This in vivo mouse study reports that systemic retinol administration promotes neural stem cell self-renewal and oriented development while downregulating certain retinoic acid receptor genes in the brain.

Modulating retinol/RA signaling could potentially stimulate neural regeneration pathways relevant to Parkinson's disease, but the work is preliminary with no PD models, limited mechanistic insight, and unclear safety or translational relevance.

Since our previous studies have indicated retinol promotes self-renewal of embryonic stem cells in vitro culture, we speculate that retinol may be directly involved in regulating adult stem cell self-renewal or developmental function in vivo. Vitamin A or retinoic acid (RA) solution was first injected into the abdominal cavities of mice, and then self-renewal and development marker gene expressions were investigated. The in vivo effects of retinol and RA on RA receptor expressions were further examined. The results showed that retinol not only significantly promotes self-renewal of neural stem cells in vivo but also induces orientational development of neural stem cells in vivo and significantly downregulates the expression of some RA receptor gene expression in the brain. This study provides experimental and theoretical bases for elucidating the regulation mechanism of retinol-mediated cell development in vivo, especially in brain, and the development of therapeutic drugs for neurodegenerative disorders including Alzheimer's disease, Parkinson's disease, Amyotrophic lateral sclerosis, Multiple sclerosis, and Huntington's disease.