Human iPSC-derived osteoblasts and osteoclasts together promote bone regeneration in 3D biomaterials.

Ok Hee Jeon,Qiaozhi Lu,Ricardo A Feldman,Leelamma M Panicker,Jennifer H Elisseeff,Jeremy J Chae

doi:10.1038/srep26761

Abstract

Bone substitutes can be designed to replicate physiological structure and function by creating a microenvironment that supports crosstalk between bone and immune cells found in the native tissue, specifically osteoblasts and osteoclasts. Human induced pluripotent stem cells (hiPSC) represent a powerful tool for bone regeneration because they are a source of patient-specific cells that can differentiate into all specialized cell types residing in bone. We show that osteoblasts and osteoclasts can be differentiated from hiPSC-mesenchymal stem cells and macrophages when co-cultured on hydroxyapatite-coated poly(lactic-co-glycolic acid)/poly(L-lactic acid) (HA–PLGA/PLLA) scaffolds. Both cell types seeded on the PLGA/PLLA especially with 5% w/v HA recapitulated the tissue remodeling process of human bone via coupling signals coordinating osteoblast and osteoclast activity and finely tuned expression of inflammatory molecules, resulting in accelerated in vitro bone formation. Following subcutaneous implantation in rodents, co-cultured hiPSC-MSC/-macrophage on such scaffolds showed mature bone-like tissue formation. These findings suggest the importance of coupling matrix remodeling through osteoblastic matrix deposition and osteoclastic tissue resorption and immunomodulation for tissue development.

Highlights

Bone grafting is required to facilitate repair and regeneration of bone defects resulting from severe fracture in elderly osteoporosis patients, trauma, tumor ablation, or congenital abnormalities
Differentiation of osteoblasts and osteoclasts from Human induced pluripotent stem cells (hiPSC). hiPSCs cultured in suspension as embryoid body (EB) for 1 week differentiated into mesenchymal precursor cells after 10 days on gelatin-coated tissue culture plates
HiPSC-mesenchymal stem cells (MSCs) displayed bone-specific alkaline phosphatase (ALP), calcium deposition, and up-regulation of runt-related transcription factor 2 (RUNX2), type I and X collagen (COLI and COLX), and osteocalcin (OCN) genes during 14 days of monolayer culture (Fig. S1C). hiPSC-MSCs grown for 28 days in 3D micromass culture or monolayer culture under chondrogenic or adipogenic conditions, respectively, produced proteoglycans and accumulated lipid with up-regulation of SOX-9 and Aggrecan (Fig. S1D) as well as gene expression of fatty acid binding protein (FABP), lipoprotein lipase (LPL), and CCAAT-enhancer-binding proteins (C/EBPα) (Fig. S1E)

Summary

Introduction

Bone grafting is required to facilitate repair and regeneration of bone defects resulting from severe fracture in elderly osteoporosis patients, trauma, tumor ablation, or congenital abnormalities. Most of the current strategies in bone tissue engineering involve the cultivation of osteoblasts (OB) derived from human bone marrow mesenchymal stem cells (MSCs) on 3D alloplastic materials (primarily calcium phosphate, CaP) prior to re-implantation[3]. This approach fails to emulate physiological bone regeneration involving a well-orchestrated series of cytokines and regulatory molecules secreted from immune cells, including monocytes, macrophages, and osteoclasts (OC). We first differentiated hiPSC-derived MSCs and macrophages into osteogenic and osteoclastogenic lineages, respectively, and established a 3D model of human bone by co-culturing these cells within HA-based scaffolds. This study offers new therapeutic approaches to treat bone defects by engineering personalized and functional bone substitutes that retain intrinsic osteogenic and remodeling capacity along with immunomodulatory signaling to promote regeneration

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