The Effect of Megakaryocytes and Platelets Derived from Human-Induced Pluripotent Stem Cells on Bone Formation

INTRODUCTION: Platelet-rich plasma (PRP) is drawing attention as a substance that can promote bone formation. The growth factors present in PRP are stable for a long time after freeze-drying. However, the effects of PRP are inconsistent, and its effects on bone union in spinal surgery remain controversial. The immortalized megakaryocyte cell lines (imMKCLs) derived from human-induced pluripotent stem cells (hiPSCs) have been developed to produce numerous stable and clinically functional platelets. In this study, growth factors present in freeze-dried hiPSC-derived imMKCLs and platelets (iPS-MK/Plts) were evaluated, and their ability to promote bone formation was examined using a rat lumbar artificial bone grafting model. METHODS: We prepared freeze-dried iPS-MK/Plts and quantified their growth factors by enzyme-linked immunosorbent assays. Surgical grafting of artificial bone to the lumbar transverse processes was performed in 8-week-old female rats, which were divided into two groups: artificial bone graft (control) and artificial bone graft plus freeze-dried iPS-MK/Plts (iPS group). Transplantation was performed only on the left side. Eight weeks after the surgery, we captured computed tomography images and compared bilateral differences in the bone volume of the graft site in each rat. We also compared the left side/right side bone volume ratio between the two groups. RESULTS: The freeze-dried iPS-MK/Plts contained numerous growth factors. While there was no significant increase in bone volume on the transplanted side than that on the non-grafted side in the control group, bone volume significantly increased on the transplanted side in the iPS group, as evidenced by augmented mean left/right bone volume ratio of the iPS group compared with that of the control group. But the new bone observed in the iPS group was histologically normal. CONCLUSIONS: Freeze-dried hiPSC-derived MKCLs and platelets contain several stable growth factors and have the potential for promoting new bone formation.