Cartilage Transplantation Research Articles

Optimization of Allograft Implantation Using Scaffold-Free Chondrocyte Plates

If a tissue-engineered cartilage transplant is to succeed, it needs to integrate with the host tissue, to endure physiological loading, and to acquire the phenotype of the articular cartilage. Although there are many reported treatments for osteochondral defects of articular cartilage, problems remain with the use of artificial matrices (scaffolds) and the stage of implantation. We constructed scaffold-free three-dimensional tissue-engineered cartilage allografts using a rotational culture system and investigated the optimal stage of implantation and repair of the remodeling site. We evaluated the amounts of extracellular matrix and gene expression levels in scaffold-free constructs and transplanted the constructs for osteochondral defects using a rabbit model. Allografted 2-week constructs expressed high levels of proteoglycan and collagen per DNA content, integrated with the host cartilage successfully, and were able to counter physiological loads, and the chondrocyte plate contributed reparative mesenchymal stem cells to the final phenotype of the articular cartilage.

Construction of Tissue-engineered Cartilage with BMP7 Gene-transfected Chondrocytes

In this study, the expression of bone morphogenetic protein-7 (BMP7) was investigated in tissue-engineered cartilage constructed using chondrocytes transfected with the BMP7 gene and that constructed using non-transfected chondrocytes after 7, 14, 21 and 28 days. The volume of the BMP7 gene-transfected tissue-engineered cartilage culture after 5 - 7 days was 9 x 9 x 2 mm, while that of the non-transfected tissue-engineered cartilage culture was 8 x 8 x 2 mm. Histomorphological analysis showed that both cultures comprised cartilaginous tissue. Both BMP7 mRNA and BMP7 protein were expressed in BMP7 gene-transfected cartilage culture grown in vitro for 7, 14, 21 or 28 days. The chondrocytes in the BMP7 gene-transfected cartilage culture were active, with increased mitochondria, Golgi bodies and rough endoplasmic reticulum compared with non-transfected cartilage. These results provide an ideal foundation for the study of BMP7 gene-transfected tissue-engineered cartilage transplantation in the repair of cartilaginous defects.

New Approaches to Allograft Transplantation: Editorial Comment

The Musculoskeletal Transplant Foundation Symposium, held in Vancouver, B.C. in October 2007, was the fifth invitational meeting since 1993. These Symposia have reflected the Foundation’s commitment to the science of allografts and bioconstructs. This 5th International Symposium celebrated the Foundation’s 20th year and recognized the founders’ dreams for a viable institution capable of furthering scientific advances in transplantation. Through the support of internal and external research, the ultimate goal has been to advance the medical treatment of patients. Dr. J. Buckwalter of the University of Iowa and Dr. M. Bolander of the Mayo Clinic were the architects and co-chairs for this international meeting. In addition to being members of the Musculoskeletal Transplant Foundation (MTF) Board of Directors, these individuals are well-known, both nationally and internationally, as advocates of scientific research. At the opening of the Symposium, Dr. William F. Enneking and Dr. V. Frankel were formally acknowledged as the two founding members of MTF who have provided key stewardship since its inception in 1987. Both Drs. Enneking and Frankel are recognized nationally and internationally as leaders in the fields of orthopaedics, education, and research. Their vision prompted the development of a peer-review grant program that encouraged young investigators to enter today’s competitive research environment. More than a grant program, this program also emphasized presentation and publication. Since 1993, the MTF grant program has awarded over $20 million for allograft and bioconstruct research to men and women representing more than 112 institutions. The five International Symposia are landmarks of this program. The 5th Symposium is of even greater importance since 32 of the 40 presentations were recipients of awards within the last seven years. The Symposium’s three sessions emphasized cartilage, soft tissue, and bone transplantation. The 40 presentations represented the work of researchers from Europe, South America, Canada, and the United States. Each session was characterized by the intermixture of basic science, tissue banking safety, or the technological improvements being explored with hard and soft tissue engineering. Twenty-three manuscripts were submitted for publication, with the 20 published here best representing the entire spectrum of the Symposium. The articles in CORR have been reordered from the original presentation to better group the topics of tissue transplantation. Thus, the reader will first encounter clinical work, such as the use of transplants in children, followed by research with autologous cartilage cell transplants in a synthetic matrix. New clinical information is also presented on the characteristics of graft failure in allografts, and the lack of immunogenic consequences to tissue transplants. The futuristic topics in tissue transplantation are of unusual interest to both professionals and the lay public. Three articles emphasize the modification of natural remodeling characteristics usually associated with transplants to enhance incorporation. Another focuses on interference with the first phase of cortical bone remodeling, namely resorption. The question remains: Does modifying the resorptive phase allow for normal incorporation and biomechanical properties of the transplants? The hard and soft tissue engineering field is the forerunner of change in today’s transplantation research. Therefore, the articles on growth factors, the use of stem cells, nano meshes and microspheres are of particular interest. This modern engineering includes newer technologies capable of assessing biological materials in vivo using a dynamic contrast-enhanced MRI to quantify vascularity, or the testing of transplant materials in an in vivo bioreactor. It seems we have an obligation to provide continuing support to evaluate transplants. Decisions must be made regarding their success in relation to the use of synthetics, which seem to emerge from many directions. It is possible the future of tissue transplants will demonstrate a greater merging with synthetics and pharmaceuticals, whereby transplants will act as carriers of future technologies. Undoubtedly, research in the next 5 decades will dazzle us even more than the scientific changes we have witnessed in the past 50 years. The most surprising advances will likely come from the direction that research takes unexpectedly by incorporating newer technologies. The recognition in the 60’s and 70’s that musculoskeletal tissue transplantation could be performed with relative immunological impunity led to tissue banking. The maturing of the newest experimental advances will lead to twists and turns not yet comprehended. I thank all of the investigators for their contributions to the Symposium. The publication process has become more detailed and exacting, and these changes reflect the greater expectations demanded from all of us to better serve the medical needs of the public. Finally, I want to express to all of you involved in the Symposium and the publication, my appreciation for your efforts and my gratitude for your dedicated support.

Osteochondritis dissecans involving the trochlea of the humerus treated with transplantation of tissue-engineered cartilage: A case report

Osteochondritis dissecans (OCD) of the elbow is typically located in the capitellum of the humerus in young teenagers. There are only a few reports of OCD in the trochlea of the humerus.9,17,28 The ideal goal of treatment for OCD lesions is to resurface the osteochondral defect with hyaline cartilage and to prevent the occurrence of osteoarthritis. Recently, to achieve this surgical goal, autologous chondrocyte implantations (ACIs) or tissue-engineered cartilage transplantations (TCTs) have been performed for OCD lesions of the knee and the ankle.

Das autologe Knorpel-Knochen-Transplantat zur Therapie der Osteochondrosis dissecans des Kniegelenkes

This study presents the results of twelve patients, treated by an autologous bone and cartilage transplant for an advanced stage (stage IV and V referring to Rodegerdts and Gleissner, 14) of osteochondritis dissecans of the knee. In a follow up examination after an average time of 3.7 years all patients could be reviewed clinically and radiologically. The clinical results have been very satisfying in all but one patient. Radiologically all patients showed early signs of gonarthrosis, but only in 4 of 12 patients more advanced signs of arthrosis were found. In their own opinion all patients were satisfied with the outcome of the operation, and two of them regarded the result as excellent. Besides the operative technique the indications practising autologous bone-cartilage-transplantation in large osteochondral defects of osteochondritis dissecans are described as well. Furthermore the advantages of autologous against homologous bone-cartilage-transplants are discussed.

Knorpeltransplantate bei der funktionell-ästhetischen Rhinoplastik

Complications after rhinoplasty could often be prevented if less of the support structures of the nose were resected and cartilage transplants were used to give stability. Long-term complications depend heavily on the nasal anatomy, Which is why the surgeon must be able to identify anatomical variants and adapt the surgical technique as necessary. Thus, rhinoplasty techniques have moved away from excisional methods and shifted toward repositioning and restructuring existing tissues. Conservative reduction and preservation of support structures will maximize the aesthetic and functional results. Checking the shape of the tip of the nose is the critical step, and stabilization of the nasal base in particular leads to a good long-term outcome with preservation of the nasal tip projection. The surgeon needs to stabilize the structure of the nose by building up the structure and must also anticipate the effects of scar contracture. This entails structural grafting with autologous cartilage. In this paper, the authors present the grafting techniques most commonly used to sculpt the nasal framework; in primary and secondary rhinoplasty. Tried and tested grafts are presented, with the appropriate nomenclature relating to each and also the anatomical locations of and clinical indications for each.

Reconstruction of microtia with laser hair removal before transplantation of costal cartilage

When scalp skin is contained in reconstruction of microtia, the hair growth on the reconstructed auricle causes aesthetic problems. Several techniques to deal with hairline, such as skin graft, skin flap, tissue expander and electroepilation, have been reported, but there are few reports using laser hair removal for microtia patients. We performed presurgical laser therapy in five patients. The low regions of hairlines in unilateral microtia children were irradiated by two kinds of laser systems for 1 year before the transplantation of costal cartilage. When hair growth was seen after the surgery, laser irradiations were performed. Video-microscopic and histological studies were examined to check the rates of epilation and skin injuries. There were no conspicuous hairs on the reconstructed ears and no side effects such as skin injury, folliculitis and deformity of cartilage. Video-microscopic examination revealed that terminal hair was rarely observed after irradiation, although the amount of vellus hair after irradiation was the same as that before irradiation. Histological examination showed that atrophy or hyperplasia of epidermis and dermis were not observed. Although patients had to undergo laser epilation from four to seven times because of a hair cycle, the laser epilation is less invasive and safer than other surgical procedures to reconstruct non-haired helix.

Myocardial Infiltration After Excision of a Pulmonary Melanotic Schwannoma

Traumatic injury to joints may involve articular cartilage alone or result in osteochondral fractures which may impair mechanical properties of articular cartilage. Injuries of articular cartilage alone with visible tissue disruption and osteochondral fractures are now visualized by MRI which is the only modality for direct non-invasive visualization of articular cartilage. Three-dimensional T1-weighted gradient-echo sequences with fat-suppression provide high accuracy in the detection of cartilage surface defects. Fast spin echo imaging with heavy T2-weighting demonstrates cartilage defects in the presence of joint effusion accurately too, but minimal slice thickness in 2D-imaging is limited. For correct staging of osteochondral fractures, which determines further therapy, intraarticular administration of contrast media may be necessary. Repetitive direct blunt trauma or high-energy joint loading can cause cartilage damage without visible tissue disruption. To demonstrate this early stage of chondral injury special techniques and agents are necessary. These include diffusion weighted imaging, measurements of magnetization transfer as a function of collagen concentration, proton density mapping to plot the distribution of water in hyaline cartilage and sodium imaging to visualize ions bound to proteoglycans or intraarticular application of Mangan selectively bound to proteoglycans. Although promising techniques, they are still experimental. With recent developments of repair of cartilage defects by cartilage grafts, osteochondral autografts and transplantation, MRI becomes the method of choice in the noninvasive evaluation of injured articular cartilage and follow-up studies.

Insertion Force of Articular Cartilage Transplantation Systems

This study compared the insertion force, plug harvest consistency, and recipient site creation consistency of 4 different articular cartilage transplantation systems (COR, OATS, Mosaicplasty, and New COR2) during plug insertion using a single-impaction technique. Maximum insertion forces fell into 3 statistically different groups: group 1, OATS 8-mm (238 N) and 10-mm (215 N) systems; group 2, COR 6-mm (133 N) and 8-mm (176 N), Mosaicplasty, 6.5-mm (147 N) and 8.5-mm (134 N), and OATS 6-mm (137 N) systems; and group 3, New COR2 6-mm (68 N), 8-mm (55 N), and 10-mm (54 N) systems (P < or = .05). OATS compaction pressures were 172 N (6 mm), 353 N (8 mm), and 550 N (10 mm). COR, New COR2, and Mosaicplasty donor plugs were created consistently, but the Mosaicplasty system required toggling. OATS plugs had inconsistent lengths but required no toggling. Insertion forces with the New COR2 system were statistically the lowest. Compaction significantly increased surface forces.

Analysis of Cartilage Tissue on a Cellular Level in Fresh Osteochondral Allograft Retrievals

Background Fresh human osteochondral allografting is a biological cartilage replacement technique used to treat articular and osteoarticular defects in the knee. A small number of grafts fail, and we analyzed every retrieved graft during a 4-year period in order to learn more about the potential causes of failure. Hypothesis A large percentage of chondrocytes still remain viable many years after fresh osteochondral allografting. Study Design Descriptive laboratory study. Methods Retrieval specimens were obtained at the time of revision surgery and immediately analyzed. Chondrocyte viability and viable cell density were determined using a live/dead staining technique followed by confocal microscopy. Glycosaminoglycan content was a measure of the cartilage matrix. Radiolabeled sulfate uptake served as a biochemical marker of chondrocyte metabolic activity. Cartilage and subchondral bone were examined histologically. Results Fourteen patients yielded a total of 26 retrieval specimens that had been originally implanted as individual fresh osteochondral allografts. Average graft survival was 42 months. Chondrocyte viability was 82% ± 17%, and chondrocyte viable cell density was 15 590 ± 5900 viable cells/mm3. Retrieved tissue demonstrated radiolabeled sulfate uptake of 437 ± 270 counts per minute and 3.5% ± 0.8% hexosamine per dry weight. Histologically, all specimens showed some degree of cartilage fibrillation. There was evidence of bone allograft incorporation in most specimens, as well as pannus formation in 4 specimens, but no evidence of immune rejection. Conclusion A small percentage of fresh osteochondral allografts fail, but the precise cause is unknown. The main theories for failure investigated here include immunologic rejection, failure of bony incorporation, and chondrocyte death causing breakdown of the cartilage matrix. We show that chondrocytes remain viable many years after transplantation, allograft bone incorporates, and immune rejection does not seem to play a primary role in failure. Clinical Relevance Fresh osteochondral allografting is becoming more common in the treatment of articular cartilage defects in the knee. Our findings support the paradigm of fresh osteochondral allografting, the transplantation of hyaline cartilage with biological incorporation of the underlying bone scaffold. The reasons for failure of a small percentage of grafts remain unclear.

Regenerative Medicine in head and neck reconstructive surgery

Autologous transplantation is regarded as the gold standard in the treatment of congenital or acquired deformities. However, the availability of autologous tissue for transplantation is often limited. Regenerative medicine aims to activate individuals' own intrinsic regenerative mechanisms and embraces tissue engineering, cell/system biology, gene therapy and stem-cell biology. Most approaches in tissue engineering are based on the expansion of small autologous cell aggregates. Tissue engineering supplemented by isolated and amplified stem cells is another very promising option for producing autologous transplants and getting over the limited availability. The association of stem cell-based tissue engineering and gene therapy allows the creation of regenerative tissue in the optimal ambience of regulatory proteins. This leads to great opportunities in the transplantation of skin, bones or cartilage. This paper presents the current status and the possible benefits, but also the limitations, of regenerative medicine in reconstructive surgery of the head and neck.

Steady-state diffusion imaging for MR in-vivo evaluation of reparative cartilage after matrix-associated autologous chondrocyte transplantation at 3 tesla—Preliminary results

Objectives To demonstrate the feasibility of time-reversed fast imaging with steady-state precession (FISP) called PSIF for diffusion-weighted imaging of cartilage and cartilage transplants in a clinical study. Material and Methods In a cross-sectional study 15 patients underwent MRI using a 3D partially balanced steady-state gradient echo pulse sequence with and without diffusion weighting at two different time points after matrix-associated autologous cartilage transplantation (MACT). Mean diffusion quotients (signal intensity without diffusion-weighting divided by signal intensity with diffusion weighting) within the cartilage transplants were compared to diffusion quotients found in normal cartilage. Results The global diffusion quotient found in repair cartilage was significantly higher than diffusion values in normal cartilage ( p < 0.05). There was a decrease between the earlier and the later time point after surgery. Conclusions In-vivo diffusion-weighted imaging based on the PSIF technique is possible. Our preliminary results show follow-up of cartilage transplant maturation in patients may provide additional information to morphological assessment.

Osteochondral Lesions of the Talus: Results of Repeat Arthroscopic Debridement

Repeat arthroscopic debridement of osteochondral lesions of the talus has a poor reputation despite a paucity of evidence in the literature. We reviewed all patients who had repeat arthroscopic debridement of an osteochondral lesion performed by the senior author. They were scored using the American Orthopaedic Foot and Ankle Society (AOFAS) Ankle-Hindfoot Scale, and lesions were graded using the system described by Berndt and Harty. Between 1993 and 2002, 808 consecutive ankle arthroscopies were performed by the senior author, of which 215 were to treat osteochondral lesions of the talus. Of these, 12 had repeat arthroscopies because of unresolved symptoms. AOFAS scores improved from a mean of 34.8 prior to arthroscopy to 80.5 after repeat arthroscopy at a mean followup of 5.9 years (18 months to 11 years). Two patients returned to professional sports after the second procedure. Six patients returned to their preinjury levels of sporting activity and three returned to the same sports but played to a lesser standard or less frequently. One patient had already had a cartilage transplantation procedure. This is the first series specifically assessing patients who have had repeat arthroscopic debridement of osteochondral lesions of the talus, using the same debridement technique by a single surgeon. Our results question the assumption that repeat arthroscopic debridement yields poor results. They also provide a baseline for the newer chondral and osteochondral transplantation techniques to compare to at the medium term.

Quantitative T2 Mapping of Matrix-Associated Autologous Chondrocyte Transplantation at 3 Tesla

To evaluate magnetic resonance (MR) T2 mapping for characterization of cartilage repair tissue following matrix-associated autologous cartilage transplantation (MACT). Fifteen patients were evaluated following MACT using a 3T MR scanner. Patients were categorized into 2 postoperative intervals: I: 3-13 months, II: 19-42 months. Mean T2 relaxation times calculated from multiple spin-echo sequence were determined in regions of interest (MACT and normal hyaline cartilage) and T2 line profiles through the repair tissue and control sites were acquired. Mean global T2 values of repair tissue in group I were significantly higher than at control sites (P < 0.05). Repair tissue in group II showed no significant difference to control sites. Repair tissue T2 line profiles normalized over time toward the control sites. T2 mapping allows visualization of cartilage repair tissue maturation. Global T2 repair tissue values approach that of control sites after more than 1.5 years, similar behavior is seen in the zonal organization.

Two-stage reconstruction of the auricle in congenital microtia using autogenous costal cartilage

The current authors reconstructed the auricles of congenital microtia patients with a two-stage method using autogenous costal cartilage. In the first stage, lobule rotation, fabrication of the cartilage framework, and implantation of the framework were performed. In the second stage, elevation of the auricle using transplantation of the costal cartilage and two local transposition flaps, formation of the tragus, and deepening of the concha were performed. A total of 125 consecutive patients were treated, ranging from seven to 53 years old, from 1990 to 2003. Sixty-nine patients were males and 56 patients were females. Unilateral microtia was present in 114 patients (right 73, left 41), bilateral in 11 patients. Ninety-four cases were the classic sausage-shaped lobule type deformity; the remaining 42 cases presented concha-type deformity. The follow-up period was 6 months to 10 years. One hundred and eighteen cases presented acceptable ear contour after ear reconstruction. Unfavourable results were blunted convolution of the reconstructed ear because of thick fibrous tissue in six cases, mild absorption of carved cartilage by infection in two cases, deformation of the constructed helix occurred in four cases, less projection of the elevated ear in three cases, and hypertrophic scars in three cases. Our procedure produced acceptable contour of the reconstructed auricle with fewer complications than conventional procedures. In addition, careful meticulous manipulation is necessary to create natural contour of the ear and to reduce complications in all stages.

Allografts in Sports Medicine

Society has long recognized the medical importance of donating and transplanting organs and tissues. Allografts are used routinely for sports medicine applications and in a large variety of other non-sports related surgical procedures. Allogeneic tissue research has been influenced by the increase in demand for transplantable grafts for both non-sport and sport related surgeries. Disease transmission prevention is a key factor in the proliferation and success of the allografts used today. Disease transmission prevention methods are accomplished by social screening, serology, and various types of secondary sterilization. These methods are increasingly assessed and regulated by the FDA, the American Association of Tissue Banks and their accredited member organization tissue banks. Sports medicine surgeons initially used allografts to augment their autograft use when autologous sources were not available. While the number of grafts and types continue to grow, demand continues to increase as well. Some allografts undergo minimal processing and only require minor preparation prior to use, however other procedures require grafts that are sized dimensionally and matched for their recipients. Our continuing experience with a variety of allograft types has led us to conclude that allograft use is a legitimate primary or alternate source in the ligamentous or cartilage reconstruction or transplant in sports medicine. Cost and availability will always limit allograft usage; however concerns regarding inferior clinical results should not. Our experience and those reported by others, indicates that comparable clinical results can be obtained with the added benefit of reduced surgical morbidity by the use of allografts.

Combined High Tibial Osteotomy, Anterior Cruciate Ligament Reconstruction, and Cartilage Transplantation in Young Athletes

Chronic anterior knee instability due to anterior cruciate ligament insufficiency, combined with varus malalignment and chondral lesions, is a problem common in young athletes. A good therapeutic strategy is necessary to preserve the level of sports ability and avoid or decrease secondary degenerative lesions. This article provides strategies on how to deal with different combined lesions and describes the authors’ preferred operative technique.

Comparison of marker gene expression in chondrocytes from patients receiving autologous chondrocyte transplantation versus osteoarthritis patients

Currently, autologous chondrocyte transplantation (ACT) is used to treat traumatic cartilage damage or osteochondrosis dissecans, but not degenerative arthritis. Since substantial refinements in the isolation, expansion and transplantation of chondrocytes have been made in recent years, the treatment of early stage osteoarthritic lesions using ACT might now be feasible. In this study, we determined the gene expression patterns of osteoarthritic (OA) chondrocytes ex vivo after primary culture and subculture and compared these with healthy chondrocytes ex vivo and with articular chondrocytes expanded for treatment of patients by ACT. Gene expression profiles were determined using quantitative RT-PCR for type I, II and X collagen, aggrecan, IL-1β and activin-like kinase-1. Furthermore, we tested the capability of osteoarthritic chondrocytes to generate hyaline-like cartilage by implanting chondrocyte-seeded collagen scaffolds into immunodeficient (SCID) mice. OA chondrocytes ex vivo showed highly elevated levels of IL-1β mRNA, but type I and II collagen levels were comparable to those of healthy chondrocytes. After primary culture, IL-1β levels decreased to baseline levels, while the type II and type I collagen mRNA levels matched those found in chondrocytes used for ACT. OA chondrocytes generated type II collagen and proteoglycan-rich cartilage transplants in SCID mice. We conclude that after expansion under suitable conditions, the cartilage of OA patients contains cells that are not significantly different from those from healthy donors prepared for ACT. OA chondrocytes are also capable of producing a cartilage-like tissue in the in vivo SCID mouse model. Thus, such chondrocytes seem to fulfil the prerequisites for use in ACT treatment.

Die Implantation von matrixfreien dreidimensionalen Knorpeltransplantaten in standardisierte Knorpeldefekte am Schafskniegelenk

The goal of the current investigation was to make a comparative analysis of regenerative tissue after autologous de novo cartilage transplantation on the femoral condyles of sheep after a chondral defect. One chondral defect measuring 4 mm in diameter was placed in the center of one medial femoral condyle of each of 48 Suffolk sheep. Twelve defects were left to heal spontaneously, 16 defects were covered with periosteal flaps, and 20 defects were filled with autologous de novo cartilage graft. Macroscopic and microscopic assessments were performed at 26 and at 52 weeks. Regeneration was significantly better (p<0.05) in the transplant group than in the control groups at both 26 weeks and 52 weeks. The differences were most evident in the grade of defect filling, cartilage stability, cell distribution, and matrix assessments. Transplantation of immature, autologous de novo cartilage leads to qualitatively better regeneration both macro- and microscopically than does periosteal flap placement alone. The transplanted, immature cartilage tissue undergoes maturation in vivo. The regenerated tissue has hyaline-like features.

Costal Cartilage Autografts to Simulated Degenerative Intervertebral Discs in the Rat

An autograft of costal cartilage was transplanted into the rat intervertebral space in the proximal tail following 2 weeks of simulated degeneration by chondroitinase ABC (CABC). The purpose of this study was to evaluate costal cartilage transplantation into a degenerated disc as a possible therapy. Reversal of degenerative disc dehydration is an attractive goal. Costal cartilage is plentiful, hydrophilic, and avascular, leading us to speculate that it would survive transplantation into the degenerated disc, increase proteoglycan content, and restore disc height. Costal cartilage fragments were transplanted into a single proximal intervertebral disc in each of the rats' tails following a 2-week period of simulated degeneration. The intervertebral space was measured on radiographs under 2.5x magnification taken pretreatment and 21 days posttreatment. Each specimen was sagittally sectioned, mounted, and stained. The slides were graded for proteoglycan content. A 64% increase in intervertebral disc height was observed in the implant group compared with a 4% increase in sham operated group and a 39% increase in the CABC only group. Histology demonstrated a viable implant in 7 of 9 rats. The transplant group had significantly more proteoglycan staining than either the CABC group or sham group (P < 0.05). Costal cartilage transplantation may rehydrate degenerated intervertebral discs and might serve as a promising model for understanding and perhaps modifying this complex degenerative disease.