Most cells in our body are specialized, meaning they perform a defined role. They might protect us from the outside world (skin cells), help us to lift a finger (muscle cells), or aid us in remembering our shopping list (nerve cells).
Let’s compare the role of different cells to people responsible for different jobs. We have all learned specifically for our fields. Whether we are fire-fighters, roofers, researchers, or doctors, we are specialized. Now, imagine a super-talented kid graduating from high-school. The world is open. He or she could learn anything to become a teacher, craftsperson, CEO, or clerk.
Stem cells are exactly like that freshly-graduated kid with endless possibilities. They are the super-talents among the cells. They are non-differentiated, meaning they can turn into any cell type, like a skin, nerve, or blood cell (see image). Their role is to provide new cells as the body grows and replace lost ones. As to which cells they turn into? The surrounding tissue decides that. If the surrounding tissue is healthy, the cells can grow. And depending on what type of growth hormone the tissue puts out, they develop into a specific type of cell. In the future, they may be used in medicine to repair cells and tissues that have been damaged.
What are the hopes for stem cells and stroke recovery?
There are two main hopes for stem cells.
The first hope of stem cells is they can protect the nerves in the early stages of stroke and limit further brain injury. In these cases, doctors deliver the stem cells intravenously, and they can stop the effects of a stroke from getting worse.
The second hope is that stem cells actually regenerate to replace dead cells in later stages of stroke. This usually involves brain surgery, where a doctor injects stem cells into healthy brain tissue close to the site of injury. The healthy tissue provides an environment where the stem cells can thrive and multiply.
What are the main obstacles that stem cell treatment faces?
“In the future, stroke patients may receive stem cell therapy as this has the potential to restore lost functions. However, the development of clinically deliverable therapy has been slower and more challenging than expected.” This citation stems amongst others from Prof. Keith Muir, who leads one of the most promising clinical trials when it comes to stem cell therapy for stroke patients, the PISCES Study.
Despite promising results from preclinical animal studies, progress in clinical trials is slow. The main obstacles to getting consistent results are the different approaches each study uses and the rehabilitation and medication that the participants might already be receiving. It is hard to filter out what positive outcomes are related to the stem cell treatment and which ones come from other interventions.
Preclinical studies are always animal studies where the animals have no other diseases or conditions and are all suffering from the same stroke. This is very different from the human situation, where every stroke is unique. Other conditions are common, and patients receive additional therapy, like medication and rehabilitation. These factors may lead researchers to overestimate the results of the tested therapy in preclinical studies.
Also, first clinical studies are usually small and lack control groups. This makes sense, as the initial intention of research is always to ensure safety and feasibility. However, small groups and no control group hinder firm conclusions about the effectiveness of a treatment. Furthermore, there is no consensus on cell types, doses, and delivery methods. Therefore, it is not surprising that clinical trials lead to somewhat conflicting results.
Strokemark’s assessment of when stem cell treatment might become available
To the best of our knowledge, articles published about 26 clinical trials are available. And there are 53 ongoing trials using stem cell-based therapy for stroke. Only two of them are Phase III studies, however. Phase III studies are the ones that are closest to finding conclusive results. And they could ultimately bring the treatment to the market.
One of these Phase III trials is estimated to be completed in September 2021. And in the best case scenario, when this study is successful, it will probably take another year to evaluate the data carefully and publish the results. In addition, FDA approval adds approximately two years to this process. And even then, this treatment will not be standard in hospitals right away. We estimate that the treatment in this trial could realistically become practice sometime around 2024/25. This study focused on the acute treatment of ischemic strokes, meaning patients received the treatment 18 – 36 hours post-stroke.
Chronic stroke treatment studies are even further away from bedside practice. The closest is STARTING-2, which is currently recruiting for a Phase III clinical trial in Korea.
However, you might not have to wait until 2025 to get stem cell treatment. There are plenty of clinical trials that are recruiting patients right now. And if you need additional assistance in locating a trial, please feel free to contact us for help.
Please visit us again to read Prof. Benedikt Berninger’s assessment of stem cell-based therapy. He is an internationally renowned stem cell researcher in London who will interview with us in the near future.