Umbilical cord-derived mesenchymal stromal cells immunomodulate and restore actin dynamics and phagocytosis of LPS-activated microglia via PI3K/Akt/Rho GTPase pathway

Abstract

Background: Microglia are the immune cells in the central nervous system constantly surveying their environment and reacting to various injuries. Activated microglia may cause impaired synaptic plasticity, therefore modulating and restoring them to more neutral phenotype is crucial to counteract a pro-inflammatory, neurotoxic state. In this study, we focused on elucidating whether human umbilical cord (UC) tissue-derived mesenchymal stromal cells (MSCs) can exert immunomodulatory effect and change the phenotype of activated microglia. Methods: Primary culture of microglia was activated by lipopolysaccharide (LPS) and was co-cultured with three lots of MSCs. We investigated immunomodulation, actin dynamics and phagocytic capacity of activated microglia, and examined change of Rho GTPase in microglia as the mechanism. Results: MSCs suppressed the expression of IL-1β and pNFκB in LPS-activated microglia, and conversely elevated the expression of IL-1β in resting-surveying microglia with lot-to-lot variation. Morphological and phagocytotic analyses revealed that LPS stimulation significantly increased active Rho GTPase, Rac1, and Cdc42 levels in the microglia, and their morphology changed to amoeboid in which F-actin spread with ruffle formation. The F-actin spreading persisted after removal of LPS stimulation and reduced phagocytosis. On the other hand, MSC co-culture induced bimodal increase in active Rac1 and Cdc42 levels in LPS-activated microglia. Moreover, extended ruffles of F-actin shrinked and concentrated to form an actin ring, thereby restoring phagocytosis. We confirmed that inhibition of the PI3K/Akt pathway attenuated F-actin dynamics and phagocytosis restored by MSCs. Conclusions: Overall, we demonstrated that MSCs immunomodulated microglia with lot-to-lot variation, and changed the phenotype of LPS-activated microglia, thereby restoring actin dynamics and phagocytosis by increase of active Rho GTPase. Modulation of the phenotype of activated microglia by MSCs can be a novel therapeutic strategy for the treatment of neurological disorders accompanied by inflammation.

Preventing Brain Damage from Hypoxic–Ischemic Encephalopathy in Neonates: Update on Mesenchymal Stromal Cells and Umbilical Cord Blood Cells

“…Morphological and phagocytotic analyses revealed that lipopolysaccharide stimulation significantly changed microglial morphology to amoeboid in which F-actin spread with ruffle formation resulting in reduced phagocytosis of Escherichia coli , while MSC co-culture induced shrinkage and concentration of F-actin to form an actin ring, thereby restoring phagocytosis. 44 These effects of UC-MSCs that modulate the activated microglia may be a therapeutic potential for the treatment of neurological disorders accompanied by inflammation.…”

“…MSCs are reported to protect brains against global and local neuroinflammatory cascades triggered by HI events. 39 44 However, at times MSCs have both anti- and proinflammatory effects. Indeed, in our study, some UC-MSCs caused inflammatory response in resting-surveying (not activated) microglia, indicating that MSCs should not be administered to healthy brain with no inflammation.…”

“…Indeed, in our study, some UC-MSCs caused inflammatory response in resting-surveying (not activated) microglia, indicating that MSCs should not be administered to healthy brain with no inflammation. 44 Some reports, however, suggest that UCBC administration reduces white matter injury after HI insult, via a combination of anti-inflammatory and other actions. 48…”

Future perspectives on cell therapy for autism spectrum disorder

“…We also demonstrated that secretomes from MSCs can change the phenotype of activated microglia. Umbilical cord derived MSCs immunomodulated microglia and changed the phenotype of LPS-activated microglia restoring actin dynamics and phagocytosis by increasing active Rho GTPase, in which microglia changed their amoeboid to a more ramified pattern (Mukai et al, 2021). This suppression and immunomodulation of activated microglia by MSCs may lead to therapeutic potential for individuals with ASD in which excessive microglial activation lead to aberrant neural connections.…”