Abstract
IntroductionThe transplantation of genetically modified progenitor cells such as bone marrow-derived mesenchymal stem cells (MSCs) is an attractive strategy to improve the natural healing of articular cartilage defects. In the present study, we examined the potential benefits of sustained overexpression of the mitogenic and pro-anabolic insulin-like growth factor I (IGF-I) via gene transfer upon the biological activities of human MSCs (hMSCs).MethodsRecombinant adeno-associated vectors (rAAV) were used to deliver a human IGF-I coding sequence in undifferentiated and chondrogenically-induced primary hMSCs in order to determine the efficacy and duration of transgene expression and the subsequent effects of the genetic modification upon the chondrogenic versus osteogenic differentiation profiles of the cells relative to control (lacZ) treatment after 21 days in vitro.ResultsSignificant and prolonged expression of IGF-I was evidenced in undifferentiated and most importantly in chondrogenically-induced hMSCs transduced with the candidate rAAV-hIGF-I vector for up to 21 days, leading to enhanced proliferative, biosynthetic, and chondrogenic activities compared with rAAV-lacZ treatment. Overexpression of IGF-I as achieved in the conditions applied here also increased the expression of hypertrophic and osteogenic markers in the treated cells.ConclusionsThese results suggest that a tight regulation of rAAV expression may be necessary for further translation of the approach in clinically relevant animal models in vivo. However, the current findings support the concept of using this type of vector as an effective tool to treat articular cartilage defects via gene- and stem cell-based procedures.
Highlights
The transplantation of genetically modified progenitor cells such as bone marrow-derived mesenchymal stem cells (MSCs) is an attractive strategy to improve the natural healing of articular cartilage defects
Genetic modification of human bone marrow-derived mesenchymal stem cell (hMSC) via Recombinant adeno-associated vectors (rAAV) has so far been performed to deliver various therapeutic candidates including transforming growth factor beta (TGFβ) [20], basic fibroblast growth factor (FGF-2) [24], and SOX9 [32], but little is known about the effects of applying insulin-like growth factor I (IGF-I) via rAAV in this clinically relevant population of regenerative cells. We focused on this particular growth factor in light of our previous work showing the benefits of overexpressing IGF-I via rAAV upon the remodeling of human osteoarthritic cartilage by activation of the anabolic and proliferative processes in damaged chondrocytes in situ [36]
Sustained expression of IGF-I in undifferentiated hMSCs via rAAV gene transfer hMSCs were first transduced with the candidate rAAVhIGF-I vector in undifferentiated monolayer cultures compared with a control condition [24,32] to examine the ability of rAAV to mediate overexpression of the growth factor over time in these cells in vitro at an undifferentiated stage
Summary
The transplantation of genetically modified progenitor cells such as bone marrow-derived mesenchymal stem cells (MSCs) is an attractive strategy to improve the natural healing of articular cartilage defects. Various therapeutic candidate sequences have been reported for their effects upon the chondrogenic differentiation of such cells, among which are cartilage oligomeric matrix protein [18], transforming growth factor beta (TGFβ) [19,20,21], bone morphogenetic proteins [21,22,23], basic fibroblast growth factor (FGF-2) [24], Indian hedgehog [21], human telomerase alone [25,26] or combined with a small interfering RNA against p53 [27], the specific transcription factors of the SOX family alone [28,29,30,31,32,33] or combined with an anti-Runx2/Cbfa small interfering RNA [34], or the zinc-finger protein 145 [35] Most of these studies, focused on the use of gene transfer vectors with relatively low or short-term efficiencies (nonviral vectors, adenoviral vectors) [18,19,21,22,23,28,29,30,31,33,34] or on constructs carrying the risk of insertional mutagenesis (retroviral vectors, lentiviral vectors) [25,26,27,35]
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