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Computed optical coherence microscopy of mouse brain ex vivo

Meiqi Wu, David M. Small, Nozomi Nishimura, Steven G. Adie

Journal of Biomedical Optics (2019)

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The compromise between lateral resolution and usable imaging depth range is a bottleneck for optical coherence tomography (OCT). Existing solutions for optical coherence microscopy (OCM) suffer from either large data size and long acquisition time or a nonideal point spread function. We present volumetric OCM of mouse brain ex vivo with a large depth coverage by leveraging computational adaptive optics (CAO) to significantly reduce the number of OCM volumes that need to be acquired with a Gaussian beam focused at different depths. We demonstrate volumetric reconstruction of ex-vivo mouse brain with lateral resolution of 2.2  μm, axial resolution of 4.7  μm, and depth range of ∼1.2  mm optical path length, using only 11 OCT data volumes acquired on a spectral-domain OCM system. Compared to focus scanning with step size equal to the Rayleigh length of the beam, this is a factor of 4 fewer datasets required for volumetric imaging. Coregistered two-photon microscopy confirmed that CAO-OCM reconstructions can visualize various tissue microstructures in the brain. Our results also highlight the limitations of CAO in highly scattering media, particularly when attempting to reconstruct far from the focal plane or when imaging deep within the sample.

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Microvessel occlusions alter amyloid-beta plaque morphology in a mouse model of Alzheimer’s disease

Yuying Zhang, Evan D Bander, Yurim Lee, Celia Muoser, Chris B Schaffer and Nozomi Nishimura

Journal of Cerebral Blood flow and Metabolism (2019)

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Vascular dysfunction is correlated to the incidence and severity of Alzheimer’s disease. In a mouse model of Alzheimer’s disease (APP/PS1) using in vivo, time-lapse, multiphoton microscopy, we found that occlusions of the microvasculature alter amyloid-beta (Ab) plaques. We used several models of vascular injury that varied in severity. Femtosecond laser induced occlusions in single capillaries generated a transient increase in small, cell-sized, Ab deposits visualized with methoxy-X04, a label of fibrillar Ab. After occlusions of penetrating arterioles, some plaques changed morphology, while others disappeared, and some new plaques appeared within a week after the lesion. Antibody labeling of Ab revealed a transient increase in non-fibrillar Ab one day after the occlusion that coincided with the disappearance of methoxy-X04- labeled plaques. Four days after the lesion, anti-Ab labeling decreased and only remained in patches unlabeled by methoxy-X04 near microglia. Histology in two additional models, sparse embolic occlusions from intracarotid injections of beads and infarction from photothrombosis, demonstrated increased labeling intensity in plaques after injury. These results suggest that microvascular lesions can alter the deposition and clearance of Ab and confirm that Ab plaques are dynamic structures, complicating the interpretation of plaque burden as a marker of Alzheimer’s disease progression

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In Vivo Calcium Imaging of Cardiomyocytes in the Beating Mouse Heart With Multiphoton Microscopy

Jason S. Jones, David M. Small and Nozomi Nishimura

Frontiers in physiology (2018)

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Background: Understanding the microscopic dynamics of the beating heart has been challenging due to the technical nature of imaging with micrometer resolution while the heart moves. The development of multiphoton microscopy has made in vivo, cell-resolved measurements of calcium dynamics and vascular function possible in motionless organs such as the brain. In heart, however, studies of in vivo interactions between cells and the native microenvironment are behind other organ systems. Our goal was to develop methods for intravital imaging of cardiac structural and calcium dynamics with microscopic resolution. Methods: Ventilated mice expressing GCaMP6f, a genetically encoded calcium indicator, received a thoracotomy to provide optical access to the heart. Vasculature was labeled with an injection of dextran-labeled dye. The heart was partially stabilized by a titanium probe with a glass window. Images were acquired at 30 frames per second with spontaneous heartbeat and continuously running, ventilated breathing. The data were reconstructed into three-dimensional volumes showing tissue structure, vasculature, and GCaMP6f signal in cardiomyocytes as a function of both the cardiac and respiratory cycle. Results: We demonstrated the capability to simultaneously measure calcium transients, vessel size, and tissue displacement in three dimensions with micrometer resolution. Reconstruction at various combinations of cardiac and respiratory phase enabled measurement of regional and single-cell cardiomyocyte calcium transients (GCaMP6f fluorescence). GCaMP6f fluorescence transients in individual, aberrantly firing cardiomyocytes were also quantified. Comparisons of calcium dynamics (risetime and tau) at varying positions within the ventricle wall showed no significant depth dependence. Conclusion: This method enables studies of coupling between contraction and excitation during physiological blood perfusion and breathing at high spatiotemporal resolution. These capabilities could lead to a new understanding of normal and disease function of cardiac cells.

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Intestinal crypts recover rapidly from focal damage with coordinated motion of stem cells that is impaired by aging

Jiahn Choi, Nikolai Rakhilin, Poornima Gadamsetty, Daniel J. Joe, Tahmineh Tabrizian, Steven M. Lipkin, Derek M. Hu man, Xiling Shen & Nozomi Nishimura

Scientific Reports (2018)

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Despite the continuous renewal and turnover of the small intestinal epithelium, the intestinal crypt maintains a ‘soccer ball-like’, alternating pattern of stem and Paneth cells at the base of the crypt. To study the robustness of the alternating pattern, we used intravital two-photon microscopy in mice with uorescently-labeled Lgr5+ intestinal stem cells and precisely perturbed the mosaic pattern with femtosecond laser ablation. Ablation of one to three cells initiated rapid motion of crypt cells that restored the alternation in the pattern within about two hours with only the rearrangement of pre-existing cells, without any cell division. Crypt cells then performed a coordinated dilation of the crypt lumen, which resulted in peristalsis-like motion that forced damaged cells out of the crypt. Crypt cell motion was reduced with inhibition of the ROCK pathway and attenuated with old age, and both resulted in incomplete pattern recovery. This suggests that in addition to proliferation and self-renewal, motility of stem cells is critical for maintaining homeostasis. Reduction of this newly-identi ed behavior of stem cells could contribute to disease and age-related changes.

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Label-free imaging of atherosclerotic plaques using third-harmonic generation microscopy

David M. Small, Jason S. Jones, Irwin I. Tendler, Paul E. Miller, Andre Ghetti, and Nozomi Nishimura

Biomedical Optics Express (2018)

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Multiphoton microscopy using laser sources in the mid-infrared range (MIR, 1,300 nm and 1,700 nm) was used to image atherosclerotic plaques from murine and human samples. Third harmonic generation (THG) from atherosclerotic plaques revealed morphological details of cellular and extracellular lipid deposits. Simultaneous nonlinear optical signals from the same laser source, including second harmonic generation and endogenous fluorescence, resulted in label-free images of various layers within the diseased vessel wall. The THG signal adds an endogenous contrast mechanism with a practical degree of specificity for atherosclerotic plaques that complements current nonlinear optical methods for the investigation of cardiovascular disease. Our use of whole-mount tissue and backward scattered epi-detection suggests THG could potentially be used in the future as a clinical tool.

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In vivo three-photon imaging of activity of GCaMP6-labeled neurons deep in intact mouse brain

Ouzounov DG, Wang T, Wang M, Feng D, Horton NG, Cruz Hernández JC, Cheng Y, Reimer J, Tolias A, Nishimura N, Xu C

Nature Methods (2017)

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High-resolution optical imaging is critical to understanding brain function. We demonstrate that three-photon microscopy at 1,300-nm excitation enables functional imaging of GCaMP6s-labeled neurons beyond the depth limit of two-photon microscopy. We record spontaneous activity from up to 150 neurons in the hippocampal stratum pyramidale at ~1-mm depth within an intact mouse brain. Our method creates opportunities for noninvasive recording of neuronal activity with high spatial and temporal resolution deep within scattering brain tissues.

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Simultaneous Optical and Electrical In Vivo Analysis of the Enteric Nervous System

Rakhilin N, Barth B, Choi J, Munoz N, Kulkarni S, LaVinka C, Dong X, Spencer M, Pasricha P, Nishimura N, Jones J, Small D, Cheng YT, Cao Y, Kan E, Shen X

Nat Commun (2016)

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The enteric nervous system (ENS) is a major division of the nervous system and vital to the gastrointestinal (GI) tract and its communication with the rest of the body. Unlike the brain and spinal cord, relatively little is known about the ENS in part because of the inability to directly monitor its activity in live animals. Here, we integrate a transparent graphene sensor with a customized abdominal window for simultaneous optical and electrical recording of the ENS in vivo. The implanted device captures ENS responses to neurotransmitters, drugs and optogenetic manipulation in real time.

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A Mathematical Model Relating Cortical Oxygenated And Deoxygenated Hemoglobin Flows And Volumes To Neural Activity

Nathan Cornelius, Nozomi Nishimura, Minah Suh, Theodore Schwartz, and Peter Doerschuk

Journal of Neural Engineering (2015)

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Objective. To describe a toolkit of components for mathematical models of the relationship between cortical neural activity and space-resolved and time-resolved flows and volumes of oxygenated and deoxygenated hemoglobin motivated by optical intrinsic signal imaging (OISI). Approach. Both blood flow and blood volume and both oxygenated and deoxygenated hemoglobin and their interconversion are accounted for. Flow and volume are described by including analogies to both resistive and capacitive electrical circuit elements. Oxygenated and deoxygenated hemoglobin and their interconversion are described by generalization of Kirchhoff's laws based on well-mixed compartments. Main results. Mathematical models built from this toolkit are able to reproduce experimental single-stimulus OISI results that are described in papers from other research groups and are able to describe the response to multiple-stimuli experiments as a sublinear superposition of responses to the individual stimuli. Significance. The same assembly of tools from the toolkit but with different parameter values is able to describe effects that are considered distinctive, such as the presence or absence of an initial decrease in oxygenated hemoglobin concentration, indicating that the differences might be due to unique parameter values in a subject rather than different fundamental mechanisms.

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Comprehensive models of human primary and metastatic colorectal tumors in immunodeficient and immunocompetent mice by chemokine targeting

Chen HJ, Sun J, Huang Z, Hou H Jr, Arcilla M, Rakhilin N, Joe DJ, Choi J, Gadamsetty P, Milsom J, Nandakumar G, Longman R, Zhou XK, Edwards R, Chen J, Chen KY, Bu P, Wang L, Xu Y, Munroe R, Abratte C, Miller AD, Gümüş ZH, Shuler M, Nishimura N, Edelmann W, Shen X, Lipkin SM.

Nature Biotechnology (2015)

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Current orthotopic xenograft models of human colorectal cancer (CRC) require surgery and do not robustly form metastases in the liver, the most common site clinically. CCR9 traffics lymphocytes to intestine and colorectum. We engineered use of the chemokine receptor CCR9 in CRC cell lines and patient-derived cells to create primary gastrointestinal (GI) tumors in immunodeficient mice by tail-vein injection rather than surgery. The tumors metastasize inducibly and robustly to the liver. Metastases have higher DKK4 and NOTCH signaling levels and are more chemoresistant than paired subcutaneous xenografts. Using this approach, we generated 17 chemokine-targeted mouse models (CTMMs) that recapitulate the majority of common human somatic CRC mutations. We also show that primary tumors can be modeled in immunocompetent mice by microinjecting CCR9-expressing cancer cell lines into early-stage mouse blastocysts, which induces central immune tolerance. We expect that CTMMs will facilitate investigation of the biology of CRC metastasis and drug screening.

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Mechanistic insight into the TH1-biased immune response to recombinant subunit vaccines delivered by probiotic bacteria-derived outer membrane vesicles

Rosenthal JA, Huang CJ, Doody AM, Leung T, Mineta K, Feng DD, Wayne EC, Nishimura N, Leifer C, DeLisa MP, Mendez S, Putnam D.

PLoS One. (2014)

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Recombinant subunit vaccine engineering increasingly focuses on the development of more effective delivery platforms. However, current recombinant vaccines fail to sufficiently stimulate protective adaptive immunity against a wide range of pathogens while remaining a cost effective solution to global health challenges. Taking an unorthodox approach to this fundamental immunological challenge, we isolated the TLR-targeting capability of the probiotic E. coli Nissle 1917 bacteria (EcN) by engineering bionanoparticlate antigen carriers derived from EcN outer membrane vesicles (OMVs). Exogenous model antigens expressed by these modified bacteria as protein fusions with the bacterial enterotoxin ClyA resulted in their display on the surface of the carrier OMVs. Vaccination with the engineered EcN OMVs in a BALB/c mouse model, and subsequent mechanism of action analysis, established the EcN OMV's ability to induce self-adjuvanted robust and protective humoral and T(H)1-biased cellular immunity to model antigens. This finding appears to be strain-dependent, as OMV antigen carriers similarly engineered from a standard K12 E. coli strain derivative failed to generate a comparably robust antigen-specific TH1 bias. The results demonstrate that unlike traditional subunit vaccines, these biomolecularly engineered "pathogen-like particles" derived from traditionally overlooked, naturally potent immunomodulators have the potential to effectively couple recombinant antigens with meaningful immunity in a broadly applicable fashion.

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