Cholesterol 24S-Hydroxylase overexpression increases the lipid droplet formation of human umbilical cord mesenchymal stem cells but does not affect adipocyte differentiation.

Dysregulation of the adipo-osteogenic differentiation balance of mesenchymal stem cells (MSCs), which are common progenitor cells of adipocytes and osteoblasts, has been associated with many pathophysiologic diseases, such as obesity, osteopenia, and several neurodegenerative disorders. Growing evidence suggests that lipid metabolism is crucial for maintaining stem cell homeostasis and cell differentiation, however, the detailed underlying mechanisms are largely unknown. In this study, we demonstrate that CYP46A1 genes are key determinants of MSC increasing lipid droplet formation. Brain cholesterol is synthesized in situ and cannot cross the blood-brain barrier: to be exported from the central nervous system into the blood circuit, excess cholesterol must be converted to 24S-hydroxycholesterol by the cholesterol 24-hydroxylase encoded by the CYP46A1 gene. To address this issue, we used an adenoassociated virus (AAV) gene transfer strategy to increase CYP46A1 expression in order to investigate the consequences on the human mesenchymal stem cell (hU-MSCs). CYP46A1 expression was assessed with Western blotting and quantitative reverse transcription PCR. We found that CYP46A1 expression was increased during adipogenesis, and treatment with exogenous CYP46A1 increased adipogenesis. Thus, we hypothesize that CYP46A1 overexpression in hU-MSCs would significantly enhance cholesterol turnover in the brain of hypoxic-ischemic encephalopathy (HIE). CYP46A1 can potentially serve as a specific target to modify the therapeutic and biological effects of hU-MSCs on HIE patients.