Okan Ozturk

University of Illinois at Chicago, Chicago, IL, United States

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Publications (4)11.81 Total impact

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    ABSTRACT: PURPOSE. To characterize fluorescent bone marrow cells (YFP+ BMCs) in the thy1-YFP mouse and determine if they promote trigeminal ganglion (TG) cell neurite growth. METHODS. Excimer laser annular keratectomy was performed in thy1-YFP mice, and corneas were imaged. BMCs were harvested from femur and tibia and the expression of surface markers on YFP+ BMCs was analyzed by flow cytometry. The immunosuppressive action of BMCs (YFP+ and YFP-) was evaluated in an allogenic mixed lymphocyte reaction (MLR). Neurotrophic action of BMCs (YFP+ and YFP-) was determined in compartmental and transwell cultures of dissociated TG cells. RESULTS. Following annular keratectomy, YFP+ BMCs infiltrated the cornea. YFP+ BMCs shared surface markers (CD11b+Gr1+Ly6C+Ly6G-F4/80low) with monocytic myeloid-derived suppressor cells (MDSC), had similar morphology, and suppressed T cell proliferation in allogenic MLR in a dose-dependent manner. YFP+ BMCs, but not YFP- BMCs, significantly increased growth of TG neurites in vitro. When cultured in a transwell with TG neurites, YFP+ BMCs expressed neurotrophins and secreted nerve growth factor (NGF) in conditioned medium. YFP+ BMCs that infiltrated the cornea maintained their phenotype and actions (neuronal and immune). CONCLUSIONS. YFP+ BMCs in thy1-YFP mice have immunophenotypic features of MDSCs. They secrete NGF and promote neuroregeneration. Their immunosuppressive and neurotrophic actions are preserved after corneal infiltration. These findings increase our understanding of the beneficial roles played by leukocyte trafficking in the cornea and may lead to therapeutic strategies that use NGF-secreting myeloid cells to repair diseased or injured neurons.
    Investigative ophthalmology & visual science 08/2013; · 3.43 Impact Factor
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    ABSTRACT: We determined Semaphorin 7a (Sema7a) localization and abundance in naive corneas and in corneas after nerve-transecting lamellar flap surgery, and determined the effect of Sema7a supplementation on corneal nerve regeneration and inflammation. Immunolocalization and Western blot analyses were performed to evaluate the abundance of Sema7a in naive corneas and corneas undergoing nerve regeneration after lamellar corneal surgery in thy1-YFP+ neurofluorescent mice. We used compartmental cultures of dissociated trigeminal ganglion cells to determine the effect of Sema7a exposure on neurite outgrowth in vitro. Finally, a Sema7a pellet was implanted under the corneal flap after lamellar transection surgery to determine the neuronal and inflammatory effects of Sema7a supplementation in vivo. Sema7a was expressed in the corneal epithelium and stromal keratocytes, but was more abundant in the epithelium (74.3%) compared to the stroma (25.7%, P = 0.02). Sema7a expression was increased significantly in the cornea after lamellar corneal surgery and was localized to stromal cells near the regenerating nerve fronds. Exposure of trigeminal neurites to Sema7a (20 nM) in the side compartment increased neurite length significantly. The implanted Sema7a pellet increased significantly YFP+ inflammatory cell influx into the cornea as well as increased corneal nerve length. Sema7a is expressed constitutively in the cornea, and potently stimulates nerve regeneration and inflammatory cell influx. Therefore, this immune semaphorin links nerve regeneration and inflammatory processes in the cornea.
    Investigative ophthalmology & visual science 06/2012; 53(8):4575-85. · 3.43 Impact Factor
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    ABSTRACT: The aim of this study was to determine and characterize the effect of topical application of benzalkonium chloride (BAK) on corneal nerves in vivo and in vitro. Thy1-YFP+ neurofluorescent mouse eyes were treated topically with vehicle or BAK (0.01% or 0.1%). Wide-field stereofluorescence microscopy was performed to sequentially image the treated corneas in vivo every week for 4 weeks, and changes in stromal nerve fiber density (NFD) and aqueous tear production were determined. Whole-mount immunofluorescence staining of corneas was performed with antibodies to axonopathy marker SMI-32. Western immunoblot analyses were performed on trigeminal ganglion and corneal lysates to determine abundance of proteins associated with neurotoxicity and regeneration. Compartmental culture of trigeminal ganglion neurons was performed in Campenot devices to determine whether BAK affects neurite outgrowth. BAK-treated corneas exhibited significantly reduced NFD and aqueous tear production, and increased inflammatory cell infiltration and fluorescein staining at 1 week (P < 0.05). These changes were most significant after 0.1% BAK treatment. The extent of inflammatory cell infiltration in the cornea showed a significant negative correlation with NFD. Sequential in vivo imaging of corneas showed two forms of BAK-induced neurotoxicity: reversible neurotoxicity characterized by axonopathy and recovery, and irreversible neurotoxicity characterized by nerve degeneration and regeneration. Increased abundance of beta III tubulin in corneal lysates confirmed regeneration. A dose-related significant reduction in neurites occurred after BAK addition to compartmental cultures of dissociated trigeminal ganglion cells. Although both BAK doses (0.0001% and 0.001%) reduced nerve fiber length, the reduction was significantly more with the higher dose (P < 0.001). Topical application of BAK to the eye causes corneal neurotoxicity, inflammation, and reduced aqueous tear production.
    Investigative ophthalmology & visual science 03/2012; 53(4):1792-802. · 3.43 Impact Factor
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    ABSTRACT: To characterize the involvement of Semaphorin 7A (Sema7a) in corneal neovascularization (NV). We generated anti-Sema7A antibodies to detect protein expression in corneal fibroblasts. Corneal fibroblast cells were cultured, stimulated with basic fibroblast growth factor (bFGF or FGF-2), immunostained with anti-Sema7A antibodies, and visualized by confocal microscopy. bFGF pellets were implanted in mouse corneal micropockets for 3-10 days, and corneal sections were immunostained with anti-Sema7A antibodies. Mouse corneas were injected with a Sema7A expression vector or a control vector for 3, 7, and 10 days. Mouse corneas were imaged by slit lamp microscopy, and areas of corneal NV were calculated using the ImageJ program. Mouse corneal sections were also immunostained with anti-macrophage marker (F4/80) and anti-vascular endothelial growth factor (VEGF)-A antibodies. Our data showed enhanced Sema7A expression levels in bFGF-stimulated cultured corneal fibroblasts. bFGF corneal implantation also demonstrated enhanced Sema7A expression. Corneas injected with a Sema7A expression vector showed evidence of significant corneal NV compared to controls on day 10 (1.8 mm(2) vs. 0.11 mm(2); p < 0.02). Additionally, immunolocalization of Sema7A expression vector-injected corneas (at day 7) revealed macrophage recruitment and enhanced VEGF-A levels. We demonstrated that Sema7A was expressed in vascularized corneas and showed pro-angiogenic properties in our corneal model. Understanding the mechanism of Sema7A in angiogenesis may provide a therapeutic target for the treatment of corneal angiogenesis-related disorders.
    Current eye research 11/2011; 36(11):989-96. · 1.51 Impact Factor