Morphologic Analysis of BMP-9 Gene Therapy-Induced Osteogenesis

Abstract

The present study was performed to determine the histological, ultrastructural, and radiographic changes that occur over time at intramuscular BMP-9 gene therapy treatment sites. Several members of the bone morphogenetic protein (BMP) family have the potential to induce osteochondrogenesis when the protein is delivered to rodents, canines, rabbits, and nonhuman primates. Previous studies have also demonstrated that BMP gene therapy utilizing adenoviral vectors can also stimulate orthotopic and heterotopic bone formation in rodents and rabbits. Athymic nude and Sprague-Dawley rats were injected with Ad-BMP-9 or Ad-beta-Gal (3.75 x 10(9) particles) in their thigh musculature and light microscopic, electron microscopic, and computerized tomography analysis was performed 3, 6, 9, 12, 15, 18, 21, and 100 days later. To assess early mesenchymal cell proliferation, a bromodeoxyuridine (BrdU) immunohistochemical analysis was also performed 48, 60, and 72 hr postinjection in athymic nude rats. All animals demonstrated extensive endochondral bone formation at the Ad-BMP-9 treatment sites within 3 weeks. The Sprague-Dawley rats also exhibited a massive, acute inflammatory infiltrate during the first week. Proliferating mesenchymal stem cells were clearly evident as early as 2 days after treatment, which differentiated into small or hypertrophied chondrocytes during the next week. During the third week, the cartilaginous matrix mineralized and formed woven bone, which converted to lamellar bone by 3 months. No evidence of bone formation was demonstrated at the Ad-beta-Gal injection sites in the athymic nude or Sprague-Dawley rats. In addition, no cellular proliferation was seen at the Ad-beta-Gal treatment sites in the athymic nude animals as assessed by light microscopy and BrdU immunohistochemistry. The extensive bone formation induced by Ad-BMP-9 suggests that BMP gene therapy may have potential utility in the treatment of degenerative, rheumatic, or traumatic bone pathology.

Osteoinduction by ex vivo adenovirus-mediated BMP2 delivery is independent of cell type

“…[1][2][3][4][5][6][7][8] Localized delivery of cells transduced ex vivo with adenoviral vectors encoding bone morphogenetic proteins (BMPs) has proven successful in induction of new bone formation in hetero-and orthotopic locations. Although safe and efficacious gene-based bone induction systems have yet to be developed, the adenoviral delivery of BMP offers the potential of rapidly achieving local effective concentrations of the protein to induce bone formation.…”

Realizing the potential of gene-based molecular therapies in bone repair

“…The impact of immune response may depend on animal model, virus type, or transgene employed because there are reports of successful bone induction in both immune-competent and immune-compromised animals. (34)(35)(36)(37)43,44) Even if a suitable combination of carrier and transgene could be found, clinical risks of viral gene delivery have to be mitigated; nonintegrating, short-acting viral expression systems (such as adenoviral vectors) might be preferable over integrating, long-acting vectors. Only a handful of studies employed "integrating" viruses (Table 1), which recognizes the preference of practitioners in the field.…”

Genetically Engineered Mesenchymal Stem Cells: The Ongoing Research for Bone Tissue Engineering

“…BMP-9 only has a moderate osteoinductive capability (Celeste et al, 1990). However, BMP-9-engineered MSCs stimulate ALP activity in vitro and induce ectopic bone formation in vivo (Ploemacher et al, 1999;Helm et al, 2000;Varady et al, 2001;Dumont et al, 2002;Dayoub et al, 2003;Li et al, 2003), promoting its future use in BTE.…”