Directed Differentiation of Human Induced Pluripotent Stem Cells Toward Bone and Cartilage: In Vitro Versus In Vivo Assays

Abstract

The ability to differentiate induced pluripotent stem cells (iPSCs) into committed skeletal progenitors could allow for an unlimited autologous supply of such cells for therapeutic uses; therefore, we attempted to create novel bone-forming cells from human iPSCs using lines from two distinct tissue sources and methods of differentiation that we previously devised for osteogenic differentiation of human embryonic stem cells, and as suggested by other publications. The resulting cells were assayed using in vitro methods, and the results were compared with those obtained from in vivo transplantation assays. Our results show that true bone was formed in vivo by derivatives of several iPSC lines, but that the successful cell lines and differentiation methodologies were not predicted by the results of the in vitro assays. In addition, bone was formed equally well from iPSCs originating from skin or bone marrow stromal cells (also known as bone marrow-derived mesenchymal stem cells), suggesting that the iPSCs did not retain a "memory" of their previous life. Furthermore, one of the iPSC-derived cell lines formed verifiable cartilage in vivo, which likewise was not predicted by in vitro assays. STEM CELLS

Skeletal stem cells

“…Many studies have aimed at differentiating ESCs or iPSCs into skeletal tissues [e.g. Harkness et al (2011);Mahmood et al (2010)]; several have shown that putative PSC-generated skeletal progenitors could establish histology-proven bone in vivo, but failed to recreate a BM cavity and stroma, and therefore SSCs (Harkness et al, 2011;Hong et al, 2014;Mahmood et al, 2010;Phillips et al, 2014). This finding resonates with the current inability to generate genuine HSCs while generating hematopoietic cells from PSCs (Kaufman, 2009).…”

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

“…hiPSCs have been differentiated into OBs on 2D plastic and 3D CaP scaffolds7891011 and produced dense bone matrix on 3D decellurized bone scaffolds in a perfusion bioreactor12. OCs have been generated from hiPSCs on 2D plastic and on mineralized substrates by embryonic body (EB) formation13 and by co-culturing with stromal cells14.…”

Injectable calcium phosphate with hydrogel fibers encapsulating induced pluripotent, dental pulp and bone marrow stem cells for bone repair

“…The two iPSC-MSC cell lines were seeded on the HA/ TCP scaffolds and subcutaneously implanted into immunocompromised mice. Bone of equal quality and frequency was made from both SF- or BMSC-derived iPSC-MSCs, suggesting that iPSCs did not retain any ‘memory’ of their origin [53]. Similarly, another research generated rhesus iPSCs from rhesus BMSCs (rhBMSCs), skin fibroblasts, and CD34+ cells and then differentiated the iPSCs into MSC-like cells before seeding on HA/TCP particles [54].…”