Use of genetically modified muscle and fat grafts to repair defects in bone and cartilage

Abstract

We report a novel technology for the rapid healing of large osseous and chondral defects, based upon the genetic modification of autologous skeletal muscle and fat grafts. These tissues were selected because they not only possess mesenchymal progenitor cells and scaffolding properties, but also can be biopsied, genetically modified and returned to the patient in a single operative session. First generation adenovirus vector carrying cDNA encoding human bone morphogenetic protein-2 (Ad.BMP-2) was used for gene transfer to biopsies of muscle and fat. To assess bone healing, the genetically modified ("gene activated") tissues were implanted into 5mm-long critical size, mid-diaphyseal, stabilized defects in the femora of Fischer rats. Unlike control defects, those receiving gene-activated muscle underwent rapid healing, with evidence of radiologic bridging as early as 10 days after implantation and restoration of full mechanical strength by 8 weeks. Histologic analysis suggests that the grafts rapidly differentiated into cartilage, followed by efficient endochondral ossification. Fluorescence in situ hybridization detection of Y-chromosomes following the transfer of male donor muscle into female rats demonstrated that at least some of the osteoblasts of the healed bone were derived from donor muscle. Gene activated fat also healed critical sized defects, but less quickly than muscle and with more variability. Anti-adenovirus antibodies were not detected. Pilot studies in a rabbit osteochondral defect model demonstrated the promise of this technology for healing cartilage defects. Further development of these methods should provide ways to heal bone and cartilage more expeditiously, and at lower cost, than is presently possible.

The rational use of animal models in the evaluation of novel bone regenerative therapies

“…Although most studies were conducted with bone marrow derived mesenchymal progenitor cells (MPCs), other tissues have been described to contain osteoprogenitor cells with similar regenerative potential including adipose tissue, muscle, umbilical cord blood, periosteum, dental pulp and periodontal ligament [4,[39][40][41][42][43][44][45]. The multilineage differentiation ability, paracrine effects and immunomodulatory properties of MPCs make them an ideal for tissue engineering and regenerative purposes [5,7,[46][47][48].…”

Overexpression of human IGF-I via direct rAAV-mediated gene transfer improves the early repair of articular cartilage defects in vivo

“…Identification of an effective therapeutic candidate sequence is of the utmost importance for cartilage repair. Different factors have been described for their ability to influence the healing processes in experimental models in vivo, including the transforming growth factor-β, 1-3 bone morphogenetic proteins, [4][5][6][7][8][9] fibroblast growth factor-2 (FGF-2), 10,11 connective tissue growth factor, 12 specific transcription factors (members of the SOX family, ZNF145) [13][14][15][16] and other molecules such as chondromodulin 1 and cartilagederived morphogenetic protein 1. 17,18 However, complete cartilage repair has not been reported so far with these factors,…”

Gene therapy for chondral and osteochondral regeneration: is the future now?

“…More than 50 adenovirus serotypes are available for gene therapy and serotype 5 (Ad5) has been the mostly used in both in vitro and in vivo studies. Adenovirus is used to transfer GF genes (TGF-β, FGF-2, IGF-1, BMPs and Growth and differentiation factor 5, GDF-5) into cells [8,20,25,[40][41][42][43][44][45][46][47][48][49]. Genes, in encapsuled viral [24] vector, can be injected directly in vivo [50,51] or through decalcified cortical bone matrix (DCBM) as scaffold that contains the viral particles [52].…”