This project was supported by a Leon J. Thal SEED grant from the California Institute for Regenerative Medicine. Tobias Henning was funded by a Research stipend from the German Research Association (DFG, HE 4578/1-2). We want to gratefully acknowledge Juanito Meneses for his advice on the culture of human embryonic stem cells.

Labeling of mesenchymal stem cells with the fluorescent dye DiD
<ol>
<li>To begin the procedure for labeling mesenchymal stem cells, trypsinize and count the cells to get a suspension with a defined number of cells. </li>
<li>Take the cells out of the incubator and aspirate out old media from the flasks containing the cells to be labeled </li>
<li>Wash the cells with 10 ml of Mg/Ca-free PBS. Aspirate out the PBS. The Mg and Ca would inhibit the Trypsin, therefore we use PBS without these.</li>
<li>Add pre-warmed 0.05% Trypsin, for a T75 flask we use 5ml. Ensure that the entire surface of the flask is covered.</li>
<li>Incubate at 37&deg;C in the incubator for about 5 minutes.</li>
<li>Confirm the detachment under the microscope. If the cells still adhere to the flask, tap it a few times and wait a little longer until the trypsinization is successful.</li>
<li>Now, it is necessary to neutralize the Trypsin by adding media containing 10% FCS. We use an equal amount of media as there is Trypsin. </li>
<li>Pipette up and down a few times to ensure that all the cells are re-suspended in the media.</li>
<li>Transfer the cell solution to a sterile 15ml capped polypropylene tube.</li>
<li>Centrifuge at 400 rcf for 5 minutes.</li>
<li>Aspirate out the supernatant ensuring not to disturb the cell pellet.</li>
<li>Resuspend the cells in DMEM and proceed with the cell count.</li>
<li>Suspend the cells to be labeled at a density of 1x10^6 per ml in serum-free culture medium (DMEM). </li>
<li>This was all preparation of the cell suspension. Now, it is ready to start the labeling.</li>
<li>First, add 5 &micro;L of DiD contrast agent per ml of cell suspension.</li>
<li>Then, mix the solution by gently pipetting.</li>
<li>Incubate the cells with the labeling solution at 37&deg;C for 20 minutes in a 6-well low-attachment dish. </li>
<li>Once the simple incubation is complete, it is necessary to transfer the cell solution to a 15 ml capped polypropylene tube.</li>
<li>Centrifuge it down at 400 rcf for 5 minutes.</li>
<li>Aspirate out the labeling medium, ensuring not to disturb cell pellet. </li>
<li>Wash the cells with PBS. Pipette the cells up and down, making sure to break up the cell pellet.</li>
<li>Repeat the latter two steps two more times, so there is a total of 3 washing steps.</li>
<li>Count the cells and perform a Trypan blue test to determine cell viability. These are standard cell culture protocols that we are not going to explain here.</li>
<li>Your cells are now ready to be imaged in optical imager.</li>
</ol>
Labeling of human embryonic stem cells with the fluorescent dye ICG
<ol>
<li>To begin the procedure for labeling human embryonic stem cells, prepare the contrast agent Indocyanine Green. Mix it with the transfection agent Protamine.</li>
<li>Measure out 1mg of the Indocyanine Green powder. Dissolve the ICG powder in 100 &micro;L of Dimethyl Sulfoxide (DMSO).</li>
<li>Add 400 &micro;L of Dulbecco's Modified Eagles Medium (DMEM + 10% Fetal Calf Serum) media to the mixture and shake it well. This results in a final concentration of 2mg/ml of Indocyanine Green.</li>
<li>Add the transfection agent Protamine. Protamine acts as a shuttle for the contrast agent, so that it gets into the cell more efficiently.</li>
<li>Mix 5 &micro;L Protamine Sulfate, which is supplied at a concentration of 10mg/ml, with 300 &micro;L ICG and 300 &micro;L serum free Dulbecco's Modified Eagles Medium. </li>
<li>Gently shake the new transfection solution for 5 minutes to allow complex to form.</li>
<li>The labeling solution is ready.</li>
<li>Aspirate out the old media from hESC 10mm Petri dish.</li>
<li>Add 5ml of pre-warmed serum-free DMEM.</li>
<li>Add the previously prepared Protamine/ICG solution to the cells. Start the 1 hour incubation by placing the dish in an incubator at 37&deg;C.</li>
<li>After the incubation is complete, remove the dish from the incubator and aspirate out the labeling solution.</li>
<li>Wash the cells by rinsing the dish with 5 ml PBS. </li>
<li>Aspirate out the PBS and replace with 5ml of 0.25% Trypsin. Incubate the dish at 37&deg;C for 5 minutes to allow trypsinization to occur. It helps to shake the dish a little every once in a while.</li>
<li>Gently pipette up and down, to break up the remaining colonies.</li>
<li>Neutralize the Trypsin by adding an equal amount of KSR to the dish.</li>
<li>Transfer the cell solution to a 15ml tube and centrifuge the solution at 400 rcf for 5 minutes.</li>
<li>Resuspend the cells in full media.</li>
<li>If there still are clumps at this point,&nbsp;trypsinize and centrifuge again.</li>
<li>Once a&nbsp;clump-free cell solution is achieved, aspirate out the old media and resuspend the pellet in 10ml of pre-warmed full ESC media.</li>
<li>At this point, it is necessary to separate the mouse feeder cells from the hESCs. This is done to ensure that, later, only imaging the stem cells occurs.</li>
<li>For this, transfer the cell solution to a gelatin coated 10 cm dish. </li>
<li>Put the dish into the 37&deg;C incubator and let it sit for 45 minutes.&nbsp;During this time, make sure not to disturb the dish.&nbsp; Now, the feeders will adhere to the dish and the stem cells will not.</li>
<li>Transfer the solution out of the Petri dish. and now we have a labeled single cells solution of human embryonic stem cells. </li>
<li>The cells can now be counted and a Trypan blue test can be performed on them.</li>
<li>The&nbsp;cells are ready to be imaged!</li>
</ol>
&nbsp;

<ol>
	<li>Daldrup-Link, H. E., Rudelius, M., Metz, S., Piontek, G., Settles, M., Pichler, B., Heinzmann, U., Weinmann, H. J., Schlegel, J., Link, T. M., Rummeny, E. J., Oostendorp, R. A. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stem+cell+tracking+with+Gadophrin-2+--+a+bifunctional+contrast+agent+for+MR+imaging,+optical+imaging+and+fluorescence+microscopy.">Stem cell tracking with Gadophrin-2 -- a bifunctional contrast agent for MR imaging, optical imaging and fluorescence microscopy.</a> Eur J Nucl Med Mol Imaging. 31, 1312-1321 (2004).</li><li>Simon, G. H., Daldrup-Link, H. E., Kau, J., Metz, S., Schlegel, J., Piontek, G., Saborowski, O., Demos, S., Duyster, J., Pichler, B. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optical+imaging+of+experimental+arthritis+using+allogeneic+leukocytes+labeled+with+a+near-infrared+fluorescent+probe.">Optical imaging of experimental arthritis using allogeneic leukocytes labeled with a near-infrared fluorescent probe.</a> Eur J Nucl Med &amp; Mol Imaging. 33, 998-1006 (2006).</li><li>Sutton, E., Henning, T., Pichler, B., Bremer, C., Daldrup-Link, H. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cell+Tracking+with+Optical+imaging.">Cell Tracking with Optical imaging.</a> Eur Radiol. 2, 350-357 (2003).</li><li>Funovics, M. A., Alencar, H., Su, H. S., Khazaie, K., Weissleder, R., Mahmood, U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Miniaturized+multichannel+near+infrared+endoscope+for+mouse+imaging.">Miniaturized multichannel near infrared endoscope for mouse imaging.</a> Mol Imaging. 2, 350-357 (2003).</li></ol>

OI is a relatively new imaging technique, based on the detection of fluorescence. OI is as sensitive as radiotracer-based imaging techniques, but not associated with any irradiation exposure. OI provides an effective means of tracking cells non-invasively and repetitively, thereby providing insight into cell migration to the target site. One major limitation of the technique is the limited tissue penetration of fluorescent probes in vivo. Thus, a tracer accumulation in deep tissues, more than about 5-10 cm from the skin ...

<table><tbody><tr><td>Indocyanine Green (IR-125)</td><td>Reagent</td><td>Fisher Scientific</td><td>AC41254-1000</td><td></td></tr><tr><td>DMSO</td><td>Reagent</td><td>Sigma-Aldrich</td><td>D-2650</td><td></td></tr><tr><td>D-MEM High Glucose </td><td>Reagent</td><td>Sigma-Aldrich</td><td>D5648</td><td></td></tr><tr><td>Gelatin</td><td>Reagent</td><td>Sigma-Aldrich</td><td>G1890</td><td>Dilute to final concentration of 0.1% in PBS</td></tr><tr><td>PBS, Mg and Ca free</td><td>Reagent</td><td>GIBCO, by Life Technologies</td><td>14190-144</td><td></td></tr><tr><td>Trypsin-EDTA 0.05% </td><td>Reagent</td><td>Invitrogen</td><td>25300-120</td><td></td></tr><tr><td>Trypsin-EDTA 0.25% </td><td>Reagent</td><td>Invitrogen</td><td>25200-114</td><td></td></tr><tr><td>FCS, characterized</td><td>Reagent</td><td>Hyclone</td><td>SH30071.03</td><td></td></tr><tr><td>Cell Strainer (40 &amp;mu;m Nylon)</td><td>Reagent</td><td>BD Biosciences</td><td>352340</td><td></td></tr><tr><td>DiD</td><td>Reagent</td><td>Molecular Probes, Life Technologies</td><td>V-22887</td><td></td></tr><tr><td>Knockout DMEM</td><td>Reagent</td><td>GIBCO, by Life Technologies</td><td>10829018</td><td></td></tr><tr><td>Knockout Serum Replacer</td><td>Reagent</td><td>GIBCO, by Life Technologies</td><td>10828028</td><td></td></tr><tr><td>b-Mercapt&amp;#8211;thanol </td><td>Reagent</td><td>Sigma-Aldrich</td><td>7522</td><td></td></tr><tr><td>Non-essential Amino Acids </td><td>Reagent</td><td>GIBCO, by Life Technologies</td><td>11140050</td><td></td></tr><tr><td>FGF-2</td><td>Reagent</td><td>R&amp;amp;D Systems</td><td>233-FB-025</td><td></td></tr><tr><td>Glutamine 200mM </td><td>Reagent</td><td>GIBCO, by Life Technologies</td><td>25030081</td><td></td></tr><tr><td>Penicillin/Streptomycin</td><td>Reagent</td><td>GIBCO, by Life Technologies</td><td>15140-122</td><td></td></tr><tr><td>Protamine Sulfate</td><td>Reagent</td><td>American Pharmaceutical Partners</td><td></td><td></td></tr></tbody></table>

labeling stem cells with fluorescent dyes for non-invasive detection with optical imaging

Optical imaging (OI) is an easy, fast and inexpensive tool for in vivo monitoring of new stem cell based therapies. The technique is based on ex vivo labeling of stem cells with a fluorescent dye, subsequent intravenous injection of the labeled cells and visualization of their accumulation in specific target organs or pathologies. The presented technique demonstrates how we label human mesenchymal stem cells (hMSC) by simple incubation with the lipophilic fluorescent dye DiD (C67H103CIN2O3S) and how we label human embryonic stem cells (hESC) with the FDA approved fluorescent dye Indocyanine Green (ICG). The uptake mechanism is via adherence and diffusion of the lypophilic dye across the phospholipid cell membrane bilayer. The labeling efficiency is usually improved if the cells are incubated with the dye in serum-free media as opposed to incubation in serum-containing media. Furthermore, the addition of the transfection agent Protamine Sulfate significantly improves contrast agent uptake.

Watch this Scientific Journal Video about Labeling Stem Cells with Fluorescent Dyes for non-invasive Detection with Optical Imaging at JoVE.com

Labeling Stem Cells with Fluorescent Dyes for non-invasive Detection with Optical Imaging

This video shows techniques for labeling of human embryonic stem cells and mesenchymal stem cells with fluorescent dyes. This technique can be used for an in vivo tracking of transplanted stem cells with optical imaging and for histopathological correlations with fluorescence microscopy.

Optical imaging (OI) is an easy, fast and inexpensive tool for in vivo monitoring of new stem cell based therapies. The technique is based on ex vivo ...

labeling-stem-cells-with-fluorescent-dyes-for-non-invasive-detection

Research

JoVE Journal

Biology

13.3K Views.  Contrast Agent Research Group at the Center for Molecular and Functional Imaging, Department of Radiology, University of California San Francisco. Deze video toont technieken voor de etikettering van menselijke embryonale stamcellen en mesenchymale stamcellen met fluorescerende kleurstoffen. Deze techniek kan worden gebruikt voor een in-vivo volgen van getransplanteerde stamcellen met optische beeldvorming en voor histopathologisch correlaties met fluorescentie microscopie.

Video: Labeling Stem Cells with Fluorescent Dyes for non-invasive Detection with Optical Imaging

A Method for Lineage Tracing of Corneal Cells Using Multi-color Fluorescent Reporter Mice

Lineage tracing experiments define the origin, fate and behavior of cells in a specific tissue or organism. This technique has been successfully applied for many decades, revealing seminal findings in developmental biology. More recently, it was adopted by stem cell biologists to identify and track different stem cell populations with minimal experimental intervention. The recent developments in mouse genetics, the availability of a large number of mouse strains, and the advancements in fluorescent microscopy allow the straightforward design of powerful lineage tracing systems for various tissues with basic expertise, using commercially available tools. We have recently taken advantage of this powerful methodology to explore the origin and fate of stem cells at the ocular surface using R26R-Confetti mouse. This model offers a multi-color genetic system, for the expression of 4 fluorescent genes in a random manner. Here we describe the principles of this methodology and provide an adaptable protocol for designing lineage tracing experiments; specifically for the corneal epithelium as well as for other tissues.

In this article we describe the principles for designing and performing a multi-color lineage tracing experiment using R26R-Confetti mice. We provide a specific protocol for tracking corneal epithelial cells which can be modified for other tissues of interest.

Lineage tracing experiments define the origin, fate and behavior of cells in a specific tissue or organism. This technique has been successfully applied ...

Developmental Biology

Analyzing In Vivo Cell Migration using Cell Transplantations and Time-lapse Imaging in Zebrafish Embryos

Cell migration is key to many physiological and pathological conditions, including cancer metastasis. The cellular and molecular bases of cell migration have been thoroughly analyzed in vitro. However, in vivo cell migration somehow differs from in vitro migration, and has proven more difficult to analyze, being less accessible to direct observation and manipulation. This protocol uses the migration of the prospective prechordal plate in the early zebrafish embryo as a model system to study the function of candidate genes in cell migration. Prechordal plate progenitors form a group of cells which, during gastrulation, undergoes a directed migration from the embryonic organizer to the animal pole of the embryo. The proposed protocol uses cell transplantation to create mosaic embryos. This offers the combined advantages of labeling isolated cells, which is key to good imaging, and of limiting gain/loss of function effects to the observed cells, hence ensuring cell-autonomous effects. We describe here how we assessed the function of the TORC2 component Sin1 in cell migration, but the protocol can be used to analyze the function of any candidate gene in controlling cell migration in vivo.

Analyzing In Vivo Cell Migration using Cell Transplantations and Time-lapse Imaging in Zebrafish Embryos

Combining cell transplantation, cytoskeletal labeling and loss/gain of function approaches, this protocol describes how the migrating zebrafish prospective prechordal plate can be used to analyze the function of a candidate gene in in vivo cell migration.

Cell migration is key to many physiological and pathological conditions, including cancer metastasis. The cellular and molecular bases of cell migration ...

Labeling hESCs and hMSCs with Iron Oxide Nanoparticles for Non-Invasive in vivo Tracking with MR Imaging

In recent years, stem cell research has led to a better understanding of developmental biology, various diseases and its potential impact on regenerative medicine. A non-invasive method to monitor the transplanted stem cells repeatedly in vivo would greatly enhance our ability to understand the mechanisms that control stem cell death and identify trophic factors and signaling pathways that improve stem cell engraftment. MR imaging has been proven to be an effective tool for the in vivo depiction of stem cells with near microscopic anatomical resolution. In order to detect stem cells with MR, the cells have to be labeled with cell specific MR contrast agents. For this purpose, iron oxide nanoparticles, such as superparamagnetic iron oxide particles (SPIO), are applied, because of their high sensitivity for cell detection and their excellent biocompatibility. SPIO particles are composed of an iron oxide core and a dextran, carboxydextran or starch coat, and function by creating local field inhomogeneities, that cause a decreased signal on T2-weighted MR images. This presentation will demonstrate techniques for labeling of stem cells with clinically applicable MR contrast agents for subsequent non-invasive in vivo tracking of the labeled cells with MR imaging.

For the evaluation of new stem cell therapies it is important to non-invasively track the injected cells in vivo. This video will show you how to label human mesenchymal and embryonic stem cells with iron oxide based contrast agents in vivo for subsequent MR imaging in vivo.

In recent years, stem cell research has led to a better understanding of developmental biology, various diseases and its potential impact on regenerative ...

In vitro and in vivo Bioluminescence Reporter Gene Imaging of Human Embryonic Stem Cells

The discovery of human embryonic stem cells (hESCs) has dramatically increased the tools available to medical scientists interested in regenerative medicine. However, direct injection of hESCs, and cells differentiated from hESCs, into living organisms has thus far been hampered by significant cell death, teratoma formation, and host immune rejection. Understanding the in vivo hESC behavior after transplantation requires novel imaging techniques to longitudinally monitor hESC localization, proliferation, and viability. Molecular imaging has given investigators a high-throughput, inexpensive, and sensitive means for tracking in vivo cell proliferation over days, weeks, and even months. This advancement has significantly increased the understanding of the spatio-temporal kinetics of hESC engraftment, proliferation, and teratoma-formation in living subjects.

A major advance in molecular imaging has been the extension of noninvasive reporter gene assays from molecular and cellular biology into in vivo multi-modality imaging platforms. These reporter genes, under control of engineered promoters and enhancers that take advantage of the host cell s transcriptional machinery, are introduced into cells using a variety of vector and non-vector methods. Once in the cell, reporter genes can be transcribed either constitutively or only under specific biological or cellular conditions, depending on the type of promoter used. Transcription and translation of reporter genes into bioactive proteins is then detected with sensitive, noninvasive instrumentation (e.g., CCD cameras) using signal-generating probes such as D-luciferin.

To avoid the need for excitatory light to track stem cells in vivo as is required for fluorescence imaging, bioluminescence reporter gene imaging systems require only an exogenously administered probe to induce light emission. Firefly luciferase, derived from the firefly Photinus pyralis, encodes an enzyme that catalyzes D-luciferin to the optically active metabolite, oxyluciferin. Optical activity can then be monitored with an external CCD camera. Stably transduced cells that carry the reporter construct within their chromosomal DNA will pass the reporter construct DNA to daughter cells, allowing for longitudinal monitoring of hESC survival and proliferation in vivo. Furthermore, because expression of the reporter gene product is required for signal generation, only viable parent and daughter cells will create bioluminescence signal; apoptotic or dead cells will not. 

In this video, the specific materials and methods needed for tracking stem cell proliferation and teratoma formation with bioluminescence imaging will be described.

With the growing interest in stem cell therapies, molecular imaging techniques are ideal for monitoring stem cell behavior after transplantation. Luciferase reporter genes have enabled non-invasive, repetitive assessment of cell survival, location, and proliferation in vivo. This video will demonstrate how to track hESC proliferation in a living mouse.

The discovery of human embryonic stem cells (hESCs) has dramatically increased the tools available to medical scientists interested in regenerative ...

Isolation of Stem-like Cells from 3-Dimensional Spheroid Cultures

Despite advances in adult stem cell research, identification and isolation of stem cells from tissue specimens remains a major challenge. While resident stem cells are relatively quiescent with niche restraints in adult tissues, they enter the cell cycle in anchor-free three-dimensional (3D) culture and undergo both symmetric and asymmetric cell division, giving rise to both stem and progenitor cells. The latter proliferate rapidly and are the major cell population at various stages of lineage commitment, forming heterogeneous spheroids. Using primary normal human prostate epithelial cells (HPrEC), a spheroid-based, label-retention assay was developed that permits the identification and functional isolation of the spheroid-initiating stem cells at a single cell resolution.
HPrEC or cell lines are two-dimensionally (2D) cultured with BrdU for 10 days to permit its incorporation into the DNA of all dividing cells, including self-renewing stem cells. Wash out commences upon transfer to the 3D culture for 5 days, during which stem cells self-renew through asymmetric division and initiate spheroid formation. While relatively quiescent daughter stem cells retain BrdU-labeled parental DNA, the daughter progenitors rapidly proliferate, losing the BrdU label. BrdU can be substituted with CFSE or Far Red pro-dyes, which permit live stem cell isolation by FACS. Stem cell characteristics are confirmed by in vitro spheroid formation, in vivo tissue regeneration assays, and by documenting their symmetric/asymmetric cell divisions. The isolated label-retaining stem cells can be rigorously interrogated by downstream molecular and biologic studies, including RNA-seq, ChIP-seq, single cell capture, metabolic activity, proteome profiling, immunocytochemistry, organoid formation, and in vivo tissue regeneration. Importantly, this marker-free functional stem cell isolation approach identifies stem-like cells from fresh cancer specimens and cancer cell lines from multiple organs, suggesting wide applicability. It can be used to identify cancer stem-like cell biomarkers, screen pharmaceuticals targeting cancer stem-like cells, and discover novel therapeutic targets in cancers.

Using human primary prostate epithelial cells, we report a novel biomarker-free method of functional characterization of stem-like cells by a spheroid-based label-retention assay. A step-by-step protocol is described for BrdU, CFSE, or Far Red 2D cell labeling; three-dimensional spheroid formation; label-retaining stem-like cell identification by immunocytochemistry; and isolation by FACS.

Despite advances in adult stem cell research, identification and isolation of stem cells from tissue specimens remains a major challenge. While resident ...

Cancer Research

Multimodal Imaging of Stem Cell Implantation in the Central Nervous System of Mice

During the past decade, stem cell transplantation has gained increasing interest as primary or secondary therapeutic modality for a variety of diseases, both in preclinical and clinical studies. However, to date results regarding functional outcome and/or tissue regeneration following stem cell transplantation are quite diverse. Generally, a clinical benefit is observed without profound understanding of the underlying mechanism(s)1. Therefore, multiple efforts have led to the development of different molecular imaging modalities to monitor stem cell grafting with the ultimate aim to accurately evaluate survival, fate and physiology of grafted stem cells and/or their micro-environment. Changes observed in one or more parameters determined by molecular imaging might be related to the observed clinical effect. In this context, our studies focus on the combined use of bioluminescence imaging (BLI), magnetic resonance imaging (MRI) and histological analysis to evaluate stem cell grafting.
BLI is commonly used to non-invasively perform cell tracking and monitor cell survival in time following transplantation2-7, based on a biochemical reaction where cells expressing the Luciferase-reporter gene are able to emit light following interaction with its substrate (e.g. D-luciferin)8, 9. MRI on the other hand is a non-invasive technique which is clinically applicable10 and can be used to precisely locate cellular grafts with very high resolution11-15, although its sensitivity highly depends on the contrast generated after cell labeling with an MRI contrast agent. Finally, post-mortem histological analysis is the method of choice to validate research results obtained with non-invasive techniques with highest resolution and sensitivity. Moreover end-point histological analysis allows us to perform detailed phenotypic analysis of grafted cells and/or the surrounding tissue, based on the use of fluorescent reporter proteins and/or direct cell labeling with specific antibodies.
In summary, we here visually demonstrate the complementarities of BLI, MRI and histology to unravel different stem cell- and/or environment-associated characteristics following stem cell grafting in the CNS of mice. As an example, bone marrow-derived stromal cells, genetically engineered to express the enhanced Green Fluorescent Protein (eGFP) and firefly Luciferase (fLuc), and labeled with blue fluorescent micron-sized iron oxide particles (MPIOs), will be grafted in the CNS of immune-competent mice and outcome will be monitored by BLI, MRI and histology (Figure 1).

This article describes an optimized sequence of events for multimodal imaging of cellular grafts in rodent brain using: (i) in vivo bioluminescence and magnetic resonance imaging, and (ii) post mortem histological analysis. Combining these imaging modalities on a single animal allows cellular graft evaluation with high resolution, sensitivity and specificity.

During the past decade, stem cell transplantation has gained increasing interest as primary or secondary therapeutic modality for a variety of diseases, ...

Neuroscience

In Vivo Tracking of Human Adipose-derived Mesenchymal Stem Cells in a Rat Knee Osteoarthritis Model with Fluorescent Lipophilic Membrane Dye

In order to support the clinical application of human adipose-derived mesenchymal stem cell (haMSC) therapy for knee osteoarthritis (KOA), we examined the efficacy of cell persistence and biodistribution of haMSCs in animal models. We demonstrated a method to label the cell membrane of haMSCs with lipophilic fluorescent dye. Subsequently, intra-articular injection of the labeled cells in rats with surgically induced KOA was monitored dynamically by an in vivo imaging system. We employed the lipophilic carbocyanines DiD (DilC18 (5)), a far-red fluorescent Dil (dialkylcarbocyanines) analog, which utilized a red laser to avoid excitation of the natural green autofluorescence from surrounding tissues. Furthermore, the red-shifted emission spectra of DiD allowed deep-tissue imaging in live animals and the labeling procedure caused no cytotoxic effects or functional damage to haMSCs. This approach has been shown to be an efficient tracking method for haMSCs in a rat KOA model. The application of this method could also be used to determine the optimal administration route and dosage of MSCs from other sources in pre-clinical studies.

In Vivo Tracking of Human Adipose-derived Mesenchymal Stem Cells in a Rat Knee Osteoarthritis Model with Fluorescent Lipophilic Membrane Dye

This protocol describes an efficient way to monitor the cell persistence and biodistribution of human adipose-derived mesenchymal stem cells (haMSCs) by far-red fluorescence labeling in a rat knee osteoarthritis (KOA) model via intra-articular (IA) injection.

In order to support the clinical application of human adipose-derived mesenchymal stem cell (haMSC) therapy for knee osteoarthritis (KOA), we examined the ...

A Label-Free Segmentation Approach for Intravital Imaging of Mammary Tumor Microenvironment

The ability to visualize complex and dynamic physiological interactions between numerous cell types and the extracellular matrix (ECM) within a live tumor microenvironment is an important step toward understanding mechanisms that regulate tumor progression. While this can be accomplished through current intravital imaging techniques, it remains challenging due to the heterogeneous nature of tissues and the need for spatial context within the experimental observation. To this end, we have developed an intravital imaging workflow that pairs collagen second harmonic generation imaging, endogenous fluorescence from the metabolic co-factor NAD(P)H, and fluorescence lifetime imaging microscopy (FLIM) as a means to non-invasively compartmentalize the tumor microenvironment into basic domains of the tumor nest, the surrounding stroma or ECM, and the vasculature. This non-invasive protocol details the step-by-step process ranging from the acquisition of time-lapse images of mammary tumor models to post-processing analysis and image segmentation. The primary advantage of this workflow is that it exploits metabolic signatures to contextualize the dynamically changing live tumor microenvironment without the use of exogenous fluorescent labels, making it advantageous for human patient-derived xenograft (PDX) models and future clinical use where extrinsic fluorophores are not readily applicable.

The intravital imaging method described here utilizes collagen second harmonic generation and endogenous fluorescence from the metabolic co-factor NAD(P)H to non-invasively segment an unlabeled tumor microenvironment into tumor, stromal, and vascular compartments for in-depth analysis of 4D intravital images.

The ability to visualize complex and dynamic physiological interactions between numerous cell types and the extracellular matrix (ECM) within a live tumor ...

Fluorescent Dye Labeling of Erythrocytes and Leukocytes for Studying the Flow Dynamics in Mouse Retinal Circulation

The retinal and choroidal blood flow dynamics may provide insight into the pathophysiology and sequelae of various ocular diseases, such as glaucoma, diabetic retinopathy, age-related macular degeneration (AMD) and other ocular inflammatory conditions. It may also help to monitor the therapeutic responses in the eye. The proper labeling of the blood cells, coupled with live-cell imaging of the labeled cells, allows for the investigation of the flow dynamics in the retinal and choroidal circulation. Here, we describe the standardized protocols of 1.5% indocyanine green (ICG) and 1% sodium fluorescein labeling of mice erythrocytes and leukocytes, respectively. Scanning laser ophthalmoscopy (SLO) was applied to visualize the labeled cells in the retinal circulation of C57BL/6J mice (wild type). Both methods demonstrated distinct fluorescently labeled cells in the mouse retinal circulation. These labeling methods can have wider applications in various ocular disease models.

Live-cell imaging of the labeled blood cells in ocular circulation can provide information about inflammation and ischemia in diabetic retinopathy and age-related macular degeneration. A protocol to label blood cells and image the labeled cells in the retinal circulation is described.

The retinal and choroidal blood flow dynamics may provide insight into the pathophysiology and sequelae of various ocular diseases, such as glaucoma, ...

Medicine

In vivo Clonal Tracking of Hematopoietic Stem and Progenitor Cells Marked by Five Fluorescent Proteins using Confocal and Multiphoton Microscopy

We developed and validated a fluorescent marking methodology for clonal tracking of hematopoietic stem and progenitor cells (HSPCs) with high spatial and temporal resolution to study in vivo hematopoiesis using the murine bone marrow transplant experimental model. Genetic combinatorial marking using lentiviral vectors encoding fluorescent proteins (FPs) enabled cell fate mapping through advanced microscopy imaging. Vectors encoding five different FPs: Cerulean, EGFP, Venus, tdTomato, and mCherry were used to concurrently transduce HSPCs, creating a diverse palette of color marked cells. Imaging using confocal/two-photon hybrid microscopy enables simultaneous high resolution assessment of uniquely marked cells and their progeny in conjunction with structural components of the tissues. Volumetric analyses over large areas reveal that spectrally coded HSPC-derived cells can be detected non-invasively in various intact tissues, including the bone marrow (BM), for extensive periods of time following transplantation. Live studies combining video-rate multiphoton and confocal time-lapse imaging in 4D demonstrate the possibility of dynamic cellular and clonal tracking in a quantitative manner.

In vivo Clonal Tracking of Hematopoietic Stem and Progenitor Cells Marked by Five Fluorescent Proteins using Confocal and Multiphoton Microscopy

Combinatorial 5 fluorescent proteins marking of hematopoietic stem and progenitor cells allows in vivo clonal tracking via confocal and two-photon microscopy, providing insights into bone marrow hematopoietic architecture during regeneration. This method allows non-invasive fate mapping of spectrally-coded HSPCs-derived cells in intact tissues for extensive periods of time following transplantation.

We developed and validated a fluorescent marking methodology for clonal tracking of hematopoietic stem and progenitor cells (HSPCs) with high spatial and ...

Labeling Stem Cells with Fluorescent Dyes for non-invasive Detection with Optical Imaging

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