title: Thymidine kinase-mediated shut down of bone morphogenetic protein-4 expression allows regulated bone production.
abstract: Bone morphogenetic Proteins (BMPs) are growth factors also involved in ossification and chondrogenesis that have generated interest for their efficiency in inducing bone neo-synthesis. BMPs expression in engineered cells has been successful in stimulating osteoblastic differentiation and ectopic and orthotopic bone formation in vivo. We have previously shown that an adenoviral vector expressing bone morphogenetic protein type-4 (BMP-4) is able to efficiently drive bone formation in a rabbit model of discontinuous bone lesions. However, unregulated secretion of BMPs has also been implicated in bone overproduction and exostosis. We have constructed a replication-defective first generation adenoviral (FG-Ad) vector containing a cassette for the expression of BMP-4 associated with the Herpes Simplex virus thymidine kinase (TK) gene (FG-B4TK) in order to shut down BMP-4 expression and, therefore, regulate bone production. TK expression does not interfere with BMP-4 ability to induce ectopic bone formation in athymic nude mice. Administration of ganciclovir blocks ectopic bone production in quadriceps muscle transduced with the FG-B4TK with no effect on the contralateral muscle transduced with a vector expressing only BMP-4. Histological findings confirmed the pro-apoptotic activity of TK and the reduction of mineralized areas in the quadriceps transduced with FG-B4TK in mice treated with ganciclovir. We have generated a system to block BMP-4 secretion by inducing apoptosis in transduced cells therefore blocking unwanted bone formation. This system is an additional tool to generate regulated amount of bone in discontinuous bone lesions and can be easily coupled with biomaterials capable of recruiting cells and generating a local bioreactor.
authors: Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università degli Studi di Napoli Federico II, Via S. Pansini 5, 80131 Napoli, Italy.
authors: Barbara
authors: B
authors: Lombardo
authors: Teresa
authors: T
authors: Rocco
authors: Maria T
authors: MT
authors: Esposito
authors: Bruno
authors: B
authors: Cantilena
authors: Sara
authors: S
authors: Gargiulo
authors: Adelaide
authors: A
authors: Greco
authors: Donatella
authors: D
authors: Montanaro
authors: Arturo
authors: A
authors: Brunetti
authors: Lucio
authors: L
authors: Pastore
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000235:genetics; D001846:Bone Development / Q000187:drug effects / Q000235:genetics*; D055415:Bone Morphogenetic Protein 4 / Q000235:genetics* / Q000378:metabolism; D001842:Bone and Bones / Q000378:metabolism; D015774:Ganciclovir / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D018014:Gene Transfer Techniques; D005822:Genetic Vectors / Q000235:genetics / Q000494:pharmacology*; D006801:Humans; D008297:Male; D051379:Mice; D008819:Mice, Nude; D010012:Osteogenesis / Q000235:genetics; D052097:Quadriceps Muscle / Q000502:physiology; D018139:Simplexvirus / Q000201:enzymology; D013937:Thymidine Kinase / Q000235:genetics*; D019076:Transgenes
chemical_list: D055415:Bone Morphogenetic Protein 4; D013937:Thymidine Kinase; D015774:Ganciclovir