The effect of triiodothyronine on maturation and differentiation of oligodendrocyte progenitor cells during remyelination following induced demyelination in male albino rat

• Demyelination of corpus callosum was induced by two weeks of cuprizone ingestion.
• T3 increased expression of MBP and PLP gene and myelinated axons compared to saline.
• T3 directs progenitors toward oligodendrocytes maturation.
• This was especially evident after three weeks of cuprizone withdrawal.

Demyelination was induced by two weeks cuprizone treatment. Rats of +ve control and triiodothyronine (T3) then received three subcutaneous injections of either saline or T3 day after day and sacrificed at the end of the third and fifth weeks. Animals in −ve control group received only standard rodent chow. After one week of cuprizone withdrawal the corpus callosum in +ve control and T3 treated rats was still demyelinated as revealed by MBP immunohistochemistry. The assay of PLP gene showed significant increase of T3 treated group compared to both the −ve control and +ve control groups. After three weeks, significant improvement in myelination was detected in T3-treated group compared to +ve control as detected by both MBP immunohistochemistry and electron microscopy. After one week of cuprizone withdrawal, PDGFRα positive cells and gene expression showed significant increase in +ve control and T3-treated groups as compared to −ve control with insignificant difference in between the former two groups. After three weeks of cuprizone withdrawal, PDGFRα positive cells in T3-treated and +ve control groups decreased to the control levels. These results suggest that T3 was effective in improving remyelination when administered during acute phase and might direct progenitor lineage toward oligodendrocytes.

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