Search

Branch retinal vein occlusion (BRVO) is a frequent retinal vascular disease that may cause extensive microvascular remodeling leading to severe visual impairment. Little is known regarding the histology of non-neovascular microvascular remodeling. Here, we examined by confocal microscopy the structure of retinal microvessels of a donor eye with longstanding BRVO. The post-mortem retina of a 91-year-old woman that had superotemporal BRVO for 2 years was examined by confocal microscopy after anti-collagen IV (collIV), alpha-smooth muscle cell (αSMA), and anti-von Willebrand factor (vWf) immunolabeling. In the retinal quadrant affected by BRVO, extensive vascular remodeling affected all vessels, from arterioles to venules, including the foveal avascular zone. Most affected vessels were either irregularly dilated or, on the opposite, reduced to micrometric-size CollIV positive, vWf negative, nuclear-staining negative strings. Telangiectatic capillaries of various sizes and shapes were seen, the largest one (233 μm) being located in the parafoveal area. Some telangiectatic capillaries had a thick, multilayered vWf- and CollIV-positive wall, that often occluded the lumen. Other features included double-channeled arterioles. The majority of microvascular abnormalities were devoid of nuclear staining, suggesting extensive loss of endothelial cells. We describe the spectrum of microvascular abnormalities upstream of a longstanding BRVO. This spectrum comprises a large parafoveal telangiectatic capillary corresponding to what has been previously clinically defined as TelCap. The absence of intraluminal nuclear staining in the majority of abnormal vessels raises the hypothesis that the loss of endothelial cells plays a crucial role in the development of the different manifestations of capillary remodeling. The presence of vWF in de-endothelialized vessels suggests deposition of plasma, hence that they may remain perfused. Our work may help to understand the clinical imaging features of TelCaps.

The ocular vasculature is critically involved in many blinding diseases and is also a popular research model for the exploration of developmental and pathological angiogenesis. The development of ocular vessels is a complex, finely orchestrated sequence of events, involving spatial and temporal coordination of hyaloid, choroidal and retinal networks. Comprehensive studies of the tridimensional dynamics of microvascular remodeling are limited by the fact that preserving the spatial disposition of ocular vascular networks is cumbersome using classical histological procedures. Here, we demonstrate that light-sheet fluorescence microscopy (LFSM) of cleared mouse eyes followed by extensive virtual dissection offers a solution to this problem. To the best of our knowledge, this is the first 3D quantification of the evolution of the hyaloid vasculature and of post-occlusive venous remodeling together with the characterization of spatial distribution of various cell populations in ocular compartments, including the vitreous. These techniques will prove interesting to obtain other insights in scientific questions addressing organ-wide cell interactions.

Retinal degenerative diseases lead to the blindness of millions of people around the world. In case of age-related macular degeneration (AMD), the atrophy of retinal pigment epithelium (RPE) precedes neural dystrophy. But as crucial as understanding both healthy and pathological RPE cell physiology is for those diseases, no current technique allows subcellular in vivo or in vitro live observation of this critical cell layer. To fill this gap, we propose dynamic full-field OCT (D-FFOCT) as a candidate for live observation of in vitro RPE phenotype. In this way, we monitored primary porcine and human stem cell-derived RPE cells in stress model conditions by performing scratch assays. In this study, we quantified wound healing parameters on the stressed RPE, and observed different cell phenotypes, displayed by the D-FFOCT signal. In order to decipher the subcellular contributions to these dynamic profiles, we performed immunohistochemistry to identify which organelles generate the signal and found mitochondria to be the main contributor to D-FFOCT contrast. Altogether, D-FFOCT appears to be an innovative method to follow degenerative disease evolution and could be an appreciated method in the future for live patient diagnostics and to direct treatment choice.

Dynamic FFOCT allows us to record the intrinsic motion of biological samples in 3D, over hours. We performed scratch assays on primary porcine RPE and human induced pluripotent stem cells derived RPE cell cultures. We plotted motion maps from the optical flow. For wounds

Pavlovian aversive conditioning requires learning of the association between a conditioned stimulus (CS) and an unconditioned, aversive stimulus (US) but also involves encoding the time interval between the two stimuli. The neurobiological bases of this time interval learning are unknown. Here, we show that in rats, the dorsal striatum and basal amygdala belong to a common functional network underlying temporal expectancy and learning of a CS–US interval. Importantly, changes in coherence between striatum and amygdala local field potentials (LFPs) were found to couple these structures during interval estimation within the lower range of the theta rhythm (3–6 Hz). Strikingly, we also show that a change to the CS–US time interval results in long-term changes in cortico-striatal synaptic efficacy under the control of the amygdala. Collectively, this study reveals physiological correlates of plasticity mechanisms of interval timing that take place in the striatum and are regulated by the amygdala., Aversive conditioning requires the learning of time intervals between conditioned and unconditioned stimuli, as well as the associations of the stimuli themselves. Here the authors show that dorsal striatum and basal amygdala are part of a functional network that encodes interval timing.

Author(s): Boulanger Bertolus, Julie; Knippenberg, Jeroen; Verschueren, Anna; Le Blanc, Pascale; Brown, Bruce L.; Mouly, Anne-Marie; Doyere, Valerie | Abstract: The accuracy of time judgments depends upon many factors, including the sensory properties of the to-be-timed stimulus. In auditory Pavlovian fear conditioning, an initially neutral tone (conditioned stimulus, CS) predicts the arrival of an aversive event (unconditioned stimulus, US) at a fixed time interval. The temporal relation between the CS and US events is encoded, leading to the development of a temporal pattern of responding. Little attention has been paid to the potential impact of the characteristics of the CS tone on the development of this temporal pattern. Here we compared the acquisition of the temporal pattern of conditioned responses of rats to different CS tone frequencies. Rats were first conditioned to lever press for food. Then, while lever pressing for food, they were presented with 60-s tones of two very different frequencies 1kHz or 11kHz, each paired with a foot-shock given 30s after tone onset. This fear conditioning led to the appearance of conditioned suppression of the lever pressing. On probe trials the tone duration was 60 s, and the reinforcer was omitted. With training, a pattern of suppression evolved during the probe trials, showing a maximum of suppression near the programmed time of the shock US, however the 11kHz CS tone yielded better temporal control than did the 1kHz tone. A second experiment investigated rats’ abilities to discriminate between two times of shock arrival (10s or 30s) predicted by the different tone frequencies (1kHz or 11kHz), In this experiment, rats showed poorer discriminative timing performance when the lower frequency (1kHz) was associated with the longer duration (30s). Our results suggest a strong impact of the CS sensory properties on the expression of temporal learning within the context of auditory fear conditioning in rats.