Biomedical subjects

Michiko Mandai

Publications and source records attributed to Michiko Mandai.

14 recordsLinked to original sources

PubMed2026

Long-term functional synaptic integration of genome-edited retinal organoids in a primate model of macular degeneration.

Retinal organoids represent a promising regenerative strategy for restoring vision in retinal degenerative diseases, but the capacity of host cone bipolar cells in the primate macula to rewire with transplanted photoreceptors has not been established. In this study, we transplanted genome-edited ISL1-/- human retinal organoids lacking ON-bipolar cells into an acute laser-induced macular photoreceptor ablation non-human primate model. Using immunohistochemistry, ultrastructural imaging, and focal macular electroretinography, we demonstrate that host rod and cone bipolar cells actively extend dendrites toward grafted photoreceptors and form synaptic contacts, with evidence of functional signal transmission in a subset of transplanted eyes. Longitudinal, per-eye analyses revealed that host ON-bipolar responses improved in two of four eyes with ISL1-/- graft by up to 21.6% and remained stable for up to 2 years post transplantation. Moreover, OFF-pathway connectivity showed potential progressive maturation, with delayed increase in d-wave after 13 months in one of those eyes. These findings provide the first demonstration of long-term anatomical host-graft synaptic integration in the primate macula, establishing that central cone bipolar circuits retain the capacity for durable rewiring with human stem-cell-derived grafts. Our results highlight ISL1-/- retinal organoids as a promising approach for central vision restoration in macular degeneration.

Animals↗

PubMed2006

Pigment epithelial detachment in polypoidal choroidal vasculopathy.

PURPOSE: To study the morphological features of serosanguineous pigment epithelial detachments (PEDs) with accompanying polypoidal lesions in eyes with polypoidal choroidal vasculopathy (PCV). DESIGN: Retrospective observational case series. METHODS: For this observational case study, we retrospectively reviewed 93 consecutive eyes of 85 patients with PCV. The lesions in eyes with PCV were examined with indocyanine green angiography (IA) and optical coherence tomography (OCT). RESULTS: Of 93 eyes with PCV, 51 eyes (55%) had serous or hemorrhagic PEDs. Of these 51 eyes, a notch in the PED was found in 27 eyes (53%) by angiography, most of which showed polypoidal lesions by IA that corresponded in location to the notch observed by angiography. Polypoidal lesions were detected outside the PED in one eye (2%), at the margin of the PED in 33 eyes (65%), and inside the PED in 12 eyes (24%). OCT revealed that PED had a notch observed tomographically in 29 eyes (57%), most of which corresponded in location to polypoidal lesions seen by IA. In eight eyes, polypoidal lesions, which were adherent to the inner surface of the serous PED, appeared to be detached from the Bruch membrane and the choroid. CONCLUSIONS: Polypoidal lesions are located at the margin of PED and make a notch in the accompanying PED that is visible by angiography and tomographically. When the polypoidal lesions have increased exudate, the fluid from the lesions infiltrates under the polypoidal lesions themselves, which results in the lesions detaching from the Bruch membrane and appearing to be located inside the PED.

Aged↗

PubMed2006

No association between complement factor H gene polymorphism and exudative age-related macular degeneration in Japanese.

Age-related macular degeneration (ARMD) is the leading cause of blindness in the elderly population not only Western but also Asian industrial countries. In Caucasian, a polymorphism of the complement factor H gene (CFH), the C allele of rs1061170 (Y402H), was established as the first strong genetic factor for excursively exudative type of ARMD. In this study, we performed an extensive sequencing of the 22 exons in the CFH gene by recruiting 146 exudative ARMD patients and 105 normal controls of Japanese origin and identified 61 polymorphisms. We found that the frequency of the C allele of rs1061170 (Y402H) is much lower (0.04) in Japanese controls than in Caucasians (0.45). No case disease susceptibility to exudative ARMD was noted for rs1061170 (Y402H) (chi (2) = 3.19, P (corr) = 0.423), or other 12 single nucleotide polymorphisms (SNPs) whose frequency is greater than 0.05. When haplotypes were inferred for 13 SNPs (these 12 SNPs with a frequency greater than 0.05 and rs1061170), three haplotypes whose pattern was similar to those in Caucasians were identified but with substantial difference in frequency. Again we failed to identify genetic association between Japanese exudative ARMD and any of the haplotypes including the J1 haplotype which was shown to be susceptible to ARMD in Caucasians (chi (2 )=( )3.92, P (corr) = 0.157). CFH does not appear to be a primary hereditary contributor to ARMD in Japanese. The absence of CFH contribution to ARMD in Japanese may correlate with the findings in ethnic differences of ARMD phenotypes.

Age Factors↗

PubMed2006

Polypoidal choroidal vasculopathy with choroidal vascular hyperpermeability.

PURPOSE: To describe the incidence and clinical characteristics of polypoidal choroidal vasculopathy (PCV) associated with choroidal vascular hyperpermeability. DESIGN: Retrospective observational case series. METHODS: We reviewed the medical records of 122 consecutive eyes with PCV and 106 consecutive eyes with exudative age-related macular degeneration (AMD). Fluorescein angiography and indocyanine green (ICG) angiography were performed using a confocal scanning laser system. In the midphase of ICG angiography, we evaluated choroidal vascular hyperpermeability, which is recognized as one of the characteristic findings in central serous chorioretinopathy (CSC). Choroidal vascular hyperpermeability appeared as multifocal patchy areas of hyperfluorescence with blurred margins within the choroid that increased in intensity with time after injection of the dye. RESULTS: Of 122 eyes with PCV, 12 (9.8%) eyes of 10 patients exhibited multifocal choroidal hyperfluorescence in the midphase of ICG angiography, whereas two (1.9%) of 106 eyes with exudative AMD showed a similar appearance (P = .013). Of the 12 eyes in 10 patients with PCV that demonstrated multifocal choroidal hyperfluorescence, we also noted that the early phase of ICG angiography showed choroidal filling delay in seven eyes (58%) and venous dilation in 12 eyes (100%). Four of these 12 eyes (33%) had a medical history of CSC, and nine (90%) of the 10 patients revealed multifocal choroidal hyperfluorescence bilaterally. CONCLUSIONS: Multifocal choroidal hyperfluorescence seen by ICG angiography occurs more frequently in eyes with PCV than in those with AMD. Choroidal vascular hyperpermeability, reportedly a characteristic finding in CSC, might be one of the risk factors of PCV.

Aged↗

PubMed2006

The simultaneous treatment of MMP-2 stimulants in retinal transplantation enhances grafted cell migration into the host retina.

The success of functional retinal cell transplantation has been limited by the low efficiency of the transplanted cell integration into the host retina. Given that the extracellular matrix (ECM) is thought to inhibit entry and axonal outgrowth of grafted neural cells into the host retina, modulation of the ECMs in the host environment may overcome this limitation. Here, we demonstrate that matrix metalloprotease-2 (MMP-2) expression is associated with the high migratory potential of adult rat hippocampus-derived neural stem cells compared with retinal progenitor cells. In addition, MMP-2, as well as its reported inducers concanavalin A and 17beta-estradiol, can trigger the migration of retinal progenitor cells into explanted retinas. Inhibitors of MMP-2 suppressed these effects. Intense cell migration is not required for photoreceptor transplantation; however, the environment that allows the transplanted cells to integrate is most important. Migration of the transplanted cells is a good index of the acceptance of grafted cell of the host tissue. Strategies modulating the environment by MMP-2 stimulation may provide an advance in the development of retinal transplantation.

Adult Stem Cells↗

PubMed2005

A new PCR-based approach for the preparation of RNA probe.

A number of PCR-based in situ hybridization (ISH) techniques have been reported to facilitate the procedure. However, those techniques require additional gene specific primers with RNA polymerase binding site. We developed a new PCR-based ISH technique without extra gene-specific primers. We amplified gene specific PCR products with regular gene-specific primer pairs. Special linker, including T7 RNA polymerase binding site, was adapted to amplified PCR products. Secondary PCR was performed with T7 primer, and forward or reverse primer, used for the first PCR to prepare template DNA for RNA transcription. We were able to generate sense and anti-sense probes for ISH in a day. Recently, real-time PCR and ISH are required to validate microarray results quantitatively and qualitatively. This technique can be expected to facilitate the high-throughput validation of transcripts detected by microarrays.

Animals↗

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

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.

Aging↗

PubMed2004

Requirement for Tec kinases in chemokine-induced migration and activation of Cdc42 and Rac.

Cell polarization and migration in response to chemokines is essential for proper development of the immune system and activation of immune responses. Recent studies of chemokine signaling have revealed a critical role for PI3-Kinase, which is required for polarized membrane association of pleckstrin homology (PH) domain-containing proteins and activation of Rho family GTPases that are essential for cell polarization and actin reorganization. Additional data argue that tyrosine kinases are also important for chemokine-induced Rac activation. However, how and which kinases participate in these pathways remain unclear. We demonstrate here that the Tec kinases Itk and Rlk play an important role in chemokine signaling in T lymphocytes. Chemokine stimulation induced transient membrane association of Itk and phosphorylation of both Itk and Rlk, and purified T cells from Rlk(-/-)Itk(-/-) mice exhibited defective migration to multiple chemokines in vitro and decreased homing to lymph nodes upon transfer to wt mice. Expression of a dominant-negative Itk impaired SDF-1alpha-induced migration, cell polarization, and activation of Rac and Cdc42. Thus, Tec kinases are critical components of signaling pathways required for actin polarization downstream from both antigen and chemokine receptors in T cells.

Animals↗

PubMed2004

Laser photocoagulation of indocyanine green angiographically identified feeder vessels to idiopathic polypoidal choroidal vasculopathy.

PURPOSE: To evaluate the efficacy of laser photocoagulation of indocyanine green angiographically identified feeder vessels to idiopathic polypoidal choroidal vasculopathic lesions. DESIGN: Interventional case series. METHODS: Fifteen eyes of 14 consecutive patients with idiopathic polypoidal choroidal vasculopathy lesions treated by laser photocoagulation of indocyanine green angiographically identified feeder vessels were investigated. RESULTS: In 10 of the 15 eyes, serous retinal detachment of sensory retina in the macula disappeared after photocoagulation of the feeder vessels. The best-corrected visual acuity improved by 2 or more lines in eight of the 15 eyes and worsened in two eyes during the mean follow-up period of 13.6 months. CONCLUSIONS: Laser photocoagulation targeted exclusively to the feeder vessels supplying the idiopathic polypoidal choroidal vasculopathy lesions is a safe and effective method and can improve vision in eyes in which a serous retinal detachment is present in the macula. Indocyanine green angiography-guided laser photocoagulation should be considered as an optional treatment for idiopathic polypoidal choroidal vasculopathy.

Aged↗

PubMed2004

Otx2 homeobox gene induces photoreceptor-specific phenotypes in cells derived from adult iris and ciliary tissue.

PURPOSE: It remains unclear which gene induction effectively generates photoreceptor-specific phenotypes from nonretinal tissues. The purpose of this study was to determine whether Crx and Otx2--homeobox genes related to photoreceptor development--can induce the generation of these phenotypes in cells derived from adult ciliary and iris tissue and in mesencephalon-derived neural stem cells. METHODS: Crx and Otx2 were transferred into adult rat ciliary- and embryonic mesencephalon-derived neurospheres and adult rat iris-derived cells with the aid of a recombinant retrovirus. The presence of photoreceptor-specific phenotypes was confirmed by immunocytochemistry and Western blot analysis. RESULTS: More than 90% of the Crx- and Otx2-transfected ciliary- and iris-derived cells exhibited rod opsin immunoreactivity, whereas few of the similarly transfected mesencephalon-derived neural stem cells expressed rod opsin. At least two additional key components of the phototransduction cascade, recoverin and Gdeltat1, were expressed by Crx- and Otx2-transfected iris-derived cells. CONCLUSIONS: Crx and Otx2 effectively induced the generation of photoreceptor-specific phenotypes from ciliary- and iris-derived cells. That both Crx and Otx2 induced phenotype generation in cells derived from iris or ciliary tissue may suggest an approach to photoreceptor cell preparation for retinal transplantation.

Animals↗

PubMed2002

Expression of estrogen receptor in the choroidal neovascular membranes in highly myopic eyes.

PURPOSE: To investigate the expression of estrogen receptor in choroidal neovascular membranes (CNVMs) surgically excised from eyes with high myopia. METHODS: The CNVMs were surgically excised from two eyes with high myopia. Immunohistochemical analysis with a monoclonal antibody to estrogen receptor and in situ hybridization with an oligodeoxynucleotide sequence coding for estrogen receptor were used to study the cellular distribution of estrogen receptor and its messenger RNA in the CNVMs. Immunohistochemical localization of glial fibrillary acidic protein and vimentin in the CNVMs was compared with localization of estrogen receptor. RESULTS: Immunohistochemical analysis with monoclonal antibody to estrogen receptor showed widespread staining throughout the CNVMs. By in situ hybridization, the expression of estrogen receptor messenger RNA was predominantly observed in the CNVMs. Staining with antibody to vimentin was widespread throughout the CNVMs, which was similar to the localization of estrogen receptor. CONCLUSION: Estrogen receptor was expressed in the CNVMs in highly myopic eyes, suggesting that estrogen may have important functions in the formation of CNVMs.

Aged↗

PubMed2002

Contrasting effect of estrogen on VEGF induction under different oxygen status and its role in murine ROP.

PURPOSE: It has been reported that 17beta-estradiol (E2) may enhance the proliferation of bovine retinal vascular endothelial cells (BRECs) by increasing the expression of VEGFR-2 and VEGF. The hypothesis in the current study was that estrogen may contribute to fetal vascular development and the cessation of exposure to estrogen of premature infants on birth may have an inhibitory effect on retinopathy of prematurity (ROP). Because ROP is thought to develop under relative hypoxia after exposure to high-dose oxygen, this study was conducted to investigate how estrogen modulates hypoxia-induced VEGF in BRECs and mouse ROP. METHODS: Gene expression of VEGF and hypoxia-inducible factor (HIF)-1alpha were studied in BRECs, with or without E2, under normoxia and hypoxia (1% O2). A binding assay was performed to determine whether estrogen interferes with HIF-1-mediated induction of VEGF. In a mouse ROP model, effects of E2 were evaluated by avascular area, subsequent extraretinal neovascularization, and retinal expression of the VEGF gene, by administering E2 during hyperoxia (75% O2) and/or after exposure to room air. RESULTS: Hypoxia-induced VEGF mRNA in BRECs was reduced dose dependently by 1 to 100 nM E2. E2 reduced hypoxia-induced binding of HIF-1 to the VEGF promoter site and reduced the HIF-1alpha mRNA level. In mouse ROP, injection of E2 during hyperoxia increased retinal VEGF mRNA and reduced the retinal avascular area at the end of hyperoxia. E2 treatment during the normoxia that followed reduced VEGF mRNA and extraretinal neovascularization. Treatment with E2 throughout both periods significantly improved retinopathy. CONCLUSIONS: Estrogen may function as a significant modulator of the level of VEGF mRNA under different oxygen conditions and could serve as a prophylactic agent for ROP.

Animals↗

PubMed2002

[Visual prognosis in polypoidal choroidal vasculopathy associated with subretinal hematoma].

PURPOSE: Although it is reported that the prognosis for polypoidal choroidal vasculopathy(PCV) is better than that for age-related macular degeneration, visual acuity is not always good in eyes with subfoveal hemorrhage. We evaluated the factors that may affect the visual prognosis after subfoveal hematoma associated with PCV. SUBJECT: We examined retrospectively the records of 37 eyes in 34 patients that were diagnosed as PCV by indocyanine green angiography from January 1998 to July 2000 at Kyoto University Hospital. Among the 37 eyes, we chose 15 eyes in 15 patients that had subfoveal hematoma of more than 1 disk diameter, and evaluated the area of hematoma, period required for absorption of the hematoma, association of choroidal neovascularization(CNV), treatment, and visual acuity change. RESULTS: The area and the absorption period of the hematoma did not correlate with the visual prognosis. Association of CNV strongly influenced the visual outcome after the absorption of subretinal hemorrhage. Four eyes with CNV received various treatments, but no restoration of visual acuity was observed. CONCLUSION: CNV association mostly affected the prognosis of PCV with hematoma. Early detection of CNV appeared important to predict visual prognosis.

Aged↗