The authors thank Dr. Minghan Tong and S. Kato for kindly providing reagents and mice. We thank the members of the Zou lab for useful discussions. This work was supported in part by grants from 973 Program from the Chinese Ministry of Science and Technology (MOST) [2014CB964704 and 2015CB964503], Clinical Research Program of 9th People&#39;s Hospital, Shanghai Jiao Tong University School of Medicine. Thanks for the help of Core Facility for Cell Biology and Core Facility for Chemical Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences.

All procedures relating to the animals were performed according to the protocol approved by the Stanford Administrative Panel on Laboratory Animal Care (APLAC) and were approved by the Animal Care and Use Committee of the Shanghai Institute of Biochemistry and Cell Biology.
1. Preparation
<ol>
	<li>Generate osteoclast specific Raptor deletion mice (Raptorfl/fl; Ctsk-cre, hereafter RapCtsk) by mating Raptorfl/fl mice with Ctsk-cre mice. Use the Raptorfl/fl mice as the WT control in this study.</li>
	<li>Have a container with ice to keep isolated bone.</li>
	<li>Prepare culture medium.
	<ol>
		<li>Prepare &#945;-MEM culture medium by supplementing minimum essential medium alpha (&#945;-MEM) with 1x glutamine, penicillin-streptomycin, and 10% fetal calf serum.</li>
		<li>Prepare bone marrow macrophage induction medium consisting of 50 mL of &#945;-MEM medium and M-CSF at 20 ng/mL.</li>
		<li>Prepare osteoclast induction medium consisting of M-CSF and RANKL at 20 ng/mL, respectively, in 50 mL of &#945;-MEM medium.</li>
	</ol>
	</li>
	<li>Prepare the following buffers before TRAP staining.
	<ol>
		<li>Prepare fix solution consisting of 6.5 mL of acetone, 2.5 mL of citrate solution and 0.8 mL of 37% (vol/vol) formaldehyde solution.</li>
		<li>Prepare TRAP staining solution.
		<ol>
			<li>Prewarm deionized water to 37 &#176;C.</li>
			<li>Add 100 &#181;L of fast garnet GBC base solution and 100 &#181;L of sodium nitrite solution into a 1.5-mL microtube and mix by gentle inversion for 30 s. Leave the mixture to stand for 2 min.</li>
			<li>Prewarm 9 mL of deionized water to 37 &#176;C. Add 200 &#181;L of diazotized fast garnet GBC base solution from step 1.4.2.2, 100 &#181;L of naphthol AS-BI phosphate solution, 400 &#181;L of acetate solution, and 200 &#181;L of tartrate solution.</li>
			<li>Keep the TRAP staining mixture solution in a water bath at 37 &#176;C.</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>Prepare the following buffer before TRAP activity quantification of culture medium.
	<ol>
		<li>Prepare tartrate buffer (50 mL): 2 mL of 0.33 M L-tartaric acid, 48 mL of 0.33 M sodium tartrate dibasic dehydrate. Adjust the pH value to 4.9.</li>
		<li>Prepare 4-Nitrophenyl phosphate disodium (pNPP) buffer (200 mL): 1.502 g of glycine, 41 mg of MgCl2, 27.2 mg of ZnCl2, and 180 mL of deionized water. Adjust the pH value to 10.4 with 3 M NaOH and the volume to 200 mL with deionized water.</li>
		<li>Prepare pNPP buffer with phosphatase substrate (for one 96-well plate): 49.37 mg of phosphatase substrate and 175 &#181;L of pNPP buffer of step 1.5.2.</li>
		<li>Prepare substrate buffer (9 mL/96-well plate): 6.24 mL of deionized water, 360 &#956;L of acetate solution, and 2.4 mL of tartrate buffer. Mix by vortex and preheat at 37 &#176;C before use.</li>
		<li>Add 90 &#956;L of pNPP buffer with phosphatase substrate(1.5.3) to 9ml of preheated substrate buffer(1.5.4) to make a substrate mixture and vortex for 10 s.</li>
	</ol>
	</li>
</ol>
2. Dissection (Day -1)
<ol>
	<li>Euthanize 3 one-month-old female WT and RapCtsk mice by CO2 separately. Perform CO2 inhalation with appropriate equipment by trained personnel.</li>
	<li>Immerse 6 mice in a beaker with 100 mL of 75% ethanol (vol/vol) for 5 min to prevent bacterial contamination and then place on a dissection board in a supine position. Make an incision at the distal of the tibia vertically and dissect the skin along the hind limb with ophthalmic scissors.</li>
	<li>Cut the articular ligament of the hip joint with scissors and dislocate the hind limbs from the trunk.</li>
	<li>Cut the articular ligament of the knee joint and carefully disassociate the tibia and femur from the knee joint. Gently remove the soft tissue with scissors.</li>
	<li>Place all bones of one genotype in of one mouse in each well of a six-well-plate with 2 mL of &#945;-MEM on ice. 
	NOTE: To preserve cell viability, the bone should be kept in these conditions for less than 1 h.</li>
</ol>
3. Isolation (Day -1)
<ol>
	<li>Fill one well of a six-well plate with 75% ethanol (3 mL) and the other 5 wells with &#945;-MEM medium (3 mL).</li>
	<li>Put all bones of one genotype in the ethanol wash for 15 s and wash bones 5 times with &#945;-MEM medium for 10 s each time.</li>
	<li>Cut off the epiphyses with the scissor and insert a 0.45-mm syringe needle into the bone cavity and flush marrow out with &#945;-MEM medium into a 50-mL centrifuge tube.</li>
	<li>Flush the bone cavity using the same method from the other end of the bone. Repeat at least twice to wash the bone cavity thoroughly until the bone is pale.</li>
	<li>Centrifuge the bone marrow to obtain a cell pellet at 800 x g and 4 &#176;C for 5 min. Aspirate the supernatant.</li>
	<li>Add 3 mL of red blood cell lysis buffer into the centrifuge tube and pipette gently to resuspend the bone marrow. Keep the centrifuge tube on ice for 8 min to lyse red blood cells.</li>
	<li>Add 6 mL of &#945;-MEM medium into the centrifuge tube to stop cell lysis. Centrifuge at 500 x g and 4 &#176;C for 10 min and aspirate the supernatant.</li>
	<li>Resuspend in 3 mL of &#945;-MEM culture medium and place the cells into a six-well plate (generally one mouse per well).</li>
	<li>Incubate at 37 &#176;C in a 5% CO2 incubator overnight.</li>
</ol>
4. Plating (Day 0)
<ol>
	<li>Transfer the supernatant to a 15 mL centrifuge tube to collect the unattached cells the next morning.</li>
	<li>Centrifuge at 800 x g and 4 &#176;C for 5 min and aspirate the supernatant.</li>
	<li>Resuspend in 4 mL of &#945;-MEM culture medium.</li>
	<li>Take 20 &#181;L of the cell solution and mix with 20 &#181;L of Trypan Blue. Add 10 &#181;L of the mixture to the counting chamber and obtain the cell count per mL of solution.</li>
	<li>Add an appropriate volume of &#945;-MEM culture medium to obtain a cell solution of 500,000 cells/mL.</li>
	<li>Add 500 &#181;L and 50 &#181;L of bone marrow macrophage induction medium into each well of a 24-well plate and 96-well plate, respectively.</li>
	<li>Add 500 &#181;L and 50 &#181;L of cell solution into each well of a 24-well plate and 96-well plate, respectively.</li>
	<li>Incubate at 37 &#176;C in a 5% CO2 incubator for 3 days.</li>
</ol>
5. Differentiation (Days 3-7)
<ol>
	<li>Three days after plating, collect 50 &#181;L medium from each well of the 96-well-plate and freeze at -20 &#176;C, and then aspirate the residual medium.</li>
	<li>Add 1 mL and 100 &#181;L osteoclast induction medium into each well of a 24-well plate and a 96-well plate, respectively.</li>
	<li>Incubate at 37 &#176;C for 2 days.</li>
	<li>Collect 50 &#181;L of medium from each well and aspirate the residual medium.</li>
	<li>Add osteoclast induction medium into each well.</li>
	<li>Incubate at 37 &#176;C for 1 day. 
	NOTE: At this time point, large, multinucleated osteoclasts should be seen under an inverted microscope (Figure 2A).</li>
	<li>If osteoclasts are not seen, change the osteoclast induction medium and observe daily until osteoclasts are seen.</li>
	<li>Collect 50 &#181;L of medium from each well of the 96-well plate after osteoclasts have formed.</li>
</ol>
6. Tartrate Resistant Acid Phosphatase (TRAP) Staining
NOTE: Mature osteoclasts may be present after 6-7 days of in vitro culture (step 4).
<ol>
	<li>Aspirate medium and wash gently 3 times with 1x PBS.</li>
	<li>Fix the cells in each well of the 96-well plate with 100 &#181;L of fix solution for 30 s at room temperature.</li>
	<li>After fixation, aspirate the fix solution and wash gently 3 times with deionized water prewarmed to 37 &#176;C. Aspirate deionized water.</li>
	<li>Add 100 &#181;L of TRAP stain into each well of the 96-well plate and place the plate in an incubator at 37 &#176;C for 30 min and shield from light.</li>
	<li>After staining, aspirate the TRAP stain and gently wash 3 times with deionized water.</li>
	<li>Image osteoclasts using an inverted microscope at 40X magnification.</li>
</ol>
7. TRAP Activity Quantification of Culture Medium
<ol>
	<li>Collect 30 &#181;L culture supernatant from each well of the 96-well plate from step 5.1, 5.4 and 5.8; Use 30 &#181;L of non-cultured osteoclast induction medium as the negative control. Place the samples in a new 96-well plate.</li>
	<li>Add 90 &#956;L of substrate mixture(1.5.5) into each well of the 96-well plate.</li>
	<li>Place the plate in an incubator at 37 &#176;C for 1 h and shield from light.</li>
	<li>Stop the reaction by adding 50 &#181;L of 3 M NaOH into each well of the 96-well plate.</li>
	<li>Measure theabsorbance at the wavelength of 405 nm.</li>
</ol>
8. Western Blotting
NOTE: After 6-7 days of in vitro culture in the 24-well plate, mature osteoclasts should be visible.
<ol>
	<li>Aspirate the medium.</li>
	<li>Wash gently with pre-cooled 1x PBS 3 times.</li>
	<li>Aspirate PBS.</li>
	<li>Add 100 &#181;L of 1x SDS lysis buffer containing protease inhibitor cocktail.</li>
	<li>Heat lysates at 105 &#176;C for 10 min and centrifuge at 12,000 &#215; g and 4 &#176;C for 10 min. Collect the supernatants containing proteins.</li>
	<li>Separate the lysates containing 30 &#181;g of protein by 10% SDS-PAGE11 and then transfer to a polyvinylidene fluoride (PVDF) membrane.</li>
	<li>Block the membranes with 5% nonfat milk for 30 min.</li>
	<li>Incubate the membranes with anti-Raptor, anti-P-S6, anti-S6, anti-&#946;-actin at 1:1,000 dilution in 5% nonfat milk at 4 &#176;C overnight.</li>
	<li>Wash the membranes with Tris Buffered Saline with Tween-20 (TBST) for 10 min at room temperature.</li>
	<li>Repeat step 8.9 twice.</li>
	<li>Incubate the membranes with horseradish peroxidase (HRP)-conjugated anti-mouse or rabbit IgG antibodies at 1:5,000 dilution in 5% nonfat milk for 1 h at room temperature.</li>
	<li>Wash the membranes 3 times with TBST for 10 min at room temperature.</li>
	<li>For chemiluminescent detection, add western chemiluminescent HRP substrate on the membranes and incubate for 5 min at room temperature. Drain the excess substrate and expose the blots to X-ray film.</li>
</ol>

<ol>
	<li>Boyle, W. J., Simonet, W. S., Lacey, D. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Osteoclast+differentiation+and+activation.">Osteoclast differentiation and activation.</a> Nature. 423 (6937), 337-342 (2003).</li><li>Jaenisch, R., Bird, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Epigenetic+regulation+of+gene+expression:+how+the+genome+integrates+intrinsic+and+environmental+signals.">Epigenetic regulation of gene expression: how the genome integrates intrinsic and environmental signals.</a> Nature Genetics. 33, 245-254 (2003).</li><li>Feng, X., McDonald, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Disorders+of+bone+remodeling.">Disorders of bone remodeling.</a> Annu Rev Pathol. 6, 121-145 (2011).</li><li>Boyce, B. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Advances+in+osteoclast+biology+reveal+potential+new+drug+targets+and+new+roles+for+osteoclasts.">Advances in osteoclast biology reveal potential new drug targets and new roles for osteoclasts.</a> J Bone Miner Res. 28 (4), 711-722 (2013).</li><li>Ibbotson, K. J., Roodman, G. D., McManus, L. M., Mundy, G. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+and+characterization+of+osteoclast-like+cells+and+their+progenitors+in+cultures+of+feline+marrow+mononuclear+cells.">Identification and characterization of osteoclast-like cells and their progenitors in cultures of feline marrow mononuclear cells.</a> J Cell Biol. 99 (2), 471-480 (1984).</li><li>Lacey, D. L., 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=Osteoprotegerin+ligand+is+a+cytokine+that+regulates+osteoclast+differentiation+and+activation.">Osteoprotegerin ligand is a cytokine that regulates osteoclast differentiation and activation.</a> Cell. 93 (2), 165-176 (1998).</li><li>Wong, B. R., 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=TRANCE+is+a+novel+ligand+of+the+tumor+necrosis+factor+receptor+family+that+activates+c-Jun+N-terminal+kinase+in+T+cells.">TRANCE is a novel ligand of the tumor necrosis factor receptor family that activates c-Jun N-terminal kinase in T cells.</a> J Biol Chem. 272 (40), 25190-25194 (1997).</li><li>Zoncu, R., Efeyan, A., Sabatini, D. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=mTOR:+from+growth+signal+integration+to+cancer,+diabetes+and+ageing.">mTOR: from growth signal integration to cancer, diabetes and ageing.</a> Nat Rev Mol Cell Biol. 12 (1), 21-35 (2011).</li><li>Bhaskar, P. T., Hay, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+two+TORCs+and+Akt.">The two TORCs and Akt.</a> Dev Cell. 12 (4), 487-502 (2007).</li><li>Dai, Q., 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=Inactivation+of+Regulatory-associated+Protein+of+mTOR+(Raptor)/Mammalian+Target+of+Rapamycin+Complex+1+(mTORC1)+Signaling+in+Osteoclasts+Increases+Bone+Mass+by+Inhibiting+Osteoclast+Differentiation+in+Mice.">Inactivation of Regulatory-associated Protein of mTOR (Raptor)/Mammalian Target of Rapamycin Complex 1 (mTORC1) Signaling in Osteoclasts Increases Bone Mass by Inhibiting Osteoclast Differentiation in Mice.</a> J Biol Chem. 292 (1), 196-204 (2017).</li><li>Sambrook, J., Fritsch, E. F., Maniatis, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Molecular cloning: a laboratory manual. , (1989).</li><li>Weischenfeldt, J., Porse, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bone+Marrow-Derived+Macrophages+(BMM):+Isolation+and+Applications.">Bone Marrow-Derived Macrophages (BMM): Isolation and Applications.</a> CSH Protoc. 2008, (2008).</li><li>Bradley, E. W., Oursler, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Osteoclast+culture+and+resorption+assays.">Osteoclast culture and resorption assays.</a> Methods Mol Biol. 455, 19-35 (2008).</li><li>Tevlin, R., 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=Osteoclast+derivation+from+mouse+bone+marrow.">Osteoclast derivation from mouse bone marrow.</a> J Vis Exp. (93), e52056 (2014).</li><li>Xing, L., Boyce, B. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=RANKL-based+osteoclastogenic+assays+from+murine+bone+marrow+cells.">RANKL-based osteoclastogenic assays from murine bone marrow cells.</a> Methods Mol Biol. 1130, 307-313 (2014).</li><li>Hsu, H., 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=Tumor+necrosis+factor+receptor+family+member+RANK+mediates+osteoclast+differentiation+and+activation+induced+by+osteoprotegerin+ligand.">Tumor necrosis factor receptor family member RANK mediates osteoclast differentiation and activation induced by osteoprotegerin ligand.</a> Proc Natl Acad Sci U S A. 96 (7), 3540-3545 (1999).</li><li>Underwood, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=From+where+comes+the+osteoclast?.">From where comes the osteoclast?.</a> J Pathol. 144 (4), 225-226 (1984).</li><li>Wein, M. N., 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=Control+of+bone+resorption+in+mice+by+Schnurri-3.">Control of bone resorption in mice by Schnurri-3.</a> Proc Natl Acad Sci U S A. 109 (21), 8173-8178 (2012).</li></ol>

All authors state that they have no conflicts of interest.

The osteoclastogenic assay is the most widely used method to isolate and culture osteoclasts in vitro12,13. While several RANKL-based osteoclast inductions have been described13,14,15, the present study described a protocol with some modifications based on the previous methods.
In the previous study, BMMs were plating immediately afte...

Bone is an ever-changing organ and is remodeled by osteoblasts and osteoclasts throughout life. Osteoclasts are responsible for mineralized matrix resorption and osteoblasts synthesize and secrete new bone matrices1. The balance between bone resorption and bone formation is crucial for bone health including maintenance of bone mass and response to stimulation and injury. If this balance is disrupted, a series of bone metabolic diseases may occur, including osteoporosis and periodontal diseases. In these diseases, bone mass loss resulting from osteoclastic bone resorption exceeds the bone forming capacity of osteoblasts2,3. Thus, in order to develop pharmaceutical targets to treat skeletal disorders such as osteoporosis, it is critical to understand the generation and biology of osteoclasts4.
Osteoclasts are unique giant multinucleated cells located at or near the bone surface, and belong to the monocyte/macrophage family1. Ibbotson K. J. et al. reported a method to generate osteoclast-like cells in vitro with medium containing 1,25-dihydroxy-vitamin D35. The identification of macrophage-colony stimulating factor (M-CSF) and receptor activator for nuclear factor-&#954; B ligand (RANKL) as essential factors of osteoclast formation has dramatically increased the efficiency of osteoclastogenesis in vitro1,6,7. The ability to culture osteoclasts in vitro has improved our understanding of the generation and regulation of osteoclasts.
The mammalian/mechanistic target of rapamycin (mTOR) functions in two structurally and functionally distinct complexes, namely mTORC1 and mTORC28,9. The two multi-protein complexes are distinct from each other due to their different components and downstream substrates. mTORC1 contains the unique regulatory-associated protein of mTOR (Raptor), while mTORC2 contains the rapamycin-insensitive companion of mTOR (Rictor)9. mTORC1 can integrate and transmit important signals to regulate cell growth, proliferation and differentiation. Recently, we demonstrated that mTORC1 plays a key role in the network of catabolic bone resorption by deletion of Raptor to inactivate mTORC1 in osteoclasts10. However, the underlying mechanisms require further study. In the present study, a RANKL-based osteoclastogenic method was used to generate osteoclasts from bone marrow-derived macrophages (BMMs) of wild-type (WT) and RapCtsk mice, and to study the influence of mTORC1 inactivation on osteoclast formation.

<table>
	<tbody>
		<tr>
			<td>Raptorfl/fl mice</td>
			<td>The Jackson Laboratory</td>
			<td>013188</td>
			<td></td>
		</tr>
		<tr>
			<td>Ctsk-cre mice</td>
			<td></td>
			<td></td>
			<td>a gift from S. Kato, University of Tokyo, Tokyo, Japan</td>
		</tr>
		<tr>
			<td>&#945;-MEM</td>
			<td>Corning</td>
			<td>10-022-CVR</td>
			<td></td>
		</tr>
		<tr>
			<td>Glutamine</td>
			<td>Gibico</td>
			<td>25030081</td>
			<td></td>
		</tr>
		<tr>
			<td>Penicillin streptomycin</td>
			<td>Gibico</td>
			<td>15140122</td>
			<td></td>
		</tr>
		<tr>
			<td>Fetal calf serum</td>
			<td>BioInd</td>
			<td>04-001-1A</td>
			<td></td>
		</tr>
		<tr>
			<td>Recombinant mouse M-CSF protein</td>
			<td>R&#38;D</td>
			<td>Q3U4F9</td>
			<td></td>
		</tr>
		<tr>
			<td>Recombinant mouse RANKL protein</td>
			<td>R&#38;D</td>
			<td>Q3TWY5</td>
			<td></td>
		</tr>
		<tr>
			<td>RBC lysis buffer</td>
			<td>Beyotime</td>
			<td>C3702</td>
			<td></td>
		</tr>
		<tr>
			<td>Trypan blue</td>
			<td>Sigma-Aldrich</td>
			<td>302643</td>
			<td></td>
		</tr>
		<tr>
			<td>Acetone</td>
			<td>Shanghai Chemical Co. Ltd.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Citrate solution</td>
			<td>Sigma-Aldrich</td>
			<td>915</td>
			<td></td>
		</tr>
		<tr>
			<td>Formaldehyde solution</td>
			<td>Shanghai Chemical Co. Ltd.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Acid Phosphatase, Leukocyte (TRAP) Kit</td>
			<td>Sigma-Aldrich</td>
			<td>387A-1KT</td>
			<td></td>
		</tr>
		<tr>
			<td>Fast Garnet GBC Base solution</td>
			<td>Sigma-Aldrich</td>
			<td>3872</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium Nitrite Solution</td>
			<td>Sigma-Aldrich</td>
			<td>914</td>
			<td></td>
		</tr>
		<tr>
			<td>Naphthol AS-BI Phosphate Solution</td>
			<td>Sigma-Aldrich</td>
			<td>3871</td>
			<td></td>
		</tr>
		<tr>
			<td>Acetate solution</td>
			<td>Sigma-Aldrich</td>
			<td>3863</td>
			<td></td>
		</tr>
		<tr>
			<td>Tartrate solution</td>
			<td>Sigma-Aldrich</td>
			<td>3873</td>
			<td></td>
		</tr>
		<tr>
			<td>Dulbecco&#39;s phosphate-buffered saline</td>
			<td>Corning</td>
			<td>21-031-CVR</td>
			<td></td>
		</tr>
		<tr>
			<td>L-tartaric acid</td>
			<td>Sigma-Aldrich</td>
			<td>251380</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium tartrate dibasic dehydrate</td>
			<td>Sigma-Aldrich</td>
			<td>s4797</td>
			<td></td>
		</tr>
		<tr>
			<td>Glycine</td>
			<td>Shanghai Chemical Co. Ltd.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>MgCl2</td>
			<td>Shanghai Chemical Co. Ltd.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>ZnCl2</td>
			<td>Shanghai Chemical Co. Ltd.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>NaOH</td>
			<td>Shanghai Chemical Co. Ltd.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Phosphatase substrate</td>
			<td>Sigma-Aldrich</td>
			<td>P4744</td>
			<td></td>
		</tr>
		<tr>
			<td>anti-Raptor</td>
			<td>Cell Signaling Technology</td>
			<td>2280</td>
			<td></td>
		</tr>
		<tr>
			<td>anti-P-ribosomal protein S6 (S235/236)</td>
			<td>Cell Signaling Technology</td>
			<td>2317</td>
			<td></td>
		</tr>
		<tr>
			<td>anti-ribosomal protein S6</td>
			<td>Cell Signaling Technology</td>
			<td>2211</td>
			<td></td>
		</tr>
		<tr>
			<td>anti-&#946;-actin</td>
			<td>Santa Cruz Biotechnology</td>
			<td>sc-130300</td>
			<td></td>
		</tr>
		<tr>
			<td>37% formaldehyde</td>
			<td>Xilong scientific</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>polyvinylidene fluoride (PVDF) membrane</td>
			<td>Bio-Rad</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Western Chemiluminescent HRP Substrate (ECL)</td>
			<td>Millipore</td>
			<td>00000367MSDS</td>
			<td></td>
		</tr>
		<tr>
			<td>IX71</td>
			<td>Olympus</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Envision</td>
			<td>Perkin Elmer</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>0.45-mm Syringe</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Scissor</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Mosquito forcep</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

a rankl-based osteoclast culture assay of mouse bone marrow to investigate the role of mtorc1 in osteoclast formation

Osteoclasts are unique bone-resorbing cells that differentiate from the monocyte/macrophage lineage of bone marrow. Dysfunction of osteoclasts may result in a series of bone metabolic diseases, including osteoporosis. To develop pharmaceutical targets for the prevention of pathological bone mass loss, the mechanisms by which osteoclasts differentiate from precursors must be understood. The ability to isolate and culture a large number of osteoclasts in vitro is critical in order to determine the role of specific genes in osteoclast differentiation. Inactivation of the mammalian/mechanistic target of rapamycin complex 1 (TORC1) in osteoclasts can decrease osteoclast number and increase bone mass; however, the underlying mechanisms require further study. In the present study, a RANKL-based protocol to isolate and culture osteoclasts from mouse bone marrow and to study the influence of mTORC1 inactivation on osteoclast formation is described. This protocol successfully resulted in a large number of giant osteoclasts, typically within one week. Deletion of Raptor impaired osteoclast formation and decreased the activity of secretory tartrate-resistant acid phosphatase, indicating that mTORC1 is critical for osteoclast formation.

Using the present protocol, a large number of giant osteoclasts were seen on day 6; if giant osteoclasts are not seen, one more day of osteoclast differentiation may be needed (Figure 1). Successful osteoclast formation was confirmed by TRAP staining (Figure 2A). Osteoclasts were giant wine red/purple cells with more than 3 nuclei. More than 250 osteoclasts were obtained in each well of the 96-well plate in WT BMMs (<strong class...

Watch this Scientific Journal Video about A RANKL-based Osteoclast Culture Assay of Mouse Bone Marrow to Investigate the Role of mTORC1 in Osteoclast Formation at JoVE.com

A RANKL-based Osteoclast Culture Assay of Mouse Bone Marrow to Investigate the Role of mTORC1 in Osteoclast Formation

This manuscript describes a protocol to isolate and culture osteoclasts in vitro from mouse bone marrow, and to study the role of the mammalian/mechanistic target of rapamycin complex 1 in osteoclast formation.

Osteoclasts are unique bone-resorbing cells that differentiate from the monocyte/macrophage lineage of bone marrow. Dysfunction of osteoclasts may result ...

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Research

JoVE Journal

Developmental Biology

12.7K Views.  National Clinical Research Center of Stomatology. This manuscript describes a protocol to isolate and culture osteoclasts in vitro from mouse bone marrow, and to study the role of the mammalian/mechanistic target of rapamycin complex 1 in osteoclast formation.

Video: A RANKL-based Osteoclast Culture Assay of Mouse Bone Marrow to Investigate the Role of mTORC1 in Osteoclast Formation

An Optogenetic Approach for Assessing Formation of Neuronal Connections in a Co-culture System

Here we describe a protocol to generate a co-culture consisting of 2 different neuronal populations. Induced pluripotent stem cells (iPSCs) are reprogrammed from human fibroblasts using episomal vectors. Colonies of iPSCs can be observed 30 days after initiation of fibroblast reprogramming. Pluripotent colonies are manually picked and grown in neural induction medium to permit differentiation into neural progenitor cells (NPCs). iPSCs rapidly convert into neuroepithelial cells within 1 week and retain the capability to self-renew when maintained at a high culture density. Primary mouse NPCs are differentiated into astrocytes by exposure to a serum-containing medium for 7 days and form a monolayer upon which embryonic day 18 (E18) rat cortical neurons (transfected with channelrhodopsin-2 (ChR2)) are added. Human NPCs tagged with the fluorescent protein, tandem dimer Tomato (tdTomato), are then seeded onto the astrocyte/cortical neuron culture the following day and allowed to differentiate for 28 to 35 days. We demonstrate that this system forms synaptic connections between iPSC-derived neurons and cortical neurons, evident from an increase in the frequency of synaptic currents upon photostimulation of the cortical neurons. This co-culture system provides a novel platform for evaluating the ability of iPSC-derived neurons to create synaptic connections with other neuronal populations.

A protocol to generate a co-culture system consisting of neurons derived from induced pluripotent stem cells (iPSCs), primary cortical neurons and astrocytes is described. This co-culture system allows detection of the formation of synaptic contacts and circuits between new, iPSC-derived neurons and pre-existing cortical neurons expressing channelrhodopsin-2.

Here we describe a protocol to generate a co-culture consisting of 2 different neuronal populations. Induced pluripotent stem cells (iPSCs) are ...

An Enzymatic Method to Rescue Mesenchymal Stem Cells from Clotted Bone Marrow Samples

Mesenchymal stem cells (MSCs) - usually obtained from bone marrow - often require expansion culture. Our protocol uses clinical grade urokinase to degrade clots in the bone marrow and release MSCs for further use. This protocol provides a rapid and inexpensive alternative to bone marrow resampling. Bone marrow is a major source of MSCs, which are interesting for tissue engineering and autologous stem cell therapies. Upon withdrawal bone marrow may clot, as it comprises all of the hematopoietic system. The resulting clots contain also MSCs that are lost for expansion culture or direct stem cell therapy. We experienced that 74% of canine bone marrow samples contained clots and yielded less than half of the stem cell number expected from unclotted samples. Thus, we developed a protocol for enzymatic digestion of those clots to avoid labor-intense and costly bone marrow resampling. Urokinase - a clinically approved and readily available thrombolytic drug &#8211; clears away the bone marrow clots almost completely. As a consequence, treated bone marrow aspirates yield similar numbers of MSCs as unclotted samples. Also, after urokinase treatment the cells kept their metabolic activity and the ability to differentiate into chondrogenic, osteogenic and adipogenic lineages. Our protocol salvages clotted blood and bone marrow samples without affecting the quality of the cells. This obsoletes resampling, considerably reduces sampling costs and enables the use of clotted samples for research or therapy.

Mesenchymal stem cells are usually obtained from bone marrow and require expansion culture. When samples clot before processing, a protocol using the (enzymatic) thrombolytic drug urokinase can be applied to degrade the clot. Thus, cells are released and available for expansion culture. This protocol provides a rapid and inexpensive alternative to resampling.

Mesenchymal stem cells (MSCs) - usually obtained from bone marrow - often require expansion culture. Our protocol uses clinical grade urokinase to degrade ...

Using Confocal Analysis of Xenopus laevis to Investigate Modulators of Wnt and Shh Morphogen Gradients

This protocol describes a method to visualise ligands distributed across a field of cells. The ease of expressing exogenous proteins, together with the large size of their cells in early embryos, make Xenopus laevis a useful model for visualising GFP-tagged ligands. Synthetic mRNAs are efficiently translated after injection into early stage Xenopus embryos, and injections can be targeted to a single cell. When combined with a lineage tracer such as membrane tethered RFP, the injected cell (and its descendants) that are producing the overexpressed protein can easily be followed. This protocol describes a method for the production of fluorescently tagged Wnt and Shh ligands from injected mRNA. The methods involve the micro dissection of ectodermal explants (animal caps) and the analysis of ligand diffusion in multiple samples. By using confocal imaging, information about ligand secretion and diffusion over a field of cells can be obtained. Statistical analyses of confocal images provide quantitative data on the shape of ligand gradients. These methods may be useful to researchers who want to test the effects of factors that may regulate the shape of morphogen gradients.

Using Confocal Analysis of Xenopus laevis to Investigate Modulators of Wnt and Shh Morphogen Gradients

The manuscript here provides a simple set of methods for analysing the secretion and diffusion of fluorescently tagged ligands in Xenopus. This provides a context for testing the ability of other proteins to modify ligand distribution and allowing experiments that may give insight into mechanisms regulating morphogen gradients.

This protocol describes a method to visualise ligands distributed across a field of cells. The ease of expressing exogenous proteins, together with the ...

Isolating Mesangiogenic Progenitor Cells (MPCs) from Human Bone Marrow

In a research study aimed to isolate human bone marrow (hBM)-derived Mesenchymal Stromal Cells (MSCs) for clinical applications, we identified a novel cell population specifically selected for growth in human serum supplemented medium. These cells are characterized by morphological, phenotypic, and molecular features distinct from MSCs and we named them Mesodermal Progenitor Cells (MPCs). MPCs are round, with a thick highly refringent core region; they show strong, trypsin resistant adherence to plastic. Failure to expand MPCs directly revealed that they are slow in cycling. This is as also suggested by Ki-67 negativity. On the other hand, culturing MPCs in standard medium designed for MSC expansion, gave rise to a population of exponentially growing MSC-like cells. Besides showing mesenchymal differentiation capacity MPCs retained angiogenic potential, confirming their multiple lineage progenitor nature. Here we describe an optimized highly reproducible protocol to isolate and characterize hBM-MPCs by flow cytometry (CD73, CD90, CD31, and CD45), nestin expression, and F-actin organization. Protocols for mesengenic and angiogenic differentiation of MPCs are also provided. Here we also suggest a more appropriate nomenclature for these cells, which has been re-named as "Mesangiogenic Progenitor Cells".

Isolating Mesangiogenic Progenitor Cells MPCs from Human Bone Marrow

Here we describe an optimized, highly reproducible protocol to isolate Mesodermal Progenitor Cells (MPCs) from human bone marrow (hBM). MPCs were characterized by flow cytometry and nestin expression. They showed the ability to give rise to exponentially growing MSC-like cell cultures while retaining their angiogenic potential.

In a research study aimed to isolate human bone marrow (hBM)-derived Mesenchymal Stromal Cells (MSCs) for clinical applications, we identified a novel ...

Culture of Murine Embryonic Metatarsals: A Physiological Model of Endochondral Ossification

The fundamental process of endochondral ossification is under tight regulation in the healthy individual so as to prevent disturbed development and/or longitudinal bone growth. As such, it is imperative that we further our understanding of the underpinning molecular mechanisms involved in such disorders so as to provide advances towards human and animal patient benefit. The mouse metatarsal organ explant culture is a highly physiological ex vivo model for studying endochondral ossification and bone growth as the growth rate of the bones in culture mimic that observed in vivo. Uniquely, the metatarsal organ culture allows the examination of chondrocytes in different phases of chondrogenesis and maintains cell-cell and cell-matrix interactions, therefore providing conditions closer to the in vivo situation than cells in monolayer or 3D culture. This protocol describes in detail the intricate dissection of embryonic metatarsals from the hind limb of E15 murine embryos and the subsequent analyses that can be performed in order to examine endochondral ossification and longitudinal bone growth.

We present a protocol to dissect and culture embryonic day 15 (E15) murine metatarsal bones. This highly physiological ex vivo model of endochondral ossification provides conditions closer to the in vivo situation than cells in monolayer or 3D culture and is a vital tool for investigating bone growth and development.

The fundamental process of endochondral ossification is under tight regulation in the healthy individual so as to prevent disturbed development and/or ...

Drug Treatment and In Vivo Imaging of Osteoblast-Osteoclast Interactions in a Medaka Fish Osteoporosis Model

Bone-forming osteoblasts interact with bone-resorbing osteoclasts to coordinate the turnover of bone matrix and to control skeletal homeostasis. Medaka and zebrafish larvae are widely used to analyze the behavior of bone cells during bone formation, degeneration, and repair. Their optical clarity allows the visualization of fluorescently labeled bone cells and fluorescent dyes bound to the mineralized skeletal matrix. Our lab has generated transgenic medaka fish that express the osteoclast-inducing factor Receptor Activator of Nuclear-factor &#954;B Ligand (RANKL) under the control of a heat&#160;shock-inducible promoter. Ectopic expression of RANKL results in the excess formation of activated osteoclasts, which can be visualized in reporter lines with nlGFP expression under the control of the cathepsin K (ctsk) promoter. RANKL induction and ectopic osteoclast formation leads to severe osteoporosis-like phenotypes. Compound transgenic medaka lines that express ctsk:nlGFP in osteoclasts, as well as mCherry under the control of the osterix (osx) promoter in premature osteoblasts, can be used to study the interaction of both cell types. This facilitates the in vivo observation of cellular behavior under conditions of bone degeneration and repair. Here, we describe the use of this system to test a drug commonly used in human osteoporosis therapy and describe a protocol for live imaging. The medaka model complements studies in cell culture and mice, and offers a novel system for the in vivo analysis of drug action in the skeletal system.

Drug Treatment and In Vivo Imaging of Osteoblast-Osteoclast Interactions in a Medaka Fish Osteoporosis Model

Small laboratory fish have become popular models for bone research on the mechanisms underlying human bone disorders and for the screening of bone-modulating drugs. In this report, we describe a protocol to assess the effect of alendronate on bone cells in medaka larvae with osteoporotic lesions.

Bone-forming osteoblasts interact with bone-resorbing osteoclasts to coordinate the turnover of bone matrix and to control skeletal homeostasis. Medaka ...

Temporal Ordering of Dynamic Expression Data from Detailed Spatial Expression Maps

During somitogenesis, pairs of epithelial somites form in a progressive manner, budding off from the anterior end of the pre-somitic mesoderm (PSM) with a strict species-specific periodicity. The periodicity of the process is regulated by a molecular oscillator, known as the "segmentation clock," acting in the PSM cells. This clock drives the oscillatory patterns of gene expression across the PSM in a posterior-anterior direction. These so-called clock genes are key components of three signaling pathways: Wnt, Notch, and fibroblast growth factor (FGF). In addition, Notch signaling is essential for synchronizing intracellular oscillations in neighboring cells. We recently gained insight into how this may be mechanistically regulated. Upon ligand activation, the Notch receptor is cleaved, releasing the intracellular domain (NICD), which moves to the nucleus and regulates gene expression. NICD is highly labile, and its phosphorylation-dependent turnover acts to restrict Notch signaling. The profile of NICD production (and degradation) in the PSM is known to be oscillatory and to resemble that of a clock gene. We recently reported that both the Notch receptor and the Delta ligand, which mediate intercellular coupling, themselves exhibit dynamic expression at both the mRNA and protein levels. In this article, we describe the sensitive detection methods and detailed image analysis tools that we used, in combination with the computational modeling that we designed, to extract and overlay expression data from distinct points in the expression cycle. This allowed us to construct a spatio-temporal picture of the dynamic expression profile for the receptor, the ligand, and the Notch target clock genes throughout an oscillation cycle. Here, we describe the protocols used to generate and culture the PSM explants, as well as the procedure to stain for the mRNA or protein. We also explain how the confocal images were subsequently analyzed and temporally ordered computationally to generate ordered sequences of clock expression snapshots, hereafter defined as "kymographs," for the visualization of the spatiotemporal expression of Delta-like1 (Dll1) and Notch1 throughout the PSM.

The segmentation clock drives oscillatory gene expression across the pre-somitic mesoderm (PSM). Dynamic Notch activity is key to this process. We use imaging and computational analyses to extract temporal dynamics from spatial expression data to demonstrate that Delta ligand and Notch receptor expression oscillate in the vertebrate PSM.

During somitogenesis, pairs of epithelial somites form in a progressive manner, budding off from the anterior end of the pre-somitic mesoderm (PSM) with a ...

Stimulation of Notch Signaling in Mouse Osteoclast Precursors

Notch signaling is a key component of multiple physiological and pathological processes. The nature of Notch signaling, however, makes in vitro investigation of its varying and sometimes contradictory roles a challenge. As a component of direct cell-cell communication with both receptors and ligands bound to the plasma membrane, Notch signaling cannot be activated in vitro by simple addition of ligands to culture media, as is possible with many other signaling pathways. Instead, Notch ligands must be presented to cells in an immobilized state. 
Variations in methods of Notch signaling activation can lead to different outcomes in cultured cells. In osteoclast precursors, in particular, differences in methods of Notch stimulation and osteoclast precursor culture and differentiation have led to disagreement over whether Notch signaling is a positive or negative regulator of osteoclast differentiation. While closer comparisons of osteoclast differentiation under different Notch stimulation conditions in vitro and genetic models have largely resolved the controversy regarding Notch signaling and osteoclasts, standardized methods of continuous and temporary stimulation of Notch signaling in cultured cells could prevent such discrepancies in the future.
This protocol describes two methods for stimulating Notch signaling specifically in cultured mouse osteoclast precursors, though these methods should be applicable to any adherent cell type with minor adjustments. The first method produces continuous stimulation of Notch signaling and involves immobilizing Notch ligand to a tissue culture surface prior to the seeding of cells. The second, which uses Notch ligand bound to agarose beads allows for temporary stimulation of Notch signaling in cells that are already adhered to a culture surface. This protocol also includes methods for detecting Notch activation in osteoclast precursors as well as representative transcriptional markers of Notch signaling activation.

Notch signaling is a form of cellular communication that relies upon direct contact between cells. To properly induce Notch signaling in vitro, Notch ligands must be presented to cells in an immobilized state. This protocol describes methods for in vitro stimulation of Notch signaling in mouse osteoclast precursors.

Notch signaling is a key component of multiple physiological and pathological processes. The nature of Notch signaling, however, makes in vitro ...

A 5-mC Dot Blot Assay Quantifying the DNA Methylation Level of Chondrocyte Dedifferentiation In Vitro

The dedifferentiation of hyaline chondrocytes into fibroblastic chondrocytes often accompanies monolayer expansion of chondrocytes in vitro. The global DNA methylation level of chondrocytes is considered to be a suitable biomarker for the loss of the chondrocyte phenotype. However, results based on different experimental methods can be inconsistent. Therefore, it is important to establish a precise, simple, and rapid method to quantify global DNA methylation levels during chondrocyte dedifferentiation.
Current genome-wide methylation analysis techniques largely rely on bisulfite genomic sequencing. Due to DNA degradation during bisulfite conversion, these methods typically require a large sample volume. Other methods used to quantify global DNA methylation levels include high-performance liquid chromatography (HPLC). However, HPLC requires complete digestion of genomic DNA. Additionally, the prohibitively high cost of HPLC instruments limits HPLC&#39;s wider application.
In this study, genomic DNA (gDNA) was extracted from human chondrocytes cultured with varying number of passages. The gDNA methylation level was detected using a methylation-specific dot blot assay. In this dot blot approach, a gDNA mixture containing the methylated DNA to be detected was spotted directly onto an N+ membrane as a dot inside a previously drawn circular template pattern. Compared with other gel electrophoresis-based blotting approaches and other complex blotting procedures, the dot blot method saves significant time. In addition, dot blots can detect overall DNA methylation level using a commercially available 5-mC antibody. We found that the DNA methylation level differed between the monolayer subcultures, and therefore could play a key role in chondrocyte dedifferentiation. The 5-mC dot blot is a reliable, simple, and rapid method to detect the general DNA methylation level to evaluate chondrocyte phenotype.

A 5-mC Dot Blot Assay Quantifying the DNA Methylation Level of Chondrocyte Dedifferentiation In Vitro

We present a method to quantify DNA methylation based on the 5-methylcytosine (5-mC) dot blot. We determined the 5-mC levels during chondrocyte dedifferentiation. This simple technique could be used to quickly determine the chondrocyte phenotype in ACI treatment.

The dedifferentiation of hyaline chondrocytes into fibroblastic chondrocytes often accompanies monolayer expansion of chondrocytes in vitro. The global ...

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 ...