Figure 1.

Therapeutic genes may be transferred to sites of articular cartilage damage or to meniscal lesions in vivo via intra-articular injection or by direct application into the lesion. Intra-articular injection (upper panel) of the therapeutic formulation (most often a viral vector) results in a nonselective transduction of many intra-articular tissues. Direct administration of the therapeutic formulation (lower panel) to the target lesion (e.g., an articular cartilage defect) can be achieved by directly applying a gene vector to the repair tissue in the defect (left), by matrix-supported application (e.g., alginate) of target cells (e.g., articular chondrocytes, meniscal fibrochondrocytes, progenitor cells) that were previously genetically modified ex vivo (middle), or by application of a gene vector attached to a biomaterial (right). In vivo, it often includes an arthrotomy.