More Homogeneous Capillary Flow and Oxygenation in Deeper Cortical Layers Correlate with Increased Oxygen Extraction

Our understanding of how capillary blood flow and oxygen distribute across cortical layers to meet the local metabolic demand is incomplete. We addressed this question by using two-photon imaging of resting-state microvascular oxygen partial pressure (PO2) and flow in the whisker barrel cortex in awake mice. Our measurements in layers I-V show that the capillary red-blood-cell flux and oxygenation heterogeneity, and the intracapillary resistance to oxygen delivery, all decrease with depth, reaching a minimum around layer IV, while the depth-dependent oxygen extraction fraction is increased in layer IV, where oxygen demand is presumably the highest. Our findings suggest that more homogeneous distribution of the physiological observables relevant to oxygen transport to tissue is an important part of the microvascular network adaptation to local brain metabolism. These results will inform the biophysical models of layer-specific cerebral oxygen delivery and consumption and improve our understanding of the diseases that affect cerebral microcirculation

CD40L-Tri, a novel formulation of recombinant human CD40L that effectively activates B cells

CD40L has a well-established role in enhancing the immunostimulatory capacity of normal and malignant B cells, but a formulation suitable for clinical use has not been widely available. Like other TNF family members, in vivo and in vitro activity of CD40L requires a homotrimeric configuration, and growing evidence suggests that bioactivity depends on higher-order clustering of CD40. We generated a novel formulation of human recombinant CD40L (CD40L-Tri) in which the CD40L extracellular domain and a trimerization motif are connected by a long flexible peptide linker. We demonstrate that CD40L-Tri significantly expands normal CD19+ B cells by over 20- to 30-fold over 14 days and induces B cells to become highly immunostimulatory antigen-presenting cells (APCs). Consistent with these results, CD40L-Tri-activated B cells could effectively stimulate antigen-specific T responses (against the influenza M1 peptide) from normal volunteers. In addition, CD40L-Tri could induce malignant B cells to become effective APCs, such that tumor-directed immune responses could be probed. Together, our studies demonstrate the potent immune-stimulatory effects of CD40L-Tri on B cells that enable their expansion of antigen-specific human T cells. The potent bioactivity of CD40L-Tri is related to its ability to self-multimerize, which may be facilitated by its long peptide linker. Electronic supplementary material The online version of this article (doi:10.1007/s00262-012-1331-4) contains supplementary material, which is available to authorized users

Capillary red blood cell velocimetry by phase-resolved optical coherence tomography

https://www.spiedigitallibrary.org/conference-proceedings-of-spie/10483/2290655/Capillary-red-blood-cell-velocimetry-by-phase-resolved-optical-coherence/10.1117/12.2290655.full?SSO=1Published versio

MATLAB code and data processing guide for phase resolved Doppler Optical Coherence Tomography

Example data is available through: https://drive.google.com/open?id=168HD4lKt0K97g09zus6H9h7lAyO0jOBZ https://drive.google.com/open?id=1QvTO_41cPN3_wM9wxCh9NECv_hypVZPCThis guide and the MATLAB code are for post data processing of prDOCT, which outputs 3D vascular blood flow velocity

Capillary red blood cell velocimetry by phase-resolved optical coherence tomography

We present a phase-resolved optical coherence tomography (OCT) method to extend Doppler OCT for the accurate measurement of the red blood cell (RBC) velocity in cerebral capillaries. OCT data were acquired with an M-mode scanning strategy (repeated A-scans) to account for the single-file passage of RBCs in a capillary, which were then high-pass filtered to remove the stationary component of the signal to ensure an accurate measurement of phase shift of flowing RBCs. The angular frequency of the signal from flowing RBCs was then quantified from the dynamic component of the signal and used to calculate the axial speed of flowing RBCs in capillaries. We validated our measurement by RBC passage velocimetry using the signal magnitude of the same OCT time series data.National Institutes of Health (NIH) (1S10RR023043, P01-NS055104, P41-EB015896, R01-EB021018, R01MH111359); Air Force Office of Scientific Research (AFOSR) (FA-9550-15-1-0473). (1S10RR023043 - National Institutes of Health (NIH); P01-NS055104 - National Institutes of Health (NIH); P41-EB015896 - National Institutes of Health (NIH); R01-EB021018 - National Institutes of Health (NIH); R01MH111359 - National Institutes of Health (NIH); FA-9550-15-1-0473 - Air Force Office of Scientific Research (AFOSR))https://www.osapublishing.org/ol/abstract.cfm?uri=ol-42-19-3976https://www.osapublishing.org/ol/abstract.cfm?uri=ol-42-19-3976Published versio

Two-photon phosphorescence lifetime microscopy of retinal capillary plexus oxygenation in mice

Impaired oxygen delivery and/or consumption in the retinal tissue underlies the pathophysiology of many retinal diseases. However, the essential tools for measuring oxygen concentration in retinal capillaries and studying oxygen transport to retinal tissue are still lacking. We show that two-photon phosphorescence lifetime microscopy can be used to map absolute partial pressures of oxygen (pO2) in the retinal capillary plexus. Measurements were performed at various retinal depths in anesthetized mice under systemic normoxic and hyperoxic conditions. We used a newly developed two-photon phosphorescent oxygen probe, based on a two-photon absorbing platinum tetraphthalimidoporphyrin, and commercially available optics without correction for optical aberrations of the eye. The transverse and axial distances within the tissue volume were calibrated using a model of the eye's optical system. We believe this is the first demonstration of in vivo depth-resolved imaging of pO2 in retinal capillaries. Application of this method has the potential to advance our understanding of oxygen delivery on the microvascular scale and help elucidate mechanisms underlying various retinal diseases.R01 NS091230 - NINDS NIH HHS; R01 AA027097 - NIAAA NIH HHS; R00 AG042026 - NIA NIH HHS; P01 NS055104 - NINDS NIH HHS; R01 MH111359 - NIMH NIH HHShttps://www.ncbi.nlm.nih.gov/pmc/articles/PMC6278707/Published versio

Optical Coherence Tomography Imaging Of Capillary Reperfusion After Ischemic Stroke

Although progress has been made for recanalization therapies after ischemic stroke, post-treatment imaging studies show that tissue reperfusion cannot be attained despite satisfactory recanalization in a significant percentage of patients. Hence, investigation of microcirculatory changes in both surface and deep cortical levels after ischemia reperfusion is important for understanding the post-stroke blood flow dynamics. In this study, we applied optical coherence tomography (OCT) imaging of cerebral blood flow for the quantification of the microcirculatory changes. We obtained OCT microangiogram of the brain cortex in a mouse stroke model and analyzed the data to trace changes in the capillary perfusion level (CPL) before, during, and after the stroke. The CPL changes were estimated in 1 and 2 h ischemia groups as well as in a non-ischemic sham-operated group. For the estimation of CPL, a decorrelation amplitude-based algorithm was implemented and used. As a result, the CPL considerably decreased during ischemia but recovered to the baseline when recanalization was performed 1 h after ischemia; however, the CPL was significantly reduced when recanalization was delayed to 2 h after ischemia. These data demonstrate that ischemia causes microcirculation dysfunction, leading to a decreased capillary reperfusion after recanalization. Microcirculatory no-reflow warrants more rigorous assessment in clinical trials, whereas advanced optical imaging techniques may provide mechanistic insight and solutions in experimental studies. (C) 2016 Optical Society of AmericaWoSScopu

Intrinsic optical signal imaging of the blood volume changes is sufficient for mapping the resting state functional connectivity in the rodent cortex

Published in final edited form as: J Neural Eng. 2018 June 01; 15(3): 035003–. doi:10.1088/1741-2552/aaafe4.Objective. Resting state functional connectivity (RSFC) allows the study of functional organization in normal and diseased brain by measuring the spontaneous brain activity generated under resting conditions. Intrinsic optical signal imaging (IOSI) based on multiple illumination wavelengths has been used successfully to compute RSFC maps in animal studies. The IOSI setup complexity would be greatly reduced if only a single wavelength can be used to obtain comparable RSFC maps. Approach. We used anesthetized mice and performed various comparisons between the RSFC maps based on single wavelength as well as oxy-, deoxy- and total hemoglobin concentration changes. Main results. The RSFC maps based on IOSI at a single wavelength selected for sensitivity to the blood volume changes are quantitatively comparable to the RSFC maps based on oxy- and total hemoglobin concentration changes obtained by the more complex IOSI setups. Moreover, RSFC maps do not require CCD cameras with very high frame acquisition rates, since our results demonstrate that they can be computed from the data obtained at frame rates as low as 5 Hz. Significance. Our results will have general utility for guiding future RSFC studies based on IOSI and making decisions about the IOSI system designs.We are grateful to Adam Bauer for his guidance on replicating their experimental setup, and Silvina Ferradal and Erin Buckley for useful discussions. We gratefully acknowledge support from the NIH grants NS091230, NS055104, NS057198, EB021018, EB00790, and EB018464, the Fondation Leducq, the State Scholarship Fund of the China Scholarship Council (Construction of high-level university projects, No. 201406100123), and the Natural Science Foundation of China (NSFC, nos. 81472150). (NS091230 - NIH; NS055104 - NIH; NS057198 - NIH; EB021018 - NIH; EB00790 - NIH; EB018464 - NIH; Fondation Leducq; 201406100123 - China Scholarship Council; 81472150 - Natural Science Foundation of China (NSFC))https://iopscience.iop.org/article/10.1088/1741-2552/aaafe4/metaAccepted manuscrip

MATLAB code and data processing guide for Dynamic Light Scattering-Optical Coherence Tomography

An example data is available through: https://drive.google.com/open?id=168HD4lKt0K97g09zus6H9h7lAyO0jOBZ https://drive.google.com/open?id=1QvTO_41cPN3_wM9wxCh9NECv_hypVZPCThis guide is for post data processing of DLSOCT, which outputs axial velocity (Vz), transverse velocity (Vx), total velocity(V), the ratio of static component (Ms), the ratio of dynamic component (Mf), and fitting accuracy (R). The speed upper limit is determined by OCT system Aline rate and 3Dvoxel size