Faculty Bibliography

Monitoring intracellular calcium is central to understanding cell signaling across nearly all cell types and organisms. Fluorescent genetically encoded calcium indicators (GECIs) remain the standard tools for in vivo calcium imaging, but require intense excitation light, leading to photobleaching, background autofluorescence and phototoxicity. Bioluminescent GECIs, which generate light enzymatically, eliminate these artifacts but have been constrained by low dynamic range and suboptimal calcium affinities. Here we show that CaBLAM ('calcium bioluminescence activity monitor'), an engineered bioluminescent calcium indicator, achieves an order-of-magnitude improvement in signal contrast and a tunable affinity matched to physiological cytosolic calcium. CaBLAM enables single-cell and subcellular activity imaging at video frame rates in cultured neurons and sustained imaging over hours in awake, behaving animals. These capabilities establish CaBLAM as a robust and general alternative to fluorescent GECIs, extending calcium imaging to regimes where excitation light is undesirable or infeasible.

BACKGROUND:Despite the high potential of transcranial ultrasound stimulation (TUS) for non-invasive brain therapy and interrogation, real-time monitoring of brain responses to TUS remains a challenge. Traditional methods to monitor direct neural responses are invasive and mostly incompatible with precise TUS delivery while other non-invasive approaches to visualize the induced responses suffer from poor penetration depth, lack of sensitivity, or low temporal resolution. OBJECTIVE:We present an integrated approach for high precision delivery of ultrasound into the mouse brain and simultaneous whole-brain oximetry with functional optoacoustic tomography to characterize the hemodynamic response elicited by TUS. METHODS:A spherically focused ultrasound array was employed to non-invasively deliver holographic TUS and simultaneously detect multispectral optoacoustic signals from the brains of anesthetized mice. Ultrasound pressure and pulse duration were varied, while the number of stimuli (5), stimulation duration (15 s), and ultrasound frequency (3 MHz) were kept constant. The acquired optoacoustic data were tomographically reconstructed and spectrally unmixed to render three-dimensional maps of oxygenated and deoxygenated hemoglobin in real time. RESULTS:TUS-evoked brain-wide hemodynamics were efficiently monitored via spectroscopic optoacoustic imaging with high spatial and temporal resolution. Holographic TUS targeted to the somatosensory cortex elicited distinct hemodynamic responses, which extended beyond the stimulated region, involving subcortical arteries and pial veins. CONCLUSIONS:Our method provides new transformative non-invasive capabilities to study the effects of ultrasound on a living brain thus help unleash the strong potential of TUS in neuroscience and medicine.

Focused transcranial ultrasound stimulation (TUS) can affect neural activity with high spatial precision, advancing noninvasive neuromodulation toward targeted treatment of brain disorders. Direct monitoring of TUS responses is crucial for ensuring optimal outcomes. Blood-oxygenation-level-dependent (BOLD) functional magnetic resonance imaging has primarily been used for studying TUS effects in both human and nonhuman primate brains. However, the physiology and mechanisms underlying BOLD remain largely unknown due to its highly convoluted nature. To address these limitations, we developed a hybrid system for concurrent optoacoustic and magnetic resonance imaging of TUS (OMRITUS) to comprehensively characterize the hemodynamic changes in murine brains. Our findings reveal paradoxical negative BOLD signals in the activated cortical regions, coupled with increased total hemoglobin levels simultaneously monitored with optoacoustic tomography. Multispectral optoacoustic readings further demonstrated a stronger increase in deoxygenated versus oxygenated hemoglobin, suggesting a potential molecular basis for the negative BOLD responses. OMRITUS enables the study of complex TUS-hemodynamic interactions, paving the way for precise neuromodulatory interventions.

Inflammation drives various diseases, including cardiovascular, neurodegenerative, and oncological disorders, by altering immune cell dynamics in hematopoietic niches. The bone marrow is the primary site for hematopoietic stem and progenitor cell activity. Here, we present a novel, noninvasive approach using multispectral optoacoustic tomography (MSOT) to track oxygenation dynamics in the murine calvarial bone marrow during acute systemic inflammation induced by lipopolysaccharide (LPS). Our MSOT system provided real-time, label-free imaging of hemoglobin oxygen saturation (sO₂), revealing significant reductions in sO₂ levels in lipopolysaccharide-treated mice, indicative of increased oxygen consumption. Co-registration with microCT enabled precise vascular mapping. Hypoxia was confirmed by ex vivo Pimonidazole staining and optical imaging and was associated with elevated neutrophil counts and enhanced hematopoietic activation. These findings demonstrate MSOT's potential for noninvasive imaging of marrow oxygenation, offering insights into inflammation-driven hematopoietic activation and supporting the development of therapies targeting oxygen-sensitive pathways.

Allergic contact dermatitis (ACD) is a delayed-type IV hypersensitivity response driven by innate and adaptive immune cells. While specific immune regulations of these cell types are amply elucidated, their regulations by extracellular matrix (ECM) components and T cell mediated adaptive immunity in ACD remains unclear. Lumican and biglycan are ECM proteoglycans abundant in the dermis and lymph node, known to regulate innate immune myeloid cells, but have not been investigated in lymphoid cell regulations in ACD. By immunohistology we localized lumican and biglycan in skin biopsies of psoriatic patients. Using wild type (WT), lumican and biglycan knockout mice, we investigated CD4⁺T cell infiltration, activation and proliferation in the skin and draining lymph node (dLN) of CHS-challenged mice by immunohistochemistry and flow cytometry. We used the OT-II adoptive transfer model to test antigen specific CD4⁺T cell activation. We assessed interactions of the proteoglycans with LFA-1 on T cells by confocal microscopy. Compared to WTs, the knockouts showed severe ear inflammation, with increased CD4⁺T cells infiltration in the dermis. CHS-challenged knockout mice dLN showed increased T-bet, STAT1 and -STAT4 signaling, indicating enhanced Th1 commitment and proliferation. We found that WT lymph node fibroblastic reticular cells (FRCs) secrete lumican, biglycan and decorin, a related proteoglycan, while none are expressed by naive or activated T cells. Lumican and biglycan interact with LFA-1 on T cell surfaces, and in vitro all three proteoglycans suppress CD4⁺T cell activation. Secreted by dLN FRCs, lumican, biglycan, and possibly decorin interact with LFA-1 on CD4⁺T cells to restrict its activation and reduce dermatitis severity.

Precision-targeted ultrasonic neuromodulation offers immense potential for studying brain function and treating neurological diseases. Yet, its application has been limited by challenges in achieving precise spatio-temporal control and monitoring of ultrasound effects on brain circuits. Here we show that transcranial ultrasound elicits direct and highly focal responses, which can be dynamically steered at spatio-temporal scales relevant for neural function. Furthermore, holographic transcranial ultrasound stimulation allows direct control of the stimulated volume and actively modulates local and mid-range network projections, effectively lowering the activation threshold by an order of magnitude. To better understand this previously unexplored excitability regime not fully explained by the conventional pressure-frequency dyad, we developed a dual modelling framework, where both an empirical and a mechanistic model were constructed to capture the intricacies of holographic transcranial ultrasound stimulation. These models achieve qualitative agreement with our experimental results, suggesting that these findings are predominantly driven by putative network interactions. Our results bring insight on the complex interaction mechanisms of ultrasound with neural tissue and highlight its potential for the noninvasive interfacing of distributed brain networks.

PURPOSE/OBJECTIVE:For accelerated 3-year MD (3YMD) pathways to be fully adopted in medical education, a comprehensive analysis of outcome data is needed. This study includes 7 accelerated 3YMD graduating classes at NYU Grossman School of Medicine (NYUGSOM) and reports on outcomes from both medical school and internship compared to their 4-year MD (4YMD) counterparts. METHOD/METHODS:Outcomes across the undergraduate-graduate medical education continuum for the first 7 classes of NYUGSOM graduates (matriculated from 2013-2019) from the accelerated 3YMD (n = 136) and 4YMD pathways (n = 681) were compared. For the internship outcomes, 3YMD interns were compared with 4YMD interns who graduated from NYUGSOM and all 4YMD interns (4YMD graduates from NYUGSOM and any other medical school) at NYUGSOM residencies. RESULTS:Accelerated 3YMD students were approximately 5 months older at admission and had higher multiple mini-interview scores than 4YMD students. Overall, accelerated 3YMD students performed similarly to 4YMD students during medical school and internship. Significant differences included higher performance by 3YMD students on preclerkship exams and lower performance on Steps 1 and 2 (average: 5.6 and 8.3 fewer points, respectively) and the physical examination portion of the NYUGSOM Comprehensive Clinical Skills Exam. Internship data indicated comparable team assessments across all residencies, statistically significant higher performance on Step 3 when compared to all 4YMD interns, and, in internal medicine, comparable clinical reasoning between 3YMD and all 4YMD interns. When comparing 3YMD interns to all 4YMD interns in the internal medicine residency program, 3YMD interns had a statistically significantly higher performance on milestones. CONCLUSIONS:The outcomes from 7 years of graduating accelerated 3YMD students at NYUGSOM show similar performance in medical school and early residency to 4YMD graduates. Long-term study of accelerated 3YMD students from NYUGSOM and other medical schools is needed to further validate the success of this innovative medical education pathway.

Measuring whole-brain distributed functional activity is an important unmet need in neuroscience, requiring high temporal resolution and cellular specificity across large volumes. Functional optoacoustic neuro-tomography (FONT) with genetically encoded calcium ion indicators is a promising approach towards this goal. However, it has not yet been applied in the near-infrared (NIR) range that provides deep penetration and low vascular background optimal for in vivo neuroimaging. Here, we study the noninvasive multimodal fluorescence and optoacoustic imaging performance of state-of-the-art NIR calcium ion indicator NIR-GECO2G in the mouse brain. We observe robust in vivo signals with widefield fluorescence, and for the first time, with FONT. We also show that in both modalities, the NIR-GECO2G signal improves more than twofold in the biliverdin-enriched Blvra

PURPOSE/OBJECTIVE:We developed human cornea organoids (HCOs) from induced pluripotent stem cells (iPSCs) where single-cell RNA-sequence (scRNA-seq) analysis suggested similarity with developing rather than mature human corneas. We performed immunohistology to determine the presence of corneal glycosaminoglycans as an assessment of maturity. We undertook a detailed comparison of the HCO scRNA-seq data with a recent scRNA-seq study of human fetal corneas at different stages to gauge the HCO's maturity. METHODS:We generated HCOs from a second iPSC line, NCRM-1, to assess the reproducibility of HCO development. We stained sections from both HCO lines with Alcian blue and picrosirius red to determine deposition of sulfated glycosaminoglycans and fibrillar collagens. We immunolocalized glycosaminoglycan biosynthetic enzymes and proteoglycan core proteins. The scRNA-seq data from IMR90.4 HCOs were compared to that of fetal corneas using MetaNeighbor analysis to assess the similarity of HCOs to different stages of human corneal development. RESULTS:The MetaNeighbor analysis suggests closer alignment of the IMR90.4 HCOs with 17-18 post-conception week fetal human corneas. HCOs from both iPSC lines deposit sulfated glycosaminoglycans and fibrillar collagens. Immunohistology showed chondroitin/dermatan sulfate (CS/DS) and keratan sulfate in the presumptive stromal and some epithelial layers. The NCRM-1-derived HCOs show increased CS/DS staining compared to the IMR90.4 derived HCOs. CONCLUSIONS:Both HCO lines show similar developmental patterns and timeline. The NCRM-1 HCO line may have more glycosaminoglycan deposition. Overall, the glycosaminoglycan deposition pattern is consistent with an immature tissue. Optimizations based on our current findings may yield more mature stromal cells and cornea-typical proteoglycans.