPG and fibronectin antibodies in SG specimens showed a greater degree of staining in the outer TM in comparison to the POAG and non-glaucomatous specimens; in contrast, the other antibodies including the type VI collagen and MYOC, did not. CONCLUSIONS: The localization of ECMs in the TM is different in SG in comparison to that in POAG patients.     

The effect of TGF-beta2 on human trabecular meshwork extracellular proteolytic system

Our study aimed to investigate whether transforming growth factor-beta2 (TGF-beta2), increased in the aqueous humor of eyes with primary open angle glaucoma (POAG), can affect factors responsible for the activity of matrix metalloproteinases (MMPs) in human trabecular cell cultures. With this goal in mind cultures of human trabecular meshwork (hTM) cells derived from 8 donors were treated with TGF-beta2 for 24, 36 and 48 hr. Influence of TGF-beta2 on expression of MMP-2, MMP-9, membrane type 1-MMP (MT1-MMP) and plasminogen activator inhibitor-1 (PAI-1) was examined using RT-PCR, Northern Blot, Western Blot and zymography. The influence of TGF-beta2 treatment on PAI-1 expression was also investigated using immunohistochemistry. It appeared that treatment with TGF-beta2 significantly increased expression of the proform of MMP-2, whereas the active form was not detectable. MMP-9 and MT1-MMP expression were not influenced by TGF-beta2 treatment. There was, however, a significant increase in PAI-1 expression. To investigate whether transformation of the proform of MMP-2 to the active form was inhibited by PAI-1, the influence of treatment with TGF-beta2 and a PAI-1 neutralizing antibody on MMP-2 was investigated using zymogram method. With this treatment protocol the active form of MMP-2 was clearly visible, indicating that TGF-beta2 enhancement of the PAI-1-expression decreases MMP activity. Inhibition of MMP activity through elevated levels of TGF-beta2 might contribute to the increase in ECM in the trabecular meshwork of glaucomatous eyes.     

Bone morphogenetic protein-7 is an antagonist of transforming growth factor-beta2 in human trabecular meshwork cells

PURPOSE: The increase in intraocular pressure in primary open-angle glaucoma (POAG) may involve transforming growth factor (TGF)-beta2 signaling, as TGF-beta2 is found in higher amounts than normal in the aqueous humor of patients with POAG. In vitro, TGF-beta2 causes an accumulation of extracellular matrix (ECM) in the trabecular meshwork (TM) and an increase in TM outflow resistance. The present study was undertaken to determine whether bone morphogenetic protein (BMP)-7 signaling antagonizes the effects of TGF-beta2 on TM cells. METHODS: Cultured TM cells from nine human donors were treated with BMP-7, TGF-beta2, or a combination of both for 24 or 72 hours. The expression of connective tissue growth factor (CTGF); thrombospondin (TSP)-1; fibronectin; collagen types I, III, and IV; plasminogen activator inhibitor (PAI)-1; and matrix metalloproteinase (MMP)-2 were analyzed by immunohistochemistry, real time RT-PCR, Western and Northern blot analysis, and zymography (MMP-2). RESULTS: Treatment with TGF-beta2 induced the expression of CTGF, TSP-1, fibronectin, collagen types IV and VI, and PAI-1. All these effects were inhibited when TGF-beta2 was added in combination with BMP-7, whereas BMP-7 alone had no effects. Treatment with TGF-beta2, BMP-7, or the combination of both had no effect on the expression of collagen types I and III. CONCLUSIONS: BMP-7 strongly antagonizes in vitro the TGF-beta-induced expression of a broad panel of molecules, which would result in an accumulation of TM ECM in situ. As BMP-7 is expressed in the adult human TM in situ, it seems reasonable to assume that it similarly modulates and antagonizes the effects of TGF-beta2 signaling on the tissues of the outflow pathways in vivo. The pharmacological modulation of BMP-7 signaling in the TM might be a promising strategy to treat POAG.     

Promotion by fibronectin of collagen gel contraction mediated by human corneal fibroblasts

Collagen contraction mediated by corneal fibroblasts (CFs) is implicated in the maintenance of corneal shape. Given that fibronectin is expressed at sites of corneal stromal wounding, we investigated the effect of fibronectin on CF-mediated collagen gel contraction. Human CFs were cultured in a three-dimensional gel of type I collagen in the absence or presence of various extracellular matrix (ECM) components. The contraction of collagen gels mediated by CFs was evaluated by measurement of changes in gel diameter. The formation of stress fibers and focal adhesions in CFs was examined by fluorescence microscopy. The abundance of paxillin, phosphorylated paxillin, integrins alpha5, beta1, and alpha2, and alpha-smooth muscle actin in CFs was examined by immunoblot analysis. Fibronectin promoted CF-mediated collagen gel contraction in a concentration- and time-dependent manner. Other ECM proteins or glycosaminoglycans did not exhibit such an effect. Fibronectin also induced cell spreading, the formation of stress fibers, and the establishment of focal adhesions containing paxillin in CFs cultured in three-dimensional collagen gels. In addition, it increased the amounts of paxillin, phosphorylated paxillin, and integrins alpha5 and beta1 in these cells. The expression of integrin alpha2 and alpha-smooth muscle actin was not affected by fibronectin, however. Furthermore, the peptide GRGDSP (an antagonist of fibronectin receptors) blocked the stimulatory effect of fibronectin on CF-mediated collagen gel contraction. These results suggest that fibronectin promoted CF-mediated collagen gel contraction in a manner dependent on the formation of stress fibers and focal adhesions, the activation of paxillin, and the up-regulation of integrin alpha5beta1. Fibronectin may therefore contribute to the maintenance of corneal shape by CFs during the healing of stromal wounds.