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Implantation of Allogenic Synovial Stem Cells Promotes Meniscal Regeneration in a Rabbit Meniscal Defect Model
Masafumi Horie, MD, PhD1; Matthew D. Driscoll, MD2; H. Wayne Sampson, PhD3; Ichiro Sekiya, MD, PhD4; Cyrus T. Caroom, MD2; Darwin J. Prockop, MD, PhD1; Darryl B. Thomas, MD5
1 Institute for Regenerative Medicine, Texas A&M Health Science Center College of Medicine at Scott & White, 5701 Airport Road, Temple, TX 76502
2 Department of Orthopedic Surgery, Scott & White Memorial Hospital, 2401 South 31st Street, Temple, TX 76508. E-mail address for M.D. Driscoll: mdriscoll@swmail.sw.org
3 Department of Systems Biology and Translational Medicine, Texas A&M Health Science Center College of Medicine, 702 SW HK Dodgen Loop, Temple, TX 76508
4 Section of Cartilage Regeneration, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo, Japan
5 Sports Medicine Service, Scott & White Healthcare-Round Rock Department of Orthopaedic Surgery, 302 University Boulevard, Round Rock, TX 78665
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Investigation performed at Scott & White Memorial Hospital and the Texas A&M Health Science Center College of Medicine Institute for Regenerative Medicine, Temple, Texas

Disclosure: One or more of the authors received payments or services, either directly or indirectly (i.e., via his or her institution), from a third party in support of an aspect of this work. In addition, one or more of the authors, or his or her institution, has had a financial relationship, in the thirty-six months prior to submission of this work, with an entity in the biomedical arena that could be perceived to influence or have the potential to influence what is written in this work. No author has had any other relationships, or has engaged in any other activities, that could be perceived to influence or have the potential to influence what is written in this work. The complete Disclosures of Potential Conflicts of Interest submitted by authors are always provided with the online version of the article.

Copyright © 2012 by The Journal of Bone and Joint Surgery, Inc.
J Bone Joint Surg Am, 2012 Apr 18;94(8):701-712. doi: 10.2106/JBJS.K.00176
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Indications for surgical meniscal repair are limited, and failure rates remain high. Thus, new ways to augment repair and stimulate meniscal regeneration are needed. Mesenchymal stem cells are multipotent cells present in mature individuals and accessible from peripheral connective tissue sites, including synovium. The purpose of this study was to quantitatively evaluate the effect of implantation of synovial tissue-derived mesenchymal stem cells on meniscal regeneration in a rabbit model of partial meniscectomy.


Synovial mesenchymal stem cells were harvested from the knee of one New Zealand White rabbit, expanded in culture, and labeled with a fluorescent marker. A reproducible 1.5-mm cylindrical defect was created in the avascular portion of the anterior horn of the medial meniscus bilaterally in fifteen additional rabbits. Allogenic synovial mesenchymal stem cells suspended in phosphate-buffered saline solution were implanted into the right knees, and phosphate-buffered saline solution alone was placed in the left knees. Meniscal regeneration was evaluated histologically at four, twelve, and twenty-four weeks for (1) quantity and (2) quality (with use of an established three-component scoring system). A similar procedure was performed in four additional rabbits with use of green fluorescent protein-positive synovial mesenchymal stem cells for the purpose of tracking progeny following implantation.


The quantity of regenerated tissue in the group that had implantation of synovial mesenchymal stem cells was greater at all end points, reaching significance at four and twelve weeks (p < 0.05). Tissue quality scores were also superior in knees treated with mesenchymal stem cells compared with controls at all end points, achieving significance at twelve and twenty-four weeks (3.8 versus 2.8 at four weeks [p = 0.29], 5.7 versus 1.7 at twelve weeks [p = 0.008], and 6.0 versus 3.9 at twenty-four weeks [p = 0.021]). Implanted cells adhered to meniscal defects and were observed in the regenerated tissue, where they differentiated into type-I and II collagen-expressing cells, at up to twenty-four weeks.


Synovial mesenchymal stem cells adhere to sites of meniscal injury, differentiate into cells resembling meniscal fibrochondrocytes, and enhance both quality and quantity of meniscal regeneration.

Clinical Relevance: 

These results may stimulate further exploration into the utility of synovial mesenchymal stem cells in the treatment of meniscal injury in large animals and humans.

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    These activities have been planned and implemented in accordance with the Essential Areas and policies of the Accreditation Council for Continuing Medical Education (ACCME) through the joint sponsorship of the American Academy of Orthopaedic Surgeons and The Journal of Bone and Joint Surgery, Inc. The American Academy of Orthopaedic Surgeons is accredited by the ACCME to provide continuing medical education for physicians.
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