Lunate arthroplasty with autologous mesenchymal stem cells in a rabbit model.

BACKGROUND: There is no ideal treatment for end-stage degenerative wrist disorders and subsequent carpal collapse. The purpose of this study was to investigate whether autologous cartilage constructs tissue-engineered from bone-marrow-derived mesenchymal stem cells can be effective for carpal bone reconstruction. METHODS: Total lunate excision was performed in twenty-seven adult New Zealand White rabbits. Mesenchymal stem cells were isolated from marrow and then were culture-expanded. Group-1 rabbits underwent excision only. Group-2 animals underwent excision followed by implantation of a scaffold consisting of gelatin and hyaluronan. Group-3 animals underwent excision followed by implantation of a mesenchymal stem cell-seeded scaffold that had been preincubated in chondrogenic medium. The group-1 animals were killed at six weeks, whereas the group-2 and group-3 animals were killed at six or twelve weeks. Tissues were harvested for radiographic and histologic analysis. RESULTS: Significant carpal collapse (a 5.4% +/- 2.8% reduction in the carpometacarpal index, p < 0.05) was observed in the group-1 animals by six weeks. In contrast, the carpal height was maintained in the group-2 and 3 animals. There was no radiographic evidence of ossification in the group-1 or 2 animals, whereas there was radiographic evidence of ossification in all six group-3 rabbits killed at the twelve-week time-point. Histologic sections from the group-3 animals showed filling of the lunate space with islands of cartilage with interspersed bone ossicles at six weeks. At twelve weeks, there was abundant bone formation as well as evidence of neovascularization. Osseous tissue was present in the central portions of the constructs while the periphery was lined with cartilage. In groups 1 and 2, the lunate space was filled with poorly organized fibrous tissue. CONCLUSIONS: Cartilaginous implants preformed from autologous mesenchymal stem cells seeded onto biodegradable scaffold can prevent carpal collapse. The newly formed osteochondral tissue appears to function as an adequate biologic lunate spacer for at least twelve weeks in this animal model.

Cervical total disc replacement, part I: rationale, biomechanics, and implant types.

Cervical total disc replacement (TDR) is an attractive alternate to arthrodesis for management of disc degeneration and herniation in the cervical spine. Theoretic advantages of TDR include preservation of normal motion and biomechanics in the cervical spine and reduction of adjacent-segment degeneration. Other potential advantages include faster return to normal activity and elimination of the need for bone graft and associated donor site morbidity. This article introduces the rationale and various implant types available for cervical TDR. Part 2 of this series reviews the results and complications of specific implant designs.

Chondrogenic potential of progenitor cells derived from human bone marrow and adipose tissue: a patient-matched comparison.

PURPOSE: Stem cell-based tissue engineering represents a possible alternative for the repair of cartilage defects. Both bone marrow and adipose tissue contain pluripotential cells capable of chondrogenesis. This study was a qualitative and quantitative comparison of the chondrogenic potential of progenitor cells isolated from bone marrow aspirates and adipose tissue. METHODS: Bone marrow aspirates (BM) and matching adipose tissue (AD) overlying the posterior superior iliac crest were obtained from patients undergoing elective spine surgery. Chondrogenesis was induced using an established aggregate culture technique. Qualitative analysis was performed by histology and immunohistochemistry. DNA and glycosaminoglycan (GAG) quantitative assays were performed. Quantitative RT-PCR analysis was performed to compare expression of type II collagen between BM and AD aggregates. Osteogenic and adipogenic assays were also performed to confirm pluripotentiality of both AD-derived progenitor cells (ADPC) and BM-derived progenitor cells (BMPC). RESULTS: Toluidine blue metachromasia and type II collagen immunohistochemical staining were more extensive in the aggregates formed by BMPC. Quantitative RT-PCR showed a 500-5000 fold higher expression of type II collagen in the BMPC aggregates. The DNA content was 68% higher in the AD aggregates (p<0.02) but proteoglycan deposition per cell was 120% greater for BM-derived cell aggregates as measured by GAG assays (p<0.05). CONCLUSIONS: The tissue formed by the aggregate culture of the expanded ADPC population was less cartilaginous. It is unclear whether this is because there are fewer chondroprogenitor cells or if the monolayer expansion culture favors cells with higher proliferative rates but without differentiation potential. Under the conditions described in this study, BMPCs may represent a better choice for progenitor cell-based strategies for cartilage repair.