Gene Delivery to Joints by Intra-Articular Injection

Abstract

Most forms of arthritis are incurable, difficult to treat, and a major cause of disability in Western countries. Better local treatment of arthritis is impaired by the pharmacokinetics of the joint that make it very difficult to deliver drugs to joints at sustained, therapeutic concentrations. This is especially true of biologic drugs, such as proteins and RNA, many of which show great promise in preclinical studies. Gene transfer provides a strategy for overcoming this limitation. The basic concept is to deliver cDNAs encoding therapeutic products by direct intra-articular injection, leading to sustained, endogenous synthesis of the gene products within the joint. Proof of concept has been achieved for both in vivo and ex vivo gene delivery using a variety of vectors, genes, and cells in several different animal models. There have been a small number of clinical trials for rheumatoid arthritis (RA) and osteoarthritis (OA) using retrovirus vectors for ex vivo gene delivery and adeno-associated virus (AAV) for in vivo delivery. AAV is of particular interest because, unlike other viral vectors, it is able to penetrate deep within articular cartilage and transduce chondrocytes in situ. This property is of particular importance in OA, where changes in chondrocyte metabolism are thought to be fundamental to the pathophysiology of the disease. Authorities in Korea have recently approved the world's first arthritis gene therapy. This targets OA by the injection of allogeneic chondrocytes that have been transduced with a retrovirus carrying transforming growth factor-β₁ cDNA. Phase III studies are scheduled to start in the United States soon. Meanwhile, two additional Phase I trials are listed on Clinicaltrials.gov , both using AAV. One targets RA by transferring interferon-β, and the other targets OA by transferring interleukin-1 receptor antagonist. The field is thus gaining momentum and promises to improve the treatment of these common and debilitating diseases.

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Figure 1.

Basic anatomy of the human knee joint.

Figure 2.

How molecules get into and out of joints. Macromolecules in the circulation enter the joint via the synovial capillaries and are sieved by the fenestrated endothelium of the capillaries. Small molecules also enter via the capillaries, but the major resistance to their entry is provided by the extracellular matrix (ECM) of the synovial interstitium. Intra-articular (IA) injection bypasses both of the constraints to entry. However, both large and small molecules rapidly exit the joint via the lymphatic system and small blood vessels, respectively. From Evans et al.

Figure 3.

Gene transfer to the synovium and articular cartilage of the equine joint after IA injection of adeno-associated virus (AAV) green fluorescent protein (GFP). Approximately 1 × 10¹² vg of scAAV.GFP packaged in serotype 2 was injected into the mid-carpal or metacarpophalangeal joints of one horse. Following sacrifice at day 10, joint tissues were harvested and analyzed for GFP expression, either directly using inverted fluorescence microscopy or following paraffin section and immunohistochemical staining. (a) Arthroscopic images of the interior of a healthy equine mid-carpal joint are shown to illustrate the anatomy and morphology of the articular tissues. The top image shows the smooth, rounded surfaces of articular cartilage with adjacent tissues of the synovial lining. The lower image illustrates the highly villous nature of the synovium. (b) scAAV.GFP expression in the synovium. (c) scAAV.GFP expression in articular cartilage. For both panels (b) and (c), the images in the top row show the distribution of GFP expression across the surfaces of the freshly harvested tissues using direct inverted fluorescence microscopy. The lower panels show GFP expression in each tissue in cross-section following paraffin section and immunohistochemical staining. From reference Watson et al.

Figure 4.

Human gene therapy protocol for Invossa™. Chondrocytes were harvested from an infant with polydactyly. One line of cells was retrovirally transduced to express TGF-β₁. Before use, the genetically modified cells are irradiated and mixed with unmodified chondrocytes from the same donor prior to injection into the joint.