Stem cell delivery of therapies for brain disorders

The blood brain barrier (BBB) poses a problem to deliver drugs for brain malignancies and neurodegenerative
disorders. Stem cells such as neural stem cells (NSCs) and mesenchymal stem cells (MSCs) can be used to delivery
drugs or RNA to the brain. This use of methods to bypass the hurdles of delivering drugs across the BBB is
particularly important for diseases with poor prognosis such as glioblastoma multiforme (GBM). Stem cell treatment
to deliver drugs to neural tumors is currently in clinical trial. This method, albeit in the early phase, could be an
advantage because stem cells can cross the BBB into the brain. MSCs are particularly interesting because to date,
the experimental and clinical evidence showed ‘no alarm signal’ with regards to safety. Additionally, MSCs do not
form tumors as other more primitive stem cells such as embryonic stem cells. More importantly, MSCs showed
pathotropism by migrating to sites of tissue insult. Due to the ability of MSCs to be transplanted across allogeneic
barrier, drug-engineered MSCs can be available as off-the-shelf cells for rapid transplantation. This review discusses
the advantages and disadvantages of stem cells to deliver prodrugs, genes and RNA to treat neural disorders.