Estradiol Promotes Myelin Repair in the Spinal Cord of Female Mice in a CXCR4 Chemokine Receptor-Independent Manner

In the adult central nervous system (CNS), myelin regeneration primarily occurs through the differentiation of oligodendrocyte progenitor cells into mature oligodendrocytes. In men, declining testosterone levels accelerate the progression of multiple sclerosis (MS), while in women, menopause worsens MS-related disability. We previously demonstrated that functional testes and testosterone are required for the spontaneous remyelination of a focal lysolecithin (LPC)-induced demyelinating lesion in the spinal cords of male mice. Testosterone-dependent myelin repair was dependent on the induction of the chemokine receptor CXCR4 in astrocytes that repopulated the lesion and on cooperation between androgen-receptor signaling and CXCR4 signaling. In the present study, we investigated whether ovaries and estradiol have a comparable key role in female mice. Ovariectomy prevents, the appearance of astrocytes, while treatment with estradiol enhances astrocyte numbers and promotes remyelination by oligodendrocytes within the LPC-demyelinated lesion. Unlike testosterone, estradiol did not induce CXCR4 expression, and its effects remained unaffected by the CXCR4 inhibitor AMD3100. As was seen with testosterone treatment, the presence of astrocytes and myelinating oligodendrocytes within the LPC lesion of estradiol-treated females prevented the incursion of Schwann cells. These findings highlight estradiol's crucial role in CNS remyelination in females, providing a strong rationale for estrogen-replacement therapy in estrogen-deficient and menopausal women with MS.