Nanotheranostics 2018; 2(2):128-143. doi:10.7150/ntno.23354

Research Paper

High-density human mesenchymal stem cell rings with spatiotemporally-controlled morphogen presentation as building blocks for engineering bone diaphyseal tissue

Samuel Herberg1,6, Daniel Varghai1, Yuxuan Cheng1, Anna D. Dikina1, Phuong N. Dang1, Marsha W. Rolle2, Eben Alsberg1,3,4,5✉

1. Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA.
2. Department of Biomedical Engineering, Worcester Polytechnic Institute, Worcester, MA, USA.
3. Department of Orthopaedic Surgery, Case Western Reserve University, Cleveland, OH, USA.
4. National Center for Regenerative Medicine, Division of General Medical Sciences, Case Western Reserve University, Cleveland, OH, USA.
5. School of Dentistry, Kyung Hee University, Seoul, South Korea.
6. Current address: Wake Forest Institute for Regenerative Medicine, Wake Forest School of Medicine, Winston-Salem, NC, USA.

Abstract

Emerging biomimetic tissue engineering strategies aim to partially recapitulate fundamental events that transpire during embryonic skeletal development; namely, cellular self-organization and targeted morphogenetic pathway activation. Here, we describe self-assembled, scaffold-free human mesenchymal stem cell (hMSC) rings featuring microparticle-mediated presentation of transforming growth factor-β1 (TGF-β1) and bone morphogenetic protein-2 (BMP-2). We tested the hypothesis that spatiotemporally-controlled dual presentation of TGF-β1 and BMP-2 is superior in modulating in vitro endochondral ossification of high-density cellular constructs compared to single morphogen delivery. hMSC rings were engineered by seeding cells with microparticles presenting (1) TGF-β1, (2) BMP-2, or (3) TGF-β1 + BMP-2 in custom agarose wells to facilitate self-assembly within 2 d, followed by horizontal culture on glass tubes for 5 weeks. At day 2, hMSC rings across groups revealed homogenous cellular organization mimetic of early mesenchymal condensation with no evidence of new matrix or mineral deposition. Significant early chondrogenic and osteogenic priming occurred with TGF-β1 + BMP-2 presentation compared to single morphogen-loaded groups. By week 5, TGF-β1-loaded hMSC rings had undergone chondrogenesis, while presentation of BMP-2 alone or in conjunction with TGF-β1 stimulated chondrogenesis, chondrocyte hypertrophy, and osteogenesis indicative of endochondral ossification. Importantly, tissue mineralization was most compelling with TGF-β1 + BMP-2 loading. Lastly, hMSC ring 'building blocks' were shown to efficiently fuse into tubes within 6 d post self-assembly. The resulting tubular tissue units exhibited structural integrity, highlighting the translational potential of this advanced biomimetic technology for potential early implantation in long bone defects.

Keywords: growth factors, TGF-β1, BMP-2, controlled delivery, microparticles, chondrogenesis, osteogenesis, mold, self-assembly, regenerative medicine

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How to cite this article:
Herberg S, Varghai D, Cheng Y, Dikina AD, Dang PN, Rolle MW, Alsberg E. High-density human mesenchymal stem cell rings with spatiotemporally-controlled morphogen presentation as building blocks for engineering bone diaphyseal tissue. Nanotheranostics 2018; 2(2):128-143. doi:10.7150/ntno.23354. Available from http://www.ntno.org/v02p0128.htm