Insulin-like growth factor-I (IGF-I) and transforming growth factor-beta (TGF-beta) modulate tenascin-C and fibrillin-1 in bullous keratopathy stromal cells in vitro

Development of Animal Models for Lens and Corneal Diseases Using N-Methyl-N-Nitrosourea

Purpose

N-methyl-N-nitrosourea (MNU) is an alkylating toxicant with potent mutagenic ability. This study was designed to induce apoptosis in lens epithelial cells (LECs) and corneal endothelial cells (CECs) via MNU administration. We sought to build ocular disease models of cataract and corneal endothelial decompensation.

Methods

MNU was delivered into the intraperitoneal cavities of neonatal rats and the anterior chambers of adult rabbits. The MNU-treated animals were then subjected to a series of functional and morphological analyses at various time points.

Results

MNU treatment induced pervasive apoptosis of LECs and CECs. These effects were dose and time dependent. Mature cataracts were found in neonatal rats 3 weeks after MNU treatment. Histological analysis revealed that MNU toxicity induced swelling, vacuolation, and liquefaction in lens fibers of MNU-treated rats. Pentacam examination showed that the average density of rat lens increased significantly after MNU administration. Terminal deoxynucleotidyl transferase-mediated nick end labeling (TUNEL) analysis showed pervasive apoptotic staining in the lenses of MNU-treated rats. In rabbit eyes, intracameral treatment with MNU induced corneal edema and significantly increased central corneal thickness, which peaked at P14. Morphological and immunohistochemical analysis showed that CECs were effectively ablated in the MNU-treated rabbits. The expression of 8-OHdG increased significantly in the cornea of MNU-treated rabbits, compared with vehicle-treated controls.

Conclusions

MNU is sufficient to induce ocular cell apoptosis in animal models. These models of MNU-induced cataract and corneal endothelial decompensation represent valuable tools for efforts to develop relevant therapies.

Late spontaneous bilateral intraocular lens subluxation accompanied with intraocular pressure elevation in a patient with acromegaly

A 53-year-old male with newly diagnosed acromegaly came to our clinic with the chief complaint of diplopia. He had the past ocular history of uneventful phacoemulsification cataract surgery with intraocular lens (IOL) implantation in the right eye 17 years ago and left eye 15 years ago. Postoperative examination showed remarkable improvement in visual acuity. Two years ago, he developed elevated intraocular pressure (IOP) in both eyes, which was well-controlled with the use of travoprost 0.004%/timolol 0.5%. At the clinic, slit-lamp examination revealed inferiorly subluxated IOL bilaterally. The patient received IOL repositioning with pars plana vitrectomy and scleral fixation in the left eye smoothly. We hypothesize that excess growth hormone is associated with dysregulation of fibrillin, resulting in zonular weakness, which causes late bilateral IOL subluxation. Elevated IOP may also be related to acromegaly. To the best of our knowledge, this is the first report to describe the association between IOL subluxation and acromegaly.

Efficacy of Anterior Stromal Puncture Surgery with Corneal Bandage Lens for Bullous Keratopathy

Objective: To investigate the safety and efficacy of the combination therapy of anterior stromal puncture (ASP) with bandage contact lens for bullous keratopathy (BK). Methods: Twelve cases (12 eyes) with vision acuity no better than light perception were treated with ASP surgery and bandage contact lens. 200 points punctures were made through the corneal epithelium and Bowman's layer vertically, using fine needles. A soft bandage contact lens was applied immediately and removed 2 weeks later. The severity of irrigating symptoms including pain, photophobia and tearing was graded and calculated before treatment and 1, 2, 4, 12 weeks after the surgery, slit-lamp microscope examination was used to quantify the time for corneal epithelial blisters disappearing, optical coherence tomography (OCT) was used to monitor the central corneal thickness. Results: No cornea infection was observed during the following up period. The average grade scores of the irrigating symptoms was 8.3 ± 2.1 before surgery, while it was reduced to 4.8 ±1.9 two weeks after the surgery (p=0.0003). Slit-lamp microscope examination showed that corneal edema relieved obviously after the operation, the average time for epithelial blisters disappearing was 15.6 ± 4.0 days. The average central corneal thickness of the eyes was 999.3 ±278.0 μm before the treatment, while it was 805.1 ± 145.0 μm four weeks after the treatment, with a statistically significant difference (p=0.043). Conclusions: ASP with bandage contact lens is an effective and safe treatment for patients with BK and low vision that not suitable for corneal transplantation.

The corneal epithelial basement membrane: structure, function, and disease

The corneal epithelial basement membrane (BM) is positioned between basal epithelial cells and the stroma. This highly specialized extracellular matrix functions not only to anchor epithelial cells to the stroma and provide scaffolding during embryonic development but also during migration, differentiation, and maintenance of the differentiated epithelial phenotype. Basement membranes are composed of a diverse assemblage of extracellular molecules, some of which are likely specific to the tissue where they function; but in general they are composed of four primary components--collagens, laminins, heparan sulfate proteoglycans, and nidogens--in addition to other components such as thrombospondin-1, matrilin-2, and matrilin-4 and even fibronectin in some BM. Many studies have focused on characterizing BM due to their potential roles in normal tissue function and disease, and these structures have been well characterized in many tissues. Comparatively few studies, however, have focused on the function of the epithelial BM in corneal physiology. Since the normal corneal stroma is avascular and has relatively low keratocyte density, it is expected that the corneal BM would be different from the BM in other tissues. One function that appears critical in homeostasis and wound healing is the barrier function to penetration of cytokines from the epithelium to stroma (such as transforming growth factor β-1), and possibly from stroma to epithelium (such as keratinocyte growth factor). The corneal epithelial BM is also involved in many inherited and acquired corneal diseases. This review examines this structure in detail and discusses the importance of corneal epithelial BM in homeostasis, wound healing, and disease.

Dehydroepiandrosterone induces ovarian and uterine hyperfibrosis in female rats

STUDY QUESTION

Do dehydroepiandrosterone (DHEA)-treated rats with polycystic ovary syndrome (PCOS) demonstrate a high level of fibrosis in ovarian and uterine tissues?

SUMMARY ANSWER

DHEA induces ovarian and uterine hyperfibrosis in rats, probably involving a transforming growth factor-β (TGF-β)-dependent mechanism.

WHAT IS KNOWN ALREADY

Chronic inflammation is the typical cause of fibrosis and is involved in the pathophysiological process of PCOS. Patients with PCOS are reported to have a higher serum level of TGF-β, a well-characterized key pro-fibrotic factor. Fibrillin-3, a protein capable of interacting with TGF-β, has been reported to be partially responsible for the fetal origin of PCOS.

STUDY DESIGN, SIZE, DURATION

Female Sprague-Dawley rats were treated with a vehicle control or DHEA for 35 days, with subsequent analyses of changes in morphology and gene expression in ovarian and uterine tissues. Rescue groups treated with metformin or simvastatin and their corresponding controls were also analyzed. A total of 80 rats were included.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The PCOS model was induced by daily administration of DHEA s.c. to 3-week-old female rats, and the rescue groups were injected daily with either metformin or simvastatin in addition to DHEA. Serum steroid hormone levels were measured by enzyme-linked immunosorbent assay. Samples were stained with hematoxylin and eosin for histological morphology, and Sirius Red and immunohistochemistry for revealing collagens. The expression of fibrosis-related genes was analyzed both at mRNA (real-time RT-PCR) and protein (western blot) levels.

MAIN RESULTS AND THE ROLE OF CHANCE

DHEA-induced rats with PCOS exhibited significantly higher levels of fibrosis (collagen IV) in both ovarian and uterine tissues. In ovarian tissue, the expression of connective tissue growth factor (CTGF) increased following DHEA treatment at both mRNA and protein levels (P < 0.05, P < 0.001 versus controls, respectively). Similar results versus controls were obtained at a protein level for TGF-β (P < 0.01) and mRNA level for fibronectin (P < 0.05) and angiotensin-II (P < 0.05). Likewise, in uterine tissue, the protein levels of both CTGF and TGF-β were higher than controls following DHEA treatment (P < 0.05). Treatment with either metformin or simvastatin attenuated the fibrosis progression induced by DHEA exposure, as evidenced by a reduction of TGF-β, plus CTGF or not, in both ovarian and uterine tissues.

LIMITATIONS, REASONS FOR CAUTION

The particular mechanism involved in the DHEA-induced fibrosis was not fully revealed.

WIDER IMPLICATIONS OF THE FINDINGS

Ovarian and uterine hyperfibrosis may occur in patients with PCOS and result in anovulation or other PCOS-related phenotypes. Anti-fibrotic therapy, for example metformin treatment, may be beneficial for patients with PCOS.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by the National Natural Science Foundation of China (81170541) and the Natural Basic Research Program of China (973 program 2010CB945103). The authors declare no conflicts of interest.

Linkage of regulators of TGF-β activity in the fetal ovary to polycystic ovary syndrome

Although not often discussed, the ovaries of women with polycystic ovary syndrome (PCOS) show all the hallmarks of increased TGF-β activity, with increased amounts of fibrous tissue and collagen in the ovarian capsule or tunica albuginea and ovarian stroma. Recent studies suggest that PCOS could have fetal origins. Genetic studies of PCOS have also found linkage with a microsatellite located in intron 55 of the extracellular matrix protein fibrillin 3. Fibrillins regulate TGF-β bioactivity in tissues by binding latent TGF-β binding proteins. We therefore examined expression of fibrillins 1-3, latent TGF-β binding proteins 1-4, and TGF-β 1-3 in bovine and human fetal ovaries at different stages of gestation and in adult ovaries. We also immunolocalized fibrillins 1 and 3. The results indicate that TGF-β pathways operate during ovarian fetal development, but most important, we show fibrillin 3 is present in the stromal compartments of fetal ovaries and is highly expressed at a critical stage early in developing human and bovine fetal ovaries when stroma is expanding and follicles are forming. These changes in expression of fibrillin 3 in the fetal ovary could lead to a predisposition to develop PCOS in later life.

Gene expression analysis of biological systems driving an organotypic model of endometrial carcinogenesis and chemoprevention

An organotypic model of endometrial carcinogenesis and chemoprevention was developed in which normal endometrial organotypic cultures exposed to the carcinogen, DMBA (7,12-dimethylbenz[a]anthracene), developed a cancerous phenotype in the absence, but not presence of subsequent treatment with a flexible heteroarotinoid (Flex-Het), called SHetA2. A discriminant function based on karyometric features of cellular nuclei and an agar clonogenic assay confirmed these histologic changes. Interpretation of microarray data using an internal standard approach identified major pathways associated with carcinogenesis and chemoprevention governed by c-myc, p53, TNFα and Jun genes. Cluster analysis of functional associations of hypervariable genes demonstrated that carcinogenesis is accompanied by a stimulating association between a module of genes that includes tumor necrosis factor α (TNFα), c-myc, and epidermal growth factor-receptor (EGF-R) and a module that includes insulin-like growth factor I-receptor (IGF-IR), p53, and Jun genes. Two secreted proteins involved in these systems, tenascin C and inhibin A, were validated at the protein level. Tenascin C is an EGF-R ligand, and therefore may contribute to the increased EGF-R involvement in carcinogenesis. The known roles of the identified molecular systems in DMBA and endometrial carcinogenesis and chemoprevention supports the validity of this model and the potential clinical utility of SHetA2 in chemoprevention.

Subtractive hybridization identifies genes differentially expressed by olfactory ensheathing cells and neural stem cells

The in vitro differentiation of embryonic stem cells into glia has received relatively limited attention to date when compared with the interest in the generation of neurons. We are interested in a particular glial phenotype, the aldynoglia, and their differentiation from multipotential neural precursors (MNP), since this type of glia can promote neuronal regeneration. We constructed cDNA libraries from cultures of purified olfactory ensheathing cells (OEC), an aldynoglia cell type, and MNP to perform subtractive hybridization. As a result, we isolated four genes from the OEC: one tenascin C (Tn-C) isoform, Insulin-like growth factor binding protein 5 (Igfbp-5), cytochrome oxidase subunit I (COX1) and a phosphodiesterase for cyclic nucleotides (CNPase). With the exception of CNPase, these genes are expressed more strongly in the OEC than in the MNP and moreover, the expression of all four is induced when MNP were exposed to OEC conditioned media. The data suggest a role for these genes in MNP differentiation, and their products appear to represent characteristic proteins of the aldynoglia phenotype.

Matrix metalloproteinase induction in the tumor stroma does not depend on CD147 expression in murine B16 melanoma

BACKGROUND

It was conclusively demonstrated that the cell surface glycoprotein CD147 on tumor cells mediates induction of matrix metalloproteinases (MMPs) by stromal cells in humans. However, for murine models such evidence remains elusive.

METHODS AND RESULTS

To address the impact of CD147 on MMP expression in the murine B16 melanoma model, we consequently stably knocked down CD147 expression in two B16 sublines. The CD147 knockdown remained stable under in vivo conditions as confirmed by immunohistochemistry. However, no differences in MMP-2, MMP-9 and MT1-MMP expression by stromal and tumor cells were detectable in CD147+ and CD147- tumors. Since the tumor microenvironment is a complex system, involving several cell types, the extracellular matrix and plethora soluble factors, we subsequently studied the role of murine CD147 in vitro. Coculture of melanoma cells with different fibroblast cell lines demonstrated that neither CD147+ nor CD147- B16 tumor cells altered the expression of MMP-2 or MMP-9 by the fibroblasts, although we could confirm the susceptibility of these fibroblasts for MMP induction.

CONCLUSIONS

At least for the murine B16 melanoma model, CD147 expression on tumor cells seems not to be crucial for MMP-2, MMP-9 and MT1-MMP induction on tumor-associated stromal cells.

Decorin-mediated regulation of fibrillin-1 in the kidney involves the insulin-like growth factor-I receptor and Mammalian target of rapamycin

Decorin, a small leucine-rich proteoglycan, affects the synthesis of the elastic fiber component fibrillin-1 in the kidney via hitherto unknown mechanisms. Here, we show that decorin binds to and induces phosphorylation of insulin-like growth factor-I (IGF-I) receptor in renal fibroblasts. Inhibition of the IGF-I receptor tyrosine kinase and its downstream target phosphoinositide-3 kinase prevented decorin-mediated synthesis of fibrillin-1. Furthermore, decorin induced phosphorylation of phosphoinositide-dependent kinase 1, protein kinase B/Akt, mammalian target of rapamycin (mTOR), and p70 S6 kinase. Accordingly, the enhanced synthesis of fibrillin-1 was blocked by rapamycin, an inhibitor of mTOR. Notably, IGF-I, which signals through the same pathway, also stimulated fibrillin-1 synthesis. Systemic administration of rapamycin to mice subjected to unilateral ureteral obstruction, a model of renal fibrosis and increased fibrillin-1 synthesis, markedly reduced the number of interstitial fibroblasts and fibrillin-1 deposition. In streptozotocin-induced diabetes, IGF-I receptor was up-regulated in the kidneys from decorin-null mice. However, this could not compensate for the decorin deficiency, resulting ultimately in decreased fibrillin-1 content. This study provides evidence for the involvement of decorin and the IGF-I receptor/mTOR/p70 S6 kinase signaling pathway in the translational regulation of fibrillin-1.

Pseudophakic corneal edema: A review of mechanisms and treatments

PURPOSE

To review the pathological mechanisms and treatments for pseudophakic corneal edema (PCE), one of the most common indications for penetrating keratoplasty.

METHODS

The literature was examined for the molecular biology associated with PCE and for the surgical and medical treatments for this disorder.

RESULTS

The incidence of PCE has recently been decreasing because of improved surgical instrumentation, including improvements in intraocular lens designs that cause less trauma to the corneal endothelium. Extracellular matrix and growth factor abnormalities occur in PCE corneas and recently, the role of aquaporins, which are involved in the regulation of fluid movement across cells, has been investigated.

CONCLUSIONS

Although newer treatment options have been suggested, penetrating keratoplasty still remains the most definitive treatment and has the highest success rate.

Matrix metalloproteinase 9 facilitates collagen remodeling and angiogenesis for vascular constructs

Degradation of the extracellular matrix, facilitated by matrix metalloproteinases (MMPs), can lead to mechanical failure of vascular constructs, suggesting that MMP inhibition could improve survival of constructs. Therefore, we investigated the role of MMP-9 in collagen remodeling in vitro, focusing on the three major steps of production, degradation, and organization. Because an adequate blood supply is essential for survival of tissue-engineered constructs, we also evaluated the influence of MMP-9 deficiency on angiogenesis in vivo by implantation of thin biodegradable polymer scaffolds. Using aortic smooth muscle cells (SMCs) from wild-type and genetically deficient (9KO) mice, we examined the role of MMP-9 in collagen mRNA expression and protein accumulation, both with and without ascorbic acid treatment. We measured collagen assembly in a fibrillogenesis assay. We investigated in vivo angiogenesis and cell invasion, using fluorescence microangiography and histology. MMP-9 deficiency did not affect collagen mRNA production or polymer scaffold degradation, but collagen accumulation was greater in cultures of 9KO SMCs than in wild-type SMCs. Both MMP-9 deficiency and chemical inhibition impaired collagen degradation. Ascorbic acid treatment enhanced collagen production by 9KO SMCs compared with wild-type SMCs at 3 days, but by 7 days this effect was reversed. MMP-9 improved fibrillogenesis of collagen, significantly more on ascorbic acid treatment. MMP-9 deficiency dramatically decreased inflammatory cell invasion, but also capillary formation within biodegradable polymer scaffolds in vivo. Our data suggest that MMP inhibition, by impairing collagen organization and angiogenesis, might have detrimental effects on the survival of vascular constructs.

Altered expression of aquaporins in bullous keratopathy and Fuchs' dystrophy corneas

Corneas with edema-related diseases lose transparency, which causes significant vision loss. This study analyzed seven aquaporins (AQPs) in normal corneas, pseudophakic/aphakic bullous keratopathy (PBK/ABK) corneas, Fuchs' dystrophy corneas, keratoconus corneas, post-cataract surgery (PCS) corneas, and normal organ-cultured corneas. RNA levels for AQP1, AQP4, and beta2-microglobulin were measured by RT-PCR. AQP1 antibody localized to stromal cells of all corneas. PBK/ABK and Fuchs' dystrophy corneas had decreased endothelial cell staining compared with normal. AQP1 mRNA was found in whole corneas and cultured stromal fibroblasts but not in isolated epithelial cells. AQP3 staining was found in basal epithelial cells of the normal, Fuchs' dystrophy, and keratoconus corneas but throughout the entire epithelium of PBK/ABK corneas. AQP4 antibody localized to endothelial cells of all corneas and in stromal cells of PBK/ABK corneas. AQP4 mRNA was identified in whole human corneas. AQP5 was found in epithelial cells of all corneas. AQP0, AQP2, and AQP9 were not found in any corneas. Normal AQP distributions were found in PCS and organ-cultured corneas, although they showed signs of swelling. Our study demonstrates that AQP abnormalities are found in PBK/ABK corneas (decreased AQP1, increased AQP3 and AQP4) and Fuchs' dystrophy corneas (decreased AQP1). Although both have vision-disrupting corneal edema, the mechanisms of fluid accumulation may be different in each disease.

Regulation of fibrillin-1 by biglycan and decorin is important for tissue preservation in the kidney during pressure-induced injury

There is growing evidence that the two small leucine-rich proteoglycans biglycan and decorin regulate the assembly of connective tissues and alter cell behavior during development and pathological processes. In this study, we have used an experimental animal model of unilateral ureteral ligation and mice deficient in either biglycan or decorin. We discovered that pressure-induced injury to the wild-type kidneys led to overexpression of decorin, biglycan, fibrillin-1, and fibrillin-2. In contrast, in biglycan-deficient kidneys the overexpression of fibrillin-1 was markedly attenuated and this was associated with cystic dilatation of Bowman's capsule and proximal tubules. Notably, we found that in ligated kidneys from decorin-null mice, fibrillin-1 expression was initially enhanced to the same extent as in wild-type animals. However, long-term obstruction resulted in down-regulation of fibrillin-1 and concurrent cystic dilatation of Bowman's capsule in 33% of kidneys at 5 months after obstruction. In all of the genotypes, no differences in fibrillin-2 expression were observed. These in vivo data correlated with a significant induction of fibrillin-1 expression in renal fibroblasts and mesangial cells by recombinant biglycan and decorin. Our results indicate a novel role for decorin and biglycan during pressure-induced renal injury by stimulating fibrillin-1 expression.