Chao Zhou

Hypothesis: A dual fiber-based optical coherence tomography (OCT) system can be used for real-time intracochlear navigation and distance computation in the human cochlea. Background: OCT is a contrast- and radiation-free modality that provides real-time 2- and 3-dimensional imaging of tissue microanatomy at higher resolutions than those of conventional MRI or CT. Because the fundamental working principle of OCT is to measure the time delay of backscattered near-infrared light using low-coherence interferometry, OCT functions as an intrinsic light-based distance sensor. Methods: A single- and dual-fiber attached to a custom-built 1310 nm swept-source (SS) OCT system was validated in cochlear phantoms and tested in a human cadaveric cochlea to compute the distance of the fibers from the lateral and medial walls. Curvature and distance of the fibers to the lateral and medial walls of the scala tympani were obtained during insertion and pull-back of the fibers as accessed through a round window approach. Results: Our fiber-based SS-OCT system can detect a maximum distance of 7.10 mm with an axial resolution of 10 µm at an acquisition speed of 8 µs. Using space-division multiplexing (SDM) for our dual fiber, we were able to simultaneously obtain distance measurements from 2 spatially separated locations without the need for mechanical rotation. Furthermore, our custom user interface provided an immediate 3-color-coded warning system, which facilitated real-time microadjustments of fiber trajectory to avoid intracochlear trauma. Conclusion: A dual fiber-based SDM-OCT system can be used to provide real-time spatial navigation and distance calculation to the cochlear walls.

Purpose: Branch retinal vein occlusion (BRVO) is a common cause of retinal ischemia, rapidly inducing neuronal death and often producing irreversible vison loss. Interventions such as thrombolysis restore perfusion but cannot recover neurons already lost, and most patients retain permanent visual deficits. Identifying which neuronal populations die, and how rapidly, may therefore reveal timing windows and targets for neuroprotective treatment. To determine the timing of pathology, we evaluated vascular changes and neuronal degeneration in a photocoagulation-induced mouse model of BRVO. To determine differences in retinal ganglion cells (RGC) type susceptibility, we tracked the survival of RGC subpopulations using immunofluorescence markers. Methods: BRVO was induced by Rose Bengal injection followed by targeted photocoagulation of a branch vein. Obstruction was confirmed by fluorescein angiography and vascular damage assessed by optical coherence tomography angiography. Cell survival was quantified by immunostaining at 3, 7, and 14 days using RNA-Binding Protein with Multiple Splicing (RBPMS, pan-RGC). RGC subtype markers for intrinsically photosensitive RGCs (TBR2), α-RGCs (SPP1), ON–OFF direction-selective RGCs (CART), and F-RGCs (FOXP2) were used to compare subtype survival. Results: Occlusion selectively disrupted the superficial and intermediate capillary plexus, sparing the deep plexuses. All examined neuronal populations were significantly depleted, but with markedly different magnitude and timing. α-RGCs and F-RGCs were the most vulnerable subtypes, both approaching complete loss by one week, whereas intrinsically photosensitive RGCs were the most resistant. Conclusions: α-RGCs, typically resilient in glaucoma, trauma, and excitotoxicity, were markedly vulnerable in BRVO, indicating that RGC subtype susceptibility is insult-specific.

Biological tissues intrinsically scatter light, which limits the depth of penetration of optical imaging. Optical coherence tomography (OCT) is a non-invasive, label-free imaging modality that generates real-time 2- and 3- dimensional in vivo images with high spatial resolution (in vivo and ex vivo animal models. In this study, we investigated the application of tartrazine to optically clear the TM of human cadaveric specimens using a custom-built 1310 nm swept-source OCT system. We demonstrate that tartrazine is an effective OCA for the TM and improves the quality of visualization for OCT imaging into the middle ear, highlighting the potential clinical application of tartrazine to improve the noninvasive diagnosis of middle ear pathologies using OCT.

Mouse models are valuable for studying the systemic effects of arrhythmia, but traditional methods of heart pacing are invasive and technically complex. Cardiac optogenetics enables precise control of cardiac activity using light-sensitive ion channels and has been used for tachypacing, resynchronization, and defibrillation in animal models. Recent advances in opsins with red-shifted activation spectra and optimized light delivery strategies have enhanced noninvasive pacing approaches, particularly in mammalian models. Here, we use an area illumination approach for light stimulation through the intact chest to perform in vivo, noninvasive optogenetic tachypacing in transgenic mice expressing ReaChR with low irradiance (2 ). We assess both cardiac and cortical hemodynamic responses via echocardiography and optical intrinsic signal imaging (OISI). Our findings reveal that whole-heart arrhythmic stimulation alters cortical hemodynamic activity, highlighting the direct impact of arrhythmias on brain perfusion and oxygenation. This work provides insight into the heart-brain connection and the broader systemic consequences of cardiac dysfunction.

Inflammatory bowel diseases, including Crohn’s Disease (CD) and Ulcerative Colitis (UC), are characterized by inflammation of the gastrointestinal tract. Early diagnoses are critical in the determination of an effective treatment. Current methods of tissue assessment remain two-dimensional and limited by lack of information under the surface of the mucosal layer. Optical coherence tomography (OCT) is a noninvasive, label-free, volumetric imaging modality which can visualize tissue structures down to the micrometer scale. Previous study has explored OCT as a method for endoscopic and benchtop assessment of colonic tissues. Here, we explore OCT in an ex vivo capacity to visualize features in IBD. Samples from human subjects with normal (not inflamed), UC, and CD diagnoses were imaged, where OCT was able to differentiate between normal ileal and colonic tissue and those from patients with CD or UC. Our study shows the promise of higher-resolution OCT to visualize both small details and overall structures in three-dimensions, informing development of future technologies.

Retinal vasculopathy with cerebral leukoencephalopathy and systemic manifestations (RVCL-S) is a disease that causes deterioration of small vessels, affecting various organs: eyes, brain, liver, and others. The RVCL-S carriers have lower life expectancy. There is no cure available to date. The disease has been linked to mutations in TREX1 gene disrupting its cytoplasmic localization. To facilitate the disease mechanism investigation, we employed model organism D. melanogaster, identified human TREX1 ortholog cg3165, and confirmed its vital significance to flies. Then, we expressed human TREX1 and its mutant form TREX1 V235Gfs in flies and used optical coherence microscopy (OCM) to monitor the dynamics of flies’ vascular system. We detected the relapse of fly dorsal vessel, movement impairment, and reduced longevity in TREX1 V235Gfs-expressing transgenic animals. Vascular deterioration and shorter life span recapitulate the RVCL-S manifestations in humans. We have established a robust quantitative Drosophila RVCL-S phenotypic system that can potentially serve as a screening platform for drug discovery and drug targets identification.

PurposeAccurate artery–vein (AV) differentiation in small-field macular optical coherence tomography angiography (OCTA) remains challenging due to a lack of standardized guidelines. We propose and validate criteria for 3×3 mm2 (10 deg× 10 deg on Spectralis; ∼2.9×2.9 mm2) macular scans.ApproachSmall field-of-view (FOV) OCTA scans were analyzed using established AV criteria for large-field (12×12 mm2) OCTA, as applied by two masked readers and validated against color fundus photographs (CFPs) and near-infrared reflectance (NIR) images. Accuracy and reliability (Cohen’s κ) were assessed. Pixel-level AV masks were annotated with a standardized threshold. Vessel diameters and intensities were compared within our dataset and in the publicly available OCTA-500 dataset to assess whether intrinsic vessel features support AV differentiation.ResultsA total of 465 vessels from 20 healthy eyes were evaluated across 3 pseudo-branching orders using the criteria for OCTA. Annotators achieved high accuracy (95.1%, 92.3%) and strong intra/inter-rater reliability (κ=0.84) with similarly high AV classification accuracy within pseudo-third-order vessels (97.15%). No significant AV diameter differences were observed in either dataset (p=0.261 and 0.442). The mean intensity was similar in our dataset (p=0.277; |Δ|=3.28, 1.45% relative difference) but higher for veins in OCTA-500 (p<0.0001; |Δ|=3.42, 1.63% relative difference).ConclusionsAccurate and reproducible AV labeling is feasible in 3×3 mm2 scans, with strong inter- and intra-rater agreement. Vessel diameter and intensity add limited value. NIR-based alignment of OCTA with CFP provides reliable ground truth, supporting consistent manual labeling and OCTA segmentation.

The knock-out mutation of the unique M13 family member, the Drosophila melanogaster (fruit fly) Neprilysin-like 15 ( Nepl15 ), resulted in marked reductions of glycogen and glycerolipid storage in adult male flies, but a significant increase of glycogen storage in adult female flies, although the mutant flies consumed the same amount of food as the isogenic w ¹¹¹⁸ controls. The findings prompted us to characterize sex and age-specific effects of Nepl15 knock-out ( Nepl15 ^KO ) mutation on lifespan, fertility and fecundity, physiology, cytophysiology, and overall health. The current study shows Nepl15 transcripts are expressed in all embryonic stages of the control flies. The mutant embryos show more glycogen storage, likely due to more maternal glycogen deposition in the eggs. Moreover, there are slight increases in the number of eggs laid, the percentage of pupariation, and the percentage of adult fly eclosion from pupae in the Nepl15 ^KO mutant flies. Interestingly, Nepl15 ^KO female, but not male flies, outlive the respective control flies when cultured on a standard diet. The mutant adult females show significantly less Target of Rapamycin ( TOR ) and more Sirtuin 6 ( Sirt6 ) expression, changes that may synergistically contribute to their lifespan extension. In contrast, mutant males exhibit significant reductions in both TOR and Sirt6 expression, potentially offsetting their effects on longevity. Cellular health is further improved in mutant females, as evidenced by a marked reduction in reactive oxygen species (ROS), associated with a 1.5-fold increase in the Superoxide dismutase 2 ( Sod2 ) expression at 7 days of age. Both sexes demonstrate improved gut barrier integrity at 40 days, with reduced “Smurf” leakage compared to age-matched controls. Optical cardiography reveals that heart rate in 40-day-old mutants is better preserved, resembling that of 7-day-old flies, whereas control flies show a pronounced age-associated decline. Functionally, Nepl15 ^KO males and females outperform controls in a 6-cm climbing assay at 10, 20, 30, and 40 days of age, with the greatest difference observed at day 40. Following a 45-minute exercise bout at 10 rpm, mutant females continue to outperform controls at both 7 and 40 days, indicating preserved neuromuscular performance. Consistently, ATP levels are significantly elevated in 7- and 40-day-old mutant females, but not in mutant males. Interestingly, only 7-day-old mutant males exhibit increased mitochondrial inner membrane potential, which may enable more rapid ATP turnover when energy demand arises. No detectable differences are observed in thoracic muscle or mitochondrial ultrastructure, nor in overall mitochondrial number. However, no observable changes are noticed in the ultrastructure of the thoracic muscle and mitochondria, and the overall number of mitochondria in the mutant flies. Collectively, our findings demonstrate that Nepl15 loss-of-function confers health benefits at cellular, organ, and organismal levels, with pronounced sex-specific differences. However, the mechanisms by which aging mutant males sustain enhanced functional performance remain elusive.

Retinal vasculopathy with cerebral leukoencephalopathy and systemic manifestations (RVCL-S) is a disease that causes deterioration of small vessels, affecting various organs: eyes, brain, liver, and others. The RVCL-S carriers have lower life expectancy. There is no cure available to date. The disease has been linked to mutations in TREX1 gene disrupting its cytoplasmic localization. To facilitate the disease mechanism investigation, we employed model organism D. melanogaster, identified human TREX1 ortholog cg3165 , and confirmed its vital significance to flies. Then, we expressed human TREX1 and its mutant form TREX1 V235Gfs in flies and used optical coherence microscopy (OCM) to monitor the dynamics of flies’ vascular system. We detected the relapse of fly dorsal vessel, movement impairment, and reduced longevity in TREX1 V235Gfs-expressing transgenic animals. Vascular deterioration and shorter life span recapitulate the RVCL-S manifestations in humans. We have established a robust quantitative Drosophila RVCL-S phenotypic system that can potentially serve as a screening platform for drug discovery and drug targets identification.