MANAGEMENT OF LARGE FULL-THICKNESS MACULAR HOLES: Long-Term Outcomes of Internal Limiting Membrane Flaps and Internal Limiting Membrane Peels.

BACKGROUND/PURPOSE: To determine and compare the efficacy of a surgical internal limiting membrane (ILM) flap technique with the traditional ILM peel on long-term visual and anatomical outcomes for large (>400 µm) full-thickness macular holes. METHODS: From October 2016 to July 2022, patients undergoing initial full-thickness macular hole repair with the ILM flap or ILM peel technique were reviewed. Final outcomes were recorded and based on size in microns: 401 to 800, 801 to 1,200, and >1,200. RESULTS: Patients treated with ILM flap (n = 52, 94.2% closure rate) or ILM peel (n = 407, 93.6% closure rate) were followed with a mean follow-up time of 15.0 ± 10.2 and 20.0 ± 13.4 months, respectively. Success rates for ILM flaps and ILM peels were compared for full-thickness macular holes of 401 to 800 (100%, 95.8%, P = 0.39), 801 to 1,200 (95%, 93%, P = 0.74), and >1,200 (86.7%, 86.7%, P = 1.0) µm. Mean best-recorded logarithm of the minimal angle of resolution visual acuity for ILM flaps and ILM peels, respectively, was 1.02 ± 0.46 and 0.87 ± 0.47 preoperatively, with follow-up acuity of 0.48 ± 0.32 (P < 0.03) and 0.39 ± 0.42 (P < 0.01) at Year 3. CONCLUSION: Both techniques provide a similar anatomical closure rate and functional improvement in vision. Comparisons should be cautiously made based on difference in preoperative hole size.

Mitochondrial influences on smooth muscle phenotype.

Smooth muscle cells transition reversibly between contractile and noncontractile phenotypes in response to diverse influences, including many from mitochondria. Numerous molecules including myocardin, procontractile miRNAs, and the mitochondrial protein prohibitin-2 promote contractile differentiation; this is opposed by mitochondrial reactive oxygen species (mtROS), high lactate concentrations, and metabolic reprogramming induced by mitophagy and/or mitochondrial fission. A major pathway through which vascular pathologies such as oncogenic transformation, pulmonary hypertension, and atherosclerosis cause loss of vascular contractility is by enhancing mitophagy and mitochondrial fission with secondary effects on smooth muscle phenotype. Proproliferative miRNAs and the mitochondrial translocase TOMM40 also attenuate contractile differentiation. Hypoxia can initiate loss of contractility by enhancing mtROS and lactate production while simultaneously depressing mitochondrial respiration. Mitochondria can reduce cytosolic calcium by moving it across the inner mitochondrial membrane via the mitochondrial calcium uniporter, and then through mitochondria-associated membranes to and from calcium stores in the sarcoplasmic/endoplasmic reticulum. Through these effects on calcium, mitochondria can influence multiple calcium-sensitive nuclear transcription factors and genes, some of which govern smooth muscle phenotype, and possibly also the production of genomically encoded mitochondrial proteins and miRNAs (mitoMirs) that target the mitochondria. In turn, mitochondria also can influence nuclear transcription and mRNA processing through mitochondrial retrograde signaling, which is currently a topic of intensive investigation. Mitochondria also can signal to adjacent cells by contributing to the content of exosomes. Considering these and other mechanisms, it is becoming increasingly clear that mitochondria contribute significantly to the regulation of smooth muscle phenotype and differentiation.

Impact of Prefilled Syringes and Masking on Postintravitreal Injection Endophthalmitis.

Purpose: To compare rates of endophthalmitis (1) following intravitreal injection of antivascular endothelial growth factor therapies with glass-vial preparation (GVP) vs prefilled syringes (PFS) and (2) before and after masking protocols were implemented. Methods: Medical records within a multicenter retina practice in Houston, Texas, from January 2015 to August 2021 were retrospectively reviewed. The primary outcome was rate of endophthalmitis after intravitreal injection. Results: A total of 307 349 injections were performed during the study period and 101 cases of endophthalmitis were identified (0.033%). PFS use was associated with a decreased risk of endophthalmitis (relative risk [RR], 0.320; 95% CI, 0.198-0.518, P < .001); 54 cases of endophthalmitis occurred in the GVP group of aflibercept and ranibizumab (0.052%) compared with 24 in the PFS group (0.017%). There was no difference in the endophthalmitis rates with or without universal masking (RR, 0.953; 95% CI 0.616-1.473, P = .91). Discussion: PFS use was associated with a significant reduction in the rate of endophthalmitis while the use of surgical face masks did not appear to significantly impact the rate of endophthalmitis.

Risk Factors for the Development of Fellow Eye Horseshoe Retinal Tears Following Horseshoe Retinal Tear in the Presenting Eye.

BACKGROUND: This study investigated factors associated with fellow eye horseshoe retinal tear (HST) development in consecutive patients with a presenting eye HST. MATERIALS AND METHODS: Medical records were reviewed for patients with initial HSTs between 2015 and 2017 and 24 factors were analyzed. Logistic regression was used to assess factors associated with fellow eye HST development. RESULTS: In total, 242 patients with an HST were identified with mean follow-up of 68.3 months. Four associations with fellow eye HST development were identified: (1) presence of fellow eye lattice degeneration, (2) subsequent presenting eye HSTs, (3) fellow eye vitreous hemorrhage at presenting eye HST occurrence, (4) OCT-determined stage 3 fellow eye posterior vitreous detachment at presenting eye HST occurrence. CONCLUSION: Four clinical findings associated with fellow eye HST development following presenting eye HST were identified. These factors may be important considerations during management patients with HST. [Ophthalmic Surg Lasers Imaging Retina 2023;54:338-345.].

USE OF OPTICAL COHERENCE TOMOGRAPHY IN DETECTING RETINAL TEARS IN ACUTE, SYMPTOMATIC POSTERIOR VITREOUS DETACHMENT.

PURPOSE: To evaluate the association of posterior vitreous opacities (PVOs) on optical coherence tomography with retinal tears identified on examination in patients with acute, symptomatic posterior vitreous detachment (PVD). METHODS: Data were retrospectively collected from the medical records of 388 patients with acute, symptomatic PVD between January 1, 2021, and June 30, 2021. Included patients had received a primary diagnosis of PVD and presented with flashes and/or floaters. Optical coherence tomography scans were reviewed by two separate readers for the presence of PVOs. The primary outcome was the presence of retinal tear on fundus photograph and on examination. RESULTS: Of 388 patients who presented with acute PVD symptoms, 90 (23.2%) were found to have a retinal tear on dilated fundus examination. Among these patients, 78 (86.7%) were found to have PVOs on optical coherence tomography. Statistical analysis demonstrated a significant relationship between the presence of PVOs and retinal tear ( P < 0.01). The sensitivity and specificity of this finding was 86.7% and 72.5%, respectively. Further analysis included area under the curve from receiver operating characteristic curve which was found to be 0.80. CONCLUSION: The presence of PVOs on optical coherence tomography is suggestive of a retinal tear in patients with acute, symptomatic PVD.

Risk factors for changes in carotid intima media thickness and plaque over 5 years in women with systemic lupus erythematosus.

OBJECTIVE: To investigate the occurrence of and risk factors for progression of carotid intima media thickness (IMT) and plaque in women with and without SLE. METHODS: A cohort of 149 women with SLE and 126 controls participated in SOLVABLE (Study of Lupus Vascular and Bone Long-term Endpoints). Demographics, cardiovascular and SLE factors, and laboratory assessments were collected at baseline. Carotid IMT and plaque were measured using B-mode ultrasound at baseline and at 5-year follow-up. Regression models were used to identify predictors of progression in carotid IMT and plaque; multivariate models were adjusted for age, hypertension and total cholesterol to high-density lipoprotein ratio. RESULTS: The mean±SD follow-up time was 5.35±0.60 years in cases and 5.62±0.66 years in controls. The mean IMT change per year was 0.008±0.015 mm in cases and 0.005±0.019 mm in controls (p=0.24). At follow-up, 31.5% of cases and 15% of controls had plaque progression, with a relative risk for plaque progression of 2.09 (95% CI 1.30 to 3.37). In SLE cases, higher fasting glucose and lower fibrinogen were associated with IMT progression after adjustment. Larger waist circumference and non-use of hydroxychloroquine were associated with plaque progression after adjustment. CONCLUSION: Potential modifiable risk factors for carotid IMT and plaque progression in women with SLE were identified, suggesting that monitoring of glucose and waist circumference and use of hydroxychloroquine may be beneficial.

Clinical outcomes following intravitreal methotrexate for primary vitreoretinal lymphoma.

PURPOSE: To describe the visual acuity and anatomic outcomes of intravitreal methotrexate (MTX) for the treatment of primary vitreoretinal lymphoma (PVRL). METHODS: Single-center retrospective case series of patients with a diagnosis of PVRL treated with intravitreal MTX. Patient records were reviewed for demographic information, ocular exam findings, and treatment regimens including number of MTX injections. Clinical outcomes recorded included visual acuity (VA), time to partial (PR) or complete response (CR), disease-free survival, time to relapse, and any CNS progression. RESULTS: Ten eyes of 7 patients (4 male, 6 female) were reviewed. The mean age ± standard deviation (SD) was 70 ± 12 years. Five patients had prior or concomitant diagnosis of primary CNS lymphoma with a history of systemic chemotherapy including MTX. Three eyes (30%) exhibited isolated vitreous involvement, four (40%) had subretinal lesions, and three (30%) presented with both vitreous and subretinal disease. Mean initial logMAR VA was 0.38 ± 0.52 (Snellen visual equivalent 20/50), while mean final logMAR VA ± SD was 0.34 ± 0.27 (Snellen visual equivalent 20/40) with a mean follow-up time of 26 months (Range, 3-49 months). Patients received an average of 6 intravitreal MTX injections (Range 1-10) over the course of treatment. Two patients received concomitant systemic chemotherapy. Mean time to either PR or CR was 57 days, and 6 eyes (60%) exhibited regression with no relapse after local treatment. For the 4 eyes that eventually relapsed, the mean time ± SD to first relapse was 193 days ± 155 days, and one eye experienced a second relapse. Two of 3 patients with subretinal disease showed complete regression with extended follow-up of 1 and 4 years following treatment with less than 3 doses of intravitreal MTX. One patient with PVRL developed CNS lymphoma during the study period. VA remained stable overall between the initial treatment visit, 3, 6, and 12-months (P > 0.05 for paired comparisons of VA over time). CONCLUSIONS: Intravitreal methotrexate was well-tolerated and led to local disease response in the majority of patients at approximately 2 months after initiation of treatment of intraocular lymphoma. Further studies on the efficacy of intravitreal treatment alone versus combined systemic and intravitreal treatment are warranted.

Postnatal development alters functional compartmentalization of myosin light chain kinase in ovine carotid arteries.

The rate-limiting enzyme for vascular contraction, myosin light chain kinase (MLCK), phosphorylates regulatory myosin light chain (MLC20) at rates that appear faster despite lower MLCK abundance in fetal compared with adult arteries. This study explores the hypothesis that greater apparent tissue activity of MLCK in fetal arteries is due to age-dependent differences in intracellular distribution of MLCK in relation to MLC20. Under optimal conditions, common carotid artery homogenates from nonpregnant adult female sheep and near-term fetuses exhibited similar values of Vmax and Km for MLCK. A custom-designed, computer-controlled apparatus enabled electrical stimulation and high-speed freezing of arterial segments at exactly 0, 1, 2, and 3 s, calculation of in situ rates of MLC20 phosphorylation, and measurement of time-dependent colocalization between MLCK and MLC20. The in situ rate of MLC20 phosphorylation divided by total MLCK abundance averaged to values 147% greater in fetal (1.06 ± 0.28) than adult (0.43 ± 0.08) arteries, which corresponded, respectively, to 43 ± 10% and 31 ± 3% of the Vmax values measured in homogenates. Confocal colocalization analysis revealed in fetal and adult arteries that 33 ± 6% and 20 ± 5% of total MLCK colocalized with pMLC20, and that MLCK activation was greater in periluminal than periadventitial regions over the time course of electrical stimulation in both age groups. Together, these results demonstrate that the catalytic activity of MLCK is similar in fetal and adult arteries, but that the fraction of total MLCK in the functional compartment involved in contraction is significantly greater in fetal than adult arteries.

Maternal Undernutrition Modulates Neonatal Rat Cerebrovascular Structure, Function, and Vulnerability to Mild Hypoxic-Ischemic Injury via Corticosteroid-Dependent and -Independent Mechanisms.

The present study explored the hypothesis that an adverse intrauterine environment caused by maternal undernutrition (MUN) acted through corticosteroid-dependent and -independent mechanisms to program lasting functional changes in the neonatal cerebrovasculature and vulnerability to mild hypoxic-ischemic (HI) injury. From day 10 of gestation until term, MUN and MUN-metyrapone (MUN-MET) group rats consumed a diet restricted to 50% of calories consumed by a pair-fed control; and on gestational day 11 through term, MUN-MET groups received drinking water containing MET (0.5 mg/mL), a corticosteroid synthesis inhibitor. P9/P10 pups underwent unilateral carotid ligation followed 24 h later by 1.5 h exposure to 8% oxygen (HI treatment). An ELISA quantified MUN-, MET-, and HI-induced changes in circulating levels of corticosterone. In P11/P12 pups, MUN programming promoted contractile differentiation in cerebrovascular smooth muscle as determined by confocal microscopy, modulated calcium-dependent contractility as revealed by cerebral artery myography, enhanced vasogenic edema formation as indicated by T2 MRI, and worsened neurobehavior MUN unmasked HI-induced improvements in open-field locomotion and in edema resolution, alterations in calcium-dependent contractility and promotion of contractile differentiation. Overall, MUN imposed multiple interdependent effects on cerebrovascular smooth muscle differentiation, contractility, edema formation, flow-metabolism coupling and neurobehavior through pathways that both required, and were independent of, gestational corticosteroids. In light of growing global patterns of food insecurity, the present study emphasizes that infants born from undernourished mothers may experience greater risk for developing neonatal cerebral edema and sensorimotor impairments possibly through programmed changes in neonatal cerebrovascular function.

PROFOUND VISUAL RECOVERY AT 16 MONTHS AFTER RESOLUTION OF SEROUS RETINAL DETACHMENTS SECONDARY TO THROMBOTIC THROMBOCYTOPENIC PURPURA: CASE REPORT AND LITERATURE REVIEW.

PURPOSE: To report a unique case of dramatic improvement in objective visual function during the recovery phase, after resolution of thrombotic thrombocytopenic purpura-related serous retinal detachments and to review prognostic trends in reported cases involving the macula. METHODS: Observational case report and literature review. RESULTS: A 36-year-old white woman with thrombotic thrombocytopenic purpura developed vision loss from serous retinal detachments in both eyes. Over a 16-month period, after both retinae remained attached, best-corrected visual acuity improved from 20/400 to 20/50 in both eyes with dramatic improvement on optical coherence tomography and autofluorescence imaging. CONCLUSION: Although thrombotic thrombocytopenic purpura is a life-threatening illness, visual prognosis in patients with macula off serous retinal detachments appears excellent. Most cases reviewed in literature improved to baseline visual acuity, but recovery periods ranged from days to many months. Hyperautofluorescent granularity on autofluorescence photography may be an indicator of chronic retinal detachment and a more delayed visual recovery.

Hypoxic modulation of fetal vascular MLCK abundance, localization, and function.

Changes in vascular contractility are among the most important physiological effects of acute and chronic fetal hypoxia. Given the essential role of myosin light-chain kinase (MLCK) in smooth muscle contractility and its heterogeneous distribution, this study explores the hypothesis that subcellular changes in MLCK distribution contribute to hypoxic modulation of fetal carotid artery contractility. Relative to common carotid arteries from normoxic term fetal lambs (FN), carotids from fetal lambs gestated at high altitude (3,802 m) (FH) exhibited depressed contractility without changes in MLCK mRNA or protein abundance. Patterns of confocal colocalization of MLCK with α-actin and 20-kDa regulatory myosin light chain (MLC20) enabled calculation of subcellular MLCK fractions: 1) colocalized with the contractile apparatus, 2) colocalized with α-actin distant from the contractile apparatus, and 3) not colocalized with α-actin. Chronic hypoxia did not affect MLCK abundance in the contractile fraction, despite a concurrent decrease in contractility. Organ culture for 72 h under 1% O2 decreased total MLCK abundance in FN and FH carotid arteries, but decreased the contractile MLCK abundance only in FH carotid arteries. Correspondingly, culture under 1% O2 depressed contractility more in FH than FN carotid arteries. In addition, hypoxia appeared to attenuate ubiquitin-independent proteasomal degradation of MLCK, as reported for other proteins. In aggregate, these results demonstrate that the combination of chronic hypoxia followed by hypoxic culture can induce MLCK translocation among at least three subcellular fractions with possible influences on contractility, indicating that changes in MLCK distribution are a significant component of fetal vascular responses to hypoxia.

Approach to Cataract Surgery in an Ebola Virus Disease Survivor with Prior Ocular Viral Persistence.

A 46-year-old patient with previously documented Ebola virus persistence in his ocular fluid, associated with severe panuveitis, developed a visually significant cataract. A multidisciplinary approach was taken to prevent and control infection. Ebola virus persistence was assessed before and during the operation to provide safe, vision-restorative phacoemulsification surgery.

Treatment of presumed Nocardia endophthalmitis and subretinal abscess with serial intravitreal amikacin injections and pars plana vitrectomy.

A 64-year-old man with a past medical history of liver transplantation on chronic immunosuppressive therapy presented with gradual worsening of vision over 2 months in his right eye. His recent history of Aspergillus and Nocardia pneumonia with positive bronchoalveolar lavage, in concert with vitritis and subretinal abscess, were concerning for endogenous endophthalmitis. A sputum culture and transbronchial lung biopsy stains grew Nocardia farcinica although aqueous humor sampling was negative. He was treated with four serial amikacin intravitreal injections over the course of 4 weeks. Pars plana vitrectomy for worsening macular traction and subsequent cataract surgery resulted in significant clinical and anatomic improvement of vision to 20/60 and consolidation of the subretinal abscess.

Metastatic breast carcinoma involving the optic disc.

PURPOSE: To report a rare case of unilateral optic nerve metastasis without choroidal involvement in a patient with known metastatic carcinoma of the breast. OBSERVATIONS: A 65-year old female with a history of metastatic breast carcinoma presented to our clinic with a one-month history of blurred vision and floaters of the left eye. Fundoscopy of the left eye revealed a flesh colored nodule with white lobules demonstrating an endophytic growth pattern from the optic nerve. Magnetic resonance imaging of the brain and orbits revealed multiple intraparenchymal enhancing lesions, leptomeningeal enhancement, and enhancement of the left optic disc and proximal optic nerve all consistent with metastatic disease. The diffuse cranial disease was treated with whole brain radiation leading to regression of the optic nerve lesion and stabilization of visual acuity. CONCLUSIONS AND IMPORTANCE: Intraocular metastases are the most common malignant tumor of the eye. Prompt identification and treatment of intraocular metastases is vital to prevent severe visual loss. Here, we document an unusual case of optic disc metastasis with unique fundoscopic features.

Acute Treatment With Gleevec Does Not Promote Early Vascular Recovery Following Intracerebral Hemorrhage in Adult Male Rats.

Intracerebral hemorrhage (ICH) remains one of the most debilitating types of stroke and is characterized by a sudden bleeding from a ruptured blood vessel. ICH often results in high mortality and in survivors, permanent disability. Most studies have focused on neuroprotective strategies designed to minimize secondary consequences and prevent further pathology. Lacking is an understanding of how ICH acutely affects cerebrovascular components and their response to therapeutic interventions. We hypothesized that ICH alters cortical vessel complexity in the parenchyma adjacent to site of the initial vascular disruption and that vascular abnormalities would be mitigated by administration of the PDGFR inhibitor, Imatinib mesylate (Gleevec). Briefly, ICH was induced in male adult rats by injection of collagenase into basal ganglia, followed by Gleevec administration (60 mg/kg) 1 h after injury. Rats were then perfused using vessel painting methodology (Salehi et al., 2018b) to stain whole brain vascular networks at 1 day post-ICH. Axial and coronal wide field fluorescence microscopy was performed. Analyses for vascular features were undertaken and fractal analysis for vascular complexity. Data were collected from four groups of rats: Sham + Vehicle; Sham + Gleevec; ICH + Vehicle; ICH + Gleevec. Microscopy revealed that cortical vessels in both ipsi- and contralateral hemispheres exhibited significantly reduced density and branching by 22 and 34%, respectively. Fractal measures confirmed reduced complexity as well. Gleevec treatment further reduced vascular parameters, including reductions in vessel density in tissues adjacent to the ICH. The reductions in brain wide vascular networks after Gleevec in the current study after ICH is contrasted by previous reports of improved behavioral outcomes and decreased lCH lesion volumes Reductions in the vascular network after Gleevec may be involved in long-term repair mechanisms by pruning injured vessels to ultimately promote new vessel growth.

Acute intranasal osteopontin treatment in male rats following TBI increases the number of activated microglia but does not alter lesion characteristics.

Intranasal recombinant osteopontin (OPN) has been shown to be neuroprotective in different models of acquired brain injury but has never been tested after traumatic brain injury (TBI). We used a model of moderate-to-severe controlled cortical impact in male adult Sprague Dawley rats and tested our hypothesis that OPN treatment would improve neurological outcomes, lesion and brain tissue characteristics, neuroinflammation, and vascular characteristics at 1 day post-injury. Intranasal OPN administered 1 hr after the TBI did not improve neurological score, lesion volumes, blood-brain barrier, or vascular characteristics. When assessing neuroinflammation, we did not observe any effect of OPN on the astrocyte reactivity but discovered an increased number of activated microglia within the ipsilateral hemisphere. Moreover, we found a correlation between edema and heme oxygenase-1 (HO-1) expression which was decreased in OPN-treated animals, suggesting an effect of OPN on the HO-1 response to injury. Thus, OPN may increase or accelerate the microglial response after TBI, and early response of HO-1 in modulating edema formation may limit the secondary consequences of TBI at later time points. Additional experiments and at longer time points are needed to determine if intranasal OPN could potentially be used as a treatment after TBI where it might be beneficial by activating protective signaling pathways.

EFFECT OF LUBRICANTS ON CORNEAL THICKNESS AFTER VITRECTOMY.

PURPOSE: This study examines the impact of corneal surface lubricants used during pars plana vitrectomy on corneal edema. METHODS: This prospective, observational, clinical study occurred at an academic institution. Participants were individuals aged 18 years and older who had already consented to undergo pars plana vitrectomy, without pre-existing corneal pathology. A corneal lubricant was chosen by the surgeon. Corneal thickness was measured preoperatively and postoperatively using pachymetry and anterior segment optical coherence tomography (AS-OCT). Main outcome measure was change in corneal thickness as measured by pachymetry. RESULTS: Forty-one patients completed the study protocol. The 23 subjects in the SHCS group had a significantly smaller increase in corneal thickness as measured by pachymetry compared with the 18 subjects in the HPMC group (29.9 µm vs. 58.1 µm, P value 0.02). When measured by anterior segment optical coherence tomography, the SHCS group had a smaller increase in corneal thickness compared with the HPMC group (0.04 mm vs. 0.06 mm, P value 0.09) but did not reach significance. CONCLUSION: SHCS is associated with reduced postoperative increase in corneal pachymetry as compared to HPMC.

Prenatal metyrapone treatment modulates neonatal cerebrovascular structure, function, and vulnerability to mild hypoxic-ischemic injury.

This study explored the hypothesis that late gestational reduction of corticosteroids transforms the cerebrovasculature and modulates postnatal vulnerability to mild hypoxic-ischemic (HI) injury. Four groups of Sprague-Dawley neonates were studied: 1) Sham-Control, 2) Sham-MET, 3) HI-Control, and 4) HI-MET. Metyrapone (MET), a corticosteroid synthesis inhibitor, was administered via drinking water from gestational day 11 to term. In Shams, MET administration 1) decreased reactivity of the hypothalamic-pituitary-adrenal (HPA) axis to surgical trauma in postnatal day 9 (P9) pups by 37%, 2) promoted cerebrovascular contractile differentiation in middle cerebral arteries (MCAs), 3) decreased compliance ≤46% and increased depolarization-induced calcium mobilization in MCAs by 28%, 4) mildly increased hemispheric cerebral edema by 5%, decreased neuronal degeneration by 66%, and increased astroglial and microglial activation by 10- and 4-fold, respectively, and 5) increased righting reflex times by 29%. Regarding HI, metyrapone-induced fetal transformation 1) diminished reactivity of the HPA axis to HI-induced stress in P9/P10 pups, 2) enhanced HI-induced contractile dedifferentiation in MCAs, 3) lessened the effects of HI on MCA compliance and calcium mobilization, 4) decreased HI-induced neuronal injury but unmasked regional HI-induced depression of microglial activation, and 5) attenuated the negative effects of HI on open-field exploration but enhanced the detrimental effects of HI on negative geotaxis responses by 79%. Overall, corticosteroids during gestation appear essential for normal cerebrovascular development and glial quiescence but induce persistent changes that in neonates manifest beneficially as preservation of postischemic contractile differentiation but detrimentally as worsened ischemic cerebrovascular compliance, increased ischemic neuronal injury, and compromised neurobehavior.

MicroRNAs in brain development and cerebrovascular pathophysiology.

MicroRNAs (miRNAs) are a class of highly conserved non-coding RNAs with 21-25 nucleotides in length and play an important role in regulating gene expression at the posttranscriptional level via base-paring with complementary sequences of the 3'-untranslated region of the target gene mRNA, leading to either transcript degradation or translation inhibition. Brain-enriched miRNAs act as versatile regulators of brain development and function, including neural lineage and subtype determination, neurogenesis, synapse formation and plasticity, neural stem cell proliferation and differentiation, and responses to insults. Herein, we summarize the current knowledge regarding the role of miRNAs in brain development and cerebrovascular pathophysiology. We review recent progress of the miRNA-based mechanisms in neuronal and cerebrovascular development as well as their role in hypoxic-ischemic brain injury. These findings hold great promise, not just for deeper understanding of basic brain biology but also for building new therapeutic strategies for prevention and treatment of pathologies such as cerebral ischemia.