Delivery of platelet-derived growth factor as a chemotactic factor for mesenchymal stem cells by bone-mimetic electrospun scaffolds

• Published in: PloS one 2012-07, Vol.7 (7), p.e40831
• Main Authors: Phipps, Matthew C, Xu, Yuanyuan, Bellis, Susan L
• Format: Article
• Language: English
• Subjects: Adhesion; Adsorption; Adsorption - drug effects; Animals; Assaying; Biocompatibility; Biological activity; Biological products; Biology; Biomaterials; Biomedical materials; Biomimetic Materials - pharmacology; Biophysics; Bone and Bones - drug effects; Bone biomaterials; Bone healing; Bone marrow; Bone morphogenetic protein 2; Bone morphogenetic proteins; Cascades; Cattle; Cell migration; Cell Migration Assays; Cell Proliferation - drug effects; Chemokines; Chemotactic factors; Chemotactic Factors - pharmacology; Chemotaxis; Chemotaxis - drug effects; Collagen; Collagen (type I); Collagen Type I - pharmacology; Collagens; Comparative analysis; Controlled release; CXCL16 protein; Cytokines; Durapatite - pharmacology; Electrospinning; Fluorescence; Green Fluorescent Proteins - metabolism; Growth factors; Humans; Hydroxyapatite; Integrins; Mesenchymal stem cells; Mesenchymal Stromal Cells - cytology; Mesenchyme; Mitogens - pharmacology; Nanoparticles - chemistry; Physiology; Platelet-derived growth factor; Platelet-derived growth factor BB; Polycaprolactone; Polyesters - pharmacology; Proteins; Proto-Oncogene Proteins c-sis - pharmacology; RANTES; Reference Standards; Scaffolds; Signaling; Stem cells; Substrates; Sustained release; Time Factors; Tissue engineering; Tissue Engineering - methods; Tissue Scaffolds - chemistry
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0040831

The recruitment of mesenchymal stem cells (MSCs) is a vital step in the bone healing process, and hence the functionalization of osteogenic biomaterials with chemotactic factors constitutes an important effort in the tissue engineering field. Previously we determined that bone-mimetic electrospun scaffolds composed of polycaprolactone, collagen I and nanohydroxyapatite (PCL/col/HA) supported greater MSC adhesion, proliferation and activation of integrin-related signaling cascades than scaffolds composed of PCL or collagen I alone. In the current study we investigated the capacity of bone-mimetic scaffolds to serve as carriers for delivery of an MSC chemotactic factor. In initial studies, we compared MSC chemotaxis toward a variety of molecules including PDGF-AB, PDGF-BB, BMP2, and a mixture of the chemokines SDF-1α, CXCL16, MIP-1α, MIP-1β, and RANTES. Transwell migration assays indicated that, of these factors, PDGF-BB was the most effective in stimulating MSC migration. We next evaluated the capacity of PCL/col/HA scaffolds, compared with PCL scaffolds, to adsorb and release PDGF-BB. We found that significantly more PDGF- BB was adsorbed to, and subsequently released from, PCL/col/HA scaffolds, with sustained release extending over an 8-week interval. The PDGF-BB released was chemotactically active in transwell migration assays, indicating that bioactivity was not diminished by adsorption to the biomaterial. Complementing these studies, we developed a new type of migration assay in which the PDGF-BB-coated bone-mimetic substrates were placed 1.5 cm away from the cell migration front. These experiments confirmed the ability of PDGF-BB-coated PCL/col/HA scaffolds to induce significant MSC chemotaxis under more stringent conditions than standard types of migration assays. Our collective results substantiate the efficacy of PDGF-BB in stimulating MSC recruitment, and further show that the incorporation of native bone molecules, collagen I and nanoHA, into electrospun scaffolds not only enhances MSC adhesion and proliferation, but also increases the amount of PDGF-BB that can be delivered from scaffolds.