The authors wish to thank Jean-Yves Rinckel, Julie Boscher, Patricia Laeuffer, Monique Freund, Ketty Knez-Hippert for technical assistance. This work has been supported by ANR (Agence National de la Recherche) Grant ANR-17-CE14-0001-01 and ANR-18-CE14-0037.

All animal experiments were performed in accordance with European standards 2010/63/EU and the CREMEAS Committee on the Ethics of Animal Experiments of the University of Strasbourg (Comit&#233; R&#233;gional d&#39;Ethique en Mati&#232;re d&#39;Exp&#233;rimentation Animale Strasbourg).
1. Preparation of reagents
<ol>
	<li>Prepare reagents as described in Table 1.
	<ol>
		<li>For the Stock I, dissolve each powder separately. Ensure that the osmolarity of the preparation is higher than 295 mOsm/L. This solution can be stored at 4 &#176;C for one year.</li>
		<li>For the Tyrode&#39;s buffer preparation, make the solution as described in Table 1, adjust the volume to 100 mL with distilled water and add 0.1 g anhydrous D (+) sucrose. Adjust to pH 7.3 using 1 N HCl as needed and the osmolarity to 295 mOsm/L. To prevent bacterial growth, add penicillin G at 10 U/mL final concentration and streptomycin sulfate at 0.29 mg/mL final concentration. Filter the final solution through 0.22 &#181;m pores.</li>
	</ol>
	</li>
</ol>
2. Preparation of the experimental set up
<ol>
	<li>On the day of the experiment, warm the Tyrode&#39;s buffer at 37 &#176;C, and turn on the heating chamber of the microscope to bring the temperature to 37 &#176;C.</li>
	<li>Prepare all the necessary tools, such as a timer, incubation chambers, 5 mL syringes, 21 G, forceps, razor blade, Pasteur pipettes, glass slides, and 15 mL centrifuge tube (Figure 1A).</li>
</ol>
3. Isolation of the mouse bone marrow
<ol>
	<li>Euthanize C57BL/6 mice aged 8-12 weeks by CO2 asphyxiation and cervical dislocation. This should be done quickly by a competent and qualified person.</li>
	<li>To avoid microbial contamination, soak the mouse body in 70% (v/v) ethanol before removing the femurs. Use instruments disinfected in 70% ethanol for the dissection. Collect the two femurs and clean them by removing any adherent tissue. After rapid immersion in ethanol, place them in 15 mL centrifuge tube containing 2 mL Tyrode&#39;s buffer.</li>
	<li>Cut away the epiphyses using a sharp razor blade and flush the bone marrow using a 5 mL syringe filled with 2 mL Tyrdode&#39;s buffer. To achieve this, introduce a 21 G needle into the opening of the femur (on the knee side) and slowly press the plunger to retrieve an intact marrow cylinder (Figure 1B,C). Keep the marrow collection session as brief as possible (under 10 min).</li>
</ol>
4. Bone marrow sectioning and placement into the incubation chamber
<ol>
	<li>Use a 3 mL plastic pipette to carefully and gently transfer the intact bone marrow onto a glass slide. It is important that the samples are covered with buffer to prevent drying out (Figure 1D). 
	NOTE: Avoid flow-reflow to minimize shears that could dissociate the tissue.</li>
	<li>Under a stereomicroscope (10x), cut off the ends of the marrow that may have been compressed at the time of the flush. Then cut transversal sections with a sharp razor blade. Sections should be thin enough to allow a detailed observation but ensure that megakaryocytes are not damaged by compression (usually thickness around 0.5 mm) (Figure 1E,F). 
	NOTE: The sections are made with a sharp razor blade and under a magnifier to adjust their thickness to about 0.5 mm. Only the sections of uniform thickness are selected. This procedure is not complicated but its standardization requires some experience.</li>
	<li>Using a plastic pipette, collect 10 sections into 1 mL tube containing Tyrode&#39;s buffer (Figure 1G).</li>
	<li>Carefully transfer the sections to an incubation chamber with a diameter of 13 mm (Figure 1H).</li>
	<li>Aspirate the buffer and adjust the volume to 30 &#181;L of Tyrode&#39;s buffer supplemented with 5 % mouse serum. 
	NOTE: It is at this stage that pharmacological agents can be added to evaluate their impact on proplatelet formation.</li>
	<li>Position the sections at distance. Seal the self-adhesive chamber with a coverslip of the dimension 22 x 55 mm. Incline the coverslip while sticking to avoid the formation of air bubbles (Figure 1I).</li>
	<li>Place the chamber in the heating chamber at 37 &#176;C. From this moment, the chronometer is started (T= 0 h). The experiment runs for 6 h at 37 &#176;C (T= 6 h).</li>
</ol>
5. Real-time observation of marrow explants
<ol>
	<li>Use an inverted phase contrast microscope (40x lens for magnification) coupled to a video camera to observe the bone marrow explants. Let the cells incubate for 30 min before starting the observation. While observing, it is necessary to adjust the focus because megakaryocytes are moving. 
	NOTE: Other observation modes are possible (e.g., DIC, fluorescence using mice whose megakaryocytes express an endogenous fluorescent marker), but phase contrast microscopy is optimal to clearly visualize the long and thin megakaryocyte extensions, allowing precise quantification. After 30 min, the marrow cells gradually migrate to the periphery of the explant, forming a monolayer. After 1 h of incubation, megakaryocytes can be identified by their large size and polylobulated nuclei (Figure 1J,K). After 3 h of incubation, the number of megakaryocytes increases and some have long extensions.</li>
	<li>Make videos to record the transformation of the megakaryocytes.</li>
</ol>
6. Quantification of the proplatelet-extending megakaryocytes
<ol>
	<li>Draw a map to localize each section in the incubation chamber (Figure 1K).</li>
	<li>After 1 h, identify the visible megakaryocytes (i.e., giant polylobulated cells) on each section&#39;s periphery and plot their positions on the drawing. Repeat this procedure after 3 and 6 h. 
	NOTE: On the basis of the drawing, each megakaryocyte can be easily located over time and the evolution of their morphology analyzed (e.g., size, deformation, proplatelet extension, etc.). Another possibility is the use of a specific navigation software.</li>
</ol>

<ol>
	<li>Thiery, J. P., Bessis, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanism+of+platelet+genesis;+in+vitro+study+by+cinemicrophotography.">Mechanism of platelet genesis; in vitro study by cinemicrophotography.</a> Reviews in Hematology. 11 (2), 162-174 (1956).</li><li>Becker, R. P., De Bruyn, P. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+transmural+passage+of+blood+cells+into+myeloid+sinusoids+and+the+entry+of+platelets+into+the+sinusoidal+circulation:+A+scanning+electron+microscopic+investigation.">The transmural passage of blood cells into myeloid sinusoids and the entry of platelets into the sinusoidal circulation: A scanning electron microscopic investigation.</a> American Journal of Anatomy. 145 (2), 183-205 (1976).</li><li>Muto, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+scanning+and+transmission+electron+microscopic+study+on+rat+bone+marrow+sinuses+and+transmural+migration+of+blood+cells.">A scanning and transmission electron microscopic study on rat bone marrow sinuses and transmural migration of blood cells.</a> Archivum Histologicum Japonicum. 39 (1), 51-66 (1976).</li><li>Cramer, E. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrastructure+of+platelet+formation+by+human+megakaryocytes+cultured+with+the+Mpl+ligand.">Ultrastructure of platelet formation by human megakaryocytes cultured with the Mpl ligand.</a> Blood. 89 (7), 2336-2346 (1997).</li><li>Kaushansky, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Promotion+of+megakaryocyte+progenitor+expansion+and+differentiation+by+the+c-Mpl+ligand+thrombopoietin.">Promotion of megakaryocyte progenitor expansion and differentiation by the c-Mpl ligand thrombopoietin.</a> Nature. 369 (6481), 568-571 (1994).</li><li>Strassel, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hirudin+and+heparin+enable+efficient+megakaryocyte+differentiation+of+mouse+bone+marrow+progenitors.">Hirudin and heparin enable efficient megakaryocyte differentiation of mouse bone marrow progenitors.</a> Experimental Cell Research. 318 (1), 25-32 (2012).</li><li>Aguilar, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Importance+of+environmental+stiffness+for+megakaryocyte+differentiation+and+proplatelet+formation.">Importance of environmental stiffness for megakaryocyte differentiation and proplatelet formation.</a> Blood. 128 (16), 2022-2032 (2016).</li><li>Scandola, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Use+of+electron+microscopy+to+study+megakaryocytes.">Use of electron microscopy to study megakaryocytes.</a> Platelets. 31 (5), 589-598 (2020).</li><li>Eckly, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+megakaryocyte+development+in+the+native+bone+marrow+environment.">Characterization of megakaryocyte development in the native bone marrow environment.</a> Methods in Molecular Biology. 788, 175-192 (2012).</li><li>Eckly, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Abnormal+megakaryocyte+morphology+and+proplatelet+formation+in+mice+with+megakaryocyte-restricted+MYH9+inactivation.">Abnormal megakaryocyte morphology and proplatelet formation in mice with megakaryocyte-restricted MYH9 inactivation.</a> Blood. 113 (14), 3182-3189 (2009).</li><li>Eckly, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Proplatelet+formation+deficit+and+megakaryocyte+death+contribute+to+thrombocytopenia+in+Myh9+knockout+mice.">Proplatelet formation deficit and megakaryocyte death contribute to thrombocytopenia in Myh9 knockout mice.</a> Journal of Thrombosis and Haemostasis. 8 (10), 2243-2251 (2010).</li><li>Ortiz-Rivero, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=C3G,+through+its+GEF+activity,+induces+megakaryocytic+differentiation+and+proplatelet+formation.">C3G, through its GEF activity, induces megakaryocytic differentiation and proplatelet formation.</a> Cell Communication and Signaling. 16 (1), 101 (2018).</li><li>Junt, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dynamic+visualization+of+thrombopoiesis+within+bone+marrow.">Dynamic visualization of thrombopoiesis within bone marrow.</a> Science. 317 (5845), 1767-1770 (2007).</li><li>Zhang, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mouse+models+of+MYH9-related+disease:+mutations+in+nonmuscle+myosin+II-A.">Mouse models of MYH9-related disease: mutations in nonmuscle myosin II-A.</a> Blood. 119 (1), 238-250 (2012).</li><li>Malara, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Extracellular+matrix+structure+and+nano-mechanics+determine+megakaryocyte+function.">Extracellular matrix structure and nano-mechanics determine megakaryocyte function.</a> Blood. 118 (16), 4449-4453 (2011).</li><li>Balduini, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Adhesive+receptors,+extracellular+proteins+and+myosin+IIA+orchestrate+proplatelet+formation+by+human+megakaryocytes.">Adhesive receptors, extracellular proteins and myosin IIA orchestrate proplatelet formation by human megakaryocytes.</a> Journal of Thrombosis and Haemostasis. 6 (11), 1900-1907 (2008).</li></ol>

The authors declare no conflicts of interests.

Here we describe a simple and low-cost in vitro method to evaluate the efficiency of megakaryocytes to extend proplatelets which have grown in the bone marrow. The bone marrow explant model for mouse has four main advantages. First, there are no advanced technical skills required. Second, the time needed to obtain megakaryocyte-extending proplatelets is quite short, only 6 hours for the explant method, compared to a minimum of 4 days for a conventional culture method starting from mouse progenitors. Third, given...

The bone marrow explant technique was first developed by Thi&#233;ry and Bessis in 1956 to describe the formation of rat megakaryocyte cytoplasmic extensions as an initial event in platelet formation1. Using phase contrast and cinematographic techniques, these authors characterized the transformation of mature round megakaryocytes into &#34;squid-like&#34; thrombocytogenic cells with cytoplasmic extensions showing dynamic movements of elongation and contraction. These arms become progressively thinner until they become filiform with small swellings along the arms and at the tips. These typical megakaryocyte elongations, obtained in vitro and in liquid media, have certain similarities with platelets observed in fixed bone marrow, where megakaryocytes protrude long extensions through the sinusoid walls into the blood circulation2,3. The discovery and cloning of TPO in 1994, allowed to differentiate megakaryocytes in culture able to form proplatelet extensions resembling those described in bone marrow explants4,5,6. However, megakaryocyte maturation is far less efficient in culture conditions, notably the extensive internal membrane network of bone marrow matured megakaryocytes is underdeveloped in cultured megakaryocytes, hampering studies on the mechanisms of platelet biogenesis7,8.
We detail here the bone marrow explant model, based on Thi&#233;ry and Bessis, to follow in real-time proplatelet formation of mouse megakaryocytes, which have fully matured in their native environment, thus circumventing possible in vitro artifacts and misinterpretations. Results obtained in wild-type adult mice are presented to illustrate the ability of megakaryocyte to extend proplatelets, their morphology and the complexity of proplatelets. We also introduce a rapid quantifying strategy for quality validation to ensure data accuracy and robustness during the megakaryocyte recording process. The protocol presented here is the most recent version of the method&#160;published as a book chapter previously9.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>5 mL syringes</td>
			<td>Terumo</td>
			<td>SS+05S1</td>
			<td></td>
		</tr>
		<tr>
			<td>21-gauge needles</td>
			<td>BD Microlance</td>
			<td>301155</td>
			<td></td>
		</tr>
		<tr>
			<td>CaCl2.6H2O</td>
			<td>Sigma</td>
			<td>21108</td>
			<td></td>
		</tr>
		<tr>
			<td>Coverwall Incubation Chambers</td>
			<td>Electron Microscopy Sciences</td>
			<td>70324-02</td>
			<td>Depth : 0,2 mm</td>
		</tr>
		<tr>
			<td>HEPES</td>
			<td>Sigma</td>
			<td>H-3375</td>
			<td>pH adjusted to 7.5</td>
		</tr>
		<tr>
			<td>Human serum albumin</td>
			<td>VIALEBEX</td>
			<td>authorized medication : n&#176; 3400956446995</td>
			<td>20% (200mg/mL -100mL)</td>
		</tr>
		<tr>
			<td>KCl</td>
			<td>Sigma</td>
			<td>P9333</td>
			<td></td>
		</tr>
		<tr>
			<td>MgCl2.6H2O</td>
			<td>Sigma</td>
			<td>BVBW8448</td>
			<td></td>
		</tr>
		<tr>
			<td>Micro Cover Glass</td>
			<td>Electron Microscopy Sciences</td>
			<td>72200-40</td>
			<td>22 mm x 55 mm</td>
		</tr>
		<tr>
			<td>Microscope</td>
			<td>Leica Microsystems SA, Westlar, Germany</td>
			<td>DMI8 - 514341</td>
			<td>air lens</td>
		</tr>
		<tr>
			<td>microscope camera</td>
			<td>Leica Microsystems SA, Westlar, Germany</td>
			<td>K5 CMS GmbH -14401137</td>
			<td>image resolution : 4.2 megapixel</td>
		</tr>
		<tr>
			<td>Mouse serum</td>
			<td>BioWest</td>
			<td>S2160-010</td>
			<td></td>
		</tr>
		<tr>
			<td>NaCl</td>
			<td>Sigma</td>
			<td>S7653</td>
			<td></td>
		</tr>
		<tr>
			<td>NaH2PO4.H2O</td>
			<td>Sigma</td>
			<td>S9638</td>
			<td></td>
		</tr>
		<tr>
			<td>NaHCO3</td>
			<td>Sigma</td>
			<td>S5761</td>
			<td></td>
		</tr>
		<tr>
			<td>PSG 100x</td>
			<td>Gibco, Life Technologies</td>
			<td>1037-016</td>
			<td>10,000 units/mL penicillin, 10,000 &#956;g/mL streptomycin and 29.2 mg/mL glutamine</td>
		</tr>
		<tr>
			<td>Razor blade</td>
			<td>Electron Microscopy Sciences</td>
			<td>72000</td>
			<td></td>
		</tr>
		<tr>
			<td>Sucrose D (+)</td>
			<td>Sigma</td>
			<td>G8270</td>
			<td></td>
		</tr>
	</tbody>
</table>

proplatelet formation dynamics of mouse fresh bone marrow explants

The last stage of megakaryopoiesis leads to cytoplasmic extensions from mature megakaryocytes, the so-called proplatelets. Much has been learned about the proplatelet formation using in vitro-differentiated megakaryocytes; however, there is an increasing evidence that conventional culture systems do not faithfully recapitulate the differentiation/maturation process that takes places inside the bone marrow. In this manuscript, we present an explant method initially described in 1956 by Thi&#233;ry and Bessis to visualize megakaryocytes which have matured in their native environment, thus circumventing potential artifacts and misinterpretations. Fresh bone marrows are collected by flushing the femurs of mice, sliced into 0.5 mm cross sections, and placed in an incubation chamber at 37 &#176;C containing a physiological buffer. Megakaryocytes become gradually visible at the explant periphery and are observed up to 6 hours under an inverted microscope coupled to a video camera. Over time, megakaryocytes change their shape, with some cells having a spherical form and others developing thick extensions or extending many thin proplatelets with extensive branching. Both qualitative and quantitative investigations are carried out. This method has the advantage of being simple, reproducible, and fast as numerous megakaryocytes are present, and classically half of them form proplatelets in 6 hours compared to 4 days for cultured mouse megakaryocytes. In addition to the study of mutant mice, an interesting application of this method is the straightforward evaluation of the pharmacological agents on the proplatelet extension process, without interfering with the differentiation process that may occur in cultures.

Qualitative results. At the beginning of the experiment, all cells are compacted in the bone marrow section. It takes 30 min for the cells to become clearly visible at the periphery of the explants. The megakaryocytes are then recognizable by their large size and their evolution can then be studied over time (size, shape, dynamic, proplatelet extension and platelet release) (Figure 2A). Small megakaryocytes have a diameter between 20 and 30 &#181;m and their nuclei are polyl...

Watch this Scientific Journal Video about Proplatelet Formation Dynamics of Mouse Fresh Bone Marrow Explants at JoVE.com

Proplatelet Formation Dynamics of Mouse Fresh Bone Marrow Explants

Here, we detail the bone marrow explant method, from sample preparation to microscopic slide analysis, to evaluate the ability of megakaryocytes which have differentiated in their physiological environment to form proplatelets.

The last stage of megakaryopoiesis leads to cytoplasmic extensions from mature megakaryocytes, the so-called proplatelets. Much has been learned about the ...

proplatelet-formation-dynamics-of-mouse-fresh-bone-marrow-explants

Research

JoVE Journal

Biology

2.4K Views.  Université de Strasbourg, INSERM, EFS Grand Est, BPPS UMR-S 1255, FMTS. Here, we detail the bone marrow explant method, from sample preparation to microscopic slide analysis, to evaluate the ability of megakaryocytes which have differentiated in their physiological environment to form proplatelets. 

Video: Proplatelet Formation Dynamics of Mouse Fresh Bone Marrow Explants

Culture of myeloid dendritic cells from bone marrow precursors

Myeloid dendritic cells (DCs) are frequently used to study the interactions between innate and adaptive immune mechanisms and the early response to infection. Because these are the most potent antigen presenting cells, DCs are being increasingly used as a vaccine vector to study the induction of antigen-specific immune responses. In this video, we demonstrate the procedure for harvesting tibias and femurs from a donor mouse, processing the bone marrow and differentiating DCs in vitro. The properties of DCs change following stimulation: immature dendritic cells are potent phagocytes, whereas mature DCs are capable of antigen presentation and interaction with CD4+ and CD8+ T cells. This change in functional activity corresponds with the upregulation of cell surface markers and cytokine production. Many agents can be used to mature DCs, including cytokines and toll-like receptor ligands. In this video, we demonstrate flow cytometric comparisons of expression of two co-stimulatory molecules, CD86 and CD40, and the cytokine, IL-12, following overnight stimulation with CpG or mock treatment. After differentiation, DCs can be further manipulated for use as a vaccine vector or to generate antigen-specific immune responses by in vitro pulsing using peptides or proteins, or transduced using recombinant viral vectors. 

This video demonstrates the procedure for differentiating myeloid dendritic cells from mouse bone marrow. Isolation of mouse tibia and femur, and processing of bone marrow are demonstrated. Pictures demonstrating cell morphology before and after differentiation, and figures depicting cell phenotype and IL-12 production following maturation using CpG are shown.

Myeloid dendritic cells (DCs) are frequently used to study the interactions between innate and adaptive immune mechanisms and the early response to ...

Generation of Bone Marrow Derived Murine Dendritic Cells for Use in 2-photon Imaging

Several methods for the preparation of murine dendritic cells can be found in the literature. Here, we present a method that produces greater than 85% CD11c high dendritic cells in culture that home to the draining lymph node after subcutaneous injection and present antigen to antigen specific T cells (see video). Additionally, we use Essen Instruments Incucyte to track dendritic cell maturation, where, at day 10, the morphology of the cultured cells is typical of a mature dendritic cell and &lt;85% of cells are CD11chigh. The study of antigen presentation in peripheral lymph nodes by 2-photon imaging revealed that there are three distinct phases of dendritic cell and T cell interaction1, 2. Phase I consists of brief serial contacts between highly motile antigen specific T cells and antigen carrying dendritic cells1, 2. Phase two is marked by prolonged contacts between antigen-specific T cell and antigen bearing dendritic cells1, 2. Finally, phase III is characterized by T cells detaching from dendritic cells, regaining motility and beginning to divide1, 2. This is one example of the type of antigen-specific interactions that can be analyzed by two-photon imaging of antigen-loaded cell tracker dye-labeled dendritic cells.

Antigen presentation in secondary lymphoid organs by dendritic cells is crucial for the initiation of the T cell mediated adaptive immune response. Here we demonstrate the culture of bone marrow derived murine dendritic cells, activation, and labeling for 2-photon imaging.

Several methods for the preparation of murine dendritic cells can be found in the literature. Here, we present a method that produces greater than 85% ...

The Preparation of Primary Hematopoietic Cell Cultures From Murine Bone Marrow for Electroporation

It is becoming increasingly apparent that electroporation is the most effective way to introduce plasmid DNA or siRNA into primary cells. The Gene Pulser MXcell  electroporation system and Gene Pulser  electroporation buffer were specifically developed to transfect nucleic acids into mammalian cells and difficult-to-transfect cells, such as primary and stem cells.This video demonstrates how to establish primary hematopoietic cell cultures from murine bone marrow, and then prepare them for electroporation in the MXcell system. We begin by isolating femur and tibia. Bone marrow from both femur and tibia are then harvested and cultures are established. Cultured bone marrow cells are then transfected and analyzed.

This procedure describes how to establish primary hematopoietic cell cultures from murine bone marrow and is followed by transfection using the Gene Pulser MXCell electroporation system.

It is becoming increasingly apparent that electroporation is the most effective way to introduce plasmid DNA or siRNA into primary cells. The Gene Pulser ...

Homing of Hematopoietic Cells to the Bone Marrow

Homing is the phenomenon whereby transplanted hematopoietic cells are able to travel to and engraft or establish residence in the bone marrow. Various chemomkines and receptors are involved in the homing of hematopoietic stem cells. [1, 2]
This paper outlines the classic homing protocol used in hematopoietic stem cell studies. In general this involves isolating the cell population whose homing needs to be investigated, staining this population with a dye of interest and injecting these cells into the blood stream of a recipient animal. The recipient animal is then sacrificed at a pre-determined time after injection and the bone marrow evaluated for the percentage or absolute number of cells which are positive for the dye of interest. In one of the most common experimental schemes, the homing efficiency of hematopoietic cells from two genetically distinct animals (a wild type animal and the corresponding knock-out) is compared. This article describes the hematopoietic cell homing protocol in the framework of such as experiment.

This article describes a protocol used to study the homing of hematopoietic cells to their niches in the bone marrow.

Homing is the phenomenon whereby transplanted hematopoietic cells are able to travel to and engraft or establish residence in the bone marrow.  Various ...

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) ...

Osteoclast Derivation from Mouse Bone Marrow

Osteoclasts are highly specialized cells that are derived from the monocyte/macrophage lineage of the bone marrow. Their unique ability to resorb both the organic and inorganic matrices of bone means that they play a key role in regulating skeletal remodeling. Together, osteoblasts and osteoclasts are responsible for the dynamic coupling process that involves both bone resorption and bone formation acting together to maintain the normal skeleton during health and disease.
As the principal bone-resorbing cell in the body, changes in osteoclast differentiation or function can result in profound effects in the body. Diseases associated with altered osteoclast function can range in severity from lethal neonatal disease due to failure to form a marrow space for hematopoiesis, to more commonly observed pathologies such as osteoporosis, in which excessive osteoclastic bone resorption predisposes to fracture formation.
An ability to isolate osteoclasts in high numbers in vitro has allowed for significant advances in the understanding of the bone remodeling cycle and has paved the way for the discovery of novel therapeutic strategies that combat these diseases. 
Here, we describe a protocol to isolate and cultivate osteoclasts from mouse bone marrow that will yield large numbers of osteoclasts.

Osteoclasts are the principal bone-resorbing cell in the body. An ability to isolate osteoclasts in large numbers has resulted in significant advances in the understanding of osteoclast biology. In this protocol, we describe a method for isolation, cultivating and quantifying osteoclast activity in vitro.

Osteoclasts are highly specialized cells that are derived from the monocyte/macrophage lineage of the bone marrow. Their unique ability to resorb both the ...

Trans-inner Cell Mass Injection of Embryonic Stem Cells Leads to Higher Chimerism Rates

In an effort to increase efficiency in the creation of genetically modified mice via ES Cell methodologies, we present an adaptation to the current blastocyst injection protocol. Here we report that a simple rotation of the embryo, and injection through Trans-Inner cell mass (TICM) increased the percentage of chimeric mice from 31% to 50%, with no additional equipment or further specialized training. 26 different inbred clones, and 35 total clones were injected over a period of 9 months. There was no significant difference in either pregnancy rate or recovery rate of embryos between traditional injection techniques and TICM. Therefore, without any major alteration in the injection process and a simple positioning of the blastocyst and injecting through the ICM, releasing the ES cells into the blastocoel cavity can potentially improve the quantity of chimeric production and subsequent germline transmission.

Here we present a protocol to increase chimera production without the use of new equipment. A simple orientation change of the embryo for injection can increase the number of embryos produced, and potentially reduce the timeline to germline transmission.

In an effort to increase efficiency in the creation of genetically modified mice via ES Cell methodologies, we present an adaptation to the current ...

Expression of Fluorescent Fusion Proteins in Murine Bone Marrow-derived Dendritic Cells and Macrophages

Dendritic cells and macrophages are crucial cells that form the first line of defense against pathogens. They also play important roles in the initiation of an adaptive immune response. Experimental work with these cells is rather challenging. Their abundance in organs and tissues is relatively low. As a result, they cannot be isolated in large numbers. They are also difficult to transfect with cDNA constructs. In the murine model, these problems can be partially overcome by in vitro differentiation from bone marrow progenitors in the presence of M-CSF for macrophages or GM-CSF for dendritic cells. In this way, it is possible to obtain large amounts of these cells from very few animals. Moreover, bone marrow progenitors can be transduced with retroviral vectors carrying cDNA constructs during early stages of cultivation prior to their differentiation into bone marrow derived dendritic cells and macrophages. Thus, retroviral transduction followed by differentiation in vitro can be used to express various cDNA constructs in these cells. The ability to express ectopic proteins substantially extends the range of experiments that can be performed on these cells, including live cell imaging of fluorescent proteins, tandem purifications for interactome analyses, structure-function analyses, monitoring of cellular functions with biosensors and many others. In this article, we describe a detailed protocol for retroviral transduction of murine bone marrow derived dendritic cells and macrophages with vectors coding for fluorescently-tagged proteins. On the example of two adaptor proteins, OPAL1 and PSTPIP2, we demonstrate its practical application in flow cytometry and microscopy. We also discuss the advantages and limitations of this approach.

In this article, we provide a detailed protocol for the expression of fluorescent fusion proteins in murine bone marrow derived dendritic cells and macrophages. The method is based on the transduction of bone marrow progenitors with retroviral constructs followed by differentiation into macrophages and dendritic cells in vitro.

Dendritic cells and macrophages are crucial cells that form the first line of defense against pathogens. They also play important roles in the initiation ...

Isolation, Purification, and Differentiation of Osteoclast Precursors from Rat Bone Marrow

Osteoclasts are large, multinucleated, and bone-resorbing cells of the monocyte-macrophage lineage that are formed by the fusion of monocytes or macrophage precursors. Excessive bone resorption is one the most significant cellular mechanisms leading to osteolytic diseases, including osteoporosis, periodontitis, and periprosthetic osteolysis. The main physiological function of osteoclasts is to absorb both the hydroxyapatite mineral component and the organic matrix of bone, generating the characteristic resorption appearance on the surface of bones. There are relatively few osteoclasts compared to other cells in the body, especially in adult bones. Recent studies have focused on how to obtain more mature osteoclasts in less time, which has always been a problem. Several improvements in the isolation and culture techniques have developed in laboratories in order to obtain more mature osteoclasts. Here, we introduce a method that isolates bone marrow in less time and with less effort compared to the traditional procedure, using a special and simple device. With the use of density gradient centrifugation, we obtain large amounts of fully differentiated osteoclasts from rat bone marrow, which are identified by classical methods.

Osteoclasts are tissue-specific macrophage polykaryons derived from the monocyte-macrophage lineage of hematopoietic stem cells. This protocol describes how to isolate bone marrow cells so that large quantities of osteoclasts are obtained while reducing the risk of accidents found in traditional methods.

Osteoclasts are large, multinucleated, and bone-resorbing cells of the monocyte-macrophage lineage that are formed by the fusion of monocytes or ...

In Vivo Two-photon Imaging of Megakaryocytes and Proplatelets in the Mouse Skull Bone Marrow

Platelets are produced by megakaryocytes, specialized cells located in the bone marrow. The possibility to image megakaryocytes in real time and their native environment was described more than 10 years ago and sheds new light on the process of platelet formation. Megakaryocytes extend elongated protrusions, called proplatelets, through the endothelial lining of sinusoid vessels. This paper presents a protocol to simultaneously image in real time fluorescently labeled megakaryocytes in the skull bone marrow and sinusoid vessels. This technique relies on a minor surgery that keeps the skull intact to limit inflammatory reactions. The mouse head is immobilized with a ring glued to the skull to prevent movements from breathing.
Using two-photon microscopy, megakaryocytes can be visualized for up to a few hours, enabling the observation of cell protrusions and proplatelets in the process of elongation inside sinusoid vessels. This allows the quantification of several parameters related to the morphology of the protrusions (width, length, presence of constriction areas) and their elongation behavior (velocity, regularity, or presence of pauses or retraction phases). This technique also allows simultaneous recording of circulating platelets in sinusoid vessels to determine platelet velocity and blood flow direction. This method is particularly useful to study the role of genes of interest in platelet formation using genetically modified mice and is also amenable to pharmacological testing (study the mechanisms, evaluating drugs in the treatment of platelet production disorders). It has become an invaluable tool, especially to complement in vitro studies as it is now known that in vivo and in vitro proplatelet formation rely on different mechanisms. It has been shown, for example, that in vitro microtubules are required for proplatelet elongation per se. However, in vivo, they rather serve as a scaffold, elongation being mainly promoted by blood flow forces.

In Vivo Two-photon Imaging of Megakaryocytes and Proplatelets in the Mouse Skull Bone Marrow

We describe here the method for imaging megakaryocytes and proplatelets in the marrow of the skull bone of living mice using two-photon microscopy.

Platelets are produced by megakaryocytes, specialized cells located in the bone marrow. The possibility to image megakaryocytes in real time and their ...