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Safety and Efficacy of Ultraviolet-A Light-Activated Gene Transduction for Gene Therapy of Articular Cartilage Defects
Michael D. Maloney, MD1; J. Jeffrey Goater, MS1; Richard Parsons, DVM1; Hiromu Ito, MD, PhD1; Regis J. O'Keefe, MD, PhD1; Paul T. Rubery, MD1; M. Hicham Drissi, PhD1; Edward M. Schwarz, PhD1
1 The Center for Musculoskeletal Research, University of Rochester Medical Center, 601 Elmwood Avenue, Box 665, Rochester, NY 14642. E-mail address for E.M. Schwarz: edward_schwarz@urmc.rochester.edu
View Disclosures and Other Information
In support of their research for or preparation of this manuscript, one or more of the authors received grants or outside funding from LAGeT, Inc. (Rochester, New York), which was founded by five of the authors (M.D.M., J.J.G., P.T.R., R.J.O'K., and E.M.S.). None of the authors received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.
Note: All of the rAAV preparations were provided by R.J. Samulski and the University of North Carolina-Chapel Hill Vector Core Facility.
Investigation performed at the Center for Musculoskeletal Research, University of Rochester, Rochester, New York

The Journal of Bone and Joint Surgery, Incorporated
J Bone Joint Surg Am, 2006 Apr 01;88(4):753-761. doi: 10.2106/JBJS.E.00400
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Background: Gene therapies for articular cartilage defects are limited by the absence of an in vivo delivery system that can mediate site-specific transduction restricted to within the margins of the defect during routine arthroscopy. We have proposed the use of ultraviolet light to stimulate gene expression following infection by recombinant adeno-associated virus (rAAV). However, research has demonstrated that short-wavelength ultraviolet light (ultraviolet C), while effective, is neither safe nor practical for this purpose. We evaluated the safety and efficacy of long-wavelength ultraviolet light (ultraviolet A) from a laser to induce light-activated gene transduction in articular chondrocytes in vitro and in vivo.

Methods: The effects of ultraviolet A from a 325-nm helium-cadmium laser, delivered through a fiberoptic cable, on cytotoxicity, mutagenesis, intracellular reactive oxygen species, and light-activated gene transduction of human articular chondrocytes were evaluated in dose-response experiments of primary cultures. Cytotoxicity was determined by trypan blue exclusion. The presence of pyrimidine dimers in purified genomic DNA was determined by enzyme-linked immunosorbent assays. Intracellular reactive oxygen species levels were determined by flow cytometry at one hour and twenty-four hours. In vitro light-activated gene transduction with rAAV vectors expressing the green fluorescent protein (eGFP) or ß-galactosidase (LacZ) was determined by fluorescence microscopy and bioluminescence assays, respectively. In vivo light-activated gene transduction was quantified by stereotactic immunohistochemistry for ß-galactosidase in rabbit articular cartilage defects in the patellar groove that had been irradiated with ±6000 J/m2 of ultraviolet A one week after direct injection of 107 transducing units of rAAV-eGFP.

Results: Ultraviolet A failed to induce significant cytotoxicity at all fluencies below 6000 J/m2. Dose-dependent cytotoxicity was observed at greater fluencies. In contrast to ultraviolet C, which induced significant (p < 0.05) pyrimidine dimer formation at all fluencies in a dose-dependent manner, ultraviolet A failed to induce DNA modifications. Conversely, ultraviolet C proved to be a poor inducer of intracellular reactive oxygen species, while ultraviolet A immediately induced high levels of intracellular reactive oxygen species, which were completely resolved twenty-four hours later. Ultraviolet A demonstrated significant light-activated gene transduction effects in vitro, which were dose-dependent (p < 0.05). In vivo, ultraviolet A mediated a tenfold increase in transduction in which 40.8% of the superficial chondrocytes adjacent to the defect stained positive for green fluorescent protein compared with 5.2% in the knees treated with no ultraviolet A (p < 0.006).

Conclusions: These results provide what we believe is the first formal demonstration of an agent that can induce rAAV transduction in the complete absence of cytotoxicity and DNA modification. They also suggest that the mechanism by which long-wavelength ultraviolet light mediates site-specific gene expression is by means of the induction of intracellular reactive oxygen species. Finally, laser-derived ultraviolet A can be readily transferred through a fiberoptic cable to mediate light-activated gene transduction in vivo.

Clinical Relevance: This is the first demonstration of in vivo site-directed gene delivery to articular defects with use of a method that is highly compatible with standard arthroscopy. Future studies with chondrogenic genes and longer outcome measurements are warranted to evaluate the potential of this gene therapy approach for superficial articular defects and meniscal tears.

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    These activities have been planned and implemented in accordance with the Essential Areas and policies of the Accreditation Council for Continuing Medical Education (ACCME) through the joint sponsorship of the American Academy of Orthopaedic Surgeons and The Journal of Bone and Joint Surgery, Inc. The American Academy of Orthopaedic Surgeons is accredited by the ACCME to provide continuing medical education for physicians.
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