Spinal cord injury (SCI) is a devastating condition that causes severe nerve damage, leading to impaired movement, sensation, and bodily functions. The injury sets off a series of damaging processes, including excessive inflammation, loss of essential nutrients, and scar tissue formation.
These factors prevent the regeneration of nerve cells, making recovery difficult. Traditional treatments provide limited improvement, but recent research by Lui et al. suggests that mesenchymal stem cells (MSCs) offer hope for patients with SCI.
How SCI Disrupts the Microenvironment
Following SCI, the body experiences a host of negative effects. Initially, the injury causes direct damage to nerve cells, leading to inflammation and the release of harmful substances.
The body’s attempt to repair the damage often backfires, as excessive inflammation worsens tissue destruction and inhibits nerve regeneration. Additionally, the blood-spinal cord barrier (BSCB) becomes compromised, allowing immune cells to flood the injured site.
These immune cells produce harmful molecules like reactive oxygen species (ROS) and cytokines, further aggravating the damage.
The prolonged inflammation creates a hostile environment that prevents new nerve growth and leads to the formation of scar tissue that blocks potential regeneration.
The Role of MSCs in Repairing the Spinal Cord
The ability of MSCs to repair spinal cord injuries (SCI) lies in their powerful secretions of bioactive molecules, which help regulate inflammation, promote nerve cell survival, and enhance tissue repair.
MSCs suppress harmful immune responses by decreasing the activity of pro-inflammatory cells like T-cells and macrophages while promoting anti-inflammatory pathways to minimize further nerve damage. They also release neurotrophic factors that nourish and support nerve cells, encouraging the survival and growth of new neurons to improve recovery.
Additionally, MSCs help prevent the formation of dense glial scar tissue, which can obstruct axon regrowth, by regulating proteins like MMP-2 and BDNF that break down scar tissue and create space for new nerve connections. Furthermore, MSCs contribute to angiogenesis, promoting blood vessel growth to ensure that the injured site receives adequate nutrients and oxygen for healing.
Optimizing MSC Therapy for SCI
To ensure MSC therapy is effective for SCI treatment, the authors call for additional research to determine the most efficient timing, dosage, and delivery method.
Timing for MSC Transplantation
Studies suggest that MSCs work best when introduced during the subacute phase (approximately two weeks after injury). This timing allows MSCs to reduce inflammation while the injury is still healing. If administered too early, the highly inflammatory environment may kill MSCs before they can have a therapeutic effect. If given too late, scar tissue may already be well established, limiting their benefits.
Optimal Dosage
According to Liu et. al, research on animals suggests that higher doses of MSCs (greater than one million cells) lead to better functional recovery.
However, an excessively high dose might provoke an unwanted immune response. In humans, doses typically range from 10 to 100 million cells, though further research is needed to determine the optimal amount.
Optimizing MSC Delivery for Spinal Cord Repair
MSCs can be delivered in different ways. Intravenous (IV) injection is the least invasive, but many cells get trapped in organs like the lungs before reaching the spinal cord. Direct injection into the injury site is more targeted but carries risks of additional damage. Intrathecal injection (into the spinal fluid) is a promising middle ground, as it allows MSCs to circulate in the cerebrospinal fluid and reach the injury without additional trauma.
Advancing MSC Therapy for Spinal Cord Injury: Challenges and Future Prospects
Although MSC therapy holds great promise, several challenges remain before it can become a routine treatment for SCI. Researchers need to refine techniques for improving MSC survival, homing (their ability to find the injured site), and integration into the spinal cord. Scientists are also exploring genetic modifications and biomaterial scaffolds to enhance MSC effectiveness. Additionally, large-scale clinical trials are necessary to confirm safety and efficacy in human patients.
In the future, personalized MSC therapy – where treatment is tailored to each patient’s specific injury and biological factors – could revolutionize SCI treatment.
Liu et al. conclude that ongoing advancements in stem cell research, MSC transplantation has the potential to improve the quality of life for SCI patients by restoring lost function and promoting recovery in ways that were once thought impossible.
Source: Liu, Y., Zhao, C., Zhang, R. et al. Progression of mesenchymal stem cell regulation on imbalanced microenvironment after spinal cord injury. Stem Cell Res Ther 15, 343 (2024). https://doi.org/10.1186/s13287-024-03914-x
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