gms | German Medical Science

Objectives: Adult articular cartilage has a restricted capability for self-repair. A highly established method is the transfer of genetically modified human bone marrow-derived mesenchymal stem cells (hMSCs) as progenitor cells to improve the natural healing of the damaged articular cartilage. In this studies, we investigated the co-transduction of FGF-2 and SOX9 via recombinant adeno-associated vector (rAAV) in hMSCs could enhance a chondrogenic cell population for articular cartilage lesions.

Methods: rAAV-RFP carries the red fluorescence protein,rAAV-hFGF-2 a human FGF-2 sequence, rAAV-SOX9 a human SOX9 sequence are controlled by the CMV-IE promoter/enhancer. Bone marrow aspirates were obtained from the distal femurs of donors undergoing total knee arthroplasty, washed, and MSCs we prepared as previously described. Cells were (co)transduced with rAAV (FGF-2 + Sox9: 40 μl each vector; lacZ: 40 μ l vector) and kept in chondrogenic medium for up to 21 days. Histological and immunohistochemical analyses were performed on paraffin-embedded sections of the constructs (5 μ μ m) (toluidine blue staining; anti-FGF-2, anti-Sox9, and anti-type-II/-I/-X collagen immunostaining). The proteoglycan contents were monitored by binding to dimethylmethylene blue dye and the DNA contents by Hoechst 33258 assay. Total RNA was extracted and reverse transcription carried out for cDNA amplification via real-time RT-PCR with GAPDH as control for normalization and the 2- Δ Δ Ct method relative to untreated samples. Each condition was performed in duplicate in three independent experiments. A t-test was employed with p≤0.05 considered statistically significant.

Results: Transgene (SOX9 and FGF-2) expression was mostly noted in rAAV -SOX9 and rAAV- FGF-2 co-transduced in hMSCs samples relative to control conditions. Successful chondrogenic differentiation was achieved in all samples co-transduced with rAAV-SOX9 andrAAV-FGF-2 (toluidine blue staining and type-II collagen immunostaining)that significantly increased the proteoglycan contents relative to control treatments (1.1-fold). Of further interest, immunoreactivity to type-I and -X collagen was less intense when rAAV -SOX9 and rAAV-FGF-2 was provided to the aspirates. These findings were corroborated by results of a real-time RT-PCR analysis showing enhanced chondrogenic differentiation with SOX9 and FGF-2 relative to the control condition (5.1-fold higher COL2A expression, p≤0.001) and reduced hypertrophic differentiation (up to 1.5-fold lower COL1A1 and COL10A1 expression, respectively; p≤0.001).

Conclusion: These results suggest that hMSCs genetically modified via co-transduction of rAAV vectors coding for SOX9 and FGF-2 undergo enhanced chondrogenic differentiation process.These results show the potential of targeting hMSCs via therapeutic rAAV Co-transduction as a promising approach to treat articular cartilage defects in animal model.