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Biomedical subjects

Tsutomu Yasukawa

Publications and source records attributed to Tsutomu Yasukawa.

11 recordsLinked to original sources
PubMed2006

Characteristics of iris and retinal pigment epithelial cells cultured on collagen type I membranes.

PURPOSE: Transplantation of pigment epithelial cells is a promising treatment modality to repair retinal damage in age-related macular degeneration. For this purpose, it is necessary to establish cell culture techniques that allow acquisition of proper functional and morphological characteristics by the cells to be transplanted. METHODS: Primary retinal pigment epithelial (RPE) and iris pigment epithelial (IPE) cells grown to confluence on collagen membranes were examined for morphology, adhesion, proliferation, apoptosis, as well as viability after ex vivo transplantation. RESULTS: Pigment epithelial cells adhere, proliferate, form monolayers, acquire differentiated properties, and remain viable during transplantation to the subretinal space. CONCLUSIONS: Pigment epithelial cells cultured on collagen membranes acquire differentiated characteristics and are amenable to be transplanted as cell monolayers.

Animals↗
PubMed2006

Drug delivery from ocular implants.

Developing an intraocular drug delivery system (DDS) is urgently needed because most vitreoretinal diseases are refractory to conventional pharmacological approaches; eye drops and systemically administered drugs cannot deliver therapeutic drug concentrations into vitreoretinal tissue. Intraocular DDSs address this problem. Intraocular sustained-drug release via implantable devices or injectable microparticles has been investigated to treat vitreoretinal diseases. A nonbiodegradable implant was first used in 1996 for cytomegalovirus retinitis secondary to the acquired immunodeficiency syndrome. Biodegradable implants, composed of hydrophilic or hydrophobic polymers, in the shape of rods, plugs, discs or sheets have been investigated. An injectable rod is presently being assessed in a Phase III trial to treat macular oedema secondary to diabetic retinopathy or branch-retinal vein occlusion. Intraocular DDSs using a biodegradable implant may soon be successfully used to treat serious intraocular disorders.

Animals↗
PubMed2005

Intraocular sustained drug delivery using implantable polymeric devices.

Vitreoretinal diseases involving age-related macular degeneration (AMD) are refractory to most topical or systemic drugs. The retina and the vitreous cavity have a unique position regarding pharmacokinetics in that the inner and outer blood retinal barriers separate the retina and vitreous from the systemic circulation. Eye drops achieve minimal therapeutic concentrations in the vitreoretinal tissue. Drug delivery systems are a strategy to address this. Intraocular sustained drug release using implantable devices has been investigated to treat vitreoretinal diseases. Possible targeted diseases include those in which repeated intraocular injections are effective (cytomegalovirus retinitis, uveitis), diseases requiring surgery (proliferative vitreoretinopathy), and chronic diseases (AMD, macular edema, retinitis pigmentosa). Hydrophobic or hydrophilic polymers shaped into a sheet, disc, rod, plug, or a larger device can be implanted into the subretinal space, intrascleral space, vitreous space, peribulbar space, or at the pars plana. Many researchers suggest the feasibility of these implants to treat AMD.

Animals↗
PubMed2005

Preliminary results of development of a single-mode Q-switched Nd: YAG ring laser at 213 nm and its application for the microsurgical dissection of retinal tissue ex vivo.

The Nd: YAG laser family offers wide possibilities for surgery applications in medicine. The radiation at 213 nm provides similar tissue effects as compared to 193 nm excimer lasers, but offers considerable practical advantages in the operating room. As such, it is of considerable interest to create single-mode Q-switched fifth harmonic Nd: YAG pulsed lasers with a high coefficient of efficiency and low divergence. Parameters of the ring three-mirror anisotropic cavity TEM00-Nd: YAG laser were calculated on the basis of the analysis of Gaussian beam behavior in the three-mirror ring cavity, with one convex spherical mirror and one intracavity positive lens. On the hand of numerical calculations a prototype of a single-mode Q-switched Nd: YAG-213 nm laser with an output energy of 4 mJ and a beam divergence of 1 mrad has been developed. At a pulse repetition rate of 50 Hz, it has a generation efficiency in the Q-switched mode of 0,6%. A hollow core wave guide is used in combination with a short length of a special fused silica optical fiber to guide the laser beam. Full-depth dissection of rabbit retina ex vivo was achieved at the intensities of 0.18-0.05 J/cm2 and a repetition rate of 50 Hz, with a linear cutting rate of 6 mm/s. Although the retina was completely cut, heat necrosis of the choroid did not occur. We are currently in the process of testing the dissection of retinal tissue during retinotomy, and the formation of holes in the trabecular meshwork in glaucoma surgery.

Animals↗
PubMed2005

Impact of endostatin on bFGF-induced proliferation, migration, and matrix metalloproteinase-2 expression/secretion of bovine choroidal endothelial cells.

PURPOSE: To investigate the potential role of endostatin, an endogenous angiogenesis inhibitor, in the prevention of choroidal angiogenesis-related disorders. METHODS: Bovine choroidal endothelial cells (CEC) were cultured and treated with basic fibroblast growth factor (bFGF) alone or combined with endostatin at concentrations ranging from 0.1 to 10 microg/ml. The proliferation and migration of CECs were evaluated by using 3, (4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) colorimetric assay and modified Boyden chamber assay, respectively. For evaluating expression and secretion of matrix metalloproteinase-2 (MMP-2), CEC-conditioned media were subjected to zymography and/or Western blot analysis, and the cells were used for semiquantitative reverse transcription polymerase chain reaction (RT-PCR) analysis. RESULTS: Endostatin did not inhibit bFGF-induced or nonstimulated CEC proliferation (p > 0.05). The bFGF-induced migration was significantly inhibited by endostatin at concentrations of 1 and 10 microg/ml (p < 0.05). The bFGF-upregulated expression of mRNA in CECs and the secretion of MMP-2 protein of CECs were both suppressed by endostatin. CONCLUSIONS: Inhibitory effect of endostatin on expression and secretion of MMP-2 and cell migration, but not on proliferation of CECs, could respond to its therapeutic action for choroidal neovascularization-dependent disorders.

Angiogenesis Inhibitors↗
PubMed2004

The role of estrogen and estrogen receptorbeta in choroidal neovascularization.

PURPOSE: Choroidal neovascularization (CNV) under the age of 50 is more often observed in women than in men. The effects of 17beta-estradiol (E2) on choroidal neovascularization development were investigated both in animal models and cultured cells to see if estrogen receptors (ERs) are involved in the process. METHODS: CNV was induced by fundus laser photocoagulation in adult male and female rats. The degree of CNV development was scored and compared between them. Gene expression levels of VEGF receptor 2 (VEGFR2) and ERs after photocoagulation were compared between genders using real time PCR. CNV formation and the gene expressions were also examined in ovariectomized females with and without E2 treatment. The roles of ERs were studied by overexpressing them in human umbilical vein endothelial cells (HUVECs). The localization of estrogen receptorbeta (ERbeta) and VEGFR2 in CNV were studied immunohistochemically. RESULTS: CNV scores were significantly higher in females than in males 14 and 21 days after photocoagulation (<0.05). VEGFR2 and ERbeta gene levels were increased more in females than in males on day 7 (3.4 fold compared to 1.8 fold) and on day 3 (5.8 fold compared to 2.3 fold) after photocoagulation, respectively. Both ERbeta and VEGFR2 gene expressions were additively enhanced by photocoagulation and E2 treatment in ovariectomized females. E2 significantly enhanced VEGFR2 gene expression and cell proliferation in HUVECs overexpressing ERbeta. ERbeta and VEGFR2 are well co-localized in CNV tissue. CONCLUSIONS: Estrogen may promote CNV development by increasing VEGFR2 gene expression via ERbeta.

Animals↗
PubMed2004

Drug delivery systems for vitreoretinal diseases.

The eye has an environment that is specific unto itself in terms of pharmacokinetics: the inner and outer blood-retinal barriers separate the retina and the vitreous from the systemic circulation and vitreous body, which physiologically has no cellular components, occupies the vitreous cavity, an inner space of the eye, and reduces practical convection of molecules. Considering this, development of a drug delivery system (DDS) is becoming increasingly important in the treatment of vitreoretinal diseases not only to facilitate drug efficacy but also to attenuate adverse effects. The DDS has three major goals: enhances drug permeation (e.g., iontophoresis and transscleral DDS), controls release of drugs (e.g., microspheres, liposomes, and intraocular implants), and targets drugs (e.g., prodrugs with high molecular weight and immunoconjugates). Comprehensive knowledge of these should lead to development of innovative treatment modalities.

Absorbable Implants↗
PubMed2004

Inhibition of experimental choroidal neovascularization in rats by an alpha(v)-integrin antagonist.

PURPOSE: Integrin alpha(v)beta3 is predominantly expressed on endothelial cells in choroidal neovascularization (CNV). We evaluated the efficacy of cyclic RGD (Arg-Gly-Asp) peptide, an alpha(v)-integrin antagonist, in a rat model of laser-induced CNV METHODS: We evaluated the effect of cyclic RGD on the adhesion and cell viability of bovine choroidal endothelial cells (BCECs) by cell counting and the trypan blue dye exclusion test. CNV was induced by laser photocoagulation in female Long Evans rats (day 0), followed by intravitreal administration of one dose of cyclic RGD of 200 (n = 9), 100 (n = 10), 50 (n = 4), or 0 microg (n = 9) on days 9 and 11. We assessed the area of CNV by fluorescein angiography and the thickness microscopically on histologic sections. Neovascular vessels were detected by an antibody against factor VIII. RESULTS: Cyclic RGD (0.02 to 200 microg/ml) inhibited adhesion of BCECs in a dose-dependent manner without changing the cell viability (p < 0.01). In eyes treated with two injections of 200 or 100 microg of cyclic RGD peptide, the development of CNV was significantly (p < 0.01) inhibited in the area of leakage on fluorescein angiography. Histologically, the CNV membrane was observed beneath the retina and the factor VIII-positive cells and red blood cells were involved. The thickness of the lesions was significantly (p < 0.01) reduced in eyes that received 200 or 100 microg of RGD. CONCLUSIONS: Cyclic RGD effectively inhibited CNV progression in a rat model of laser-induced CNV, suggesting that this alpha(v)-integrin antagonist may be beneficial in the treatment of CNV.

Animals↗
PubMed2002

Sustained release of cis-hydroxyproline in the treatment of experimental proliferative vitreoretinopathy in rabbits.

PURPOSE: To evaluate the efficacy of sustained-release cis-4-hydroxyproline (CHP), a proline analog that inhibits collagen secretion, on experimental proliferative vitreoretinopathy (PVR) in rabbits. METHODS: To demonstrate the sustained release of CHP we developed scleral implants weighing 8.5 mg made of a homogeneous mixture of poly( D, L-lactide-co-glycolide) (PLGA) and various doses of CHP. The CHP release profiles were evaluated by high-performance liquid chromatography in vitro. Scleral implants loaded with 20% and 15% of CHP and made from PLGA (copolymer ratios 65/35 and 50/50; mean molecular weights 103,000 and 93,000, respectively) were used to treat experimental PVR and the efficacy was studied. In treated eyes, two PLGA 65/35 implants ( n=7), PLGA 50/50 implants ( n=6), or a PLGA 65/35 and a PLGA 50/50 implant ( n=9) were inserted at the pars plana, followed by PVR induction with autologous fibroblasts. Control eyes ( n=18) received two implants without CHP. Ocular tissue toxicity was evaluated histologically. RESULTS: In vitro release studies demonstrated a triphasic release pattern. The PLGA 65/35 and PLGA 50/50 implants released CHP over 4 and 7 weeks, respectively. The PLGA 65/35 implants decreased the incidence of retinal detachment from 89% (in controls) to 57% on day 28. When both PLGA 65/35 and PLGA 50/50 implants were used, the inhibitory effect was synergistically enhanced ( p=0.0034), while implantation with only PLGA 50/50 implants had no significant effect on PVR. No toxic reactions were observed. CONCLUSION: These results suggest that the biodegradable polymeric implants containing CHP represent a potential treatment for PVR.

Absorbable Implants↗
PubMed2002

Targeting of interferon to choroidal neovascularization by use of dextran and metal coordination.

PURPOSE: Bioactive proteins such as interferon (IFN) have been reported to be combined with water-soluble polymers, such as dextran, through metal coordination, without need for complicated procedures. In the current study, the targeting and inhibitory effects of IFN combined with dextran on experimental choroidal neovascularization (CNV) were studied in vivo. METHODS: Interferon (IFN)beta was conjugated to dextran, which has metal-chelating, diethylenetriaminepentaacetic acid (DTPA) residues. Based on metal coordination, conjugation of IFNbeta with DTPA-dextran resulted from simply mixing both substances in an aqueous solution containing Zn(2+). The effects of IFNbeta on the proliferation of human umbilical vein endothelial cells (HUVECs) and bovine retinal pigment epithelial cells (BRPECs) were evaluated. To evaluate the activity loss of IFNbeta by conjugation, the effect of the conjugate on HUVECs was compared with that of free IFNbeta. Experimental CNV was induced by subretinal injection of gelatin microspheres containing basic fibroblast growth factor in rabbits. The rabbits with CNV were intravenously treated twice weekly with 7.5 million international units (MIU)/kg per day free IFNbeta (for 4 weeks), with IFNbeta-DTPA-dextran conjugate containing 7.5 (for 2 weeks) or 0.75 (for 4 weeks) MIU/kg per day IFNbeta, or with saline. The effects of these substances were evaluated by fluorescein angiography and histology. To observe the accumulation of conjugate, the doses of IFNbeta in CNV tissues were measured by enzyme-linked immunosorbent assay. RESULTS: IFNbeta inhibited the growth of HUVECs and enhanced the proliferation of BRPECs. The conjugate seemed to preserve approximately 44% of IFNbeta activity. Although both doses of IFNbeta-DTPA-dextran inhibited progression of CNV in rabbits, longer term administration of a lower dose of IFNbeta-DTPA-dextran had a sustained inhibitory effect on progression of CNV (P < 0.05). Histologic studies revealed the inhibitory effect of IFNbeta-DTPA-dextran on progression of CNV. This conjugate prolonged the plasma half-life of IFNbeta and enabled IFNbeta to accumulate in the CNV in rabbits. CONCLUSIONS: In this study, human IFNbeta was successfully used to target CNV, an enhanced antiangiogenic effect was achieved by combining it with dextran, based on metal coordination. This targeted delivery of IFNbeta may have potential as a treatment modality for CNV.

Angiogenesis Inhibitors↗