Name: real-time visualization and analysis of chondrocyte injury due to mechanical loading in fully intact murine cartilage explants
Uploaded: 2019-01-07T14:00:00
Description: Watch this Scientific Journal Video about Real-time Visualization and Analysis of Chondrocyte Injury Due to Mechanical Loading in Fully Intact Murine Cartilage Explants at JoVE.com

The authors would like to thank Dr. Richard Waugh and Luis Delgadillo for the generous use of their pH meter and osmometer. Additionally, the authors would like to thank Andrea Lee for contributing to the initial development of the mechanical testing system. This study was funded by NIH P30 AR069655.

All animal work was approved by the University of Rochester Committee on Animal Resources.
1. Solutions
<ol>
	<li>Prepare Hank&#39;s Balanced Salt Solution (1X HBSS) containing calcium, magnesium and no phenol red. Adjust the pH to 7.4 by adding small amounts of HCl or NaOH.</li>
	<li>Adjust the osmolarity to 303 mOsm by adding NaCl or deionized water. Use the buffer during the dissections, specimen preparation and mechanical testing.</li>
</ol>
2. Dissections of the Di...

<ol>
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The methods described above were successfully employed to visualize viable and injured/dead in situ articular chondrocytes from mouse joints after prescribed mechanical loads or impacts. In particular, we were able to analyze the mechanical vulnerability of chondrocytes within fully intact articular cartilage from two different synovial joints: the knee joint (distal femurs) and shoulder (humeri). Our representative results show that the spatial extent of cell injury on the articular surface depends sensitively ...

Articular cartilage (AC) is a load bearing tissue that covers and protects bones in synovial joints, providing smooth joint articulation. Tissue homeostasis is dependent on the viability of chondrocytes, the sole cell type residing in AC. However, exposure of cartilage to extreme forces due to trauma (e.g., falls, vehicle accident or sports injuries) or due to post-traumatic joint instability can induce chondrocyte death, leading to irreversible breakdown of the joint (osteoarthritis)1. Furthermore, in osteochondral grafting procedures that aim to repair local defects in damaged cartilage, graft insertion-associated mechanical trauma reduces chondrocyte viability and has detrimental effects on surgical outcomes2.
Cartilage explant models are commonly used to study the susceptibility of articular chondrocytes to mechanically-induced cell death. These models typically use explants from large animals to study the effects of loading conditions, environmental conditions and other factors on cell vulnerability3,4,5,6,7,8,9,10,11,12,13,14,15. However, due to the large size of the native joints, these models generally require removal of a plug from the articular surface of an intact joint, thereby compromising native boundary conditions. Moreover, they generally require application of large mechanical loads to induce cell injury. Alternatively, murine cartilage explant models provide several advantages over larger animal models in studying the mechanical vulnerability of in situ chondrocytes. In particular, due to their smaller dimensions, these models facilitate testing of fully intact articular cartilage without altering native tissue integrity. In addition, loading of murine cartilage occurs over small contact areas such that chondrocyte death/injury can be induced with small loads (&#60;1 N). Finally, the mouse genome is easily manipulated, enabling testing of how specific genes impact the susceptibility of in situ chondrocytes to mechanical injury.
The overall goal of the method introduced in this manuscript is to quantify and visualize-in real-time-the spatial extent of in situ cell death/injury due to applied mechanical loads on fully intact mouse cartilage-on-bone explants in vitro. This method requires careful dissection of mouse synovial joints without compromising chondrocyte viability, followed by mechanical testing of vitally stained explants using a microscope-mounted device similar to a testing platform that we recently developed to quantify murine cartilage mechanical properties16. During mechanical testing, a large portion of the (intact) articular surface of the dissected bone is visible on a single fluorescence micrograph, enabling rapid analysis of cell viability after a load is applied. A similar analysis of surface cell viability in murine cartilage explants has been performed previously, but without simultaneous application of load17. Potential applications of our method include comparative studies to investigate the vulnerability of articular chondrocytes to different controlled environmental and mechanical conditions, as well as screening of treatments aimed at reducing the sensitivity of chondrocytes to mechanical loading.

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	<tbody>
		<tr height="42">
			<td height="42" style="height:42px;width:223px;">Calcein, AM&#160;</td>
			<td style="width:205px;">Invitrogen by Thermo Fisher Scientific</td>
			<td style="width:220px;">C3100MP</td>
			<td style="width:379px;">20x50mg , Eugene, OR, USA</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:223px;">Propidium Iodide</td>
			<td style="width:205px;">Invitrogen by Thermo Fisher Scientific</td>
			<td style="width:220px;">P3566</td>
			<td>1 mg/mL solution in water, 10mL, Eugene, OR, USA</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Dimethyl sulfoxide (DMSO)</td>
			<td style="width:205px;">Sigma-Aldrich</td>
			<td style="width:220px;">276855</td>
			<td>1L DMSO, anhydrous, &#8805;99.9%, St. Louis, MO, USA</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:223px;">HBSS (calcium, magnesium, no phenol red)&#160;</td>
			<td style="width:205px;">Gibco by Thermo Fisher Scientific</td>
			<td style="width:220px;">14025-092</td>
			<td>1X, 500mL, Grand Island, NY, USA</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Feather surgical blade (#11)</td>
			<td style="width:205px;">VWR</td>
			<td style="width:220px;">102097-822</td>
			<td>Hatfield, PA, USA</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:223px;">Vapor pressure osmometer, VAPRO</td>
			<td style="width:205px;">ELITechGroup</td>
			<td style="width:220px;">Model 5520</td>
			<td>Puteaux, France</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">pH meter&#160;</td>
			<td style="width:205px;">Beckman</td>
			<td style="width:220px;">Model Phi 32&#160;</td>
			<td>Brea, CA, USA</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Eppendorf thermomixer&#160;</td>
			<td style="width:205px;">Eppendorf AG&#160;</td>
			<td style="width:220px;">Model 5350</td>
			<td>Hamburg, Germany</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:223px;">Motorized inverted research microscope</td>
			<td style="width:205px;">Olypmus</td>
			<td style="width:220px;">Model IX-81</td>
			<td>Center Valley, PA, USA</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:223px;">Wooden applicator</td>
			<td style="width:205px;">Puritan Medical Products Company, LLC</td>
			<td style="width:220px;">807</td>
			<td>6&#34;x100, Guilford, ME, USA</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">1.5 Glass coverslips</td>
			<td style="width:205px;">Warner Instruments, LLC</td>
			<td style="width:220px;">64-1696</td>
			<td>#1.5, 0.17mm thick, 40mm diameter, Hamden, CT, USA</td>
		</tr>
	</tbody>
</table>

real-time visualization and analysis of chondrocyte injury due to mechanical loading in fully intact murine cartilage explants

Homeostasis of articular cartilage depends on the viability of resident cells (chondrocytes). Unfortunately, mechanical trauma can induce widespread chondrocyte death, potentially leading to irreversible breakdown of the joint and the onset of osteoarthritis. Additionally, maintenance of chondrocyte viability is important in osteochondral graft procedures for optimal surgical outcomes. We present a method to assess the spatial extent of cell injury/death on the articular surface of intact murine synovial joints after application of controlled mechanical loads or impacts. This method can be used in comparative studies to investigate the effects of different mechanical loading regimens, different environmental conditions or genetic manipulations, as well as different stages of cartilage degeneration on short- and/or long-term vulnerability of in situ articular chondrocytes. The goal of the protocol introduced in the manuscript is to assess the spatial extent of cell injury/death on the articular surface of murine synovial joints. Importantly, this method enables testing on fully intact cartilage without compromising native boundary conditions. Moreover, it allows for real-time visualization of vitally stained articular chondrocytes and single image-based analysis of cell injury induced by application of controlled static and impact loading regimens. Our representative results demonstrate that in healthy cartilage explants, the spatial extent of cell injury depends sensitively on load magnitude and impact intensity. Our method can be easily adapted to investigate the effects of different mechanical loading regimens, different environmental conditions or different genetic manipulations on the mechanical vulnerability of in situ articular chondrocytes.

Six different applied loading protocols (static loading: 0.1 N, 0.5 N and 1 N for 5 min; and impact loading: 1 mJ, 2 mJ and 4 mJ) reproducibly induced quantifiable localized areas of cell injury in femoral and humeral cartilage obtained from 8-10-week-old BALB/c mice (Figure 2). Importantly, the spatial extent of chondrocyte injury on the articular surface was measured quickly and easily in ImageJ. Representative results demonstrate that the mechanical vulner...

Watch this Scientific Journal Video about Real-time Visualization and Analysis of Chondrocyte Injury Due to Mechanical Loading in Fully Intact Murine Cartilage Explants at JoVE.com

Real-time Visualization and Analysis of Chondrocyte Injury Due to Mechanical Loading in Fully Intact Murine Cartilage Explants

We present a method to assess the spatial extent of cell injury/death on the articular surface of intact murine joints after application of controlled mechanical loads or impacts. This method can be used to investigate how osteoarthritis, genetic factors and/or different loading regimens affect the vulnerability of in situ chondrocytes.

Homeostasis of articular cartilage depends on the viability of resident cells (chondrocytes). Unfortunately, mechanical trauma can induce widespread ...

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An In Vitro Organ Culture Model of the Murine Intervertebral Disc

An In Vitro Organ Culture Model of the Murine Intervertebral Disc

Intervertebral disc (IVD) degeneration is a significant contributor to low back pain. The IVD is a fibrocartilaginous joint that serves to transmit and ...

A Test Bed to Examine Helmet Fit and Retention and Biomechanical Measures of Head and Neck Injury in Simulated Impact

Conventional wisdom and the language in international helmet testing and certification standards suggest that appropriate helmet fit and retention during ...

Manufacturing of a Nafion-coated, Reduced Graphene Oxide/Polyaniline Chemiresistive Sensor to Monitor pH in Real-time During Microbial Fermentation

Here, we report the engineering of a solid-state micro pH sensor based on polyaniline-functionalized, electrochemically reduced graphene oxide (ERGO-PA). ...

Environmental Dynamic Mechanical Analysis to Predict the Softening Behavior of Neural Implants

When using dynamically softening substrates for neural implants, it is important to have a reliable in vitro method to characterize the softening behavior ...

Characterization of Intra-Cartilage Transport Properties of Cationic Peptide Carriers

Several negatively charged tissues in the body, like cartilage, present a barrier to the targeted drug delivery due to their high density of negatively ...

Real-Time Intravital Multiphoton Microscopy to Visualize Focused Ultrasound and Microbubble Treatments to Increase Blood-Brain Barrier Permeability

The blood-brain barrier (BBB) is a key challenge for the successful delivery of drugs to the brain. Ultrasound exposure in the presence of microbubbles ...