Leukemia Inhibitory Factor Is Required for Subventricular Zone Astrocyte Progenitor Proliferation and for Prokineticin-2 Production after a Closed Head Injury in Mice

Abstract

Astrogliosis is one of the hallmarks of brain injury, and after a mild injury activated astrocytes subserve neuroprotective and pro-regenerative functions. We previously found that the astroglial response to closed head injury (CHI) was blunted in mice that were haplodeficient in leukemia inhibitory factor (LIF); therefore, the goal of these studies was to determine if the delayed astrogliosis was due to decreased recruitment of subventricular zone (SVZ) progenitors. CHI's were performed on post-natal day 20 on LIF heterozygous (Het) and wild-type (WT) mice. At 48 h post-CHI, astrocyte progenitor proliferation within the SVZ increased *250% in WT mice but was reduced by *200% in LIF Het mice compared with sham controls. Using neurospheres to model the SVZ, LIF increased the percentage of proliferating astrocyte progenitors by 2-fold compared with controls but had no effect on neural stem cell proliferation. To rule out the involvement of other cytokines, 105 cytokines were analyzed using a multi-plex array and with targeted validation on injured LIF Het versus WT neocortex. Of the cytokines analyzed, only prokineticin-2 (ProK2) required LIF signaling. Correspondingly, LIF-treated neurospheres expressed higher levels of ProK2, the ProK1 and ProK2 receptors (ProKR1 and ProKR2). Using in situ hybridization, ProK2 messenger RNA (mRNA) was most abundant in neocortical neurons and highly expressed within the SVZ. However, in contrast to LIF, ProK2 decreased astrocyte progenitor proliferation 2-fold. Altogether, these data demonstrate that LIF is necessary for astrocyte progenitor proliferation after injury and reveal a new role for LIF as an essential regulator of the neurotrophic factor ProK2.

Intranasal Leukemia Inhibitory Factor Attenuates Gliosis and Axonal Injury and Improves Sensorimotor Function After a Mild Pediatric Traumatic Brain Injury

“…Using this mTBI model, we recently established that ProK2 messenger RNA and protein increase in the neocortex between 48 and 96 h after injury and that ProK2 induction requires intact LIF signaling. 24 ProK2, produced by neurons, has been shown to prevent neuronal cell death by inhibiting lipid peroxidation and ferroptosis after TBI. 25 …”

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

“…The authors concluded that LIF was not exerting a direct action on the oligodendrocytes, but rather that LIF was increasing the production and release of IGF‐1 from the macrophages, that was promoting the survival of the oligodendrocytes (Kerr & Patterson, 2005). Furthermore, arguing against an indirect mechanism, we used a PCR array to screen mRNAs for 85 growth factors and cytokines and did not find any that were differentially expressed by the injured LIF Het neocortex versus the WT injured cortex (Frondelli & Levison, 2021).…”

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 ).…”