title: Human Articular Cartilage Progenitor Cells Are Responsive to Mechanical Stimulation and Adenoviral-Mediated Overexpression of Bone-Morphogenetic Protein 2.
abstract: Articular cartilage progenitor cells (ACPCs) represent a new and potentially powerful alternative cell source to commonly used cell sources for cartilage repair, such as chondrocytes and bone-marrow derived mesenchymal stem cells (MSCs). This is particularly due to the apparent resistance of ACPCs to hypertrophy. The current study opted to investigate whether human ACPCs (hACPCs) are responsive towards mechanical stimulation and/or adenoviral-mediated overexpression of bone morphogenetic protein 2 (BMP-2). hACPCs were cultured in fibrin-polyurethane composite scaffolds. Cells were cultured in a defined chondro-permissive medium, lacking exogenous growth factors. Constructs were cultured, for 7 or 28 days, under free-swelling conditions or with the application of complex mechanical stimulation, using a custom built bioreactor that is able to generate joint-like movements. Outcome parameters were quantification of BMP-2 and transforming growth factor beta 1 (TGF-β1) concentration within the cell culture medium, biochemical and gene expression analyses, histology and immunohistochemistry. The application of mechanical stimulation alone resulted in the initiation of chondrogenesis, demonstrating the cells are mechanoresponsive. This was evidenced by increased GAG production, lack of expression of hypertrophic markers and a promising gene expression profile (significant up-regulation of cartilaginous marker genes, specifically collagen type II, accompanied by no increase in the hypertrophic marker collagen type X or the osteogenic marker alkaline phosphatase). To further investigate the resistance of ACPCs to hypertrophy, overexpression of a factor associated with hypertrophic differentiation, BMP-2, was investigated. A novel, three-dimensional, transduction protocol was used to transduce cells with an adenovirus coding for BMP-2. Over-expression of BMP-2, independent of load, led to an increase in markers associated with hypertropy. Taken together ACPCs represent a potential alterative cell source for cartilage tissue engineering applications.
authors: AO Research Institute Davos, AO Foundation, Clavadelerstrasse 8, 7270, Davos Platz, Switzerland; Cardiff School of Biosciences, Cardiff University, CF10 3 AX, Cardiff, Wales, United Kingdom.
authors: Alexander J
authors: AJ
authors: Neumann
authors: AO Research Institute Davos, AO Foundation, Clavadelerstrasse 8, 7270, Davos Platz, Switzerland; Cardiff School of Biosciences, Cardiff University, CF10 3 AX, Cardiff, Wales, United Kingdom.
authors: Oliver F W
authors: OF
authors: Gardner
authors: Cardiff School of Biosciences, Cardiff University, CF10 3 AX, Cardiff, Wales, United Kingdom.
authors: Rebecca
authors: R
authors: Williams
authors: AO Research Institute Davos, AO Foundation, Clavadelerstrasse 8, 7270, Davos Platz, Switzerland.
authors: Mauro
authors: M
authors: Alini
authors: Swansea School of Medicine, Swansea University, SA2 8PP, Swansea, Wales, United Kingdom.
authors: Charles W
authors: CW
authors: Archer
authors: AO Research Institute Davos, AO Foundation, Clavadelerstrasse 8, 7270, Davos Platz, Switzerland.
authors: Martin J
authors: MJ
authors: Stoddart
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D055396:Bone Morphogenetic Protein 2 / Q000235:genetics*; D002358:Cartilage, Articular / Q000166:cytology*; D002478:Cells, Cultured; D020219:Chondrogenesis; D024043:Collagen Type II / Q000378:metabolism; D005337:Fibrin / Q000737:chemistry; D005786:Gene Expression Regulation; D005822:Genetic Vectors / Q000235:genetics; D006025:Glycosaminoglycans / Q000378:metabolism; D006801:Humans; D013234:Stem Cells / Q000166:cytology* / Q000378:metabolism; D013314:Stress, Mechanical; D054457:Tissue Scaffolds / Q000737:chemistry; D014161:Transduction, Genetic; D053773:Transforming Growth Factor beta1 / Q000378:metabolism; D015854:Up-Regulation
chemical_list: C525718:BMP2 protein, human; D055396:Bone Morphogenetic Protein 2; D024043:Collagen Type II; D006025:Glycosaminoglycans; D053773:Transforming Growth Factor beta1; D005337:Fibrin