Name: an efficient and reproducible protocol for distraction osteogenesis in a rat model leading to a functional regenerated femur
Uploaded: 2017-10-23T15:00:00
Description: Watch this Scientific Journal Video about An Efficient and Reproducible Protocol for Distraction Osteogenesis in a Rat Model Leading to a Functional Regenerated Femur at JoVE.com

This work was supported and funded by the CNRS Mecabio challenge.
The authors thank the animal care technician for taking care of the animals throughout the procedure. The authors also acknowledge IVTV central Lyon, through Thierry Hoc. Thanks to Marjorie Sweetko for language revision.
We are greatful to Maryl&#232;ne Lallemand, C&#233;cile G&#233;nov&#233;sio, and Patrick Laurent for their contribution to this experimental study.

All procedures described were approved by the University of Aix-Marseille institutional animal care and use committee and the French research ministry and performed in the conventional animal house of Marseille Medical Faculty (France).
1. Define Functional Specifications of the External Fixator Based on the Following Guidelines
<ol>
	<li>Optimize bone anchorage.
	<ol>
		<li>Implant half-threaded pins with a diameter (of the threaded section) of 1 mm.</li>
	</ol>
	</li>
	<li...

<ol>
	<li>Jauregui, J. J., Ventimiglia, A. V., Grieco, P. W., Frumberg, D. B., Herznberg, J. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regenerate+Bone+stimulation+following+limb+lengthening:+a+meta-analysis.">Regenerate Bone stimulation following limb lengthening: a meta-analysis.</a> BMC Musculoskelet Disord. 17 (1), 407 (2016).</li><li>Morcos, M. W., Al-Jallad, H., Hamdy, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comprehensive+review+of+Adipose+Stem+Cells+and+Their+Implication+in+Distraction+Osteogenesis+and+Bone+Regeneration.">Comprehensive review of Adipose Stem Cells and Their Implication in Distraction Osteogenesis and Bone Regeneration.</a> Biomed Res Int. 2015 (842975), 1-20 (2015).</li><li>Cans&#252;, E., &#220;nal, M. B., Parmaksizoglu, F., G&#252;rcan, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Distraction+lengthening+of+the+proximal+phalanx+in+distal+thumb+amputations.">Distraction lengthening of the proximal phalanx in distal thumb amputations.</a> Acta Orthop Traumatol Turc. 49 (3), 227-232 (2014).</li><li>Singh, M., Vashistha, A., Chaudhary, M., Kaur, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biological+Basis+of+Distraction+Osteogenesis+-+A+Review.">Biological Basis of Distraction Osteogenesis - A Review.</a> J Oral Maxillofac Surg Med Pathol. 28 (1), 1-7 (2016).</li><li>Sailhan, F., Gleyzolle, B., Parot, R., Guerini, H., Viguier, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rh-BMP-2+in+Distraction+Osteogenesis:+Dose+Effect+and+Premature+Consolidation.">Rh-BMP-2 in Distraction Osteogenesis: Dose Effect and Premature Consolidation.</a> Injury. 41 (7), 680-686 (2010).</li><li>Schiller, J. R., Moore, D. C., Ehrlich, M. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Increased+Lengthening+Rate+Decreases+Expression+of+Fibroblast+Growth+Factor+2,+Platelet-Derived+Growth+Factor,+Vascular+Endothelial+Growth+Factor,+and+CD31+in+a+Rat+Model+of+Distraction+Osteogenesis.">Increased Lengthening Rate Decreases Expression of Fibroblast Growth Factor 2, Platelet-Derived Growth Factor, Vascular Endothelial Growth Factor, and CD31 in a Rat Model of Distraction Osteogenesis.</a> J Pediatr Orthop. 27 (8), 961-968 (2007).</li><li>Aronson, J., Shen, X. C., Skinner, R. A., Hogue, W. R., Badger, T. M., Lumpkin, C. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rat+Model+of+Distraction+Osteogenesis.">Rat Model of Distraction Osteogenesis.</a> J Orthop Res. 15 (2), 221-226 (1997).</li><li>Aida, T., Yoshioka, I., Tominaga, K., Fukuda, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+latency+period+in+a+rabbit+mandibular+distraction+osteogenesis.">Effects of latency period in a rabbit mandibular distraction osteogenesis.</a> Int J Oral Maxillofac Surg. 32, 54-62 (2003).</li><li>Lammens, J., Liu, Z., Aerssend, J., Dequeker, J., Fabry, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=distraction+Bone+Healing+Versus+Osteotomy+Healing:+A+Comparative+Biochemical+Analysis.">distraction Bone Healing Versus Osteotomy Healing: A Comparative Biochemical Analysis.</a> J Bone Miner Res. 13 (2), 279-286 (1998).</li><li>Isefuku, S., Joyner, C. J., Simpson, A. H. R. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Murine+Model+of+Distraction+Osteogenesis.">A Murine Model of Distraction Osteogenesis.</a> Bone. 27 (5), 661-665 (2000).</li><li>Eberson, C. P., Hogan, K. A., Moore, D. C., Ehrlich, M. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+Low-Intensity+Ultrasound+Stimulation+on+Consolidation+of+the+Regenerate+Zone+in+a+Rat+Model+of+Distraction+Osteogenesis.">Effect of Low-Intensity Ultrasound Stimulation on Consolidation of the Regenerate Zone in a Rat Model of Distraction Osteogenesis.</a> J Pediatr Orthop. 23 (1), 46-51 (2003).</li><li>&#214;zdel, A., Saris&#246;zen, B., Yal&#231;inkaya, U., Demirag, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Effect+of+HIF+Stabilizer+on+Distraction+Osteogenesis.">The Effect of HIF Stabilizer on Distraction Osteogenesis.</a> Acta Orthop Traumatol Turc. 49 (1), 80-84 (2015).</li><li>Takamine, 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=Distraction+Osteogenesis+Enhanced+by+Osteoblastlike+Cells+and+Collagen+Gel.">Distraction Osteogenesis Enhanced by Osteoblastlike Cells and Collagen Gel.</a> Clin Orthop Relat Res. 399, 240-246 (2002).</li><li>Wang, X., Zhu, S., Jiang, X., Li, Y., Song, D., Hu, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Systemic+Administration+of+Lithium+Improves+Distracted+Bone+Regeneration+in+Rats.">Systemic Administration of Lithium Improves Distracted Bone Regeneration in Rats.</a> Calcif Tissue Int. 96 (6), 534-540 (2015).</li><li>Xu, J., 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=Human+Fetal+Mesenchymal+Stem+Cell+Secretome+Enhances+Bone+Consolidation+in+Distraction+Osteogenesis.">Human Fetal Mesenchymal Stem Cell Secretome Enhances Bone Consolidation in Distraction Osteogenesis.</a> Stem Cell Res Ther. 7 (1), (2016).</li><li>Yasui, 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=Three+Modes+of+Ossification+during+Distraction+Osteogenesis+in+the+Rat.">Three Modes of Ossification during Distraction Osteogenesis in the Rat.</a> Bone Joint J. 79 (5), 824-830 (1997).</li><li>Chang, F., 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=Stimulation+of+EP4+Receptor+Enhanced+Bone+Consolidation+during+Distraction+Osteogenesis.">Stimulation of EP4 Receptor Enhanced Bone Consolidation during Distraction Osteogenesis.</a> J Orthop Res. 25 (2), 221-229 (2007).</li><li>Nyman, J. 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=Quantitative+Measures+of+Femoral+Fracture+Repair+in+Rats+Derived+by+Micro-Computed+Tomography.">Quantitative Measures of Femoral Fracture Repair in Rats Derived by Micro-Computed Tomography.</a> J Biomech. 42 (7), 891-897 (2009).</li><li>Hsu, J. T., Wang, S. P., Huang, H. L., Chen, Y. J., Wu, J., Tsai, M. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+assessment+of+trabecular+bone+parameters+and+cortical+bone+strength:+a+comparison+of+micro-CT+and+dental+cone-beam+CT.">The assessment of trabecular bone parameters and cortical bone strength: a comparison of micro-CT and dental cone-beam CT.</a> J Biomech. 46, 2611-2618 (2013).</li><li>Xue, J., 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=NELL1+Promotes+High-Quality+Bone+Regeneration+in+Rat+Femoral+Distraction+Osteogenesis+Model.">NELL1 Promotes High-Quality Bone Regeneration in Rat Femoral Distraction Osteogenesis Model.</a> Bone. 48 (3), 485-495 (2011).</li><li>Mark, H., Bergholm, J., Nilsson, A., Rydevik, B., Str&#246;mberg, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+External+Fixation+Method+and+Device+to+Study+Fracture+Healing+in+Rats.">An External Fixation Method and Device to Study Fracture Healing in Rats.</a> Acta Orthop. 74 (4), 476-482 (2003).</li></ol>

This study describes a reproducible protocol comprising an appropriate external fixator design for rat limb lengthening, with a detailed surgical technique that permits physiological weight-bearing by the animal after removal of the external fixator. Our DO protocol led to a functional regenerated bone. After 47 days of consolidation, removal of the homemade external fixator and 2 days of physiological weight-bearing by the animal did not induce any fracture of the regenerating callus. Thanks to the micro-CT reconstructi...

Distraction osteogenesis (DO) is a surgical technique widely used clinically1,2,3,4 in humans for lower1,2 and upper3 limb lengthening, treatment after a bone nonunion, or the regeneration of a bone defect following surgery for bone tumor excision as well as in maxillofacial reconstruction4. DO leads to bone regeneration after placement of an external fixator in bone and osteotomy. The osteotomized extremities are moved away from each other by gradual distraction2 to reach the desired elongation. A consolidation period follows, during which there is no more elongation.
The DO procedure is divided into three distinct phases: latency, distraction, and consolidation. Generally, a 7-day latency period starts just after osteotomy4. This allows bone repair to begin the initial step of the healing process4. The latency period is followed by a distraction period where traction forces are applied to the regenerated callus and surrounding soft tissues1,2,4. When the desired elongation is reached, distraction stops and the consolidation period begins. During this period, the external fixator is maintained until the regenerated bone is functional enough to support its removal.
Various parameters of DO influence bone repair such as length and rate of lengthening, type of external fixator, frequency of distraction, length of the consolidation period, or type of mechanical stress applied to the distracted callus. As an example, the rate and frequency of lengthening can lead either to premature consolidation5 or disruption of the process by creating non-recoverable damage like necrotic tissue or cysts within the callus6,7.
Many DO protocols have been applied to different animal models8,9,10 to study bone repair processes and to maximize bone consolidation. In rats, most studies11,12,13,14,15 focused on how to shorten the DO protocol by speeding up callus consolidation. Some of these experimental studies used external fixators already commercially available for human clinical applications5,13,15,16. However, these types of external fixator are not suitable for DO on the rat femur, which exhibits different anatomical characteristics from the human femur. Moreover, only a few studies clearly demonstrate the efficiency of their protocols in obtaining a functional regenerated bone7,16. It is therefore difficult to compare results from various DO studies, due to their differing protocols and lack of information regarding the external fixator12,13,14,17.
Thus, the aim of this study was to describe, in a rat model, an efficient and reproducible protocol for DO on the femur that leads to a functional regenerated bone. To this end, we designed a homemade and easy-to-use external fixator especially for the rat femur, which we have described in detail in this protocol. In drafting the technical specifications for this device, we took into account all the fundamental constraints for a good distribution of mechanical stresses and avoiding the production of residual stress. The technical specification included an appropriate geometry for the device to allow pure traction force on bones and surrounding tissue, an appropriate weight for the gait of the animal, control of the length of bone elongation, and a good alignment of bone segments without production of shear stress at the intersection of pins and bone. Moreover, this device had to be usable without sedation of the animal during distraction, biocompatible, and sterilizable without damage. After 7 weeks of consolidation, this protocol for DO on the rat femur led to a functional regenerated bone, demonstrated by the animals&#39; physiological weight-bearing without fracture of the regenerated callus after removal of the external fixator. The physiological gait of the animals was consistent with architectural parameters obtained from micro-CT analysis of regenerated callus and X-ray analysis.

<table>
	<tbody>
		<tr>
			<td>K&#233;tamine</td>
			<td>Renaudin</td>
			<td>578 540-2</td>
			<td>Supply by animal house</td>
		</tr>
		<tr>
			<td>M&#233;d&#233;tomidine</td>
			<td>Virbac</td>
			<td>6799091</td>
			<td>Supply by animal house</td>
		</tr>
		<tr>
			<td>Sevoflurane</td>
			<td>Centravet</td>
			<td>567 477-2</td>
			<td>Supply by animal house</td>
		</tr>
		<tr>
			<td>Buprenorphine</td>
			<td>Indivor France</td>
			<td>3400932731060</td>
			<td>Supply by animal house</td>
		</tr>
		<tr>
			<td>Enrofloxacine</td>
			<td>ChannelPharmaceutical Facturing</td>
			<td>FR/V/4955220</td>
			<td>Supply by animal house</td>
		</tr>
		<tr>
			<td>Piezotome</td>
			<td>Satelec Acteon</td>
			<td>F57510</td>
			<td></td>
		</tr>
		<tr>
			<td>Heating pet pad</td>
			<td>Therasage</td>
			<td>AL8365936</td>
			<td>Supply by the animal house</td>
		</tr>
		<tr>
			<td>Dental X-ray</td>
			<td>S.A.R.L Innovation m&#233;dicales et dentaires</td>
			<td>WYZ - BLUEX</td>
			<td></td>
		</tr>
		<tr>
			<td>Winiwix Software</td>
			<td>Softys Dental</td>
			<td>PFT</td>
			<td></td>
		</tr>
		<tr>
			<td>Micro-CT system</td>
			<td>nanoScan SPECT/CT</td>
			<td>GEIT-31105EN (05/14)</td>
			<td>Subcontract by IVTV central Lyon</td>
		</tr>
		<tr>
			<td>Micro-CT analysis Software</td>
			<td>phoenix datos X2 reconstruction</td>
			<td>none</td>
			<td>Free software</td>
		</tr>
		<tr>
			<td>Electric razor</td>
			<td>Brawn</td>
			<td>GT415</td>
			<td>Supply by animal house</td>
		</tr>
		<tr>
			<td>Senn&#8217;s retractors</td>
			<td>Word Precision Instruments</td>
			<td>501718</td>
			<td>Blunt version</td>
		</tr>
		<tr>
			<td>Betadine Solution</td>
			<td>Mundipharma Medical Company</td>
			<td>D08AG02</td>
			<td>Supply by animal house</td>
		</tr>
		<tr>
			<td>Resorbable suture thread (5.0)</td>
			<td>Ethicon</td>
			<td>JV1023</td>
			<td>Supply by animal house</td>
		</tr>
		<tr>
			<td>Rugine</td>
			<td>Word Precision Instruments</td>
			<td>503406</td>
			<td></td>
		</tr>
		<tr>
			<td>Mayo-Hegar needle holder</td>
			<td>Word Precision Instruments</td>
			<td>V503382</td>
			<td></td>
		</tr>
		<tr>
			<td>Metal drill</td>
			<td>Beuterlock</td>
			<td>V020944018003</td>
			<td></td>
		</tr>
		<tr>
			<td>Micro Olsen-Hegar Needle-holder</td>
			<td>Word Precision Instruments</td>
			<td>501989</td>
			<td></td>
		</tr>
		<tr>
			<td>Mayo scissor</td>
			<td>Word Precision Instruments</td>
			<td>501752</td>
			<td></td>
		</tr>
		<tr>
			<td>Scalpel</td>
			<td>Word Precision Instruments</td>
			<td>500236</td>
			<td></td>
		</tr>
		<tr>
			<td>Sprague-Dawley</td>
			<td>Janvier</td>
			<td>none</td>
			<td>12 weaks and male</td>
		</tr>
	</tbody>
</table>

an efficient and reproducible protocol for distraction osteogenesis in a rat model leading to a functional regenerated femur

This protocol describes the use of a newly developed external fixator for distraction osteogenesis in a rat femoral model. Distraction osteogenesis (DO) is a surgical technique leading to bone regeneration after an osteotomy. The osteotomized extremities are moved away from each other by gradual distraction to reach the desired elongation. This procedure is widely used in humans for lower and upper limb lengthening, treatment after a bone nonunion, or the regeneration of a bone defect following surgery for bone tumor excision, as well as in maxillofacial reconstruction. Only a few studies clearly demonstrate the efficiency of their protocol in obtaining a functional regenerated bone, i.e., bone that will support physiological weight-bearing without fracture after removal of the external fixator. Moreover, protocols for DO vary and reproducibility is limited by lack of information, making comparison between studies difficult. The aim of this study was to develop a reproducible protocol comprising an appropriate external fixator design for rat limb lengthening, with a detailed surgical technique that permits physiological weight-bearing by the animal after removal of the external fixator.

The X-ray images taken from the end of surgical procedure to the end of consolidation showed no loosening of the half-threaded pins in the femur, indicating stable anchorage. The pins were parallel and well-preserved. The osteotomized extremities were well-aligned along the longitudinal axis of the bone during the DO process (Figure 2). At the end of the latency period, no calcified areas were visible (Figure 2B)...

Watch this Scientific Journal Video about An Efficient and Reproducible Protocol for Distraction Osteogenesis in a Rat Model Leading to a Functional Regenerated Femur at JoVE.com

An Efficient and Reproducible Protocol for Distraction Osteogenesis in a Rat Model Leading to a Functional Regenerated Femur

This study describes a reproducible and detailed protocol using a newly developed external fixator for distraction osteogenesis (DO) in a femoral rat model which permits physiological weight-bearing by the animal after removal of the external fixator.

This protocol describes the use of a newly developed external fixator for distraction osteogenesis in a rat femoral model. Distraction osteogenesis (DO) ...

The overall goal of this protocol is to reproduibly and efficiently induce femoral distraction osteogenesis in a rat model to assess functional bone regeneration. This method can help answer key questions in the osteogenesis medicine field about determining and shortening the consolidation period or about identifying the mechanism of bone repair. The main advantage of this technique is vital to who made external fixator and to guide who is doing the surgery, provide a stable environment for optimal bone regeneration.The implications of this technique extend to all therapeutic upper and lower limb lengthening or of bone defect that occur after bone tumor excision surgery. The demonstration of the procedure is done by Edouard Lamy, a pharmacy lecturer from my laboratory. Begin by placing an anesthetized 12-week old male Sprague Dawley rat in the left lateral position and removing the hair from the right hind limb.After applying eye ointment, disinfect the surgical area with Povidone-iodine solution and place the animal in the supine position. With the external fixator positioned along the mediolateral axis, use a marker to make one point at the knee and a second point at the hip along the medial line of the sagittal plane. Connect the two points and use a scalpel to make a skin incision along the line, cutting between the biceps femoris and the vastus lateralis until the femur is fully exposed.Lift the periosteum and use a rougine to disconnect the soft tissue from the bone. Insert pins into the most proximal and distal holes of the external fixator. If both pins can be anchored, use two Senn's retractors to open the muscles and tighten the clamp of a drilling guide in the middle of the femur, starting with the proximal and distal holes, and finishing with the middle two holes, pass a metal 0.6 millimeter drill bit through the bone to create four guide holes.Using a 0.8-millimeter half-threaded pin, work the pin back and forth to enlarge the four pre-holes, taking care to stay perpendicular to the femur. To implant the pins, use a needle holder to grasp the head of each 1-millimeter half-thread pin and individually sink the pins to enlarge the guide holes. Use a Senn's retractor to confirm that the pins penetrate both of the cortices without protruding more than 1 millimeter.When the pins are in place, connect the external fixator to the half-threaded pins, making sure that the offset is about 6 millimeters to allow easy stitching and good rigidity. Then secure the four locking screws so that the external fixator is locked to the pins. Using a Piezotome, perform an osteotomy between the two central pins.Then use a Mayo-Hegar Needle Holder, a resorbable 5-0 suture thread and a continuous stitch to close the wound. Immediately after the surgery, x-ray the animal to check the depth of the pins and the alignment of the osteotomized extremities along the long axis. Then allow rat to recover fully with monitoring.After one week, x-ray the limb to recheck the positioning of the pins and the alignment of the bone segments. To perform the distraction, manually turn the square nut one-half turn clockwise every 12 hours for 10 days. X-ray the limb halfway through and at the end of the distraction process to monitor the positioning of the pins and the alignment of the bone segments.At the end of the distraction, x-ray the limb weekly, removing the external fixator on day 64. On day 66, use a scalpel to make a skin incision through the surgery scar from the top of the hip to the front of the knee. Cut between the biceps femoris and the vastus lateralis until the femur is fully exposed, disconnecting the muscle from the bone as much as possible.Cut all of the ligaments of the knee, dismantle the articulation, and cut the joint capsule of the hip. Clean the bone thoroughly without removing the pins, using a scalpel to remove all of the soft tissue. When the contralateral femur has been cleaned, x-ray both femurs.Remove the pins and store the femurs at minus 20-degree Celsius for micro-computed tomography scan analysis. In this representative experiment, x-ray imaging from immediately after the surgery through the end of the consolidation, revealed that the half-threaded pins within the femur pins remained parallel, well preserved, and unloosened throughout the procedure, indicative of a stable anchorage. Moreover, the osteotomized extremities had clearly been well aligned along the longitudinal axis of the bone during the distraction osteogenesis process.At the end of the latency period, no calcified areas were visible near the osteotomized extremities. At the end of the distraction period, a few calcified areas were visible close to the pre-existing cortices. After 28 days of consolidation, the non-calcified region of the gap between the osteotomized extremities was smaller, and a periosteal callus could be observed near the gap level with the pins.After 47 days of consolidation, the regenerating callus was completely bridged. After removal of the external fixator and two days of physiological weightbearing, the animals displayed a physiological gait and no evidence of fracture could be observed. 3D micro-computed tomography analysis of the serial longitudinal sections of the regenerating callus demonstrated that calcified bridging was always present with a continuous outer cortical observed at the periphery of the regenerating callus.After 49 days of consolidation, no fracture was observed despite the persistence of a less mineralized region at the center of the regenerated callus. Once mastered, this surgical technique can be completed in 45 minutes if it is performed properly. While attempting this procedure, it is important to remember to maintain a sterile environment during the surgery and to thoroughly monitor the animal after the surgery.After it's development, this technique pave the way for researcher in the field of medicine to improve the distraction osteogenesis technique, particularly for shortening the consolidation period in the clinical practice. Following this procedure, other methods like adding growth factors or build materials can be performed to answer additional questions such as, can the consolidation of the bone be improved. After watching this video, you should have a good understanding of how to perform femoral lengthening in a rat model using these techniques as a guide to ensure parallelism between the pins.

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Research

JoVE Journal

Bioengineering

Creating Two-Dimensional Patterned Substrates for Protein and Cell Confinement

Microcontact printing provides a rapid, highly reproducible method for the creation of well-defined patterned substrates.1 While microcontact printing can be employed to directly print a large number of molecules, including proteins,2 DNA,3 and silanes,4 the formation of self-assembled monolayers (SAMs) from long chain alkane thiols on gold provides a simple way to confine proteins and cells to specific patterns containing adhesive and resistant regions. This confinement can be used to control cell morphology and is useful for examining a variety of questions in protein and cell biology. Here, we describe a general method for the creation of well-defined protein patterns for cellular studies.5 This process involves three steps: the production of a patterned master using photolithography, the creation of a PDMS stamp, and microcontact printing of a gold-coated substrate. Once patterned, these cell culture substrates are capable of confining proteins and/or cells (primary cells or cell lines) to the pattern.
The use of self-assembled monolayer chemistry allows for precise control over the patterned protein/cell adhesive regions and non-adhesive regions; this cannot be achieved using direct protein stamping. Hexadecanethiol, the long chain alkane thiol used in the microcontact printing step, produces a hydrophobic surface that readily adsorbs protein from solution. The glycol-terminated thiol, used for backfilling the non-printed regions of the substrate, creates a monolayer that is resistant to protein adsorption and therefore cell growth.6 These thiol monomers produce highly structured monolayers that precisely define regions of the substrate that can support protein adsorption and cell growth. As a result, these substrates are useful for a wide variety of applications from the study of intercellular behavior7 to the creation of microelectronics.8
While other types of monolayer chemistry have been used for cell culture studies, including work from our group using trichlorosilanes to create patterns directly on glass substrates,9 patterned monolayers formed from alkane thiols on gold are straight-forward to prepare. Moreover, the monomers used for monolayer preparation are commercially available, stable, and do not require storage or handling under inert atmosphere. Patterned substrates prepared from alkane thiols can also be recycled and reused several times, maintaining cell confinement.10

Self-assembled monolayers (SAMs) formed from long chain alkane thiols on gold provide well-defined substrates for the formation of protein patterns and cell confinement. Microcontact printing of hexadecanethiol using a polydimethylsiloxane (PDMS) stamp followed by backfilling with a glycol-terminated alkane thiol monomer produces a pattern where protein and cells adsorb only to the stamped hexadecanethiol region.

Microcontact printing provides a rapid, highly reproducible method for the creation of well-defined patterned substrates.1  While microcontact printing ...

Design of a Cyclic Pressure Bioreactor for the Ex Vivo Study of Aortic Heart Valves

The aortic valve, located between the left ventricle and the aorta, allows for unidirectional blood flow, preventing backflow into the ventricle. Aortic valve leaflets are composed of interstitial cells suspended within an extracellular matrix (ECM) and are lined with an endothelial cell monolayer. The valve withstands a harsh, dynamic environment and is constantly exposed to shear, flexion, tension, and compression. Research has shown calcific lesions in diseased valves occur in areas of high mechanical stress as a result of endothelial disruption or interstitial matrix damage1-3. Hence, it is not surprising that epidemiological studies have shown high blood pressure to be a leading risk factor in the onset of aortic valve disease4. 
The only treatment option currently available for valve disease is surgical replacement of the diseased valve with a bioprosthetic or mechanical valve5. Improved understanding of valve biology in response to physical stresses would help elucidate the mechanisms of valve pathogenesis. In turn, this could help in the development of non-invasive therapies such as pharmaceutical intervention or prevention. Several bioreactors have been previously developed to study the mechanobiology of native or engineered heart valves6-9. Pulsatile bioreactors have also been developed to study a range of tissues including cartilage10, bone11 and bladder12. The aim of this work was to develop a cyclic pressure system that could be used to elucidate the biological response of aortic valve leaflets to increased pressure loads. 
The system consisted of an acrylic chamber in which to place samples and produce cyclic pressure, viton diaphragm solenoid valves to control the timing of the pressure cycle, and a computer to control electrical devices. The pressure was monitored using a pressure transducer, and the signal was conditioned using a load cell conditioner. A LabVIEW program regulated the pressure using an analog device to pump compressed air into the system at the appropriate rate. The system mimicked the dynamic transvalvular pressure levels associated with the aortic valve; a saw tooth wave produced a gradual increase in pressure, typical of the transvalvular pressure gradient that is present across the valve during diastole, followed by a sharp pressure drop depicting valve opening in systole. The LabVIEW program allowed users to control the magnitude and frequency of cyclic pressure. The system was able to subject tissue samples to physiological and pathological pressure conditions. This device can be used to increase our understanding of how heart valves respond to changes in the local mechanical environment.

Design of a Cyclic Pressure Bioreactor for the Ex Vivo Study of Aortic Heart Valves

A cyclic pressure bioreactor capable of subjecting heart valve tissue to physiological and pathological pressure conditions has been designed. A LabVIEW program allows users to control pressure magnitude, amplitude and frequency. This device can be used to study the mechanobiology of heart valve tissue or isolated cells.

The aortic valve, located between the left ventricle and the aorta, allows for unidirectional blood flow, preventing backflow into the ventricle. Aortic ...

Athymic Rat Model for Evaluation of Engineered Anterior Cruciate Ligament Grafts

Anterior cruciate ligament (ACL) rupture is a common ligamentous injury that often requires surgery because the ACL does not heal well without intervention. Current treatment strategies include ligament reconstruction with either autograft or allograft, which each have their associated limitations. Thus, there is interest in designing a tissue-engineered graft for use in ACL reconstruction. We describe the fabrication of an electrospun polymer graft for use in ACL tissue engineering. This polycaprolactone graft is biocompatible, biodegradable, porous, and is comprised of aligned fibers. Because an animal model is necessary to evaluate such a graft, this paper describes an intra-articular athymic rat model of ACL reconstruction that can be used to evaluate engineered grafts, including those seeded with xenogeneic cells. Representative histology and biomechanical testing results at 16 weeks postoperatively are presented, with grafts tested immediately post-implantation and contralateral native ACLs serving as controls. The present study provides a reproducible animal model with which to evaluate tissue engineered ACL grafts, and demonstrates the potential of a regenerative medicine approach to treatment of ACL rupture.

Animal models are important tools for the evaluation of tissue-engineered grafts. This paper presents the protocol for preparing an electrospun biodegradable polymer graft for use in anterior cruciate ligament tissue engineering, as well as a surgical protocol for implantation in a rat model.

Anterior cruciate ligament (ACL) rupture is a common ligamentous injury that often requires surgery because the ACL does not heal well without ...

Use of a Rat Model to Study Ventral Abdominal Hernia Repair

Ventral abdominal hernia is a relatively common clinical condition that sometimes requires herniorraphy (surgical repair). The repair of ventral abdominal hernia typically requires implantation of a material to serve as a mechanical bridge across the defect in the abdominal wall. Biomaterials, such as porcine small intestinal submucosa (SIS), also serve as a lattice for cell growth into the implant and can naturally incorporate into the host tissue. Development of such repair materials benefits from use of animal models in which experimental abdominal wall defects are easily created and are amenable to repair in a reproducible fashion. The method offered here describes surgical creation and repair of ventral abdominal hernia in a rat model. When SIS is used to repair an experimental ventral abdominal hernia in this model, it is rapidly incorporated into host tissue within 28 days of implantation. Histologically, incorporation of their implanted material into host tissue is characterized by a robust fibrovascular response. Future refinements and applications of the rat abdominal hernia model may likely involve diabetic and/or obese animals as a means to more closely mimic common co-morbidities of man.

This manuscript describes methods associated with creation and repair of a ventral abdominal wall defect (hernia). This model can be used to study repair strategies such as those that use implanted materials. In this manuscript, repair of the experimental hernia with porcine small intestinal submucosa is presented as an example.

Ventral abdominal hernia is a relatively common clinical condition that sometimes requires herniorraphy (surgical repair). The repair of ventral abdominal ...

Applications of In Vivo Functional Testing of the Rat Tibialis Anterior for Evaluating Tissue Engineered Skeletal Muscle Repair

Despite the regenerative capacity of skeletal muscle, permanent functional and/or cosmetic deficits (e.g., volumetric muscle loss (VML) resulting from traumatic injury, disease and various congenital, genetic and acquired conditions are quite common. Tissue engineering and regenerative medicine technologies have enormous potential to provide a therapeutic solution. However, utilization of biologically relevant animal models in combination with longitudinal assessments of pertinent functional measures are critical to the development of improved regenerative therapeutics for treatment of VML-like injuries. In that regard, a commercial muscle lever system can be used to measure length, tension, force and velocity parameters in skeletal muscle. We used this system, in conjunction with a high power, bi-phase stimulator, to measure in vivo force production in response to activation of the anterior crural compartment of the rat hindlimb. We have previously used this equipment to assess the functional impact of VML injury on the tibialis anterior (TA) muscle, as well as the extent of functional recovery following treatment of the injured TA muscle with our tissue engineered muscle repair (TEMR) technology. For such studies, the left foot of an anaesthetized rat is securely anchored to a footplate linked to a servomotor, and the common peroneal nerve is stimulated by two percutaneous needle electrodes to elicit muscle contraction and dorsiflexion of the foot. The peroneal nerve stimulation-induced muscle contraction is measured over a range of stimulation frequencies (1-200 Hz), to ensure an eventual plateau in force production that allows for an accurate determination of peak tetanic force. In addition to evaluation of the extent of VML injury as well as the degree of functional recovery following treatment, this methodology can be easily applied to study diverse aspects of muscle physiology and pathophysiology. Such an approach should assist with the more rational development of improved therapeutics for muscle repair and regeneration.

Applications of In Vivo Functional Testing of the Rat Tibialis Anterior for Evaluating Tissue Engineered Skeletal Muscle Repair

We describe an in vivo protocol to measure dorsiflexion of the foot following stimulation of the peroneal nerve and contraction of the anterior crural compartment of the rat hindlimb. Such measurements are an indispensable translational tool for evaluating skeletal muscle pathology and tissue engineering approaches to muscle repair and regeneration.

Despite the regenerative capacity of skeletal muscle, permanent functional and/or cosmetic deficits (e.g., volumetric muscle loss (VML) resulting from ...

A Method to Estimate Cadaveric Femur Cortical Strains During Fracture Testing Using Digital Image Correlation

This protocol describes the method using digital image correlation to estimate cortical strain from high speed video images of the cadaveric femoral surface obtained from mechanical testing. This optical method requires a texture of many contrasting fiduciary marks on a solid white background for accurate tracking of surface deformation as loading is applied to the specimen. Immediately prior to testing, the surface of interest in the camera view is painted with a water-based white primer and allowed to dry for several minutes. Then, a black paint is speckled carefully over the white background with special consideration for the even size and shape of the droplets. Illumination is carefully designed and set such that there is optimal contrast of these marks while minimizing reflections through the use of filters. Images were obtained through high speed video capture at up to 12,000 frames/s. The key images prior to and including the fracture event are extracted and deformations are estimated between successive frames in carefully sized interrogation windows over a specified region of interest. These deformations are then used to compute surface strain temporally during the fracture test. The strain data is very useful for identifying fracture initiation within the femur, and for eventual validation of proximal femur fracture strength models derived from Quantitative Computed Tomography-based Finite Element Analysis (QCT/FEA).

In this protocol, the femur surface strains are estimated during fracture testing using the digital image correlation technique. The novelty of the method involves application of a high-contrast stochastic speckle pattern on the femur surface, carefully specified illumination, high speed video capture, and digital image correlation analysis for strain calculations.

This protocol describes the method using digital image correlation to estimate cortical strain from high speed video images of the cadaveric femoral ...

An Experimental and Finite Element Protocol to Investigate the Transport of Neutral and Charged Solutes across Articular Cartilage

Osteoarthritis (OA) is a debilitating disease that is associated with degeneration of articular cartilage and subchondral bone. Degeneration of articular cartilage impairs its load-bearing function substantially as it experiences tremendous chemical degradation, i.e. proteoglycan loss and collagen fibril disruption. One promising way to investigate chemical damage mechanisms during OA is to expose the cartilage specimens to an external solute and monitor the diffusion of the molecules. The degree of cartilage damage (i.e. concentration and configuration of essential macromolecules) is associated with collisional energy loss of external solutes while moving across articular cartilage creates different diffusion characteristics compared to healthy cartilage. In this study, we introduce a protocol, which consists of several steps and is based on previously developed experimental micro-Computed Tomography (micro-CT) and finite element modeling. The transport of charged and uncharged iodinated molecules is first recorded using micro-CT, which is followed by applying biphasic-solute and multiphasic finite element models to obtain diffusion coefficients and fixed charge densities across cartilage zones.

We propose a protocol to investigate the transport of charged and uncharged molecules across articular cartilage with the aid of recently developed experimental and numerical methods.

Osteoarthritis (OA) is a debilitating disease that is associated with degeneration of articular cartilage and subchondral bone. Degeneration of articular ...

Development of an Electrochemical DNA Biosensor to Detect a Foodborne Pathogen

Vibrio parahaemolyticus (V. parahaemolyticus) is a common foodborne pathogen that contributes to a large proportion of public health problems globally, significantly affecting the rate of human mortality and morbidity. Conventional methods for the detection of V. parahaemolyticus such as culture-based methods, immunological assays, and molecular-based methods require complicated sample handling and are time-consuming, tedious, and costly. Recently, biosensors have proven to be a promising and comprehensive detection method with the advantages of fast detection, cost-effectiveness, and practicality. This research focuses on developing a rapid method of detecting V. parahaemolyticus with high selectivity and sensitivity using the principles of DNA hybridization. In the work, characterization of synthesized polylactic acid-stabilized gold nanoparticles (PLA-AuNPs) was achieved using X-ray Diffraction (XRD), Ultraviolet-visible Spectroscopy (UV-Vis), Transmission Electron Microscopy (TEM), Field-emission Scanning Electron Microscopy (FESEM), and Cyclic Voltammetry (CV). We also carried out further testing of stability, sensitivity, and reproducibility of the PLA-AuNPs. We found that the PLA-AuNPs formed a sound structure of stabilized nanoparticles in aqueous solution. We also observed that the sensitivity improved as a result of the smaller charge transfer resistance (Rct) value and an increase of active surface area (0.41 cm2). The development of our DNA biosensor was based on modification of a screen-printed carbon electrode (SPCE) with PLA-AuNPs and using methylene blue (MB) as the redox indicator. We assessed the immobilization and hybridization events by differential pulse voltammetry (DPV). We found that complementary, non-complementary, and mismatched oligonucleotides were specifically distinguished by the fabricated biosensor. It also showed reliably sensitive detection in cross-reactivity studies against various food-borne pathogens and in the identification of V. parahaemolyticus in fresh cockles.

A protocol for the development of an electrochemical DNA biosensor comprising a polylactic acid-stabilized, gold nanoparticles-modified, screen-printed carbon electrode to detect Vibrio parahaemolyticus is presented.

Vibrio parahaemolyticus (V. parahaemolyticus) is a common foodborne pathogen that contributes to a large proportion of public health problems globally, ...

Rodent Behavioral Testing to Assess Functional Deficits Caused by Microelectrode Implantation in the Rat Motor Cortex

Medical devices implanted in the brain hold tremendous potential. As part of a Brain Machine Interface (BMI) system, intracortical microelectrodes demonstrate the ability to record action potentials from individual or small groups of neurons. Such recorded signals have successfully been used to allow patients to interface with or control&#160;computers, robotic limbs, and their own limbs. However, previous animal studies have shown that a microelectrode implantation in the brain not only damages the surrounding tissue but can also result in functional deficits. Here, we discuss a series of behavioral tests to quantify potential motor impairments following the implantation of intracortical microelectrodes into the motor cortex of a rat. The methods for open field grid, ladder crossing, and grip strength testing provide valuable information regarding the potential complications resulting from a microelectrode implantation. The results of the behavioral testing are correlated with endpoint histology, providing additional information on the pathological outcomes and impacts of this procedure on the adjacent tissue.

We have shown that a microelectrode implantation in the motor cortex of rats causes immediate and lasting motor deficits. The methods proposed herein outline a microelectrode implantation surgery and three rodent behavioral tasks to elucidate potential changes in the fine or gross motor function due to implantation-caused damage to the motor cortex.

Medical devices implanted in the brain hold tremendous potential. As part of a Brain Machine Interface (BMI) system, intracortical microelectrodes ...

A Novel Surgical Technique As a Foundation for In Vivo Partial Liver Engineering in Rat

Organ engineering is a novel strategy to generate liver organ substitutes that can potentially be used in transplantation. Recently, in vivo liver engineering, including in vivo organ decellularization followed by repopulation, has emerged as a promising approach over ex vivo liver engineering. However, postoperative survival was not achieved. The aim of this study is to develop a novel surgical technique of in vivo selective liver lobe perfusion in rats as a prerequisite for in vivo liver engineering. We generate a circuit bypass only through the left lateral lobe. Then, the left lateral lobe is perfused with heparinized saline. The experiment is performed with 4 groups (n = 3 rats per group) based on different perfusion times of 20 min, 2 h, 3 h, and 4 h. Survival, as well as the macroscopically visible change of color and the histologically determined absence of blood cells in the portal triad and the sinusoids, is taken as an indicator for a successful model establishment. After selective perfusion of the left lateral lobe, we observe that the left lateral lobe, indeed, turned from red to faint yellow. In a histological assessment, no blood cells are visible in the branch of the portal vein, the central vein, and the sinusoids. The left lateral lobe turns red after reopening the blocked vessels. 12/12 rats survived the procedure for more than one week. We are the first to report a surgical model for in vivo single liver lobe perfusion with a long survival period of more than one week. In contrast to the previously published report, the most important advantage of the technique presented here is that perfusion of 70% of the liver is maintained throughout the whole procedure. The establishment of this technique provides a foundation for in vivo partial liver engineering in rats, including decellularization and recellularization.

A Novel Surgical Technique As a Foundation for In Vivo Partial Liver Engineering in Rat

We establish a novel surgical technique for an in vivo single liver lobe perfusion model in rat as a prerequisite for further studying in vivo partial liver engineering in the future.