Gunter Kaul

Enhanced repair of articular cartilage defects in vivo by transplanted chondrocytes overexpressing insulin-like growth factor I (IGF-I)

Traumatic articular cartilage lesions have a limited capacity to heal. We tested the hypothesis that overexpression of a human insulin-like growth factor I (IGF-I) cDNA by transplanted articular chondrocytes enhances the repair of full-thickness (osteochondral) cartilage defects in vivo. Lapine articular chondrocytes were transfected with expression plasmid vectors containing the cDNA for the Escherichia coli lacZ gene or the human IGF-I gene and were encapsulated in alginate. The expression patterns of the transgenes in these implants were monitored in vitro for 36 days. Transfected allogeneic chondrocytes in alginate were transplanted into osteochondral defects in the trochlear groove of rabbits. At three and 14 weeks, the quality of articular cartilage repair was evaluated qualitatively and quantitatively. In vitro, IGF-I secretion by implants constructed from IGF-I-transfected chondrocytes and alginate was 123.2±22.3 ng/107 cells/24 h at day 4 post transfection and remained elevated at day 36, the longest time point evaluated. In vivo, transplantation of IGF-I implants improved articular cartilage repair and accelerated the formation of the subchondral bone at both time points compared to lacZ implants. The data indicate that allogeneic chondrocytes, transfected by a nonviral method and cultured in alginate, are able to secrete biologically relevant amounts of IGF-I over a prolonged period of time in vitro. The data further demonstrate that implantation of these composites into deep articular cartilage defects is sufficient to augment cartilage defect repair in vivo. These results suggest that therapeutic growth factor gene delivery using encapsulated and transplanted genetically modified chondrocytes may be applicable to sites of focal articular cartilage damage.

Local stimulation of articular cartilage repair by transplantation of encapsulated chondrocytes overexpressing human fibroblast growth factor 2 (FGF-2) in vivo†

Defects of articular cartilage are an unsolved problem in orthopaedics. In the present study, we tested the hypothesis that gene transfer of human fibroblast growth factor 2 (FGF‐2) via transplantation of encapsulated genetically modified articular chondrocytes stimulates chondrogenesis in cartilage defects in vivo.

Menisci are Efficiently Transduced by Recombinant Adeno-Associated virus Vectors in Vitro and in Vivo

Background Meniscal tears remain an unsolved problem in sports medicine. Gene transfer is a potential approach to enhancing meniscal repair. Recombinant adeno-associated virus is a method of gene transfer that has advantages over previously used approaches to this problem. Hypothesis Direct gene transfer to meniscal cells can be accomplished using recombinant adeno-associated virus in vitro and in vivo. Study Design Controlled laboratory study. Methods Recombinant adeno-associated viruses containing the reporter gene lacZ were tested for their ability to achieve gene transfer into lapine and human meniscal cells in vitro and into lapine meniscal defects in vivo. Results were assessed by detecting β-galactosidase, the enzyme encoded by the lacZ gene. Results Maximal efficiency of gene transfer was 81.6% ± 6.6% for lapine and 87.2% ± 14.8% for human meniscal cells in vitro. Expression of the transferred gene continued for the 28-day duration of the study. When the recombinant adeno-associated virus vector was injected into meniscal tears in a lapine meniscal tear model, transgene expression continued in meniscal cells adjacent to the tear for at least 20 days in vivo. Conclusions The data suggest that recombinant adeno-associated virus vectors can directly and efficiently transfer and stably express foreign genes in isolated lapine and human meniscal cells in vitro and in lapine meniscal defects in vivo. Clinical Relevance This direct gene transfer approach may form a basis for improved treatments of meniscal tears.

Effect of transforming growth factor-beta 1 (TGF-ß1) released from a scaffold on chondrogenesis in an osteochondral defect model in the rabbit

Articular cartilage repair might be stimulated by the controlled delivery of therapeutic factors. We tested the hypotheses whether TGF-ß1 can be released from a polymeric scaffold over a prolonged period of time in vitro and whether its transplantation modulates cartilage repair in vivo. Unloaded control or TGF-ß1 poly(ether-ester) copolymeric scaffolds were applied to osteochondral defects in the knee joints of rabbits. In vitro, a cumulative dose of 9 ng TGF-ß1 was released over 4 weeks. In vivo, there were no adverse effects on the synovial membrane. Defects treated with TGF-ß1 scaffolds showed no significant difference in individual parameters of chondrogenesis and in the average cartilage repair score after 3 weeks. There was a trend towards a smaller area (42.5 %) of the repair tissue that stained positive for safranin O in defects receiving TGF-ß1 scaffolds. The data indicate that TGF-ß1 is released from emulsion-coated scaffolds over a prolonged period of time in vitro and that application of these scaffolds does not significantly modulate cartilage repair after 3 weeks in vivo. Future studies need to address the importance of TGF-ß1 dose and release rate to modulate chondrogenesis.