Automatic Segmentation and Measurement of Choroid Layer in High Myopia for OCT Imaging Using Deep Learning.

Automatic segmentation and measurement of the choroid layer is useful in studying of related fundus diseases, such as diabetic retinopathy and high myopia. However, most algorithms are not helpful for choroid layer segmentation due to its blurred boundaries and complex gradients. Therefore, this paper aimed to propose a novel choroid segmentation method that combines image enhancement and attention-based dense (AD) U-Net network. The choroidal images obtained from optical coherence tomography (OCT) are pre-enhanced by algorithms that include flattening, filtering, and exponential and linear enhancement to reduce choroid-independent information. Experimental results obtained from 800 OCT B-scans of the choroid layers from both normal eyes and high myopia showed that image enhancement significantly increased the performance of ADU-Net, with an AUC of 99.51% and a DSC of 97.91%. The accuracy of segmentation using the ADU-Net method with image enhancement is superior to that of the existing networks. In addition, we describe some algorithms that can measure automatically choroidal foveal thickness and the volume of adjacent areas. Statistical analyses of the choroidal parameters variation indicated that compared with normal eyes, high myopia has a reduction of 86.3% of the choroidal foveal thickness and 90% of the adjacent volume. It proved that high myopia is likely to cause choroid layer attenuation. These algorithms would have wide application in the diagnosis and precaution of related fundus lesions caused by choroid thinning from high myopia in future studies.

Deep-MSIM: Fast Image Reconstruction with Deep Learning in Multifocal Structured Illumination Microscopy.

Fast and precise reconstruction algorithm is desired for for multifocal structured illumination microscopy (MSIM) to obtain the super-resolution image. This work proposes a deep convolutional neural network (CNN) to learn a direct mapping from raw MSIM images to super-resolution image, which takes advantage of the computational advances of deep learning to accelerate the reconstruction. The method is validated on diverse biological structures and in vivo imaging of zebrafish at a depth of 100 µm. The results show that high-quality, super-resolution images can be reconstructed in one-third of the runtime consumed by conventional MSIM method, without compromising spatial resolution. Last but not least, a fourfold reduction in the number of raw images required for reconstruction is achieved by using the same network architecture, yet with different training data.

The MCK mouse heart model of Friedreich's ataxia: Alterations in iron-regulated proteins and cardiac hypertrophy are limited by iron chelation.

There is no effective treatment for the cardiomyopathy of the most common autosomal recessive ataxia, Friedreich's ataxia (FA). The identification of potentially toxic mitochondrial (MIT) iron (Fe) deposits in FA suggests that Fe plays a role in its pathogenesis. This study used the muscle creatine kinase conditional frataxin (Fxn) knockout (mutant) mouse model that reproduces the classical traits associated with cardiomyopathy in FA. We examined the mechanisms responsible for the increased cardiac MIT Fe loading in mutants. Moreover, we explored the effect of Fe chelation on the pathogenesis of the cardiomyopathy. Our investigation showed that increased MIT Fe in the myocardium of mutants was due to marked transferrin Fe uptake, which was the result of enhanced transferrin receptor 1 expression. In contrast to the mitochondrion, cytosolic ferritin expression and the proportion of cytosolic Fe were decreased in mutant mice, indicating cytosolic Fe deprivation and markedly increased MIT Fe targeting. These studies demonstrated that loss of Fxn alters cardiac Fe metabolism due to pronounced changes in Fe trafficking away from the cytosol to the mitochondrion. Further work showed that combining the MIT-permeable ligand pyridoxal isonicotinoyl hydrazone with the hydrophilic chelator desferrioxamine prevented cardiac Fe loading and limited cardiac hypertrophy in mutants but did not lead to overt cardiac Fe depletion or toxicity. Fe chelation did not prevent decreased succinate dehydrogenase expression in the mutants or loss of cardiac function. In summary, we show that loss of Fxn markedly alters cellular Fe trafficking and that Fe chelation limits myocardial hypertrophy in the mutant.

Proteomic analysis of hearts from frataxin knockout mice: marked rearrangement of energy metabolism, a response to cellular stress and altered expression of proteins involved in cell structure, motility and metabolism.

A frequent cause of death in Friedreich's ataxia patients is cardiomyopathy, but the molecular alterations underlying this condition are unknown. We performed 2-DE to characterize the changes in protein expression of hearts using the muscle creatine kinase frataxin conditional knockout (KO) mouse. Pronounced changes in protein expression profile were observed in 9 week-old KO mice with severe cardiomyopathy. In contrast, only several proteins showed altered expression in asymptomatic 4 week-old KO mice. In hearts from frataxin KO mice, components of the iron-dependent complex-I and -II of the mitochondrial electron transport chain and enzymes involved in ATP homeostasis (creatine kinase, adenylate kinase) displayed decreased expression. Interestingly, the KO hearts exhibited increased expression of enzymes involved in the citric acid cycle, catabolism of branched-chain amino acids, ketone body utilization and pyruvate decarboxylation. This constitutes evidence of metabolic compensation due to decreased expression of electron transport proteins. There was also pronounced up-regulation of proteins involved in stress protection, such as a variety of chaperones, as well as altered expression of proteins involved in cellular structure, motility and general metabolism. This is the first report of the molecular changes at the protein level which could be involved in the cardiomyopathy of the frataxin KO mouse.

Sustained expression of heme oxygenase-1 alters iron homeostasis in nonerythroid cells.

Heme oxygenases initiate the catabolism of heme, releasing carbon monoxide, iron, and biliverdin. Sustained induction of heme oxygenase-1 (HO-1) in nonerythroid cells plays a key role in many pathological processes, yet the effect of long-term HO-1 expression on cellular iron metabolism in the absence of exogenous heme is poorly understood. Here we report that in a model nonerythroid cell, both transient and stable HO-1 expression increased heme oxygenase activity, but total cellular heme content was decreased only with transient enzyme expression. Sustained HO-1 activity increased the expression of both the mitochondrial iron importer mitoferrin-2 and the rate-limiting enzyme in heme synthesis, aminolevulinate synthase-1, and it augmented the mitochondrial content of heme. Also, the expression of transferrin receptor-1 and the activities of iron-regulatory proteins 1 and 2 decreased, whereas total labile iron and the regulatory activity of the heme-binding transcription factor Bach1 were unaltered. In addition, stable, but not transient, HO-1 expression decreased the activities of aconitase, as well as increasing proteasomal degradation of ferritin. Together, our results reveal a novel and coordinated adaptive response of nonerythroid cells to sustained HO-1 induction that has an impact on cellular iron homeostasis.