Toward the realization of a better aged society: messages from gerontology and geriatrics.

1. BACKGROUND: Recent medical advancements, and improvements in hygiene and food supply have led to Japan having the longest life expectancy in the world. Over the past 50 years, the percentage of the elderly population has increased fourfold from 5.7% in 1960 to 23.1% in 2010. This change has occurred at the fastest rate in the world. Compared with France, where the percentage of the elderly population has increased just twofold in the past 100 years, Japanese society is aging at an unprecedented rate. In addition, the percentage of the very elderly (aged 75 years and over), comprising more frail people, exceeded 10% of the nation's population in 2008. In such a situation, many elderly Japanese wish to spend their later years healthy, and wish to achieve great accomplishments in their lives. To achieve that, rather than considering an aging population as a negative social phenomenon, we should create a society where elderly people can enjoy a healthy, prosperous life through social participation and contribution. Factors that hamper the elderly from leading a healthy life include various psychological and social problems occurring in older age, as well as a high incidence of diseases. Therefore, gerontology, which focuses on health promotion of the elderly by encompassing the study of social welfare, psychology, environment and social systems; and geriatrics, which focuses on health care of elderly people and carried out research, education and practices to promote health in the elderly, are becoming more important. Furthermore, along with a need for multidisciplinary care to support geriatric medicine, the development of a comprehensive education system for aged-care professionals is awaited. Thus, we should now recognize the importance of gerontology and geriatrics, and a reform of medical-care services should be made in order to cope with the coming aged society. Population aging is a global phenomenon. The actions being taken by Japan, the world's most aged society, have been closely watched by the rest of the world. Japan's aged society has been posing not only medical, nursing and welfare problems, but also complex problems closely associated with economy, industry and culture. Therefore, to solve these problems, a macroscopic integration and cooperation among industries, education institutions, administration and community through an interdisciplinary approach including medical science, nursing science, nursing care, study of social welfare, social science, engineering, psychology, economics, religion and ethics should be made. Regarding the promotion of gerontology, the "Committee for Establishing a Scientific Community for Sustainable Aged Society" of the Science Council of Japan also prepared a proposal and this was announced on 20 April 2011. 2. CURRENT SITUATION AND PROBLEMS: (1) Promotion of social participation and contribution of elderly people In Japan, the overall labor force rate is expected to decrease in the near future as a result of the low birth rate and high life expectancy. In contrast, many elderly people, particularly the young-old, have sufficient physical strength to fulfil their job duties and make a social contribution. For these people, a social structure where elderly people can work should be developed through re-educating the elderly and providing various job types. Promotion of social participation and contribution of the elderly is expected to cause a substantial increase in the labor force. Furthermore, it is also expected to contribute to not only the upturn of national economic activity through an increase in total consumption, but also a decrease in the number of elderly people who are likely to be in need of care. Therefore, in order for elderly people to be engaged in various social activities, strategies for developing a social structure for re-education, various employment statuses and employment opportunities should be prepared. However, as the total number of jobs is fixed, consideration should also be given to young workers. (2) Fostering medical specialists for aging Older people often suffer from many diseases, together with geriatric syndromes with multiple etiologies. Signs and symptoms vary according to each individual, and are often atypical; therefore, the patients visit different hospitals and receive many screening tests and prescriptions at the same time. To solve this problem, an effective screening system carried out by a primary-care doctor, and privacy-preserving medical data sharing among hospitals and clinics are needed. In a geriatric clinical setting, health-care professionals should be aware of the physical traits of older people who often develop not only dementia, but also geriatric syndromes, such as depression, falls and urinary incontinence, so that a holistic approach with consideration of nursing care is required. However, the existing Japanese medical education system is not prepared for medical professionals enabled to respond to the aforementioned requirements. Thus, the fostering of medical professionals who can provide comprehensive care - especially for the oldest-old - such as geriatric specialists and medical professionals who understand the principles of elderly care, is urgently needed. (3) Diagnosis of elderly-specific diseases and reform of medical-care services In Japan, the diagnostic system for elderly-specific diseases, including dementia, and reform of medical care services are markedly delayed. The current status concerning diagnosis, care and nursing should be investigated to collect academic data. In order to accumulate evidence for providing safe elderly care and nursing, the promotion of clinical research and a marked expansion of geriatric medical centers with high-level medical services are eagerly awaited. (4) Promotion of home-based care and multidisciplinary care To reduce the length of stay in acute hospitals, to reduce the physical burden of health-care professionals working at acute hospitals and to meet the demand of older people who prefer to remain in their own homes, further promotion of home-based care is needed. In addition, "multidisciplinary care" is increasingly needed to meet various demands in the medical care and welfare of the elderly. It is considered important to share countermeasures against the problems of disease prevention, medicine, care and welfare among health-care professionals in medicine, care and welfare, and cooperate by making the best use of health-care professionals' specialties. 3. CONTENTS OF THE PROPOSAL: The subcommittee for aging, thus, provided the following proposal: 1 Development and promotion of systems that enable elderly people to participate socially and make a contribution using an interdisciplinary approach among the various areas, including nursing science, nursing care, study of social welfare, social science, psychology, economics, religion and ethics, as well as medical sciences; 2 Promotion of gerontology, reform and enhancement of geriatrics in undergraduate, postgraduate and lifelong education; 3 Building geriatric medical centers in each area, and accumulating large-scale evidence of geriatric diseases and geriatrics; and 4 Structural development and promotion of home-based care and multidisciplinary care. Through implementation of the above measures, Japan is expected to function as a successful example for the rest of the world.

[Pilot study to resolve problems of visual acuity assessment in grading vision of the physically handicapped--visual acuity and difficulties in daily life of age-related macular degeneration-].

PURPOSE: To resolve the problems of visual acuity assessment in grading the vision of the physically handicapped as proposed by the Subcommittee for Promoting the Realization of a Cohesive Society with the Visually Disabled, Science Council of Japan, a method suitable for assessing visual disturbances, and the relationship between the degree of visual disturbances and the degree of difficulty in activities of daily life are clarified. SUBJECTS AND METHODS: 151 persons with age-related macular degeneration were studied. Examination methods for measuring visual acuity and reading performance were studied, and interviews using the daily living task dependent on vision (DLTV) questionnaire were performed. The correlations between total DLTV score and each examination method were analyzed. The median total DLTV score for each grade of visual acuity of the better eye was calculated. RESULTS: Spearman's correlation coefficient between distance corrected visual acuity of the better eye and total DLTV score was 0.76. Median DLTV scores for visual acuities (better eye) of 0.2, 0.3, 0.4, 0.5 were 65, 73.5, 62, 79 respectively. CONCLUSION: Visual acuity can be assessed by measuring distant corrected visual acuity of the better eye and setting the upper limit of visual disturbance at either 0.3 or 0.4.

Cyclic stretch-induced reactive oxygen species generation enhances apoptosis in retinal pericytes through c-jun NH2-terminal kinase activation.

Hypertension is known to exacerbate diabetic complications, such as retinopathy and nephropathy. Apoptosis of retinal vascular pericytes has been well established as the earliest conceivable change in diabetic retinopathy. In this study, we investigated the contribution of cyclic stretch, which mimics a hypertensive state to pericyte apoptosis. A 48-hour cyclic stretch induced DNA fragmentation in porcine retinal pericytes and increased the number of TUNEL+ cells at a pathophysiologically relevant extension level (10%/60 cycles per minute). Stretch also increased intracellular reactive oxygen species generation and increased c-Jun NH(2)-terminal kinase phosphorylation in a time- and magnitude-dependent manner, which were reduced by the nicotinamide-adenine dinucleotide phosphate oxidase inhibitor diphenylene iodonium or dominant-negative protein kinase C-delta. Stretch activated protein kinase C-delta and increased its association with p47phox. Stretch induced cleavage of caspase-9 and -3 and increased caspase-3 activity. Protein kinase C-delta or c-Jun NH(2)-terminal kinase inhibition normalized stretch-induced caspase-3 activity and prevented stretch-induced apoptosis. These data indicate that cyclic stretch induces apoptosis in porcine retinal pericytes by activation of the reactive oxygen species-c-Jun NH(2)-terminal kinase-caspase cascades, suggesting a novel molecular mechanism to explain the exacerbation of early diabetic retinopathy by concomitant hypertension.

Molecular properties of rhodopsin and rod function.

Signal transduction in rod cells begins with photon absorption by rhodopsin and leads to the generation of an electrical response. The response profile is determined by the molecular properties of the phototransduction components. To examine how the molecular properties of rhodopsin correlate with the rod-response profile, we have generated a knock-in mouse with rhodopsin replaced by its E122Q mutant, which exhibits properties different from those of wild-type (WT) rhodopsin. Knock-in mouse rods with E122Q rhodopsin exhibited a photosensitivity about 70% of WT. Correspondingly, their single-photon response had an amplitude about 80% of WT, and a rate of decline from peak about 1.3 times of WT. The overall 30% lower photosensitivity of mutant rods can be explained by a lower pigment photosensitivity (0.9) and the smaller single-photon response (0.8). The slower decline of the response, however, did not correlate with the 10-fold shorter lifetime of the meta-II state of E122Q rhodopsin. This shorter lifetime became evident in the recovery phase of rod cells only when arrestin was absent. Simulation analysis of the photoresponse profile indicated that the slower decline and the smaller amplitude of the single-photon response can both be explained by the shift in the meta-I/meta-II equilibrium of E122Q rhodopsin toward meta-I. The difference in meta-III lifetime between WT and E122Q mutant became obvious in the recovery phase of the dark current after moderate photobleaching of rod cells. Thus, the present study clearly reveals how the molecular properties of rhodopsin affect the amplitude, shape, and kinetics of the rod response.

EphrinA1 inhibits vascular endothelial growth factor-induced intracellular signaling and suppresses retinal neovascularization and blood-retinal barrier breakdown.

The Eph receptor/ephrin system is a recently discovered regulator of vascular development during embryogenesis. Activation of EphA2, one of the Eph receptors, reportedly suppresses cell proliferation and adhesion in a wide range of cell types, including vascular endothelial cells. Vascular endothelial growth factor (VEGF) plays a primary role in both pathological angiogenesis and abnormal vascular leakage in diabetic retinopathy. In the study described herein, we demonstrated that EphA2 stimulation by ephrinA1 in cultured bovine retinal endothelial cells inhibits VEGF-induced VEGFR2 receptor phosphorylation and its downstream signaling cascades, including PKC (protein kinase C)-ERK (extracellular signal-regulated kinase) 1/2 and Akt. This inhibition resulted in the reduction of VEGF-induced angiogenic cell activity, including migration, tube formation, and cellular proliferation. These inhibitory effects were further confirmed in animal models. Intraocular injection of ephrinA1 suppressed ischemic retinal neovascularization in a dose-dependent manner in a mouse model. At a dose of 125 ng/eye, the inhibition was 36.0 +/- 14.9% (P < 0.001). EphrinA1 also inhibited VEGF-induced retinal vascular permeability in a rat model by 46.0 +/- 10.0% (P < 0.05). These findings suggest a novel therapeutic potential for EphA2/ephrinA1 in the treatment of neovascularization and vasopermeability abnormalities in diabetic retinopathy.

Recovery of rod-mediated a-wave during light-adaptation in mGluR6-deficient mice.

The purpose of this study was to compare the a-waves of mGluR6-deficient mice (KO) to that of wild-type mice (WT), and to determine whether the light-adapted electroretinogram of the KO mice originate exclusively from cones. Dark-adapted a-waves were recorded under the same conditions from both types of mice. With a 96-cd/m(2) background, the a-wave from both types of mice showed a rapid recovery over a 50-min period. The analysis of the a-waves in KO mice indicated that the recovery was determined mainly by the rod component. The light-adapted b-wave of WT mice showed no corresponding recovery. We conclude that rod contribution must be considered in the analyses of the light-adapted a-waves of KO mice.

Generation of knock-in mice carrying third cones with spectral sensitivity different from S and L cones.

Red-green color vision in primates is unique in the sense that it is mediated by two photoreceptor cells that are indistinguishable in all aspects except for their visual pigments. In order to generate an animal model for investigation of the interaction between red-green inputs at the molecular level, we applied knock-in technology and X-chromosome inactivation machinery to make a mouse model with cone cells possessing visual pigments with different spectral sensitivities. We introduced a S308A point mutation into the Green opsin gene allele on the X-chromosome. This manipulation generated a 24 nm red-shift of absorption maximum in the cone pigment with negligible functional differences in other molecular properties. Amplitudes of responses in ERG and ganglion cell recordings of homozygotes were similar to those of wild-types, although the spectral sensitivities differed. Heterozygotes showed variable spectral sensitivities of ganglion cell responses due to the different integration of the native and the S308A cone inputs on the dendritic fields. In situ hybridization experiments showed that cone cells with respective pigments formed patch-like clusters of specific L cone-types, approximately 30 mum in diameter, which were randomly distributed in the dorsal region of the retinas. Since the patch-like clustering was arranged by X-inactivation, such clustering could be present in the peripheral retinas of New World monkeys with polymorphic L pigments, indicating that our mice would be a suitable model to study evolution of the mammalian color vision system.

Expression of connective tissue growth factor and its potential role in choroidal neovascularization.

BACKGROUND: To determine the expression of connective tissue growth factor (CTGF) in choroidal neovascularization. METHODS: Surgically excised choroidal neovascular membranes (CNVMs) were obtained at vitrectomy from eight eyes with age-related macular degeneration, five eyes with high myopia, and two eyes with angioid streaks. Light microscopic immunohistochemical analysis was performed to detect CTGF, transforming growth factor beta 1 (TGF-beta1), vascular endothelial growth factor (VEGF), pancytokeratin, and smooth muscle actin (SMA). RESULTS: CNVMs were classified by fibrotic status as cellular CNVM, moderate fibrous CNVM, and extensive fibrous CNVM. CTGF expression was found in vascular cells, stromal cells, and retinal pigment epithelium (RPE) cells. For the stromal cells, fibroblastlike cells were most strongly positive for CTGF. CTGF immunoreactivity in the stroma was stronger in the fibrous CNVMs than in the cellular CNVMs. Immunohistochemical analysis of serial sections revealed colocalization of CTGF with TGF-beta1 and VEGF; colocalization of CTGF with pancytokeratin and SMA was also found. CONCLUSION: Our findings suggest that transdifferentiated RPE cells and vascular cells possess remarkable CTGF expression in CNVMs. This expression of CTGF may stimulate fibroblasts to produce extracellular matrix and may promote angiogenesis in vascular cells. Colocalized TGF-beta1 and VEGF may also contribute the upregulation of CTGF.

Iris-derived cells from adult rodents and primates adopt photoreceptor-specific phenotypes.

PURPOSE: The purpose of this study was to investigate the effects of various genes related to photoreceptor development on rodent and primate iris cells and the potential of iris cells as donor cells for retinal transplantation. METHODS: Adult rat and monkey iris tissue were cultured in serum-free medium containing basic fibroblast growth factor. Gene deliveries of Crx, Nrl, NeuroD and some combinations (Crx-Nrl, Crx-NeuroD) were performed with recombinant retrovirus. Immunocytochemistry, Western blot analysis, RT-PCR, and intracellular recording were used to examine the expression of photoreceptor-specific phenotypes in the iris-derived cells after gene transfer, . Coculture of the iris-derived cells with embryonic retinal explant was conducted, to investigate the potential integration of these cells in coculture conditions. RESULTS: Misexpression of Crx induced adult rat iris cells to express several photoreceptor-specific antigens and transcripts, such as rhodopsin, recoverin, cGMP-gated channel, arrestin, interphotoreceptor retinal-binding protein, rhodopsin kinase, and NeuroD. In primates, a combination of Crx and NeuroD was needed to induce monkey iris-derived cells to adopt photoreceptor-specific phenotypes. Furthermore, the photoreceptor-like cells derived from both rat- and primate-iris tissues showed rod photoreceptor-specific electrophysiological response to light stimuli after Crx and Crx-NeuroD gene transfer, respectively. The results further showed that iris-derived cells integrated in the developing host retina in coculture conditions. CONCLUSIONS: Adult iris-derived cultured cells of both rodents and primates expressed photoreceptor-specific phenotypes by inductions of transcription factors. These iris-derived photoreceptor-like cells have electrophysiological characteristics of rod photoreceptors. Furthermore, they can integrate in the developing retina under coculture conditions.

Generation of Rx+/Pax6+ neural retinal precursors from embryonic stem cells.

We report directed differentiaion of retinal precursors in vitro from mouse ES cells. Six3+ rostral brain progenitors are generated by culturing ES cells under serum-free suspension conditions (SFEB culture) in the presence of Wnt and Nodal antagonists (Dkk1 and LeftyA), and subsequently steered to differentiate into Rx+ cells (16%) by treatment with activin and serum. Consistent with the characteristics of early neural retinal precursors, the induced Rx+ cells coexpress Pax6 and the mitotic marker Ki67, but not Nestin. The ES cell-derived precursors efficiently generate cells with the photoreceptor phenotype (rhodopsin+, recoverin+) when cocultured with embryonic retinal cells. Furthermore, organotypic culture studies demonstrate the selective integration and survival of ES cell-derived cells with the photoreceptor phenotype (marker expression and morphology) in the outer nuclear layer of the retina. Taken together, ES cells treated with SFEB/Dkk1/LeftyA/serum/activin generate neural retinal precursors, which have the competence of photoreceptor differentiation.

Angiopoietin-1 attenuates H2O2-induced SEK1/JNK phosphorylation through the phosphatidylinositol 3-kinase/Akt pathway in vascular endothelial cells.

Oxidative stress activates various signal transduction pathways, including Jun N-terminal kinase (JNK) and its substrates, that induce apoptosis. We reported here the role of angiopoietin-1 (Ang1), which is a prosurvival factor in endothelial cells, during endothelial cell damage induced by oxidative stress. Hydrogen peroxide (H2O2) increased apoptosis of endothelial cells through JNK activation, whereas Ang1 inhibited H2O2-induced apoptosis and concomitant JNK phosphorylation. The inhibition of H2O2-induced JNK phosphorylation was reversed by inhibitors of phosphatidylinositol (PI) 3-kinase and dominant-negative Akt, and constitutively active-Akt attenuated JNK phosphorylation without Ang1. These data suggested that Ang1-dependent Akt phosphorylation through PI 3-kinase leads to the inhibition of JNK phosphorylation. H2O2-induced phosphorylation of SAPK/Erk kinase (SEK1) at Thr261, which is an upstream regulator of JNK, was also attenuated by Ang1-dependent activation of the PI 3-kinase/Akt pathway. In addition, Ang1 induced SEK1 phosphorylation at Ser80, suggesting the existence of an additional signal transduction pathway through which Ang1 attenuates JNK phosphorylation. These results demonstrated that Ang1 attenuates H2O2-induced SEK1/JNK phosphorylation through the PI 3-kinase/Akt pathway and inhibits the apoptosis of endothelial cells to oxidative stress.

Is removal of internal limiting membrane always necessary during stage 3 idiopathic macular hole surgery?

PURPOSE: To determine the indications for internal limiting membrane (ILM) removal in stage 3 idiopathic macular holes (MHs). METHODS: Focal posterior vitreous detachments (PVDs) at MH rims were examined preoperatively by optical coherence tomography and binocular slit-lamp fundus examination in 19 patients retrospectively. All eyes underwent pars plana vitrectomy and creation of a PVD, and some eyes underwent a second surgery to remove the ILM. Indications of ILM removal for MH closure were discussed. RESULTS: Preoperatively, 9 eyes did not (non-PVD group) and 10 eyes did (PVD group) have complete focal PVDs. In all nine eyes in the non-PVD group, MHs were closed after the creation of a PVD without ILM peeling (P <0.05, chi test). In the PVD group, 5 eyes (50%) had MHs closed by making PVD complete without ILM removal, and 5 eyes (50%) required ILM removal in a second surgery. In the end, closure of MHs was achieved in all eyes. CONCLUSION: Anatomic closure of stage 3 idiopathic MHs without a PVD at the rim of the hole may be achieved only by creating a PVD without ILM removal.

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.

In vivo three-dimensional evaluation of leukocyte behavior in retinal microcirculation of mice.

PURPOSE: To evaluate new physiologic and three-dimensional methods for monitoring leukocyte behavior in mouse retina. METHODS: Endotoxin-induced uveitis (EIU) was produced in mice by footpad injection of lipopolysaccharide (LPS). Leukocytes were labeled with acridine orange (AO). Leukocyte rolling in the retinal microcirculation was evaluated in vivo with AO digital fluorography. The number of migrated leukocytes was counted in flatmounted retina. The behavior of leukocyte migration was observed three-dimensionally at the time of peak migration. After leukocytes were labeled with AO, the mice were perfused with rhodamine-labeled concanavalin A lectin to stain the vascular endothelium. Leukocyte migration into the retina was then monitored three-dimensionally with confocal microscopy, and the velocity of the migration was measured. RESULTS: Both leukocyte rolling and migration peaked at 48 hours after LPS injection. Leukocytes were seen to extravasate from the deeper capillary layers and to migrate toward the outer layer of the retina. The traveling velocity of extravasated leukocytes in retinal tissue was 2.0 +/- 0.1 microm/h. CONCLUSIONS: New methods have been demonstrated for the three-dimensional and quantitative evaluation of leukocyte behavior in mouse retina.

Tlx, an orphan nuclear receptor, regulates cell numbers and astrocyte development in the developing retina.

Tlx belongs to a class of orphan nuclear receptors that underlies many aspects of neural development in the CNS. However, the fundamental roles played by Tlx in the control of eye developmental programs remain elusive. By using Tlx knock-out (KO) mice, we show here that Tlx is expressed by retinal progenitor cells in the neuroblastic layer during the period of retinal layer formation, and it is critical for controlling the generation of appropriate numbers of retinal progenies through the activities of cell cycle-related molecules, cyclin D1 and p27Kip1. Tlx expression is restricted to Müller cells in the mature retina and appears to control their proper development. Furthermore, we show that Tlx is expressed by immature astrocytes that migrate from the optic nerve onto the inner surface of the retina and is required for their generation and maturation, as assessed by honeycomb network formation and expression of R-cadherin, a critical component for vasculogenesis. The impaired astrocyte network formation on the inner retinal surface is accompanied by the loss of vasculogenesis in Tlx KO retinas. Our studies thus indicate that Tlx underlies a fundamental developmental program of retinal organization and controls the generation of the proper numbers of retinal progenies and development of glial cells during the protracted period of retinogenesis.

Potential for neural regeneration after neurotoxic injury in the adult mammalian retina.

It has long been believed that the retina of mature mammals is incapable of regeneration. In this study, using the N-methyl-D-aspartate neurotoxicity model of adult rat retina, we observed that some Müller glial cells were stimulated to proliferate in response to a toxic injury and produce bipolar cells and rod photoreceptors. Although these newly produced neurons were limited in number, retinoic acid treatment promoted the number of regenerated bipolar cells. Moreover, misexpression of basic helix-loop-helix and homeobox genes promoted the induction of amacrine, horizontal, and rod photoreceptor specific phenotypes. These findings demonstrated that retinal neurons regenerated even in adult mammalian retina after toxic injury. Furthermore, we could partially control the fate of the regenerated neurons with extrinsic factors or intrinsic genes. The Müller glial cells constitute a potential source for the regeneration of adult mammalian retina and can be a target for drug delivery and gene therapy in retinal degenerative diseases.

Alterations in expression of angiopoietins and the Tie-2 receptor in the retina of streptozotocin induced diabetic rats.

PURPOSE: The angiopoietin (Ang)/Tie-2 system may play a role in vascular integrity and angiogenesis. In this study, we investigated alterations of the gene expression of Ang-1 and Ang-2 in the retinas of streptozotocin (STZ) induced diabetic rats. METHODS: In situ hybridization, reverse transcriptase polymerase chain reaction (RT-PCR) and western blot analyses were performed to determine the mRNA and protein content for Ang-1 and Ang-2 and the Tie2 receptor in the retinas of STZ diabetic and age matched control rats. RESULTS: Using in situ hybridization analysis, Ang-1, Ang-2, and Tie2 mRNA expression was observed in the ganglion cell layer (GCL) and the inner nuclear layer (INL). While Ang-2 mRNA expression did not changed after 2 weeks, 1 month, or 3 months of STZ induced diabetes, it was increased in the GCL and slightly elevated in the INL after 6 months of diabetes. In contrast, Ang-1 and Tie2 mRNA expression was stable at every timepoint during 6 months of STZ induced diabetes. RT-PCR and western blot analyses confirmed the increase of Ang-2 expression after 6 months of diabetes. Furthermore, double staining of alpha-smooth muscle actin (alphaSMA) and Ang-2 mRNA demonstrated that the SMA positive cells surrounding Ang-2-expressing cells were decreased in the GCL. CONCLUSIONS: Diabetes increases Ang-2 expression in the GCL accompanied by a reduction of alphaSMA positive perivascular cells. These changes may suggest a role for Ang-2 in the mechanism of pericyte loss in diabetic retinopathy.

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.