title: Stem cell-coated titanium implants for the partial joint resurfacing of the knee.
abstract: The goal of the present study was to evaluate the partial surface replacement of the knee with stem cell-coated titanium implants and to provide a basis for a successful treatment of large osteochondral defects. Mesenchymal stem cells (MSCs) were isolated from bone marrow aspirates of adult sheep. Round titanium implants with a diameter of 2 x 7.3 mm were seeded with autologous MSC and inserted into an osteochondral defect in the medial femoral condyle. As controls, defects received either an uncoated implant or were left untreated. Nine animals with 18 defects were sacrificed after 6 months. Histological evaluation was performed by intravital polychrome fluorescent labelling, intravital perfusion with Indian ink, microradiographs and differential staining with toluidine blue. The quality of regenerated cartilage was assessed by in situ hybridization of collagen type II and immunohistochemistry of collagen types I and II. In 50% of the cases, defects treated with MSC-coated implants showed a complete regeneration of the subchondral bone layer. In these cases collagen type II and only traces of collagen type I were detected. A high level of collagen type II mRNA expression compared to articular cartilage indicates regenerating hyaline-like cartilage. A total of 50% of MSC-coated and uncoated implants failed to osseointegrate and formation of fibrocartilage was observed. Untreated defects as well as defects treated with uncoated implants demonstrated incomplete healing of subchondral bone and formation of fibrous cartilage. A modified histological score according to Wakitani significantly demonstrated better results for cell-coated implants (8.8+/-6.4) than for uncoated implants (5.5+/-3.9) and for untreated defects (2.8+/-2.5). Our results demonstrate that, in a significant number of cases, a partial joint resurfacing of the knee with stem cell-coated titanium implants occur. A slow bone and cartilage regeneration and an incomplete healing in half of the MSC-coated implants are limitations of the presented method. To improve our approach and optimize the experimental parameters, further investigations are needed prior to clinical application.
authors.affiliation: Department of Trauma Surgery, Plastic and Reconstructive Surgery, Georg-August-University Goettingen, Robert-Koch-Strasse 40, D-37075 Goettingen, Germany. khfrosch@med.uni-goettingen.de
authors.forename: Karl-Heinz
authors.initials: KH
authors.lastname: Frosch
authors.forename: Anja
authors.initials: A
authors.lastname: Drengk
authors.forename: Petra
authors.initials: P
authors.lastname: Krause
authors.forename: Volker
authors.initials: V
authors.lastname: Viereck
authors.forename: Nicolai
authors.initials: N
authors.lastname: Miosge
authors.forename: Carola
authors.initials: C
authors.lastname: Werner
authors.forename: Detlev
authors.initials: D
authors.lastname: Schild
authors.forename: Ewa K
authors.initials: EK
authors.lastname: Stürmer
authors.forename: Klaus M
authors.initials: KM
authors.lastname: Stürmer
mesh_terms: D000818:Animals; D020099:Coated Materials, Biocompatible; D024042:Collagen Type I / Q000235:genetics / Q000378:metabolism; D024043:Collagen Type II / Q000235:genetics / Q000378:metabolism; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000033:anatomy & histology / Q000473:pathology; D007720:Knee Prosthesis; D059630:Mesenchymal Stem Cells / Q000166:cytology; D019736:Prostheses and Implants; D012756:Sheep; D013499:Surface Properties; D014025:Titanium / Q000378:metabolism*
chemical_list: D020099:Coated Materials, Biocompatible; D024042:Collagen Type I; D024043:Collagen Type II; D014025:Titanium