1477.7.2 Oligodendrocyte Progenitor Cells
Oligodendrocyte progenitor cells (OPCs) are a subtype of glial cells found in the
CNS and are particularly prevalent in the hippocampus and neocortex [ 351 , 352 ].
The primary function of OPCs is to maintain oligodendrocyte populations, the
myelinating glia in the central nervous system [ 347 ]. Because of this, OPCs have
been used extensively as a method to produce myelin building blocks for repair of
injured white matter in rodent models of TBI and SCI [ 353 – 356 ]. Some groups have
found that injection of OPCs in spinal cord transplant experiments increased remy-
elination [ 357 , 358 ], with one group seeing these results only 7 days post-injury in
thoracic contusion SCI models [ 359 ]. OPC and oligodendrocyte-conditioned media
have been shown to increase axonal length and augment tissue sparing in vitro
[ 360 ]. Lastly, OPCs have been observed to survive, migrate, and differentiate into
adult oligodendrocytes after transplantation into a complete transection spinal cord
injury model [ 361 ]. Similarly, in the brain, OPCs transplanted into dysmyelinated
mouse brains differentiated into oligodendrocytes and signifi cantly increased axo-
nal myelination [ 353 ]. Similar effects were observed with induced pluripotent stem
cell (iPSC)-derived OPCs transplanted into a hypomyelinated mouse brain [ 362 ].
OPCs transplanted in a rodent model of periventricular leukomalacia not only sig-
nifi cantly increased myelination, but also increased proliferation of NPSCs and
decreased neuronal cell loss [ 351 ]. Nonetheless, there is currently no sustainable
source of OPCs , and OPC transplants are diffi cult to maintain at high phenotypic
purity, thus limiting current clinical translation [ 358 , 361 ].
7.7.3 Schwann Cells
Schwann cells are the myelinating cells of the peripheral nervous system that sus-
tain peripheral axon regeneration. Nonetheless, there is strong evidence suggesting
that Schwann cells can facilitate CNS axon regeneration as well. Schwann cells
have been shown to promote remyelination of CNS axons, reduce lesion cavitation,
and express various trophic factors when delivered via injection or biomaterial scaf-
fold into SCI lesions [ 210 , 363 – 365 ]. Further, Schwann cells are easily isolated
from peripheral nerves and expanded in vitro [ 363 ]. Some groups have found that
treatment of spinal cord transection with grafted Schwann cells was suffi cient to
allow damaged axons to extend into implanted grafts and become myelinated; how-
ever, the axons were unable to leave the grafts distally and re-innervate caudally
located tissues [ 366 – 368 ]. In a contusion SCI model, transplanted Schwann cells
signifi cantly reduced cavitation at the injury site and promoted remyelination of
endogenous axons growing into the graft [ 369 ]. Other studies have corroborated
fi ndings of reduced cavitation and further suggest that transplantation of Schwann
cells may promote tissue sparing and form a bridge across the lesion site [ 370 ]. It
has been postulated that the mechanism by which Schwann cells promote axonal
7 Regenerative Strategies for the Central Nervous System