According to two studies published in Cell Transplantation, stroke victims may benefit from human mesenchymal stem cell (hMSC) or bone marrow stromal cell (BMSCs) transplantation. In both studies, the migration of chemically “tagged” transplanted stem cells were tracked to determine the degree to which the transplanted cells reached damaged areas of the brain and became therapeutically active.

“Both studies lend important support to a growing body of laboratory evidence that bone marrow is a remarkable adult stem cell source for transplant therapy following stroke,” says Cell Transplantation associate editor Cesar V. Borlongan, Ph.D. of the Medical College of Georgia. “The non-invasive MRI visualization of pre-labeled BMSCs could become a routine clinical marker for transplanted cells as well as for safety and efficacy.”

Tracking transplanted hMSCs to infarcted areas

In a study carried out by Korean researchers, labeled hMSCs (early precursor cells to musculoskeletal, blood, vascular and urogenital systems) were transplanted into animal stroke models with cerebral artery occlusion and tracked by magnetic resonance imaging (MRI) at two days, one week, two weeks, six weeks and ten weeks after transplant.

“Cells started showing indications of migration as early as one or two weeks following transplantation,” said lead author Jihwan, Song, DPhil, of the Pochon CHA University College of Medicine. “At 10 weeks, the majority of the cells were detected in the core of the infarcted area.”

The study concluded that there is a strong tendency for transplanted hMSCs to migrate toward the infarcted area regardless of injection site but that the degree of migration was likely based on differences in each animal’s ischemic condition.

“We speculate that the extensive migratory nature of stem cells and their utilization will provide an important tool for developing novel stroke therapies,” said Song.

BMSCs migrate to damaged brain tissue, improve neural function

In a joint Canadian, Chinese study, BMSCs - connective tissue cells - were injected into animals 24 hours following middle cerebral artery occlusion. Using laser scanning confocal microscopy to track fluorescent signals and immuno markers attached to the cells, researchers found that within seven days of the injection the BMSCs had migrated through the region of the middle cerebral artery into the scar area and border zone of the ischemic region.

“We evaluated vascular density in the ischemic region in all animals seven days after cell transplantation,” said study lead author Ren-Ke Li, MD, PhD. “The animals exhibited significant reductions in scar size and cell death and improvements in neurological function when compared to controls that received no BMSCs.”

Researchers concluded that the intravenous delivery of bone marrow-derived cells may enhance tissue repair and, in turn, functional recovery after a stroke. While the potential mechanisms for this recovery are unclear, among the possibilities are that the brain microenvironment early on following a stroke may mimic brain development. Subsequent elevated levels of growth factors might enhance homing of BMSCs to the injured area and induce cell proliferation.

“Our results support the potential therapeutic use of BMSCs after a stroke,” concluded Li.