In vivo, label-free, three-dimensional quantitative imaging of kidney microcirculation using Doppler optical coherence tomography

Fangchinoline alleviates cognitive impairments through enhancing autophagy and mitigating oxidative stress in Alzheimer's disease models

Introduction: Alzheimer's disease (AD) is a debilitating, progressive, neurodegenerative disorder characterized by the deposition of amyloid-β (Aβ) peptides and subsequent oxidative stress, resulting in a cascade of cytotoxic effects. Fangchinoline (Fan), a bisbenzylisoquinoline alkaloid isolated from traditional Chinese herb Stephania tetrandra S. Moorec, has been reported to possess multiple potent biological activities, including anti-inflammatory and antioxidant properties. However, the potential neuroprotective efficacy of Fan against AD remains unknown. Methods: N2AAPP cells, the mouse neuroblastoma N2A cells stably transfected with human Swedish mutant APP695, were served as an in vitro AD model. A mouse model of AD was constructed by microinjection of Aβ1-42 peptides into lateral ventricle of WT mice. The neuroprotective effects of Fan on AD were investigated through a combination of Western blot analysis, immunoprecipitation and behavioral assessments. Results and discussion: It was found that Fan effectively attenuated the amyloidogenic processing of APP by augmenting autophagy and subsequently fostering lysosomal degradation of BACE1 in N2AAPP cells, as reflected by the decrease in P62 levels, concomitant with the increase in Beclin-1 and LC3-II levels. More importantly, Fan significantly ameliorated cognitive impairment in an Aβ1-42-induced mouse model of AD via the induction of autophagy and the inhibition of oxidative stress, as evidenced by an increase in antioxidants including glutathione reductase (GR), total antioxidant capacity (T-AOC), nuclear factor erythroid-2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), and superoxide dismutase-1 (SOD-1) and a decrease in pro-oxidants including hydrogen peroxide (H2O2) and inducible nitric oxide synthase (i-NOS), coupled with a reduction in apoptosis marker, cleaved caspase-3. Taken together, our study demonstrate that Fan ameliorates cognitive dysfunction through promoting autophagy and mitigating oxidative stress, making it a potential therapeutic agent for AD.

In vivo imaging of renal microvasculature in a murine ischemia-reperfusion injury model using optical coherence tomography angiography

Optical coherence tomography angiography (OCTA) provides three-dimensional structural and semiquantitative imaging of microvasculature in vivo. We developed an OCTA imaging protocol for a murine kidney ischemia-reperfusion injury (IRI) model to investigate the correlation between renal microvascular changes and ischemic damage. Mice were divided into mild and moderate IRI groups according to the duration of ischemia (10 and 35 mins, respectively). Each animal was imaged at baseline; during ischemia; and at 1, 15, 30, 45, and 60 mins after ischemia. Amplitude decorrelation OCTA images were constructed with 1.5-, 3.0-, and 5.8-ms interscan times, to calculate the semiquantitative flow index in the superficial (50-70 μm) and the deep (220-340 μm) capillaries of the renal cortex. The mild IRI group showed no significant flow index change in both the superfial and the deep layers. The moderate IRI group showed a significantly decreased flow index from 15 and 45 mins in the superficial and deep layers, respectively. Seven weeks after IRI induction, the moderate IRI group showed lower kidney function and higher collagen deposition than the mild IRI group. OCTA imaging of the murine IRI model revealed changes in superficial blood flow after ischemic injury. A more pronounced decrease in superficial blood flow than in deep blood flow was associated with sustained dysfunction after IRI. Further investigation on post-IRI renal microvascular response using OCTA may improve our understanding of the relationship between the degree of ischemic insult and kidney function.

Peripheral intravenous infusion for children based on computer digital video technology

PURPOSE

Intravenous infusion techniques often take a long time and require continuous monitoring of the infusion, and the needle must be removed promptly at the end of the injection, placing a burden on the patient, family and medical workers. Thus, this paper presents a droplet flow rate monitoring system based on an embedded system.

METHODS

In our retrospective study, according to different intervention measures, 80 patients were divided into two groups to compare the improvement of children's adverse psychological conditions. The patients were divided into control and intervention groups, with 40 patients in each group. Patients in the intervention group received psychological care and Online Real-Time Fusion Method to monitor the infusion state. Patients in the control group received routine infusions. Computer digital video technology and online real-time fusion algorithm were utilized to determine whether the parameters of the intravenous infusion model were optimized. The model's accuracy was used to evaluate whether the success rate of one-time needle insertion was improved.

RESULTS

The system can also be used for other monitoring. It is simple and convenient to set up and dismantle. The system can significantly relieve medical workers and patients. It was found that the observation group is significantly better than the control group in terms of psychological improvement (P<0.05). Comparing the patient's satisfaction, the difference between the two groups was statistically significant.

CONCLUSION

When administering intravenous infusions in children, applying various forms of psychological interventions and giving emotional support can significantly improve their compliance and their mental state. It is of great significance to enhance the effect of infusions in patients.

Optical coherence microangiography of the mouse kidney for diagnosis of circulatory disorders

Optical coherence tomography (OCT) has become widespread in clinical applications in which precise three-dimensional functional imaging of living organs is required. Nevertheless, the kidney is inaccessible for the high resolution OCT imaging due to a high light attenuation coefficient of skin and soft tissues that significantly limits the penetration depth of the probing laser beam. Here, we introduce a surgical protocol and fixation scheme that enables functional visualization of kidney's peritubular capillaries via OCT microangiography. The model of reversible/irreversible glomerulus embolization using drug microcarriers confirms the ability of OCT to detect circulatory disorders. This approach can be used for choosing optimal carriers, their dosages and diagnosis of other blood flow pathologies.

Toward image quality assessment in optical coherence tomography (OCT) of rat kidney

BACKGROUND

Optical coherence tomography (OCT) is a useful tool for the evaluation of structure and function of the kidney, but the image quality can be effected by many factors.

OBJECTIVE

The objective of this study was to assess the image quality of different OCT systems in OCT imaging of the living kidney.

METHODS

One swept-source OCT (SSOCT) of 1300 nm, one spectral domain OCT (SDOCT) of 1300 nm and another of 900 nm were used. A FeO phantom was used to establish the point spread function (PSF). Rat kidneys were imaged for image quality assessment. Light penetration in the kidney and the optical attenuation coefficient were also evaluated. The quantification of uriniferous tubules was carried out via the threshold segmentation of 3D OCT images.

RESULTS

The quality of kidney images was resolution dependent. SDOCT of 900 nm showed higher peak signal-to noise ratio and dynamic range. The spatial resolution in the light field could be derived from the PSF distribution along three mutually orthogonal axes. In conjunction with the PSF, the Lucy-Richardson algorithm could improve image quality but could not reveal more microstructural information. The penetration depth of 1300 nm was deeper than that of 900 nm. The attenuation coefficient of the kidney was 29 cm^-1 at 1300 nm and 50 cm^-1 at 900 nm (P < 0.001). More accurate measurement of uriniferous tubules was achieved with the SDOCT-900 due to its higher resolution.

CONCLUSIONS

Both SSOCT and SDOCT systems could be useful for imaging uriniferous tubules in the superficial layers of the cortex. The OCT image quality was highly correlated with the spatial resolution of OCT system.

Morphological and functional characteristics of aging kidneys based on two-photon microscopy in vivo

Age-related kidney disease, which is chronic and naturally occurring, is a general term for a set of heterogeneous disorders affecting kidney structures and characterized by a decline in renal function. Age-related renal insufficiency has important implications with regard to body homeostasis, drug toxicity and renal transplantation. In our study, two-photon microscopy was used to image kidney morphological and functional characteristics in an age-related rat model in vivo. The changes in morphology are analyzed based on autofluorescence and Hoechst 33342 labeling in rats with different ages. Structural parameters including renal tubular diameter, cell nuclei density, size and shape are studied and compared with Hematoxylin and Eosin histological analysis. Functional characteristics, such as blood flow, and glomerular filtration rate are studied with high-molecular weight (MW) 500-kDa dextran-fluorescein and low-MW 10-kDa dextran-rhodamine. Results indicate that morphology changes significantly and functional characteristics deteriorate with age. These parameters are potential indicators for evaluating age-related renal morphology and function changes. Combined analyses of these parameters could provide a quantitative, novel method for monitoring kidney diseases and/or therapeutic effects of kidney drugs.

Fully automated analysis of OCT imaging of human kidneys for prediction of post-transplant function

Current measures for assessing the viability of donor kidneys are lacking. Optical coherence tomography (OCT) can image subsurface tissue morphology to supplement current measures and potentially improve prediction of post-transplant function. OCT imaging was performed on donor kidneys before and immediately after implantation during 169 human kidney transplant surgeries. A system for automated image analysis was developed to measure structural parameters of the kidney's proximal convoluted tubules (PCTs) visualized in the OCT images. The association of these structural parameters with post-transplant function was investigated. This study included kidneys from live and deceased donors. 88 deceased donor kidneys in this study were stored by static cold storage (SCS) and an additional 15 were preserved by hypothermic machine perfusion (HMP). A subset of both SCS and HMP deceased donor kidneys were classified as expanded criteria donor (ECD) kidneys, with elevated risk of poor post-transplant function. Post-transplant function was characterized as either immediate graft function (IGF) or delayed graft function (DGF). In ECD kidneys stored by SCS, increased PCT lumen diameter was found to predict DGF both prior to implantation and following reperfusion. In SCD kidneys preserved by HMP, reduced distance between adjacent lumen following reperfusion was found to predict DGF. Results suggest that OCT measurements may be useful for predicting post-transplant function in ECD kidneys and kidneys stored by HMP. OCT analysis of donor kidneys may aid in allocation of kidneys to expand the donor pool as well as help predict post-transplant function in transplanted kidneys to inform post-operative care.

Optical coherence tomography and computer-aided diagnosis of a murine model of chronic kidney disease

Chronic kidney disease (CKD) is characterized by a progressive loss of renal function over time. Histopathological analysis of the condition of glomeruli and the proximal convolutional tubules over time can provide valuable insights into the progression of CKD. Optical coherence tomography (OCT) is a technology that can analyze the microscopic structures of a kidney in a nondestructive manner. Recently, we have shown that OCT can provide real-time imaging of kidney microstructures in vivo without administering exogenous contrast agents. A murine model of CKD induced by intravenous Adriamycin (ADR) injection is evaluated by OCT. OCT images of the rat kidneys have been captured every week up to eight weeks. Tubular diameter and hypertrophic tubule population of the kidneys at multiple time points after ADR injection have been evaluated through a fully automated computer-vision system. Results revealed that mean tubular diameter and hypertrophic tubule population increase with time in post-ADR injection period. The results suggest that OCT images of the kidney contain abundant information about kidney histopathology. Fully automated computer-aided diagnosis based on OCT has the potential for clinical evaluation of CKD conditions.

Multi-modality Optical Imaging of Rat Kidney Dysfunction: In Vivo Response to Various Ischemia Times

We observed in vivo kidney dysfunction with various ischemia times at 30, 75, 90, and 120 min using multi-modality optical imaging: optical coherence tomography (OCT), Doppler OCT (DOCT), and two-photon microscopy (TPM). We imaged the renal tubule lumens and glomerulus at several areas of each kidney before, during, and after ischemia of 5-month-old female Munich-Wistar rats. For animals with 30 and 75 min ischemia times, we observed that all areas were recovered after ischemia, that tubule lumens were re-opened and the blood flow of the glomerulus was re-established. For animals with 90 and 120 min ischemia times, we observed unrecovered areas, and that tubule lumens remained close after ischemia. TPM imaging verified the results of OCT and provided higher resolution images than OCT to visualize renal tubule lumens and glomerulus blood flow at the cellular level.

Monitoring kidney microanatomy changes during ischemia-reperfusion process using texture analysis of OCT images

kidney ischemia-reperfusion (I/R) accounts for the majority of acute kidney injury cases, whose consequences are commonly encountered after kidney transplantation. Optical coherence tomography (OCT) has been applied to image changes in kidney microanatomy and microcirculation. In this paper, we demonstrate a quantitative method for monitoring kidney status during ischemia-reperfusion process using texture properties of OCT images. This approach employs skewness to measure the distribution of en face OCT image intensities at different depths, thus allowing differentiating ischemia-reperfusion status of kidney. The skewness analysis based on quantitative intensity shows promise for monitoring kidney status during ischemia-reperfusion, and the potential for evaluating the viability of transplant kidney.

Renal contrast microangiography with synchrotron radiation: a novel method for visualizing structures within nephrons in vivo

Background No non-invasive method of observing renal microcirculation in vivo has been established as yet. Although angiography is considered to be ideally suited for the purpose, conventional X-rays cannot be used to image structures smaller than 100 µm. Purpose To develop a method for visualizing the renal arterioles, glomeruli, and proximal tubules of rats in vivo making use of synchrotron radiation. Material and Methods Male Wistar rats were anesthetized, and a catheter was inserted via laparotomy into the abdominal aorta with its tip placed above the renal arteries. The rats were paralyzed with a neuromuscular blocking agent and mechanically ventilated. An inorganic iodine contrast medium was injected via the catheter. The SR derived X-rays transmitted through the subjects were recorded with a CCD camera. Two-dimensional images with a pixel size of 9 µm were obtained. The exposure time was fixed at 50 ms, with a maximum acquisition rate of three images/s. Results Renal arterioles as small as 18 µm in diameter, glomeruli with an average diameter of 173 ± 21 µm, as well as proximal tubules, were clearly visualized. In addition, glomerular density at the peripheral renal cortex was measurable. Conclusion Rat renal microcirculation could be successfully observed in real-time, without exteriorization of the kidney in this study.

Functional optical coherence tomography: principles and progress

In the past decade, several functional extensions of optical coherence tomography (OCT) have emerged, and this review highlights key advances in instrumentation, theoretical analysis, signal processing and clinical application of these extensions. We review five principal extensions: Doppler OCT (DOCT), polarization-sensitive OCT (PS-OCT), optical coherence elastography (OCE), spectroscopic OCT (SOCT), and molecular imaging OCT. The former three have been further developed with studies in both ex vivo and in vivo human tissues. This review emphasizes the newer techniques of SOCT and molecular imaging OCT, which show excellent potential for clinical application but have yet to be well reviewed in the literature. SOCT elucidates tissue characteristics, such as oxygenation and carcinogenesis, by detecting wavelength-dependent absorption and scattering of light in tissues. While SOCT measures endogenous biochemical distributions, molecular imaging OCT detects exogenous molecular contrast agents. These newer advances in functional OCT broaden the potential clinical application of OCT by providing novel ways to understand tissue activity that cannot be accomplished by other current imaging methodologies.

Three dimensional mesoscale analysis of translamellar cross-bridge morphologies in the annulus fibrosus using optical coherence tomography

The defining characteristic of the annulus fibrosus (AF) of the intervertebral disc (IVD) has long been the lamellar structures that consist of highly ordered collagen fibers arranged in alternating oblique angles from one layer to the next. However, a series of recent histologic studies have demonstrated that AF lamellae contain elastin- and type VI collagen-rich secondary "cross-bridge" structures across lamellae. In this study, we use optical coherence tomography (OCT) to elucidate the three-dimensional (3-D) morphologies of these translamellar cross-bridges in AF tissues. Mesoscale volumetric images by OCT revealed a 3-D network of heterogeneously distributed cross-bridges. The results of this study confirm the translamellar cross-bridge is identifiable as a distinguishable structure, which lies in the interbundle space of adjacent lamellae and crisscrosses multiple lamellae in the radial direction. In contrast to previously proposed models extrapolated from 2-D sections, results from this current study show that translamellar cross-bridges exist as a complex, interconnected network. We also found much greater variation in lengths of cross-bridges within the interbundle space of lamellae (0.8-1.4 mm from the current study versus 0.3-0.6 mm from 2-D sections). OCT-based 3-D morphology of translamellar cross-bridge provides novel insight into the AF structure.

In vivo pump-probe optical coherence tomography imaging in Xenopus laevis

Currently, optical coherence tomography (OCT), is not capable of obtaining molecular information often crucial for identification of disease. To enable molecular imaging with OCT, we have further developed a technique that harnesses transient changes in light absorption in the sample to garner molecular information. A Fourier-domain Pump-Probe OCT (PPOCT) system utilizing a 532 nm pump and 830 nm probe has been developed for imaging hemoglobin. Methylene blue, a biological dye with well-know photophysics, was used to characterize the system before investigating the origin of the hemoglobin PPOCT signal. The first in vivo PPOCT images were recorded of the vasculature in Xenopus laevis. The technique was shown to work equally well in flowing and nonflowing vessels. Furthermore, PPOCT was compared with other OCT extensions which require flow, such as Doppler OCT and phase-variance OCT. PPOCT was shown to better delineate tortuous vessels, where nodes often restrict Doppler and phase-variance reconstruction.

Mannitol infusion within 15 min of cross-clamp improves living donor kidney preservation

Background

Optical coherence tomography (OCT) revealed that cells lining proximal convoluted tubules of living donor kidneys (LDKs) procured by laparoscopic procedures were very swollen in response to the brief period of ischemia experienced between the time of arterial vessel clamping and flushing the excised kidney with cold preservation solution. Damage to the tubules as a result of this cell swelling resulted in varying degrees of acute tubular necrosis (ATN) that slowed the recovery of the donor kidneys during the first 2 weeks after their transplantation.

Methods

To prevent this cell damage during LDK procurement, we changed the protocol for intravenous administration of mannitol (i.e., 12.5 or 25 g) to the donor. Specifically, we reduced the time of mannitol administration from 30 to 15 min or less before clamping the renal artery.

Result

OCT revealed that this change in the timing of mannitol administration protected the human donor proximal tubules from normothermic-induced cell swelling. An evaluation of posttransplant recovery of renal function showed that patients treated with this modified protocol returned to normal renal function significantly faster than those treated with mannitol 30 min or more before clamping the renal artery.

Conclusion

Because slow graft recovery in the first weeks after transplantation represents a risk factor for long-term graft function and survival, we believe that this change in pretreatment protocol will improve renal transplants in patients receiving LDK.

Clinical applications of optical coherence tomography in urology

Since optical coherence tomography (OCT) was first demonstrated in 1991, it has advanced significantly in technical aspects such as imaging speed and resolution, and has been clinically demonstrated in a diverse set of medical and surgical applications, including ophthalmology, cardiology, gastroenterology, dermatology, oncology, among others. This work reviews current clinical applications in urology, particularly in bladder, urether, and kidney. Clinical applications in bladder and urether mainly focus on cancer detection and staging based on tissue morphology, image contrast, and OCT backscattering. The application in kidney includes kidney cancer detection based on OCT backscattering attenuation and non-destructive evaluation of transplant kidney viability or acute tubular necrosis based on both tissue morphology from OCT images and function from Doppler OCT (DOCT) images. OCT holds the promise to positively impact the future clinical practices in urology.

'Go with the flow ': a review of methods and advancements in blood flow imaging

Physics has delivered extraordinary developments in almost every facet of modern life. From the humble thermometer and stethoscope to X-Ray, CT, MRI, ultrasound, PET and radiotherapy, our health has been transformed by these advances yielding both morphological and functional metrics. Recently high resolution label-free imaging of the microcirculation at clinically relevant depths has become available in the research domain. In this paper, we present a comprehensive review on current imaging techniques, state-of-the-art advancements and applications, and general perspectives on the prospects for these modalities in the clinical realm.