Oligodendrocyte progenitor proliferation is disinhibited following traumatic brain injury in leukemia inhibitory factor heterozygous mice

Abstract

Traumatic brain injury (TBI) is a significant problem that affects over 800,000 children each year. As cell proliferation is disturbed by injury and required for normal brain development, we investigated how a pediatric closed head injury (CHI) would affect the progenitors of the subventricular zone (SVZ). Additionally, we evaluated the contribution of leukemia inhibitory factor (LIF) using germline LIF heterozygous mice (LIF Het), as LIF is an injury-induced cytokine, known to influence neurogenesis and gliogenesis. CHIs were performed on P20 LIF Het and wild-type (WT) mice. Ki-67 immunostaining and stereology revealed that cell proliferation increased ~250% in injured LIF Het mice compared to the 30% increase observed in injured WT mice at 48-hr post-CHI. OLIG2+ cell proliferation increased in the SVZ and white matter of LIF Het injured mice at 48-hr recovery. Using an 8-color flow cytometry panel, the proliferation of three distinct multipotential progenitors and early oligodendrocyte progenitor cell proliferation was significantly increased in LIF Het injured mice compared to WT injured mice. Supporting its cytostatic function, LIF decreased neurosphere progenitor and oligodendrocyte progenitor cell proliferation compared to controls. In highly enriched mouse oligodendrocyte progenitor cell cultures, LIF increased phospho-protein kinase B after 20 min and increased phospho-S6 ribosomal protein at 20 and 40 min of exposure, which are downstream targets of the mammalian target of rapamycin pathway. Altogether, our data provide new insights into the regulatory role of LIF in suppressing neural progenitor cell proliferation and, in particular, oligodendrocyte progenitor cell proliferation after a mild TBI.

Analyzing mouse neural stem cell and progenitor cell proliferation using EdU incorporation and multicolor flow cytometry

“…These GRPs produced both “type 1” astrocytes and oligodendrocytes. We have used this method extensively to define how specific growth factors, receptors and injuries affect the composition of the SVZ ( Buono et al., 2015a ; Chen et al., 2015 ; Chidambaram et al., 2020 ; Frondelli and Levison, 2021 ; Frondelli et al., 2021 ; Goodus et al., 2015 ; Kumari et al., 2020 ; Ziegler et al., 2014 , 2019 ). To further evaluate the proliferation of these neural progenitors the incorporation of the thymidine analogue ethenyl deoxyuridine (EdU) was added to the flow cytometry protocol which is readily compatible with flow cytometry ( Buck et al., 2008 ).…”

“…ND = not determined. c Note: See Frondelli et al. (2021 ) (EdU was administered as two intraperitoneal (IP) injections).…”

“…2012;34(5):449-62. https://doi.org/10.1159/000345155 and Frondelli et al. (2021) Journal of Neuroscience Research, https://doi.org/10.1016/j.ymeth.2017.08.015 .…”