Assesment of apoptosis induced changes in scattering using optical coherence tomography

The impacts of resveratrol on the retinal degeneration in a rat model of retinitis pigmentosa induced by alkylation: an in-vivo study

Upregulation of Sirtuin Type 1 (SIRT1), a nicotinamide adeninedinucleotide (NAD⁺)-dependent deacetylase, has been proved to protect against ample ocular diseases, while its effect on retinitis pigmentosa (RP) has not been illustrated. The study was aimed to explore the impacts of resveratrol (RSV), a SIRT1 activator, on the photoreceptor degeneration in a rat model of RP induced by N-methyl-N-nitrosourea (MNU), an alkylation. The rats were induced RP phenotypes via the intraperitoneal injection of MNU. The electroretinogram was conducted and revealed that RSV could not prevent the decline of retinal function in the RP rats. The optical coherence tomography (OCT) and the retinal histological examination were performed and showed that the reduced thickness of the outer nuclear layer (ONL) was not preserved by RSV intervention. The immunostaining technique was applied. Afther the MNU administration, the number of the apoptotic photoreceptors in the ONL throughout the retinasand the number of microglia cells present among the outer part throughout the retinas were not significantly reduced by RSV. Western blotting was also performed. The data showed that the level of SIRT1 protein was decreased after MNU administration, while RSV was not able to obviously alleviate the downregulation. Our data together indicated that RSV was not able to rescue the photoreceptor degeneration in the MNU-induced RP rats, which might be due to the MNU-induced consumption of the NAD⁺.

Multiparametric Quantitative Analysis of Photodamage to Skin Using Optical Coherence Tomography

Ultraviolet (UV) irradiation causes 90% of photodamage to skin and long-term exposure to UV irradiation is the largest threat to skin health. To study the mechanism of UV-induced photodamage and the repair of sunburnt skin, the key problem to solve is how to non-destructively and continuously evaluate UV-induced photodamage to skin. In this study, a method to quantitatively analyze the structural and tissue optical parameters of artificial skin (AS) using optical coherence tomography (OCT) was proposed as a way to non-destructively and continuously evaluate the effect of photodamage. AS surface roughness was achieved based on the characteristic peaks of the intensity signal of the OCT images, and this was the basis for quantifying AS cuticle thickness using Dijkstra's algorithm. Local texture features within the AS were obtained through the gray-level co-occurrence matrix method. A modified depth-resolved algorithm was used to quantify the 3D scattering coefficient distribution within AS based on a single-scattering model. A multiparameter assessment of AS photodamage was carried out, and the results were compared with the MTT experiment results and H&E staining. The results of the UV photodamage experiments showed that the cuticle of the photodamaged model was thicker (56.5%) and had greater surface roughness (14.4%) compared with the normal cultured AS. The angular second moment was greater and the correlation was smaller, which was in agreement with the results of the H&E staining microscopy. The angular second moment and correlation showed a good linear relationship with the UV irradiation dose, illustrating the potential of OCT in measuring internal structural damage. The tissue scattering coefficient of AS correlated well with the MTT results, which can be used to quantify the damage to the bioactivity. The experimental results also demonstrate the anti-photodamage efficacy of the vitamin C factor. Quantitative analysis of structural and tissue optical parameters of AS by OCT enables the non-destructive and continuous detection of AS photodamage in multiple dimensions.

Optical coherence tomography of small intestine allograft biopsies using a handheld surgical probe

SIGNIFICANCE

The current gold standard for monitoring small intestinal transplant (IT) rejection is endoscopic visual assessment and biopsy of suspicious lesions; however, these lesions are only superficially visualized by endoscopy. Invasive biopsies provide a coarse sampling of tissue health without depicting the true presence and extent of any pathology. Optical coherence tomography (OCT) presents a potential alternative approach with significant advantages over traditional white-light endoscopy.

AIM

The aim of our investigation was to evaluate OCT performance in distinguishing clinically relevant morphological features associated with IT graft failure.

APPROACH

OCT was applied to evaluate the small bowel tissues of two rhesus macaques that had undergone IT of the ileum. The traditional assessment from routine histological observation was compared with OCT captured using a handheld surgical probe during the days post-transplant and subsequently was compared with histophaology.

RESULTS

The reported OCT system was capable of identifying major biological landmarks in healthy intestinal tissue. Following IT, one nonhuman primate (NHP) model suffered a severe graft ischemia, and the second NHP graft failed due to acute cellular rejection. OCT images show visual evidence of correspondence with histological signs of IT rejection.

CONCLUSIONS

Results suggest that OCT imaging has significant potential to reveal morphological changes associated with IT rejection and to improve patient outcomes overall.

Optical scattering as an early marker of apoptosis during chemotherapy and antiangiogenic therapy in murine models of prostate and breast cancer

Monitoring of the in vivo tumor state to track therapeutic response in real time may help to evaluate new drug candidates, maximize treatment efficacy, and reduce the burden of overtreatment. Current preclinical tumor imaging methods have largely focused on anatomic imaging (e.g., MRI, ultrasound), functional imaging (e.g., FDG-PET), and molecular imaging with exogenous contrast agents (e.g., fluorescence optical tomography). Here we utalize spatial frequency domain imaging (SFDI), a noninvasive, label-free optical technique, for the wide-field quantification of changes in tissue optical scattering in preclinical tumor models during treatment with chemotherapy and antiangiogenic agents. Optical scattering is particularly sensitive to tissue micro-architectural changes, including those that occur during apoptosis, an early indicator of response to cytotoxicity induced by chemotherapy, thermotherapy, cryotherapy, or radiation therapy. We utilized SFDI to monitor responses of PC3/2G7 prostate tumors and E0771 mammary tumors to treatment with cyclophosphamide or the antiangiogenic agent DC101 for up to 49 days. The SFDI-derived scattering amplitude was highly correlated with cleaved caspase-3, a marker of apoptosis (ρ_p = 0.75), while the exponent of the scattering wavelength-dependence correlated with the cell proliferation marker PCNA (ρ_p = 0.69). These optical parameters outperformed tumor volume and several functional parameters (e.g., oxygen saturation and hemoglobin concentration) as an early predictive biomarker of treatment response. Quantitative diffuse optical scattering is thus a promising new early marker of treatment response, which does not require radiation or exogenous contrast agents.

Protection of retinal function and morphology in MNU-induced retinitis pigmentosa rats by ALDH2: an in-vivo study

Background

Retinitis pigmentosa (RP) is a kind of inherited retinal degenerative diseases characterized by the progressive loss of photoreceptors. RP has been a conundrum without satisfactory countermeasures in clinic until now. Acetaldehyde dehydrogenase 2 (ALDH2), a major enzyme involved in aldehyde detoxification, has been demonstrated to be beneficial for a growing number of human diseases, such as cardiovascular dysfunction, diabetes mellitus and neurodegeneration. However, its protective effect against RP remains unknown. Our study explored the impact of ALDH2 on retinal function and structure in N-methyl-N-nitrosourea (MNU)-induced RP rats.

Methods

Rats were gavaged with 5 mg/kg Alda-1, an ALDH2 agonist, 5 days before and 3 days after MNU administration. Assessments of retinal function and morphology as well as measurement of specific proteins expression level were conducted.

Results

Electroretinogram recordings showed that Alda-1 administration alleviated the decrease in amplitude caused by MNU, rendering protection of retinal function. Mitigation of photoreceptor degeneration in MNU-treated retinas was observed by optical coherence tomography and retinal histological examination. In addition, Western blotting results revealed that ALDH2 protein expression level was upregulatedwith increased expression of SIRT1 protein after the Alda-1 intervention. Besides, endoplasmic reticulum stress (ERS) was reduced according to the significant downregulation of GRP78 protein, while apoptosis was ameliorated as shown by the decreased expression of PARP1 protein.

Conclusions

Together, our data demonstrated that ALDH2 could provide preservation of retinal function and morphology against MNU-induced RP, with the underlying mechanism at least partly related to the modulation of SIRT1, ERS and apoptosis.

Grading upper tract urothelial carcinoma with the attenuation coefficient of in-vivo optical coherence tomography

INTRODUCTION

With catheter based optical coherence tomography (OCT), high resolution images of the upper urinary tract can be obtained, thereby facilitating the detection of upper tract urothelial carcinomas (UTUC). We hypothesized that the attenuation coefficient of the OCT signal (μOCT ) is related to the histopathologic grade of the tumor.

OBJECTIVES

In this study, we aimed to define the μOCT cut-off for discriminating high grade and low grade papillary UTUC.

METHODS

For this post-hoc analysis, data from OCT imaging of papillary UTUC was obtained from patients during ureterorenoscopy. OCT images and raw data were simultaneously analyzed with in-house developed software. The μOCT determined in papillary UTUCs and corresponding histopathologic grading from either biopsies or radical resection specimens were compared.

RESULTS

Thirty-five papillary UTUC from 35 patients were included. μOCT analysis was feasible in all cases. The median μOCT was 3.3 mm-1 (IQR 2.7-3.7 mm-1 ) for low-grade UTUC and 4.9 mm-1 (IQR 4.3-6.1 mm-1 ) for high-grade UTUC (P = 0.004). ROC analysis yielded a μOCT cut-off value of >4.0 mm-1 (AUC = 0.85, P < 0.001) with a sensitivity of 83% and a specificity of 94% for high-grade papillary UTUC.

CONCLUSIONS

This study proposes a μOCT cut-off of 4.0 mm-1 for quantitative grading of UTUC with ureterorenoscopic OCT imaging. The promising diagnostic accuracy calculations justify further studies to validate the proposed cut-off value. Implementation of the software for the μOCT analysis in OCT systems may allow for μOCT assessment at real time during ureterorenoscopy. Lasers Surg. Med. 51:399-406, 2019. © 2019 Wiley Periodicals, Inc.

Quantitative attenuation analysis for identification of early Barrett's neoplasia in volumetric laser endomicroscopy

Early neoplasia in Barrett’s esophagus (BE) is difficult to detect. Volumetric laser endomicroscopy (VLE) incorporates optical coherence tomography, providing a circumferential scan of the esophageal wall layers. The attenuation coefficient (μVLE) quantifies decay of detected backscattered light versus depth, and could potentially improve BE neoplasia detection. The aim is to investigate feasibility of μVLE for identification of early BE neoplasia. In vivo and ex vivo VLE scans with histological correlation from BE patients ± neoplasia were used. Quantification by μVLE was performed manually on areas of interest (AoIs) to differentiate neoplasia from nondysplastic (ND)BE. From ex vivo VLE scans from 16 patients (13 with neoplasia), 68 AoIs were analyzed. Median μVLE values (mm−1) were 3.7 [2.1 to 4.4 interquartile range (IQR)] for NDBE and 4.0 (2.5 to 4.9 IQR) for neoplasia, not statistically different (p=0.82). Fourteen in vivo scans were used: nine from neoplastic and five from NDBE patients. Median μVLE values were 1.8 (1.5 to 2.6 IQR) for NDBE and 2.1 (1.9 to 2.6 IQR) for neoplasia, with no statistically significant difference (p=0.37). In conclusion, there was no significant difference in μVLE values in VLE scans from early neoplasia versus NDBE. Future studies with a larger sample size should explore other quantitative methods for detection of neoplasia during BE surveillance.

Ellagic acid protects against neuron damage in ischemic stroke through regulating the ratio of Bcl-2/Bax expression

An oxygen-glucose deprivation and reoxygenation model in primary cultured rat cortical neurons was developed for this study to investigate the effects of ellagic acid (EA), a low-molecular-weight polyphenol, on neuron cells and their function, and to evaluate whether EA can be safely utilized by humans as a functional food or therapeutic agent. Administration of EA significantly decreased the volume of cerebrum infarction and the neurological deficit scores of the rats; EA treatment also increased the number of Bcl-2-positive cells and the ratio of Bcl-2-positive to Bax-positive neurons in the semidarkness zone near the brain ischemic focus in the photothrombotic cerebral ischemia model. Treatment of EA resulted in increased neuron viability, cell nuclear integrity, and the ratio of Bcl-2/Bax expression in the primary cultured neuron model; EA treatment also lead to a decrease in the number of apoptotic cells. Our results therefore suggest a specific mechanism for the beneficial effects of EA, providing new insights into how it provides neuroprotection. To the best of our knowledge, these results represent new insights on the mechanisms of the brain cell protective activity of EA. Thus, EA may be used in functional foods or medicines to help treat nerve dysfunction, neurodegenerative disease, and aging.