Improved Stem Cell-Derived Motoneuron Survival, Migration, Sprouting, and Innervation with Enhanced Expression of Polysialic Acid

Abstract

Motoneurons (MNs) derived from mouse embryonic stem cells (ESCs) begin to express low levels of polysialic acid (PSA) at the time when they acquire an ability to migrate and extend neurites. PSA is known to promote cell migration and process outgrowth/guidance in the developing nervous system. To test if experimentally enhanced expression of PSA would augment these cellular events, the PSA-synthesizing polysialyltransferase was introduced into ESCs. In culture, the resulting higher PSA expression specifically increased neurite outgrowth and cell migration from differentiated embryoid bodies. In addition, the MN population obtained after sorting for HB9::GFP expression showed enhanced survival as well as extensive neurite outgrowth. Following transplantation of ESC-derived MNs into an adult sciatic nerve devoid of endogenous axons, the PSA augmentation increased the numbers of axons growing toward the denervated muscles. Migration of some transplanted cells inside the nerve toward muscle was also enhanced. Moreover, higher PSA expression selectively affected target innervation. It produced greater numbers of neuromuscular junctions in a predominantly fast twitch muscle and had no effect in a slow twitch muscle. These findings suggest that engineering of PSA expression in ESC could serve as an enhancement for MN cell therapy.

Effects of the Genetic Depletion of Polysialyltransferases on the Structure and Connectivity of Interneurons in the Adult Prefrontal Cortex

“…Interestingly, similar effects on dendritic structure have been found in motor neurons of polySia-deficient NCAM −/− mice, which exhibit a reduction in their dendritic field (Franz et al, 2005). Conversely, the enhancement of polySia expression increases neurite outgrowth in motoneurons derived from mouse embryonic stem cells (ESCs; El Maarouf et al, 2015). Future experiments should explore this putative effect of polySia on neuritogenesis by studying the structure of the dendritic arbor of interneurons during early postnatal development.…”

Moving Stem Cells to the Clinic: Potential and Limitations for Brain Repair

“…Overexpression of PSA in dopamine precursors significantly increased axonal growth of tyrosine hydroxylase positive fibers into the dopamine-depleted striatum, which was correlated with more efficient amelioration of the Parkinsonian phenotype in these animals (Battista et al, 2014) (Figure 2C). In a related approach, spinal motorneuron precursors overexpressing PSA transplanted into the lesioned sciatic nerve extended axons in higher numbers towards the denervated muscle (El Maarouf et al, 2014). A recent strategy for PSA addition was developed that does not require the genetic manipulation of the target cell and relies on direct exposure of purified enzyme and substrate, a technology suitable for increasing PSA in various cell types and tissues (El Maarouf et al, 2012).…”