Name: drug treatment and in vivo imaging of osteoblast-osteoclast interactions in a medaka fish osteoporosis model
Uploaded: 2017-01-01T14:00:00
Description: Watch this Scientific Journal Video about Drug Treatment and In Vivo Imaging of Osteoblast-Osteoclast Interactions in a Medaka Fish Osteoporosis Model at JoVE.com

This project was funded by grants from the Singapore Ministry of Education (MOE, grant number 2013-T2-2-126) and the National Institute of Health, USA (NIH, grant number 1R21AT008452-01A1). T.Y. received a graduate scholarship from the NUS Department of Biological Sciences. We thank the confocal unit of the NUS Centre for Bioimaging Sciences (CBIS) for their constant support.

All experiments were performed in accordance with approved Institutional Animal Care and Use Committee (IACUC) protocols of the National University of Singapore (R14-293).
1. Fish Husbandry and the Collection of Embryos
<ol>
	<li>Raise WT, ctsk:nlGFP24, RANKL:HSE:CFP24, and osx:mCherry21 single- or compound-transgenic medaka fish at 26 &#176;C under a controlled light cycle (14 h light, 10 h dark) to induce spawning.</li>
	<li>Daily...

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Critical Steps within the Protocol
It is essential that the conditions for heat&#160;shock treatment are consistent and stable when comparing different samples. Stable temperature conditions guarantee similar levels of RANKL induction in the transgenic larvae and, consequently, comparable osteoclast formation, which can be confirmed by screening for ctsk:nlGFP expression. Ultimately, this leads to a similar degree of induced ectopic bone resorption and osteoporosis-like lesions, as valid...

The vertebrate skeleton provides structural support and protection for organs, allows mobility, and serves as a source of calcium. Throughout life, the extracellular bone matrix is continuously turned over to maintain bone stability and rigidity. This process requires the tightly coordinated activity and interplay of bone-forming osteoblasts and bone-resorbing osteoclasts. Osteoblasts are derived from multipotent mesenchymal progenitors and produce collagen to form the osteoid, the proteinaceous part of the bone matrix10. Osteoblasts interact with osteoclasts to achieve a balanced activity of both cell types, which is required to control bone homeostasis7. Because of these intricate regulatory interactions, responses to drug treatment and bone homeostasis cannot be fully examined using in vitro studies. Hence, there is a strong demand for animal models. Compared to the cell&#160;culture settings, in vivo models can provide valuable insight into the multicellular networks within the bone environment.
Numerous mouse models exist for a variety of human bone disorders including osteoporosis16. However, the size and accessibility of mouse embryos represent significant limitations for live imaging of skeletal processes. Small teleost fish, on the other hand, serve as an attractive alternative for in vivo imaging. Zebrafish (Danio rerio) and medaka (Oryzias latipes) have become popular animal models for skeletal research over the last two decades17, 19, 22, 24. Bone in teleost fish and in mammals is very similar, both on a structural and on a physiological level, and many of the key regulatory genes and signaling pathways are conserved3. As in mammals, teleost fish carefully regulate the activity of osteoblasts and osteoclasts to balance bone formation and resorption26. Most importantly, the optical clarity of fish larvae allows the use of fluorescent reporters to label bone cells and the calcified skeletal matrix8, 9, 12, 21, 23, which&#160;facilitates the observation of cellular processes in the living animal. In addition, a series of genetic tools has been generated to facilitate biomedically relevant research in fish. For medaka in particular, methods for targeted gene mutation by CrispR/Cas92, cell-lineage tracing6, and site-specific transgenesis14 have been recently established and are now widely in use15.
Small teleost larvae have been successfully used for chemical screens, which led to the discovery of several pharmacologically relevant drugs1, 18.
Fish larvae are tolerant to low concentrations of DMSO and are able to absorb compounds from their aquatic environment, either through the skin or through the gastrointestinal tract1, 5. Our lab previously reported transgenic medaka lines that express fluorescent reporters in bone cells under the control of various osteoblast- and osteoclast-specific promoters. These include premature osteoblasts (collagen 10a1, col10a1; osterix, osx)20, 21, mature osteoblasts (osteocalcin, osc)27, and osteoclasts (cathepsin K, ctsk)24. We also generated a transgenic line that expresses the osteoclast-inducing factor Receptor Activator of Nuclear-factor &#954;B Ligand (RANKL) under the control of a heat&#160;shock-inducible promoter24.
Induction of RANKL in this system results in the ectopic formation of active osteoclasts. This leads to increased bone resorption and a severe osteoporosis-like phenotype, with drastically reduced mineralization in the vertebral bodies. We recently showed that osteoclast activity in this model can be blocked by the bisphosphonates etidronate and alendronate, two drugs commonly used in human osteoporosis therapy, thus validating medaka as a suitable model system for osteoporosis27.
Due to their large brood size, rapid development, and small size of embryos, transgenic medaka larvae are uniquely suited for the large-scale screening of osteoporosis drugs and for the in vivo analysis of bone cell behavior. Studies in medaka thus can efficiently complement experiments in cell cultures and in mice that are aimed at discovering new therapeutic targets and novel therapies for human bone disorders.
In the present study, we describe a protocol to treat medaka bone-reporter larvae with the common osteoporosis drug, alendronate. We also describe in detail how treated larvae are mounted and prepared for the live imaging of bone matrix and bone cells. These protocols can be easily adapted to other small chemical compounds that either work as bone anabolic or antiresorptive drugs.

<table border="0" cellpadding="0" cellspacing="0" width="1101">
	<tbody>
		<tr height="20">
			<td height="20" style="height:20px;width:249px;">Alendronate&#160;</td>
			<td style="width:177px;">Sigma</td>
			<td style="width:140px;">A4978</td>
			<td style="width:535px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:249px;">alizarin-3-methyliminodiacetic acid, Alizarin Complexone</td>
			<td>Sigma</td>
			<td>A3882</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Calcein</td>
			<td>Sigma</td>
			<td>C0875</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:249px;">ethyl 3-aminobenzoate methanesulfonate (Tricaine)</td>
			<td>Sigma</td>
			<td>A5040</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">ImageJ (1.4.3.67)</td>
			<td style="width:177px;">National Institute of Health (NIH)</td>
			<td></td>
			<td>https://imagej.nih.gov/ij/</td>
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		<tr height="20">
			<td height="20" style="height:20px;width:249px;">LSM 510 Meta confocal&#160;</td>
			<td>Zeiss</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:249px;">LSM Image Browser (4.2.0.121)</td>
			<td>Zeiss</td>
			<td></td>
			<td>http://www.zeiss.com/microscopy/en_de/downloads/lsm-5-series.html</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Micro-loader</td>
			<td>Eppendorf</td>
			<td>5242956003</td>
			<td>Eppendorf ep T.I.P.S 20 &#956;l</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:249px;">NIS-Elements BR 3.0 software</td>
			<td>Nikon</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:249px;">Photoshop CS6 (13.0.0.0)</td>
			<td>Adobe</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:249px;">SMZ1000 stereomicroscope&#160;</td>
			<td>Nikon</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

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.

Abundant egg numbers, as well as the small size of the larvae, make medaka an excellent model for drug screening. A single six-well plate was used to culture up to 36 larvae, which was sufficient to provide statistically significant data. Another big advantage of using fish for skeletal analysis is the possibility of doing live imaging. The transparency of fish larvae allows the use of fluorescent proteins to label bone cells, as well as the use of dyes that bind to bone matrix in order to visualize mineralization. Fish ...

Watch this Scientific Journal Video about Drug Treatment and In Vivo Imaging of Osteoblast-Osteoclast Interactions in a Medaka Fish Osteoporosis Model at JoVE.com

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.

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 ...

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