Name: real-time imaging of ccl5-induced migration of periosteal skeletal stem cells in mice
Uploaded: 2020-09-16T14:00:00.000+00:00
Duration: 6 min 10 s
Description: Watch this Scientific Journal Video about Real-Time Imaging of CCL5-Induced Migration of Periosteal Skeletal Stem Cells in Mice at JoVE.com

This work was supported by the Bone Disease Program of Texas Award, the Caroline Wiess Law Fund Award, and the NIAMS of the National Institutes of Health under award numbers R01 AR072018, R21 AG064345, R01 CA221946 to D.P.&#160; We thank M.E. Dickinson and T.J. Vadakkan in the BCM Optical Imaging and Vital Microscopy Core&#160;and the&#160;BCM Advanced Technology Cores&#160;with funding from NIH (AI036211,&#160;CA125123, and DK056338).
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All mice were maintained in pathogen-free conditions, and all procedures were approved by Baylor College of Medicine&#8217;s Institutional Animal Care and Use Committee (IACUC).
1. Mouse preparation
<ol>
	<li>Cross Mx1-Cre17 and Rosa26-loxP-stop-loxP-tdTomato (Tom)18 mice (purchased from the Jackson Laboratory) with &#945;SMA-GFP mice (provided here by Drs. Ivo Kalajzic and Henry Kronenberg) to generate Mx1-Cre+Rosa26-Tomato+&#945;SMA-GFP+ (Mx1/Tomato/&#945;SMA-GFP) reporter mice (Figure 2A).&#160;</li>
	<li>For Mx1-Cre induction, inject mice with 25 mg/kg pIpC every other day for 10 days.&#160;</li>
	<li>Irradiate mice with 9.5 Gy 1 day prior to intravenous transplantation of 1 x 106 whole bone marrow mononuclear cells from wild-type C57BL/6 mice (WT-BMT)19. &#160;</li>
	<li>After 6 to 8 weeks of recovery, subject mice to the in vivo imaging of periosteal cell migration protocol described below. 
	NOTE: Irradiation and WT-BMT of Mx1-Cre mice are necessary to eliminate endogenously Mx1-labeled hematopoietic cells that may respond to an injury. Six to eight weeks post-irradiation, the host&#39;s hematopoietic cell count is at &#60;5% and thus ready for imaging19.</li>
</ol>
2. Mouse restraint and imaging mount
<ol>
	<li>Create a mouse restraint with a 50 mL conical tube (Figure 1A).
	<ol>
		<li>Using pointed scissors, poke a hole through the bottom of the conical. Cut from the bottom hole to the top of the conical (the cut side will be the top of the restraint).&#160;</li>
		<li>Make a cut approximately 4&#8211;5 cm long parallel to the previous cut and halfway down (~2 cm) from the top of the restraint. Remove this section of the conical and smooth the edges were necessary.</li>
	</ol>
	</li>
	<li>Construct a conical tube imaging mount using an adjustable angle plate, a 0.5&#8221; optical post, and a right-angle clamp for the 0.5&#8221; post, 0.1875&#8221; Hex (Figure 1B and Table of Materials).
	<ol>
		<li>Adjust the angle plate to a 35&#176; angle. On the left side of the angle plate, screw the optical post into the second hole from the back of the plate.</li>
		<li>On the right side of the adjustable plate, insert a spring-loaded 0.1875&#8221; Hex-locking 0.25&#8221; thumbscrew into the second hole from the front and last holes on the plate. The right-angle clamp will be used with the optical post to secure the conical mouse restraint in place.</li>
	</ol>
	</li>
</ol>
3. Preoperative surgical procedure
<ol>
	<li>Mouse anesthesia
	<ol>
		<li>For pain management, subcutaneously inject the mouse with sustained release buprenorphine (1 mg/kg BW) 30&#8211;60 min prior to surgery.</li>
		<li>Anesthetize mice using rodent III CCM combination (combo III) anesthesia containing 37.5 mg/mL ketamine, 1.9 mg/mL xylazine, and 0.37 mg/mL acepromazine. The appropriate dosage for mice is 0.75&#8211;1.50 mL per 1 kg of body weight. The dose will last 30&#8211;45 min.</li>
		<li>Once the mouse is anesthetized, apply ophthalmic ointment to the eyes with a sterile cotton swab to prevent eye dehydration.</li>
		<li>For long-term imaging (&#62;45 min), administer anesthesia again to maintain proper anesthetic depth as follows.
		<ol>
			<li>Prepare a 1 mL syringe with a sufficient amount of combo III to maintain anesthesia for the planned imaging duration (0.75 mL/kg BW per 30 min of additional sedation). Attach a 25 G butterfly needle infusion set with 12&#8221; tubing to the syringe and push anesthetic through the tubing and needle.</li>
			<li>Insert the butterfly needle intraperitoneally, then tape the needle in place.&#160; 
			NOTE: This is how the additional combo III will be administered during imaging such that there is no need to move the animal or disrupt the plane of view.</li>
		</ol>
		</li>
		<li>Provide thermal support with a heating pad kept at 37&#176;C throughout the procedure.&#160;For prolonged imaging (&#62;1hr) additional fluid support will be necessary.&#160; Supplemental fluids can be provided I.P. with additional Combo III during imaging or 33 mL/kg saline (0.9 NaCl) subcutaneously.</li>
	</ol>
	</li>
	<li>Mouse restraint and preparation of the surgical site
	<ol>
		<li>Use clippers to remove as much hair as possible from the top of the head. Apply depilatory cream to the shaved area to remove any remaining hair at the surgical site.&#160;</li>
		<li>Ensure that the mouse is fully anesthetized by a lack of response to toe pinches. After 15 min, if the mouse is not fully anesthetized, administer a second smaller dose of combo III (&#60;0.75 mL/kg BW).</li>
		<li>Place the mouse in the restraint tail-first, sliding it far enough backwards such that the nose slightly hangs over the edge of the conical. &#160;</li>
		<li>Tape the front paws to the bottom of the conical tube using medical tape.</li>
		<li>Place conical tube with mouse on an imaging mount that is set at a 35&#176; angle and secure using the right-angle clamp (Figure 1C).</li>
		<li>Once the mouse is secure in the imaging mount, clean the surgical site 3x with alternating scrubs of betadine scrub and 70% isopropyl alcohol. Again, check that the animal is fully sedated.</li>
		<li>Move the mouse to a clean absorbent pad and place a drape over the mouse to create a large sterile field.&#160;&#160;&#160;</li>
	</ol>
	</li>
</ol>
4. Surgical procedure
<ol>
	<li>Opening incision
	<ol>
		<li>Using fine-tipped forceps, pick up the skin immediately medial to the right ear. With microdissection scissors, cut the skin being held by the forceps.&#160; 
		NOTE: Initiating the incision using the method described above creates a rounded incision that is more suitable for suturing after the procedure.</li>
		<li>Make a transverse incision starting from the initial incision toward the left ear (&#60;1 cm).&#160; Make another incision, starting from the initial incision, towards the nose of the animal (~2&#8211;3 mm past the right eye).</li>
		<li>Separate the skin from the periosteum using the forceps and scissors to gently cut through the connective tissue separating the skin from calvaria periosteum.&#160;</li>
		<li>Using a sterile cotton swab, apply some ophthalmic ointment to the top of the skin flap.&#160; Gently pick up the skin flap and fold it over the left eye. The intersection of the sagittal and coronal sutures should be clearly exposed (Figure 1E). 
		NOTE: The ophthalmic ointment is used to keep the skin flap in place.</li>
		<li>Flush the open surface with sterile PBS to clean the area of any blood and residual hair.&#160; 
		NOTE: If necessary, use fine-tipped forceps to remove hairs that remain after flushing, but be careful not to damage the periosteum.</li>
	</ol>
	</li>
	<li>Microfracture
	<ol>
		<li>To generate microfractures on the calvaria, remove the plunger of a 29 G insulin syringe and cut the back end of the syringe, around the 300&#8211;400 uL marks. 
		NOTE: This step makes it easier to maneuver under a dissection scope when producing the injury.</li>
		<li>Place the tip of a bevel (one to two needle widths) towards the nose from the coronal suture and one to two needle widths to the right of the sagittal suture (Figure 1E).</li>
		<li>Gently rotate the syringe clockwise, then counterclockwise several times. 
		NOTE: In young mice, a very small amount of downward pressure is needed to create a circular microfracture. Be careful not to let the needle penetrate the brain, as this will cause bleeding and interfere with imaging.</li>
		<li>Use a 27 G needle to widen the microfracture to ~0.4 mm. If bone fragments remain in the microfracture, flush the area with PBS. If bone fragments still remain in the microfracture, use the 29 G needle to gently scoop them out.&#160;</li>
		<li>Repeat steps 4.2.1&#8211;4.2.4 to create an injury on the left side of the sagittal suture. 
		NOTE: At this point, there are two options: 1) immediately proceed to CCL5 treatment (section 4.3) and imaging (section 5); or 2) close the surgical site following the postoperative procedures in section 6. At 24 h later, anesthetize the mouse again, reopen the surgical sight, treat the injury with CCL5 (section 4.3), and perform intravital imaging (section 5) and postoperative care (section 6).</li>
	</ol>
	</li>
	<li>CCL5 treatment
	<ol>
		<li>From a stock of RANTES (100 ng/mL), make a solution of 10 ng/mL using basement membrane matrix (Table of Materials). Keep this solution on ice to keep the matrix in liquid form.</li>
		<li>Treat each injury with 2 &#956;L of CCL5 (10 ng/&#956;L) by using a 2-20 &#956;L pipette (this pipette tip has a larger diameter, which is more effective when using a viscous liquid). Allow the matrix to solidify.</li>
		<li>Once the matrix has solidified, gently cover the calvaria with the skin flap to ensure the tissue does not become dehydrated. Incubate for 1 h prior to imaging.</li>
	</ol>
	</li>
</ol>
5. Intravital imaging
<ol>
	<li>Microscope settings
	<ol>
		<li>Turn on the multiphoton laser (femtosecond titanium-sapphire laser). Set the wavelength to 880 nm and adjust the power for second harmonic generation (SHG) imaging (440 nm) of the bone.</li>
		<li>Turn on the 488 nm and 561 nm solid state lasers for excitation of GFP- and tdTomato-expressing cells, respectively.</li>
		<li>Turn on PMT (photomultiplier tube) detectors for second harmonic generation (405&#8211;455 nm detection) and GFP (505&#8211;550 nm detection) signals. Turn on HyD 3 detector for tomato (590&#8211;620 nm detection) signal.&#160;</li>
	</ol>
	</li>
	<li>Mounting
	<ol>
		<li>Before moving the mouse to the scope, check the visual plane of the calvaria by gently pressing the back of the mouse&#8217;s head. If the plane is not level, adjust the position by gently rotating the mouse restraint to the left or the right.&#160; 
		NOTE: This is a critical step to ensure sufficient image quality.</li>
		<li>Apply sterile 2% methylcellulose in water (w/v) to cover the entire calvaria and skin flap and prevent drying of the tissue.</li>
		<li>Place the mouse on the XYZ-axis motorized microscope stage (Figure 1G). Using the epifluorescent light, align the mouse so that 1) it is facing to the microscope and 2) the intersection of the coronal and sagittal sutures is the centered reference point of the stage.</li>
		<li>Place the glass cover on the imaging area and double-check the alignment (Figure 1H).</li>
	</ol>
	</li>
	<li>Time-lapse imaging
	<ol>
		<li>Use a low magnification lens (25x water immersion objective with NA = 0.95) to scan the calvaria. Acquire a reference image of the sagittal and coronal suture intersection.</li>
		<li>Using the SHG and fluorescent signals from the cells, locate each injury sight and record the XYZ coordinates as well as the distances from the sagittal and coronal sutures (Figure 2B).</li>
		<li>Pick a location on either the coronal or sagittal sutures for long-term imaging. Take a detailed Z-stack image of this area from reference during imaging.&#160; 
		NOTE: Since the sutures represent a known P-SSC niche, this is where the cells will be migrating from in response to the calvaria injury.</li>
		<li>Use the time-lapse software settings to record an image every 1 min for at least 1 h. In the time between snapshots, compare the current field of view with the initial field of view. If they are different, use the Z-stack image to determine in which direction the field of view needs to be adjusted.</li>
	</ol>
	</li>
</ol>
6. Postoperative animal care
<ol>
	<li>After imaging, rinse the exposed calvaria with sterile PBS to remove the methylcellulose.&#160;</li>
	<li>To close the incision, gently place the skin flap over the calvaria. Use sterile cotton swabs to remove residual ophthalmic ointment and dry the incision site.</li>
	<li>Using monofilament nylon 5-0 size nonabsorbable sutures with an attached C-1 reverse cutting needle, close the surgical site. Use a sterile cotton swab to apply triple antibiotic ointment to the closed incision. 
	NOTE: Scarring is reduced with high quality suturing techniques and minimum bleeding.</li>
	<li>Place mouse in a clean cage on a warm surface and check every 15 min until sternal recumbency is achieved.</li>
	<li>Administer a second dose of sustained release buprenorphine 72 h post-surgery.</li>
	<li>Monitor daily for huddling behavior, ruffled fur, and/or lack of ambulation until sutures are removed (~1 week).&#160;</li>
</ol>

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L.C.O. and D.P. disclose a pending patent entitled &#8220;Periosteal Skeletal Stem Cells in Bone Repair&#8221; (BAYM.P0264US.P1). The remaining authors declare no competing interests.

During bone healing, periosteal cells are the main source of newly differentiated chondrocytes and osteoblasts within an injury callus3. Similar to bone marrow, osteogenic/chondrogenic SSCs have also been identified in the periosteum4,5,6. Assessing endogenous P-SSC functional characteristics is technically challenging. Often, migratory dynamics of SSCs are assessed in vitro, making interpretation of thei...

Fracture repair is a dynamic, multicellular process that is distinct from embryonic skeletal development and remodeling. During this process, the induction of injury signals from damaged tissue is followed by the rapid recruitment, proliferation, and subsequent differentiation of skeletal stem/progenitor cells, which are all critical for the overall stability and fixation of fractures1. In particular, early stages of fracture healing require soft callus formation, which is mainly attributed to periosteal resident cells2. When bones are injured, a subset of periosteal cells rapidly respond and contribute to newly differentiated cartilage intermediates and osteoblasts within the callus3, implicating the presence of a distinct skeletal stem/progenitor cell population within the periosteum. Therefore, the identification and functional characterization of the periosteum-resident skeletal stem cells (SSCs) constitute a promising therapeutic approach for degenerative bone diseases and bone defects4.&#160;
SSCs are thought to reside in multiple tissue locations, including the bone marrow. Similar to bone marrow, osteogenic/chondrogenic SSCs have also been identified in the periosteum4,5,6.&#160; These periosteal SSCs (P-SSCs) can be labeled with early mesenchymal lineage markers (i.e., Prx1-Cre5, Ctsk-Cre7, and Axin2-CreER8) during fetal bone development4,7,8,9,10. A significant limitation of these single genetic lineage tracing models is that there is substantial heterogeneity within labeled cell populations. Furthermore, they cannot distinguish labeled SSCs from their progeny in vivo. To address this limitation, we recently developed a dual reporter mouse (Mx1-Cre+Rosa26-Tomato+&#945;SMA-GFP+) to distinctly visualize P-SSCs from bone marrow SSCs (BM-SSCs)11. With this model, it has been determined that P-SSCs are marked by Mx1+&#945;SMA+ dual labeling, whereas more differentiated Mx1+ cells reside in the bone marrow, endosteal and periosteal surfaces, and cortical and trabecular bones11,12.&#160;
Multiple cytokines and growth factors are known to regulate bone remodeling and repair and have been tested for the enhancement of skeletal repair in critical segment defects1,13. However, due to the cellular complexity of injury models generated through disruption of the bone compartment&#39;s physical barrier, the direct effects of these molecules on endogenous P-SSC migration and activation during healing are unclear. The functional characteristics and migratory dynamics of SSCs are often assessed in vitro by performing a transwell or scratch assay, in combination with cytokines or growth factors known to induce migration in other cell populations. Thus, interpretation of results from these in vitro experiments for application in their corresponding in vivo systems is challenging. Currently, in vivo assessment of skeletal stem/progenitor cell migration is not typically observed in real-time; rather, it is measured at fixed timepoints post-fracture5,7,14,15,16.&#160;&#160;
A limitation of this method is that migration is not assessed at a single-cell level; rather, it is measured via changes in cell populations. Due to recent advances in live animal intravital microscopy and generation of additional reporter mice, in vivo tracking of individual cells is now possible. Using live animal intravital microscopy, we observed the distinct migration of P-SSCs from the calvaria suture niche to a bone injury within 24&#8211;48 h post-injury in Mx1/Tomato/&#945;SMA-GFP mice.&#160;
CCL5/CCR5 was recently identified as a regulatory mechanism influencing the recruitment and activation P-SSCs during the early injury response. Interestingly, there was no detection of substantial P-SSC migration in response to an injury in real-time. However, treatment of an injury with CCL5 produces a robust, directionally distinct migration of P-SSCs, which can be captured in real-time. Therefore, the objective of this protocol is to provide a detailed methodology for recording the in vivo migration of P-SSCs in real-time after treatment with CCL5.

<table><tbody><tr><td>&amp;frac12;&amp;rdquo; optical post</td><td>ThorLabs</td><td>TR2</td><td>For imaging mount</td></tr><tr><td>1 mL syringe</td><td>BD</td><td>309659</td><td></td></tr><tr><td>27G needle</td><td>BD PercisionGlide</td><td>305111</td><td></td></tr><tr><td>29G insulin syringe</td><td>McKesson</td><td>102-SN05C905P</td><td></td></tr><tr><td>50 mL conicol tube</td><td>Falcon</td><td>352098</td><td>For mouse restraint</td></tr><tr><td>Adjustable angle plate</td><td>Renishaw</td><td>R-PCA-5023-50-20</td><td>For imaging mount</td></tr><tr><td>Alcohol wipes</td><td>Coviden</td><td>6818</td><td></td></tr><tr><td>betadine surgical scrub</td><td>Henry Schen</td><td>67618-151-16</td><td></td></tr><tr><td>Buprenorphine SR-LAB</td><td>ZooPharm</td><td></td><td>1mg/mL Sustained Release</td></tr><tr><td>Combo III</td><td>Obtained from staff veterinarian</td><td>N/A</td><td>37.6 mg/mL Ketamine; 1.9 mg/mL Xylazine; 0.37 mg/mL Acepronazine</td></tr><tr><td>Coverslip</td><td>Fisher</td><td>12-545-87</td><td>24 x 40 premium superslip</td></tr><tr><td>Fine tip forcepts</td><td>FST</td><td>11254-20</td><td></td></tr><tr><td>Ketamine</td><td>KetaVed</td><td>50989-161-06</td><td>100 mg/mL</td></tr><tr><td>Leica TCS SP8MP with DM6000CFS</td><td>Leica Microsystems</td><td>N/A</td><td></td></tr><tr><td>Matrigel</td><td>R &amp;amp; D Systems</td><td>344500101</td><td></td></tr><tr><td>Medical tape</td><td>McKesson</td><td>100199</td><td>3&quot; x 10 yds (7.6 cm x 9.1 m)</td></tr><tr><td>Methocellulose</td><td>Electron Microscopy Sciences</td><td>19560</td><td></td></tr><tr><td>Microdissection scissors</td><td>FST</td><td>1456-12</td><td></td></tr><tr><td>Motorized stage</td><td>Anaheim automation</td><td>N/A</td><td></td></tr><tr><td>Needle holder</td><td>FST</td><td>12500-12</td><td></td></tr><tr><td>Nonabsorbable sutures</td><td>McKesson</td><td>S913BX</td><td>monofilament nylon 5-0 nonabsorbable sutures with attached C-1 reverse cutting needle</td></tr><tr><td>Opthalmic ointment</td><td>Rugby</td><td>0536-1086-91</td><td></td></tr><tr><td>RANTES</td><td>Biolegend</td><td>594202</td><td>10 &amp;micro;g/50 &amp;micro;L</td></tr><tr><td>Right-angle clamp for &amp;frac12;&amp;rdquo; post, 3/16&amp;rdquo; Hex</td><td>ThorLabs</td><td>RA90</td><td>For imaging mount</td></tr><tr><td>Spring-loaded 3/16&amp;rdquo; Hex-locking &amp;frac14;&amp;rdquo; thumbscrew</td><td>ThorLabs</td><td>TS25H</td><td>For imaging mount</td></tr><tr><td>Sterile cotton swabs</td><td>Henry Schen</td><td>100-9249</td><td></td></tr><tr><td>Sterile DPBS (1x)</td><td>Corning</td><td>21-030-CV</td><td></td></tr><tr><td>Sterile drapes</td><td>McKessen</td><td>25-517</td><td></td></tr><tr><td>Surgical gloves</td><td>McKessen</td><td>3158VA</td><td></td></tr><tr><td>Triple antibiotic ointment</td><td>Taro Pharmaceuticals U.s.a., Inc.</td><td>51672-2120-2</td><td></td></tr><tr><td>Vacutainer blood collection set</td><td>BD</td><td>REF 367298</td><td>25G butterfly needle infusion set with 12&quot; tubing</td></tr></tbody></table>

real-time imaging of ccl5-induced migration of periosteal skeletal stem cells in mice

Periosteal skeletal stem cells (P-SSCs) are essential for lifelong bone maintenance and repair, making them an ideal focus for the development of therapies to enhance fracture healing.&#160; Periosteal cells rapidly migrate to an injury to supply new chondrocytes and osteoblasts for fracture healing. Traditionally, the efficacy of a cytokine to induce cell migration has only been conducted in vitro by performing a transwell or scratch assay. With advancements in intravital microscopy using multiphoton excitation, it was recently discovered that 1) P-SSCs express the migratory gene CCR5 and 2) treatment with the CCR5 ligand known as CCL5 improves fracture healing and the migration of P-SSCs in response to CCL5. These results have been captured in real-time. Described here is a protocol to visualize P-SSC migration from the calvarial suture skeletal stem cell (SSC) niche towards an injury after treatment with CCL5. The protocol details the construction of a mouse restraint and imaging mount, surgical preparation of the mouse calvaria, induction of a calvaria defect, and acquisition of time-lapse imaging.

Skeletal progenitors have been proposed to have migratory or circulatory potential20. Recently, Mx1-Cre+Rosa26-Tomato+&#945;SMA-GFP+ (Mx1/Tomato/&#945;SMA-GFP) reporter mice were generated, in which P-SSCs are marked by Mx1+&#945;SMA+ dual labeling (Figure 2A,B). Substantial migration of Mx1+&#945;SMA+...

Watch this Scientific Journal Video about Real-Time Imaging of CCL5-Induced Migration of Periosteal Skeletal Stem Cells in Mice at JoVE.com

Real-Time Imaging of CCL5-Induced Migration of Periosteal Skeletal Stem Cells in Mice

This protocol describes the detection of CCL5-mediated periosteal skeletal stem cell migration in real-time using live animal intravital microscopy.

Periosteal skeletal stem cells (P-SSCs) are essential for lifelong bone maintenance and repair, making them an ideal focus for the development of ...

real-time-imaging-ccl5-induced-migration-periosteal-skeletal-stem

Research

JoVE Journal

Developmental Biology

2.2K Views.  Baylor College of Medicine. This protocol describes the detection of CCL5-mediated periosteal skeletal stem cell migration in real-time using live animal intravital microscopy.

Video: Real-Time Imaging of CCL5-Induced Migration of Periosteal Skeletal Stem Cells in Mice

Bioengineering of Humanized Bone Marrow Microenvironments in Mouse and Their Visualization by Live Imaging

Human hematopoietic stem cells (HSCs) reside in the bone marrow (BM) niche, an intricate, multifactorial network of components producing cytokines, growth factors, and extracellular matrix. The ability of HSCs to remain quiescent, self-renew or differentiate, and acquire mutations and become malignant depends upon the complex interactions they establish with different stromal components. To observe the crosstalk between human HSCs and the human BM niche in physiological and pathological conditions, we designed a protocol to ectopically model and image a humanized BM niche in immunodeficient mice. We show that the use of different cellular components allows for the formation of humanized structures and the opportunity to sustain long-term human hematopoietic engraftment. Using two-photon microscopy, we can live-image these structures in situ at the single-cell resolution, providing a powerful new tool for the functional characterization of the human BM microenvironment and its role in regulating normal and malignant hematopoiesis.

A method to create and live-image different humanized bone-marrow niches in mice is presented. Based on the supportive niche created by human mesenchymal cells, the addition of human endothelial cells induces the formation of human vessels, while the addition of rhBMP-2 induces the formation of human-mouse chimeric mature bone tissue.

Human hematopoietic stem cells (HSCs) reside in the bone marrow (BM) niche, an intricate, multifactorial network of components producing cytokines, growth ...

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 ...

Sequential In vivo Imaging of Osteogenic Stem/Progenitor Cells During Fracture Repair

Bone turns over continuously and is highly regenerative following injury. Osteogenic stem/progenitor cells have long been hypothesized to exist, but in vivo demonstration of such cells has only recently been attained. Here, in vivo imaging techniques to investigate the role of endogenous osteogenic stem/progenitor cells (OSPCs) and their progeny in bone repair are provided. Using osteo-lineage cell tracing models and intravital imaging of induced microfractures in calvarial bone, OSPCs can be directly observed during the first few days after injury, in which critical events in the early repair process occur. Injury sites can be sequentially imaged revealing that OSPCs relocate to the injury, increase in number and differentiate into bone forming osteoblasts. These methods offer a means of investigating the role of stem cell-intrinsic and extrinsic molecular regulators for bone regeneration and repair.

Sequential In vivo Imaging of Osteogenic Stem/Progenitor Cells During Fracture Repair

Quantitative measurement of bone progenitor function in fracture healing requires high resolution serial imaging technology. Here, protocols are provided for using intravital microscopy and osteo-lineage tracking to sequentially image and quantify the migration, proliferation and differentiation of endogenous osteogenic stem/progenitor cells in the process of repairing bone fracture.

Bone turns over continuously and is highly regenerative following injury. Osteogenic stem/progenitor cells have long been hypothesized to exist, but in ...

Medicine

Tracking Mouse Bone Marrow Monocytes In Vivo

Real time multiphoton imaging provides a great opportunity to study cell trafficking and cell-to-cell interactions in their physiological 3-dimensionnal environment. Biological activities of immune cells mainly rely on their motility capacities. Blood monocytes have short half-life in the bloodstream; they originate in the bone marrow and are constitutively released from it. In inflammatory condition, this process is enhanced, leading to blood monocytosis and subsequent infiltration of the peripheral inflammatory tissues. Identifying the biomechanical events controlling monocyte trafficking from the bone marrow towards the vascular network is an important step to understand monocyte physiopathological relevance. We performed in vivo time-lapse imaging by two-photon microscopy of the skull bone marrow of the Csf1r-Gal4VP16/UAS-ECFP (MacBlue) mouse. The MacBlue mouse expresses the fluorescent reporters enhanced cyan fluorescent protein (ECFP) under the control of a myeloid specific promoter 1, in combination with vascular network labelling. We describe how this approach enables the tracking of individual medullar monocytes in real time to further quantify the migratory behaviour within the bone marrow parenchyma and the vasculature, as well as cell-to-cell interactions. This approach provides novel insights into the biology of the bone marrow monocyte subsets and allows to further address how these cells can be influenced in specific pathological conditions.

Tracking Mouse Bone Marrow Monocytes In Vivo

Monocytes are key regulators of innate immunity and play a critical role in the renewal of the peripheral mononuclear phagocytic system and in case of inflammation. This manuscript describes the procedure of real time imaging of the mouse calvaria bone marrow to study the monocyte mobilisation mechanism.

Real time multiphoton imaging provides a great opportunity to study cell trafficking and cell-to-cell interactions in their physiological 3-dimensionnal ...

Immunology and Infection

Femur Window Chamber Model for In Vivo Cell Tracking in the Murine Bone Marrow

Bone marrow is a complex organ that contains various hematopoietic and non-hematopoietic cells. These cells are involved in many biological processes, including hematopoiesis, immune regulation and tumor regulation. Commonly used methods for understanding cellular actions in the bone marrow, such as histology and blood counts, provide static information rather than capturing the dynamic action of multiple cellular components in vivo. To complement the standard methods, a window chamber (WC)-based model was developed to enable serial in vivo imaging of cells and structures in the murine bone marrow. This protocol describes a surgical procedure for installing the WC in the femur, in order to facilitate long-term optical access to the femoral bone marrow. In particular, to demonstrate its experimental utility, this WC approach was used to image and track neutrophils within the vascular network of the femur, thereby providing a novel method to visualize and quantify immune cell trafficking and regulation in the bone marrow. This method can be applied to study various biological processes in the murine bone marrow, such as hematopoiesis, stem cell transplantation, and immune responses in pathological conditions, including cancer.

Femur Window Chamber Model for In Vivo Cell Tracking in the Murine Bone Marrow

The protocol describes a novel murine femur window chamber model that can be used to track movement of cells in the femoral bone marrow in vivo. Intravital multiphoton fluorescence microscopy is used to image three components of the femoral bone marrow (vasculature, collagen matrix, and neutrophils) over time.

Bone marrow is a complex organ that contains various hematopoietic and non-hematopoietic cells. These cells are involved in many biological processes, ...

Intravital Microscopy of the Microcirculation in the Mouse Cremaster Muscle for the Analysis of Peripheral Stem Cell Migration

In the era of intravascular cell application protocols in the context of regenerative cell therapy, the underlying mechanisms of stem cell migration to nonmarrow tissue have not been completely clarified. We describe here the technique of intravital microscopy applied to the mouse cremaster microcirculation for analysis of peripheral bone marrow stem cell migration in vivo. Intravital microscopy of the M. cremaster has been previously introduced in the field of inflammatory research for direct observation of leucocyte interaction with the vascular endothelium. Since sufficient peripheral stem and progenitor cell migration includes similar initial steps of rolling along and firm adhesion at the endothelial lining it is conceivable to apply the M. cremaster model for the observation and quantification of the interaction of intravasculary administered stem cells with the endothelium. As various chemical components can be selectively applied to the target tissue by simple superfusion techniques, it is possible to establish essential microenvironmental preconditions, for initial stem cell recruitment to take place in a living organism outside the bone marrow.

Intravital microscopy of the mouse M. cremaster microcirculation offers a unique and well-standardized in vivo model for the analysis of peripheral bone marrow stem cell migration.

In the era of intravascular cell application protocols in the context of regenerative cell therapy, the underlying mechanisms of stem cell migration to ...

Biology

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 ...

In Vivo 4-Dimensional Tracking of Hematopoietic Stem and Progenitor Cells in Adult Mouse Calvarial Bone Marrow

Through a delicate balance between quiescence and proliferation, self renewal and production of differentiated progeny, hematopoietic stem cells (HSCs) maintain the turnover of all mature blood cell lineages. The coordination of the complex signals leading to specific HSC fates relies upon the interaction between HSCs and the intricate bone marrow microenvironment, which is still poorly understood[1-2].
We describe how by combining a newly developed specimen holder for stable animal positioning with multi-step confocal and two-photon in vivo imaging techniques, it is possible to obtain high-resolution 3D stacks containing HSPCs and their surrounding niches and to monitor them over time through multi-point time-lapse imaging. High definition imaging allows detecting ex vivo labeled hematopoietic stem and progenitor cells (HSPCs) residing within the bone marrow. Moreover, multi-point time-lapse 3D imaging, obtained with faster acquisition settings, provides accurate information about HSPC movement and the reciprocal interactions between HSPCs and stroma cells.
Tracking of HSPCs in relation to GFP positive osteoblastic cells is shown as an exemplary application of this method. This technique can be utilized to track any appropriately labeled hematopoietic or stromal cell of interest within the mouse calvarium bone marrow space.

In Vivo 4-Dimensional Tracking of Hematopoietic Stem and Progenitor Cells in Adult Mouse Calvarial Bone Marrow

The nature of the interactions between hematopoietic stem and progenitor cells (HSPCs) and bone marrow niches is poorly understood. Custom hardware modifications and a multi-step acquisition protocol allow the use of two-photon and confocal microscopy to image ex vivo labeled HSPCs homed within bone marrow areas, tracking interactions and movement.

Through a delicate balance between quiescence and proliferation, self renewal and production of differentiated progeny, hematopoietic stem cells (HSCs) ...

In vitro Time-lapse Live-Cell Imaging to Explore Cell Migration toward the Organ of Corti

To study the effects of mesenchymal stem cells (MSCs) on cell regeneration and treatment, this method tracks MSC migration and morphological changes after co-culture with cochlear epithelium. The organ of Corti was immobilized on a plastic coverslip by pressing a portion of the Reissner's membrane generated during the dissection. MSCs confined by a glass cylinder migrated toward cochlear epithelium when the cylinder was removed. Their predominant localization was observed in the modiolus of the organ of Corti, aligned in a direction similarly to that of the nerve fibers. However, some MSCs were localized in the limbus area and showed a horizontally elongated shape. In addition, migration into the hair cell area was increased, and the morphology of the MSCs changed to various forms after kanamycin treatment. In conclusion, the results of this study indicate that the coculture of MSCs with cochlear epithelium will be useful for the development of therapeutics via cell transplantation and for studies of cell regeneration that can examine various conditions and factors.

In this study, we present a real-time imaging method using confocal microscopy to observe cells moving toward damaged tissue by ex vivo incubation with the cochlear epithelium containing the organ of Corti.

To study the effects of mesenchymal stem cells (MSCs) on cell regeneration and treatment, this method tracks MSC migration and morphological changes after ...

Real-Time Imaging of CCL5-Induced Migration of Periosteal Skeletal Stem Cells in Mice

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Bioengineering of Humanized Bone Marrow Microenvironments in Mouse and Their Visualization by Live Imaging

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

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

Sequential In vivo Imaging of Osteogenic Stem/Progenitor Cells During Fracture Repair

Tracking Mouse Bone Marrow Monocytes In Vivo

Femur Window Chamber Model for In Vivo Cell Tracking in the Murine Bone Marrow

Intravital Microscopy of the Microcirculation in the Mouse Cremaster Muscle for the Analysis of Peripheral Stem Cell Migration

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

In Vivo 4-Dimensional Tracking of Hematopoietic Stem and Progenitor Cells in Adult Mouse Calvarial Bone Marrow

In vitro Time-lapse Live-Cell Imaging to Explore Cell Migration toward the Organ of Corti