Background: To clarify the role of apolipoprotein D (Apod) in alleviating glucocorticoid-induced osteogenesis suppression in bone marrow mesenchymal stem cells (MSCs) via the PI3K/Akt pathway, thus influencing the progression of osteoporosis (OP).

Methods: Osteogenesis in MSCs was induced by dexamethasone (DEX) stimulation. Dynamic expressions of Apod in MSCs undergoing osteogenesis for different time points were determined by qRT-PCR. Relative levels of osteogenesis-associated genes, including ALP, RUNX2, and Osterix, in DEX-induced MSCs overexpressing Apod or not were examined. Moreover, the protein level of RUNX2, ALP, and Osterix; ALP activity; and mineralization ability influenced by Apod in osteogenic MSCs were assessed. At last, the potential influences of Apod on the PI3K/Akt pathway were identified through detecting the expression levels of PI3K and Akt in MSCs by Western blot.

Results: Apod was time-dependently upregulated in MSCs undergoing osteogenesis. DEX induction downregulated ALP, RUNX2, and Osterix and attenuated ALP activity and mineralization ability in MSCs undergoing osteogenesis, which were partially reversed by overexpression of Apod. In addition, Apod overexpression upregulated the reduced levels of PI3K and Akt in DEX-induced MSCs.

Conclusion: Apod alleviates glucocorticoid-induced osteogenesis suppression in MSCs via the PI3K/Akt pathway, thus protecting the progression of OP.