Abstract
Use of human induced pluripotent stem cells (h-iPSCs) for bone tissue engineering is most appealing, because h-iPSCs are an inexhaustible source of osteocompetent cells. The present study investigated the contribution of undifferentiated h-iPSCs and elucidated aspects of the underlying mechanism(s) of the involvement of these cells to new bone formation. Implantation of undifferentiated h-iPSCs seeded on coral particles in ectopic sites of mice resulted in expression of osteocalcin and DMP-1, and in mineral content similar to that of the murine bone. The number of the implanted h-iPSCs decreased with time and disappeared by 30 days post-implantation. In contrast, expression of the murine osteogenic genes at day 15 and 30 post-implantation provided, for the first time, evidence that the implanted h-iPSCs affected the observed outcomes via paracrine mechanisms. Supporting evidence was provided because supernatant conditioned media from h-iPSCs (h-iPSC CM), promoted the osteogenic differentiation of human mesenchymal stem cells (h-MSCs) in vitro. Specifically, h-iPSC CM induced upregulation of the BMP-2, BMP-4 and BMP-6 genes, and promoted mineralization of the extracellular matrix. Given the current interest in the use of h-iPSCs for regenerative medicine applications, our study contributes new insights into aspects of the mechanism underlying the bone promoting capability of h-iPSCs.
Highlights
Availability of stem cells, and the potential of inducing them towards the osteogenic lineage, are motivating the exploration and development of custom-tailored, cell-containing implants known as “bioengineered bone constructs”[1,2]
When analyzed by flow cytometry, 85% human iPSCs (h-iPSCs) were positive for the TRA 1-81 and SSEA4 pluripotency markers (Supplemental Data section Fig. S1, Frame D)
Ten weeks after the h-iPSCs VAX1024 graft into the quadriceps of rat, teratomas were formed, exhibiting all three embryonic germ layers (Supplemental Data section Fig. S1, Frames G to K). These results demonstrate that newly derived h- iPSCs closely resemble undifferentiated human embryonic stem cells
Summary
Availability of stem cells, and the potential of inducing them towards the osteogenic lineage, are motivating the exploration and development of custom-tailored, cell-containing implants known as “bioengineered bone constructs”[1,2] Such approaches are promising alternatives to physiological limitation, for example, the fact that endogenous regenerative mechanisms do not suffice to repair extensive segmental long-bone defects in humans. An alternative approach aiming at alleviating the drawbacks of BM-MSCs and enhancing the bone forming ability of cell-containing constructs is to substitute pluripotent stem cells for BM-MSCs in these implants These cells opened new avenues in the field of regenerative medicine because they have an unlimited capacity of self-renewal and can be induced to differentiate into various cell types present in adult mammals (for review[15]). Identification of the mediators responsible for the observed iPSCs biological functions was achieved using biochemical analyses at the molecular level
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
