Introduction Myelin wraps around axons, providing rapid neuronal conduction and metabolic support. Failure of repair following myelin damage (demyelination) results in axonal degeneration and eventually neuronal loss, which is the key component in demyelinating diseases such as multiple sclerosis (MS), and this also contributes to the pathogenesis of Alzheimer’s disease (AD).

 In the central nervous system (CNS), myelin is formed by oligodendrocytes. Regeneration of myelin (remyelination) involves the activation and maturation of the oligodendrocyte progenitor cells (OPCs), the crucial cellular processes recapitulating the lineage progression of developmental myelination. Isoflavones, as plant-derived compounds with a structural similarity to estrogen, interact with estrogen receptors (ERs) and play a significant role in the biology and function of oligodendrocytes. It has been shown that isoflavones and estrogen have a positive influence on OPC proliferation and differentiation, promoting myelin repair¹. This study investigated whether isoflavones promote the generation of human induced pluripotent stem cell (hiPSC)-derived OPCs and enhances remyelination in rodent models.

Methods All animal procedures accorded with the UK Animals (Scientific Procedures) Act 1986 Amendment Regulations 2012 following ethical review by the Animal Welfare and Ethical Review Body (AWERB). Primary OPCs were isolated from cerebral cortices of neonatal Sprague-Dawley rats (P2–3) killed by pentobarbital overdose (n=3−4 independent cultures). Organotypic cerebellar slices were prepared from P4–8 rat pups (n=3). For in vivo studies, focal demyelination was induced in the ventral spinal cord of anaesthetized C57BL/6 mice^1,2 (9–10-month-old; n=4−6/group) via 1% lysolecithin injection; buprenorphine was administered for analgesia. Animals were treated with puerarin or calycosin (100 or 80mg/kg i.p.) or vehicle daily for 7 days post-lesion. iPSC-OPCs were generated according to Fossati protocol³. Mitochondrial function was assessed via Seahorse extracellular flux analysis. Data are presented as mean ± S.E.M. Statistical significance was determined using unpaired Student’s t-test or one-way ANOVA.

Results We have shown that puerarin treatment significantly increases the differentiation of iPSC-derived O4+ pre-oligodendrocytes. It promotes rat OPC proliferation with an increased mitochondrial activity. In ex vivo cerebellar slices, puerarin (200μM) significantly improved myelination and remyelination following lysolecithin-induced damage. In vivo, puerarin treatment in mice (9 months) significantly increased the density of Olig2+ lineage cells and CC-1+ mature oligodendrocytes within lesions compared to controls¹. Recently, we have found that calycosin, another traditional Chinese isoflavone, known for its antioxidant and anti-inflammatory properties, promotes OPC proliferation which is indicated by an increased percentage of Ki67+ cells in Olig2+ lineage cells, and differentiation which is indicated as increased O4+ and MBP+ cell number (p <0.05).  Calycosin also increases remyelination ex vivo (p <0.05) and in vivo (p <0.05), similarly to puerarin.

Conclusion Our findings suggest that isoflavones are beneficial to oligodendrocyte lineage progression and myelin repair, with a potential to be developed into preventive or therapeutic agents for CNS diseases associated with myelin damage.