Autofluorescence is a biomarker of neural stem cell activation state

Neural stem cells (NSCs) must exit quiescence to produce neurons; however, our understanding of this process remains constrained by the technical limitations of current technologies. Fluorescence lifetime imaging (FLIM) of autofluorescent metabolic cofactors has been used in other cell types to study shifts in cell states driven by metabolic remodeling that change the optical properties of these endogenous fluorophores. Using this non-destructive, live-cell, and label-free strategy, we found that quiescent NSCs (qNSCs) and activated NSCs (aNSCs) have unique autofluorescence profiles. Specifically, qNSCs display an enrichment of autofluorescence localizing to a subset of lysosomes, which can be used as a graded marker of NSC quiescence to predict cell behavior at single-cell resolution. Coupling autofluorescence imaging with single-cell RNA sequencing, we provide resources revealing transcriptional features linked to deep quiescence and rapid NSC activation. Together, we describe an approach for tracking mouse NSC activation state and expand our understanding of adult neurogenesis.

Abstract 2472: Tumor/normal and live/dead classification in live tumor fragments using label-free multiphoton microscopy

We have developed a live tumor fragment (LTF) platform for predicting clinical response to cancer drugs. The success of this approach depends on screening tissue fragments derived from biopsies and excisions before drug treatment to select those that have acceptable levels of viability and tumor content. To enable this screening, we are developing label-free methods for integrated assessment of LTF histology, viability, and metabolic status using intrinsic multiphoton-excited fluorescence lifetime microscopy (MP-FLIM). We cut live EMT6 tumors and mammary fat pad into rectangular fragments that were then sorted and cultured in glass-bottomed multi-well plates. To induce cancer cell death, we treated one group with a therapeutic agent, e.g., the multi-kinase inhibitor, staurosporine, or the alkylating agent, cisplatin. Before and after treatment, we imaged LTF structure and metabolic status based on the intrinsically fluorescent metabolic co-factors nicotinamide dinucleotides (NAD(P)H) and flavin adenine dinucleotides (FAD) fluorescence intensity and lifetime using dual-excitation multiphoton microscopy. As a ground truth viability reference, we then stained and re-imaged the fragments using nuclear and cell viability probes such as Hoechst, SYTOX, TMRE and/or propidium iodide (PI). We analyzed the data by fitting fluorescence decay curves with dual or triple exponents to generate images of lifetime parameters, including the mean and individual component lifetimes and amplitudes. Finally, we co-registered the extrinsically labeled and autofluorescent lifetime images for 3D spatial analysis using commercial and custom software. We verified the methods using monolayer cell cultures and ATP luminescence and flow cytometry viability assays. Image spatial heterogeneity was quantified utilizing entropy metrics. Intrinsic contrast from multiphoton imaging revealed cellular and tissue structures. The median entropy was higher and its distribution negatively skewed for EMT6 (p<0.01), allowing us to distinguish tumor from its corresponding normal tissue of origin. In viable cells, nuclei were distinguishable from the cytoplasm via higher cytoplasmic NADH signal. Upon loss of cell viability, nuclear NADH signals increased, with characteristically short lifetimes, and the overall NADH intensity decreased, reducing the contrast between nuclei and their surrounding cytoplasm. We detected an increase in the whole fragment mean lifetime (τm p<0.002) and concomitant decrease in the short lifetime component (α1 p< 0.002) within 24 hours of staurosporine exposure. We have demonstrated that MP-FLIM can distinguish tumor from normal and live from dead in LTFs without labels. This approach will facilitate selection of fragments with acceptable viability and tumor content for subsequent drug treatment as part of a platform built for personalizing cancer therapy.

Citation Format: Jonathan Ouellette, John Rafter, Kelsey Tweed, Leung Kau Tang, Christina Scribano, Pichet Adstamongkonkul, Mikaela Schultz, Justine Coburn, Maged Aldeeb, Neil Anthony, Christin Johnson, Kevin Eliceiri, Jonathan Oliner, Tomasz Zal. Tumor/normal and live/dead classification in live tumor fragments using label-free multiphoton microscopy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2472.

Abstract 630: Dynamic imaging of T cell surveillance in live tumor fragments using camelid nanobodies

Immunotherapies (ITx) have revolutionized the oncology landscape. However, predicting patient responses to ITx is difficult based solely on static correlates such as TIL localization and molecular signatures. Anti-tumor immune response depends on motile surveillance by tumor infiltrating lymphocytes (TIL) which recognize antigenic determinants and engage target cells in serial stop-and-go interactions that result in cell killing. However, the hostile tumor microenvironment (TME) can cause TIL dysfunction and lack of cytotoxicity which is manifested as either suppressed or aimless TIL motility. To determine which ITx works best for a given patient, we are developing a diagnostic platform using live tumor fragments (LTF) that preserves the TME and its immune cells. Antibody-based labeling of live tissues is hampered by slow diffusion and function-altering cross-linking. To overcome these limitations, we have used small camelid-derived monovalent antibodies (nanobodies) to monitor TIL motility in LTFs. Human tumor excisions were cut into 300 x 300 x 200 µm LTFs, sorted into glass bottom multi-well plates and cultured. CD8+ cells in LTFs were labeled using an anti-hCD8a camelid VHH nanobody covalently labeled with AF594. The same reagent or a mouse anti-hCD8a whole IgG antibody was used to stain human peripheral blood mononuclear cells, and staining patterns were compared by flow cytometry. Immune responsiveness of LTFs to ITx was ascertained by flow cytometry and secreted protein assays (data shown in a companion abstract). Multiphoton microscopy revealed LTF collagen fibrils and cellular autofluorescence. A fluorescent anti-CD8a nanobody, but not a similarly labeled whole IgG, yielded good contrast and fast staining of two cell subsets. The smaller cells were 12 µm in diameter, cell surface-stained, and lacking autofluorescence, consistent with T cells. The larger cells were elongated, ramified, intracellularly stained, and distinctly autofluorescent, consistent with macrophages. 3D motility tracking revealed characteristic translational motility of the smaller cells at ~10 µm/min along collagenous structures. In contrast, larger cells exhibited only slow motility. Our results show that the motility of human CD8+ T lymphocytes can be revealed in LTF culture using a fluorescent CD8-binding camelid nanobody, likely due to its small size and monovalent binding. Further examination is needed to understand if T cell function is altered. The autofluorescence of larger, immotile cells was consistent with tumor-associated macrophages. Based on this distinction, T cells could be distinguished from the macrophages clearly. Our results support the use of camelid-derived VHH and other small monovalent reagents for live tissue lymphocyte tracking, possibly to evaluate TIL response to ITx in an LTF assay.

Citation Format: Leung Kau Tang, Kelsey Tweed, Christina Scribano, David Wahl, Christin Johnson, M. Anna Zal, Jonathan Oliner, Tomasz Zal. Dynamic imaging of T cell surveillance in live tumor fragments using camelid nanobodies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 630.

Abstract 2779: A live tumor fragment (LTF) platform with real-time imaging for immune response assays

Immuno-Oncology (IO) therapies provide remarkable clinical benefits. However, too few patients respond, and there are no diagnostic tools that predict IO response with high accuracy. Moreover, as more IO drugs and combinations are approved, selecting the best IO-based regimen for each patient will become more complex. To facilitate this selection, we are developing an ex vivo live tumor fragment (LTF) screening platform that retains representation of a patient’s tumor microenvironment (TME) including immune cells, enabling development of deep neural networks to predict IO response and thereby individualize therapy. Here we present preliminary data from our proof-of-concept platform that performs tissue fragmentation/sorting, liquid handling, drug treatment, high-resolution dynamic imaging, and multiplex immuno-assays. Human tumor excisions were obtained from the Univ. of Wisconsin (IRB approved), and CT26 tumors were grown in mice subcutaneously. Live tumors were cut into 300 x 300 µm fragments of 100 - 300 µm thickness, sorted into multi-well plates, and cultured for 48 or 72 h in the presence or absence of anti-PD1 (nivolumab or mouse equivalent), anti-PD1 plus anti-CTLA4 (ipilimumab or mouse equivalent), or concanavalin A (ConA) as a positive control. Cell viability was measured by ATP luminescence assay or flow cytometry. Motility of CD8+ cells was tracked in human LTF using camelid VHH anti-hCD8a-AF594 and 3D multiphoton microscopy for 30 min. Supernatant cytokines were measured using bead immunoassay and T cell markers by flow cytometry. T cells were retained within LTFs, and the proportion of lymphocytes in LTFs was independent of fragment thickness (1.6%/2.1% for 300 µm, 1.4%/2.3% for 200 µm and 1.4%/2.8% for 100 µm thickness, for CD4+ and CD8+ T cells, respectively). Total cell viability and T cell viability exceeded 80% at 48h, and 3D LTF structure remained intact for at least 48 h. We treated LTFs with anti-PD1, anti-PD1 plus anti-CTLA4, or ConA and confirmed the presence of IFN-γ and 10 (mouse) or 16 (human) other cytokines associated with immune activation in both the ConA and anti-PD1 treated samples, but not the control. In human LTFs, cytokine panel upregulation was observed for anti-PD1 vs. control (p=1.1e-5) and anti-PD1 plus anti-CTLA4 vs. anti-PD1 (p=3.7e-9). Using multiphoton microscopy and CD8-binding nanobodies, we observed vigorous CD8+ T cell motility in human LTFs, with a speed of 10 µm/min, which is comparable to that reported in vivo. Our LTF platform has an immuno-competent TME in which we can detect cellular and secreted immune response markers, compare alternative treatments, and track the surveillance activity of infiltrating T cells. Future work will further advance the platform, enabling clinical trials for training and validating deep neural networks to predict response to checkpoint inhibitors and other IO drugs.

Citation Format: Tomasz Zal, Leung Kau Tang, Laura Hrycyniak, Anura Shrestha, Dinesh Joshi, Pichet Adstamongkonkul, Kelsey Tweed, Wesley A. Cox-Muranami, Sean Caenepeel, Hinco J. Gierman, Kevin Eliceiri, Kristina A. Matkowskyj, Sam J. Lubner, John Rafter, Mike Szulczewski, Maneesh Arora, Jonathan Oliner. A live tumor fragment (LTF) platform with real-time imaging for immune response assays [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2779.

Extracellular pH affects the fluorescence lifetimes of metabolic co-factors

SIGNIFICANCE

Autofluorescence measurements of the metabolic cofactors NADH and flavin adenine dinucleotide (FAD) provide a label-free method to quantify cellular metabolism. However, the effect of extracellular pH on flavin lifetimes is currently unknown.

AIM

To quantify the relationship between extracellular pH and the fluorescence lifetimes of FAD, flavin mononucleotide (FMN), and reduced nicotinamide adenine dinucleotide (phosphate) [NAD(P)H].

APPROACH

Human breast cancer (BT474) and HeLa cells were placed in pH-adjusted media. Images of an intracellular pH indicator or endogenous fluorescence were acquired using two-photon fluorescence lifetime imaging. Fluorescence lifetimes of FAD and FMN in solutions were quantified over the same pH range.

RESULTS

The relationship between intracellular and extracellular pH was linear in both cell lines. Between extracellular pH 4 to 9, FAD mean lifetimes increased with increasing pH. NAD(P)H mean lifetimes decreased with increasing pH between extracellular pH 5 to 9. The relationship between NAD(P)H lifetime and extracellular pH differed between the two cell lines. Fluorescence lifetimes of FAD, FAD-cholesterol oxidase, and FMN solutions decreased, showed no trend, and showed no trend, respectively, with increasing pH.

CONCLUSIONS

Changes in endogenous fluorescence lifetimes with extracellular pH are mostly due to indirect changes within the cell rather than direct pH quenching of the endogenous molecules.

Carbomer-based adjuvant elicits CD8 T-cell immunity by inducing a distinct metabolic state in cross-presenting dendritic cells

There is a critical need for adjuvants that can safely elicit potent and durable T cell-based immunity to intracellular pathogens. Here, we report that parenteral vaccination with a carbomer-based adjuvant, Adjuplex (ADJ), stimulated robust CD8 T-cell responses to subunit antigens and afforded effective immunity against respiratory challenge with a virus and a systemic intracellular bacterial infection. Studies to understand the metabolic and molecular basis for ADJ's effect on antigen cross-presentation by dendritic cells (DCs) revealed several unique and distinctive mechanisms. ADJ-stimulated DCs produced IL-1β and IL-18, suggestive of inflammasome activation, but in vivo activation of CD8 T cells was unaffected in caspase 1-deficient mice. Cross-presentation induced by TLR agonists requires a critical switch to anabolic metabolism, but ADJ enhanced cross presentation without this metabolic switch in DCs. Instead, ADJ induced in DCs, an unique metabolic state, typified by dampened oxidative phosphorylation and basal levels of glycolysis. In the absence of increased glycolytic flux, ADJ modulated multiple steps in the cytosolic pathway of cross-presentation by enabling accumulation of degraded antigen, reducing endosomal acidity and promoting antigen localization to early endosomes. Further, by increasing ROS production and lipid peroxidation, ADJ promoted antigen escape from endosomes to the cytosol for degradation by proteasomes into peptides for MHC I loading by TAP-dependent pathways. Furthermore, we found that induction of lipid bodies (LBs) and alterations in LB composition mediated by ADJ were also critical for DC cross-presentation. Collectively, our model challenges the prevailing metabolic paradigm by suggesting that DCs can perform effective DC cross-presentation, independent of glycolysis to induce robust T cell-dependent protective immunity to intracellular pathogens. These findings have strong implications in the rational development of safe and effective immune adjuvants to potentiate robust T-cell based immunity.

Classification of T-cell activation via autofluorescence lifetime imaging

The function of a T cell depends on its subtype and activation state. Here, we show that the imaging of autofluorescence-lifetime signals from quiescent and activated T cells can be used to classify the cells. T cells isolated from human peripheral blood and activated in culture via a tetrameric antibody against the surface ligands CD2, CD3 and CD28 showed specific activation-state-dependent patterns of autofluorescence lifetime. Logistic-regression models and random-forest models classified T cells according to activation state with 97–99% accuracy, and according to activation state (quiescent or activated) and subtype (CD3⁺ CD8⁺ or CD3⁺ CD4⁺) with 97% accuracy. Autofluorescence-lifetime imaging could be used to non-destructively determine T-cell function.

Improving Stem Cell Delivery to the Trabecular Meshwork Using Magnetic Nanoparticles

Glaucoma is a major cause of blindness and is frequently associated with elevated intraocular pressure. The trabecular meshwork (TM), the tissue that primarily regulates intraocular pressure, is known to have reduced cellularity in glaucoma. Thus, stem cells, if properly delivered to the TM, may offer a novel therapeutic option for intraocular pressure control in glaucoma patients. For this purpose, targeted delivery of stem cells to the TM is desired. Here, we used magnetic nanoparticles (Prussian blue nanocubes [PBNCs]) to label mesenchymal stem cells and to magnetically steer them to the TM following injection into the eye's anterior chamber. PBNC-labeled stem cells showed increased delivery to the TM vs. unlabeled cells after only 15-minute exposure to a magnetic field. Further, PBNC-labeled mesenchymal stem cells could be delivered to the entire circumference of the TM, which was not possible without magnetic steering. PBNCs did not affect mesenchymal stem cell viability or multipotency. We conclude that this labeling approach allows for targeted, relatively high-efficiency delivery of stem cells to the TM in clinically translatable time-scales, which are necessary steps towards regenerative medicine therapies for control of ocular hypertension in glaucoma patients.

Fall-related risk factors and osteoporosis in women with rheumatoid arthritis

BACKGROUND

Rheumatoid arthritis (RA) is associated with an increased risk of osteoporotic fractures. Whilst numerous studies have demonstrated low bone density in RA, few studies have examined the risk of falling, which is another major contributor to the pathogenesis of fractures (particularly hip fractures).

OBJECTIVES

The aim of this study was to see if fall risk is increased in women with RA, define high-risk subgroups, and determine what proportion of women have increased risk of hip fracture due to osteoporosis and due to increased fall risk.

METHODS

We performed a case-control study of older women with RA (n = 103) compared with women without RA referred for open access bone densitometry (n = 203). We measured bone density using dual-energy X-ray absorptiometry and fall risk factors (visual acuity, ability to perform standups, and heel-toe walking).

RESULTS

More women with RA gave a history of a previous fall compared with controls (54 vs 44%), although this was just short of being statistically significant (difference 10%, 95% CI -2 to 22). Women with RA were more likely to have abnormal heel-toe walking and inability to perform standups compared with controls (P<0.001); however, visual acuity was similar between cases and controls. Femoral neck osteoporosis was found in 31% and increased fall risk in 68% of women with RA. Women with RA who underperformed in heel-toe walking and were unable to do standups had significantly higher ESR, Health Assessment Questionnaire score and tender joint count. RA symptoms/signs localized to the knees and ankles were more likely to be associated with the presence of fall risk factors.

CONCLUSIONS

Fall-related risk factors predictive of hip fracture are common in women with RA. Fall risk needs to be considered when RA patients are being treated for osteoporosis and further work needs to be done to help reduce the risk of falling and fracture in women with RA.