To realize visualization of the skin microvascular dysfunction of type 1 diabetic mice, we combined laser speckle contrast imaging and hyperspectral imaging to simultaneously monitor the noradrenaline (NE)-induced responses of vascular blood flow and blood oxygen with the development of diabetes through optical clearing skin window. The main results showed that venous and arterious blood flow decreased without recovery after injection of NE; furthermore, the decrease of arterious blood oxygen induced by NE greatly weakened, especially for 2- and 4-week diabetic mice. This change in vasoconstricting effect of NE was related to the expression of α1-adrenergic receptor. This study demonstrated that skin microvascular function was a potential research biomarker for early warning in the occurrence and development of diabetes. The in vivo skin optical clearing method provides a feasible solution to realize visualization of cutaneous microvessels for monitoring microvascular reactivity under pathological conditions. In addition, visual monitoring of skin microvascular function response has guiding significance for early diagnosis of diabetes and clinical research.
To monitor skin microvascular dysfunction of alloxan-induced type 1 diabetic mice model. In this work, we used laser speckle contrast imaging and hyperspectral imaging through in vivo skin optical clearing method to simultaneously monitor the noradrenaline-induced response of microvascular blood flow and blood oxygen with the development of diabetes. The main results showed that venous and arterious blood flow steadily decreased without recovery after injecting noradrenaline (NE), furthermore the influence of NE-induced arterious blood oxygen response greatly decreased, especially for 2-weeks and 4-weeks diabetic mice. This study demonstrated that skin microvascular function was a potential research biomarker for early warning in the occurrence and development of diabetes. And it provides a feasible solution to realize visualization of cutaneous microvessels for monitoring microvascular reactivity.
Neonatal hemorrhagic stroke (NHS) is a major problem of future generation’s health due to the high rate of death and cognitive disability of newborns after NHS. The incidence of NHS in neonates cannot be predicted by standard diagnostic methods. Therefore, the identification of prognostic markers of NHS is crucial. There is evidence that stress-related alterations of cerebral blood flow (CBF) may contribute to NHS. Here, we assessed the stroke-associated CBF abnormalities for high prognosis of NHS using a new model of NHS induced by sound stress in the pre- and post-stroke state. With this aim, we used interdisciplinary methods such as a histological assay of brain tissues, laser speckle contrast imaging and Doppler coherent tomography to monitor cerebral circulation. Our results suggest that the venous stasis with such symptoms as progressive relaxation of cerebral veins, decrease the velocity of blood flow in them are prognostic markers for a risk of NHS and are an informative platform for a future study of corrections of cerebral venous circulatory disturbance related to NHS.
Skin optical clearing can significantly enhance the ability of biomedical optical imaging. Some alcohols and sugars have been selected to be optical clearing agents (OCAs). In this work, we paid attention to the optical clearing potential of disaccharides. Sucrose and maltose were chosen as typical disaccharides to compare with fructose, an excellent monosaccharide-OCA, by using molecular dynamics simulation and an ex vivo experiment. The experimental results indicated that the optical clearing efficacy of skin increases linearly with the concentration for each OCA. Both the theoretical predication and experimental results revealed that the two disaccharides exerted a better optical clearing potential than fructose at the same concentration, and sucrose is optimal. Since maltose has an extremely low saturation concentration, the other two OCAs with saturation concentrations were treated topically on rat skin in vivo, and optical coherence tomography imaging was applied to monitor the optical clearing process. The results demonstrated that sucrose could cause a more significant increase in imaging depth and signal intensity than fructose.
In vivo cortex optical imaging is of great important for revealing both structural and functional architecture of brain with high temporal-spatial resolution. To reduce the limitation of turbid skull, researchers had to establish various skull windows or directly expose cortex through craniotomy. Here we developed a skull optical clearing method to make skull transparent. Laser speckle contrast imaging technique was used to monitor the cortical blood flow after topical treatment with the optical clearing agents. The results indicated that the image contrast increased gradually, and then maintained at a high level after 15 min for adult mice, which made the image quality and resolution of micro-vessels nearly approximate to those of exposed cortex. Both the cortical blood flow velocity almost kept constant after skull became transparent. Besides, the treatment of physiological saline on the skull could make skull return to the initial state again and the skull could become transparent again when SOCS retreated it. Thus, we could conclude that the skull optical clearing method was rapid, valid, reversible and safe, which provided us available approach for performing the cortical structural and functional imaging at high temporal-spatial resolution.
Tissue optical clearing (TOC) is helpful for reducing scattering and enhancing the penetration depth of light, and shows promising potential in optimizing optical imaging performances. A mixture of fructose with PEG-400 and thiazone (FPT) is used as an optical clearing agent in mouse dorsal skin and evaluated with OCT angiography (Angio-OCT) by quantifying optical properties and blood flow imaging simultaneously. It is observed that FPT leads to an improved imaging performance for the deeper tissues. The imaging performance improvement is most likely caused by the FPT-induced dehydration of skin, and the reduction of scattering coefficient (more than ∼40.5%) and refractive-index mismatching (more than ∼25.3%) in the superficial (epidermal, dermal, and hypodermal) layers. A high correlation (up to ∼90%) between the relative changes in refractive-index mismatching and Angio-OCT signal strength is measured. The optical clearing rate is ∼5.83×10−5 cm/s. In addition, Angio-OCT demonstrates enhanced performance in imaging cutaneous hemodynamics with satisfactory spatiotemporal resolution and contrast when combined with TOC, which exhibits a powerful practical application in studying microcirculation.
The study of blood microcirculation is one of the most important problems of the medicine. This paper presents results of experimental study of cerebral blood flow microcirculation in mice with alloxan-induced diabetes using Temporal Laser Speckle Imaging (TLSI). Additionally, a direct effect of glucose water solution (concentration 20% and 45%) on blood flow microcirculation was studied. In the research, 20 white laboratory mice weighing 20-30 g were used. The TLSI method allows one to investigate time dependent scattering from the objects with complex dynamics, since it possesses greater temporal resolution. Results show that in brain of animal diabetic group diameter of sagittal vein is increased and the speed of blood flow reduced relative to the control group. Topical application of 20%- or 45%-glucose solutions also causes increase of diameter of blood vessels and slows down blood circulation. The results obtained show that diabetes development causes changes in the cerebral microcirculatory system and TLSI techniques can be effectively used to quantify these alterations.
Laser speckle contrast imaging technique has been playing an important role in monitoring cutaneous microcirculation, but the strong scattering of skin restricts the imaging depth and contrast, and also makes it impossible to assess the cutaneous microcirculation response dynamically with high sensitivity. The tissue optical clearing is helpful for opening a visible window on mouse dorsal skin. In this work, the cutaneous microcirculation response to vasoactive noradrenaline is monitored with the laser speckle contrast imaging system before and after skin optical clearing. The results show that the optical clearing method can significantly enhance the contrast of laser speckle contrast imaging, and small blood vessels whose diameter less than 20μm can be distinguished with high resolution. The dynamic changes in cutaneous microvascular diameter and blood flow velocity caused by drug can be monitored sensitively. In contrast, it is difficult to detect the cutaneous microcirculation response that occurred in the blood vessels more than 100μm in the intact skin, and the signal-to-noise ratio is too low to monitor the dynamic changes caused by the same drug. Thus, skin optical clearing method can enhance the ability of laser speckle contrast imaging in accessing cutaneous microcirculation response, including the imaging contrast, resolution and sensitivity.
Chemical agents with high refractive index, hyperosmotic, and biocompatibility are introduced into tissue, which will
reduce the scattering of tissue, and enhance the penetration of light in tissue. Diffuse reflectance, as a common method,
has been applied to assess optical clearing of skin in vivo, but the scattering characteristic during the in-vivo optical
clearing process has not been valuated quantitatively. In this work, a diffuse reflectance spectroscopy, based on a lookuptable (LUT) based inverse model, is applied to calculate the reduced scattering coefficient and absorption coefficient of skin. Optical clearing agents (OCAs) were topically treated on mouse skin in vivo. The diffuse reflectance during optical clearing was recorded, and the optical properties can be extracted by the reflectance spectroscopy. The results show that the diffuse reflectance spectra and the reduced scattering coefficient are decreased obviously, whilst the absorption coefficient is increased after the application of OCAs. This study provides evident directly for explore the mechanisms of optical clearing of skin in vivo.
Optical imaging techniques have shown tremendous potential for assessing cutaneous microcirculation, but the imaging depth and contrast is limited by the strong scattering of skin. Current skin windows have to be fulfilled by surgical operation and suffer from some side effects. In this study, a switchable skin window was developed by topical application of an optical clearing agent (OCA) and saline on rat skin in vivo. The validity of the skin window was evaluated by the laser speckle contrast imaging technique, and the safety of OCA to the body was tested through histologic examinations. The results indicated that administration of OCA or saline on rat skin in vivo can open or close the window of skin repeatedly for three days. With the repair effect of hyaluronic acid and Vaseline, it is able to repeatedly visualize the dermal blood vessels and flow distribution. Long-term observation shows that there is no abnormal reflection in micro-structure, body weight, organ coefficients, histopathologic lesions, or toxic reactions compared with a control group. This switchable window will provide an effective tool not only for cutaneous microcirculation with laser speckle contrast imaging, but also for diagnosis and treatment of peripheral vascular diseases, including tumor research with various optical imaging techniques.
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