Name: proplatelet formation dynamics of mouse fresh bone marrow explants
Uploaded: 2021-05-20T15:00:00
Description: Watch this Scientific Journal Video about Proplatelet Formation Dynamics of Mouse Fresh Bone Marrow Explants at JoVE.com

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 hig...

<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. 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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>

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 ...

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