title: Crystal structures of CaSiO3polymorphs control growth and osteogenic differentiation of human mesenchymal stem cells on bioceramic surfaces.
abstract: The repair and replacement of damaged or diseased human bone tissue requires a stable interface between the orthopedic implant and living tissue. The ideal material should be both osteoconductive (promote bonding to bone) and osteoinductive (induce osteogenic differentiation of cells and generate new bone). Partially resorbable bioceramic materials with both properties are developed by expensive trial-and-error methods. Structure-reactivity relationships for predicting the osteoinductive properties of ceramics would significantly increase the efficiency of developing materials for bone tissue engineering. Here we propose the novel hypothesis that the crystal structure of a bioceramic controls the release rates, subsequent surface modifications due to precipitation of new phases, and thus, the concentrations of soluble factors, and ultimately, the attachment, viability and osteogenic differentiation of human Mesenchymal Stem Cells (hMSCs). To illustrate our hypothesis, we used two CaSiO3polymorphs, pseudo-wollastonite (psw, β-CaSiO3) and wollastonite (wol, α-CaSiO3) as scaffolds for hMSC culture. Polymorphs are materials which have identical chemical composition and stoichiometry, but different crystal structures. We combined the results of detailed surface characterizations, including environmental Scanning Electron Microscopy (SEM) back-scattered imaging, and spot-analysis and 2D elemental mapping by SEM-Energy Dispersive X-ray (SEM-EDX), High Resolution Transmission Electron Microscopy (HRTEM) and surface roughness analysis; culture medium solution analyses; and molecular/genetic assays from cell culture. Our results confirmed the hypothesis that the psw polymorph, which has a strained silicate ring structure, is more osteoinductive than the wol polymorph, which has a more stable, open silicate chain structure. The observations could be attributed to easier dissolution (resorption) of psw compared to wol, which resulted in concentration profiles that were more osteoinductive for the former. Thus, we showed that crystal structure is a fundamental parameter to be considered in the intelligent design of pro-osteogenic, partially resorbable bioceramics.
authors.affiliation: Materials Science Program, University of Wisconsin, Madison, WI53706, USA ; Department of Biologic and Materials Science, 1011 N. University Avenue, School of Dentistry, University of Michigan, Ann Arbor, MI 48109, USA.
authors.forename: Nianli
authors.initials: N
authors.lastname: Zhang
authors.affiliation: Department of Biomedical Engineering, University of Wisconsin, Madison, WI 53706, USA.
authors.forename: James A
authors.initials: JA
authors.lastname: Molenda
authors.affiliation: Department of Polymer Science, 170 University Avenue, Akron, OH 44325, USA. Tel: +1 330-972-5795.
authors.forename: Steven
authors.initials: S
authors.lastname: Mankoci
authors.affiliation: Department of Polymer Science, 170 University Avenue, Akron, OH 44325, USA. Tel: +1 330-972-5795.
authors.forename: Xianfeng
authors.initials: X
authors.lastname: Zhou
authors.affiliation: Materials Science Program, University of Wisconsin, Madison, WI53706, USA ; Department of Biomedical Engineering, University of Wisconsin, Madison, WI 53706, USA ; Department of Orthopedics and Rehabilitation, University of Wisconsin, Madison, WI 53706, USA ; Department of Pharmacology, University of Wisconsin, Madison, WI 53706, USA.
authors.forename: William L
authors.initials: WL
authors.lastname: Murphy
authors.affiliation: Department of Polymer Science, 170 University Avenue, Akron, OH 44325, USA. Tel: +1 330-972-5795.
authors.forename: Nita
authors.initials: N
authors.lastname: Sahai