Age-dependent effects of metformin on human oligodendrocyte lineage cell ensheathment capacity.
Metformin restores myelination potential of aged rat A2B5+ oligodendroglia (OL) progenitor cells and may enhance recovery in children with post-radiation brain injury. Human late progenitor cells (O4+A2B5+) have superior capacity to ensheath nanofibers compared to mature OLs, with cells from pediatric sources exceeding adults. In this study we assessed effects of metformin on ensheathment capacity of human adult and pediatric progenitors and mature OLs and relate differences to transcriptional changes.  A2B5+ progenitors and mature OLs, derived from surgical tissues by immune-magnetic separation, were assessed for ensheathment capacity in nanofiber plates over 2 weeks. Metformin (10µM every other day) was added to selected cultures. RNA was extracted from treated and control cultures after 2 days. For all ages, ensheathment by progenitors exceeded mature OLs.  Metformin enhanced ensheathment by adult donor cells but reduced ensheathment by pediatric cells. Metformin marginally increased cell death in pediatric progenitors. Metformin induced changes in gene expression distinct for each cell type. Adult progenitors showed up-regulation of pathways involved in process outgrowth and promoting lipid biosynthesis. Pediatric progenitors showed a relatively greater proportion of down- versus up-regulated pathways, these involved cell morphology, development, and synaptic transmission. Metformin induced AMPK activation in all cell types; AMPK inhibitor BML-275 reduced functional metformin effects only with adult cells. Our results indicate age and differentiation stage related differences of human OL lineage cells in response to metformin. Clinical trials for demyelinating conditions will indicate how these differences translate in vivo. Overall design: RNA was extracted from dissociated cultures of A2B5+ or A2B5- cells after two days in culture under control conditions or with addition of metformin. Bulk sequencing studies were conducted on 3 or 4 samples from each of the age groups