Can PPARδ agonist increase cell yield of nucleus pulposus progenitor cells positive for angiopoietin-1 receptor (= TIE2) after cell isolation?
Introduction: Nucleus pulposus progenitor cells (NPPC), Tie2+ cells (positive for angiopoietin receptor), which possess multi-lineage differential potential is a potential cell population for cell therapy. However, the number of Tie2+ cells in NP is extremely limited. Referring to the recent research of Tie2+ hematopoietic stem cells we attempted to increase the Tie2+ cell sub-population in nucleus pulposus cells (NPC) by PPARδ agonist treatment and increasing mitophagy. Methods: Cells were isolated from fresh human IVD tissue from spinal surgery with written consent. The passage 1 human NP cells were cultured in low glucose Dulbecco’s Modified Eagle’s Medium media containing PPARδ agonist (GW501516, Sigma), i.e., 25 µM, or vehicle control (N = 2 donors). After 10 days NP, the Tie2 marker expression was then detected by flow cytometry cells and relative gene expression was determined by real-time qPCR, i.e. at ACAN, col1, col2, and PTEN-induced kinase 1 (PINK1). Results: PPARδ-agonist-treated NP population had ~3 times more Tie2+ cells and PINK1 gene expression tended to be higher than in the vehicle control group. Conclusion: PPARδ agonist possibly increases the Tie2+ cell population in NPC by increasing mitophagy similar to hematopoietic stem cells.