We reported that
mesenchymal stromal cells (MSCs) enhance neurological recovery from
experimental stroke and increase tissue plasminogen activator (tPA) expression
in astrocytes. Here, we investigate mechanisms by which tPA mediates MSC
enhanced axonal outgrowth. Primary murine neurons and astrocytes were isolated
from wild-type (WT) and tPA-knockout (KO) cortices of embryos. Mouse MSCs (WT)
were purchased from Cognate Inc. Neurons (WT or KO) were seeded in soma side of
Xona microfluidic chambers, and astrocytes (WT or KO) and/or MSCs in axon side.
The chambers were cultured as usual (normoxia) or subjected to oxygen
deprivation. Primary neurons (seeded in plates) were co-cultured with astrocytes
and/or MSCs (in inserts) for Western blot. In chambers, WT axons grew
significantly longer than KO axons and exogenous tPA enhanced axonal outgrowth.
MSCs increased WT axonal outgrowth alone and synergistically with WT astrocytes
at both normoxia and oxygen deprivation conditions.