TITLE:
Application of Hypoxic Exposure Combined with Osteogenic Induction for the Enhancement of Multiple Osteoinductive Capabilities in Rat Mesenchymal Cells
AUTHORS:
Naoaki Saito, Hiroko Kato, Yosuke Akiba, Yuko Hara, Taku Kojima, Michiko Yoshizawa, Atsushi Ohazama, Takeyasu Maeda, Tadaharu Kobayashi, Kenji Izumi
KEYWORDS:
Osteogenesis, Hypoxia, Angiogenesis, Cell Recruitment, Mesenchymal Stem Cells
JOURNAL NAME:
Open Journal of Stomatology,
Vol.8 No.2,
February
26,
2018
ABSTRACT: Objective: The
enhancement of multiple functions, including osteogenesis, angiogenesis, and
cell recruitment, is required for efficient bone regeneration therapy.
Recently, special attention has been focused on the microenvironment of stem
cells to facilitate bone regeneration. Herein, we examined the effects of
various combinations of hypoxic conditions and osteogenic induction on rat
mesenchymal cells, to develop a specific protocol for enhancing the multiple
cellular functions beneficial to bone regeneration. Methods: Rat
mesenchymal cells, isolated from bone marrow, adipose tissue, and periodontal
ligament, were examined. The cells were cultured under varied conditions of O2 tension (hypoxia) and duration and timing of hypoxic exposure, with or without osteogenic induction. Consequently, four
different protocols were examined by measuring the gene expression
levels of Runx2, Vegfa, and Cxcl12,
indicating a capability for osteogenesis, angiogenesis, and cell recruitment, respectively. Finally, the mineralization ability
of the rat mesenchymal cells was assessed by quantitating their
calcified nodule formation. Results: The simultaneous application of
hypoxic exposure and osteogenic induction promoted Vegfa expression in all types of cells, but suppressed Runx2. In contrast, hypoxic preconditioning,
followed by osteogenic induction, did not increase the expression of these genes; in fact, Vegfa expression decreased significantly. Among the various protocols, 0.5% O2 exposure for 12 h after osteogenic induction exhibited the largest fold changes
of gene expression level, especially of Vegfa.
Hypoxic post-conditioning enhanced the formation of calcified nodules in
periodontal ligament-derived cells. Conclusion: Short-term hypoxic
exposure after osteogenic induction could be used to improve the efficiency of
mesenchymal cells for bone regeneration.