Stem cell therapy: A possible solution to save our coral reefs

Photo credit: Grace Snyder

This article was the 2022 first-place winner of the University of Miami Graduate Op-Ed Challenge.

Imagine your next snorkeling vacation at a barren underwater desert. The vibrant corals and bright flashes of darting fish reduced to nothing but a bleak wasteland.This reality is around the corner.

We’ve been seeing a decline in coral reef health for decades. Scientists have undeniably proven that greenhouse gas emissions are responsible for the global increase in temperature and ocean acidification, the top contributors to coral decline. Yet, political and economic restraints prevent the reversal of greenhouse gas emissions at a sufficient rate.

So how can we buy corals the time they need until such drastic changes can be met? The answer might be in human medicine.

Patients diagnosed with leukemia or Non-Hodgkin’s lymphoma are often faced with intense, harmful treatments of chemotherapy or radiation. This leaves the body with a diminished blood cell supply. It’s becoming common to follow these treatments with stem cell therapies to reintroduce healthy stem cells, ultimately providing new blood cells and mitigating unpleasant symptoms. Could the same be done for corals?

Coral gardening is currently the favored practice of coral preservation amongst coral conservationists. Artificial structures, usually made out of PVC pipes or plastic mesh, are built to provide a “nursery.” On these nurseries, small coral fragments are cultivated by conservationists and volunteers until they reach an optimal size. At this point they are “outplanted” on the reef using a marine epoxy, or glue. While efforts can focus on corals that are more tolerant of higher temperatures, this technique requires endless hours of manpower, reduces the diversity of corals on the reef and is time-consuming due to corals’ slow-growing nature. While this method has undoubtedly provided relief for many reefs, it is not sustainable enough for the future of corals.

Optimal solutions would be able to prevent the declining health of adult corals already present on the reef. To this end, genome editing and probiotic treatments are examples of solutions under consideration. These methods hold water and should be further explored, but they present their own issues.

As in human cancer patients, stem cell therapy may be the ideal solution. Transplanting stem cells from a resilient coral to one more susceptible, would preserve adult corals already existing on the reef, maintain the genetic diversity, require less maintenance by conservationists and volunteers and maintain the reef structure which is so necessary for the entire ecosystem. So why haven’t we tried stem cell therapy on corals?

The problem is simple: we don’t know if corals have stem cells. Closely related animals (think anemones and jellyfish) have been shown to possess these regenerative cells, suggesting corals might, too.

Testing this is no simple task, unfortunately. A common method of identifying stem cells in other animals is to use a fluorescent tag for common stem cell-associated markers, similar to how we detect antibodies. However, corals possess a wide range of natural fluorescent proteins, making it impossible to distinguish the stem cell markers. To overcome this, researchers at the University of Miami have identified a population of cells that exhibit many characteristics of stem cells across the animal kingdom. These small, structurally simple and rare cells show a gene expression signature similar to an unspecialized cell, which provides convincing evidence that these are indeed stem cells.

Photo credit: Grace Snyder

With this kernel of hope, the next stage of this research is addressing the logistics: How do we transplant stem cells, and which corals should act as the donors? Corals are essentially animals in rock-form, making classic needle-based injections a challenging mode of transplantation.

One avenue to explore is the application of short-term hydrogels. Commonly used as wound dressings in humans, hydrogels are an ideal substance for donor cell transfers, and act as a physical barrier against physical damage and infection.

The second factor to consider is which corals should serve as the donors. Just as our blood type determines from whom we can receive blood transfusions, there may be genetic compatibility factors that will need to be considered on top of resiliency to heat and other stressors. However, considering that many coral species are capable of growing and fusing together, the probability of successful transplantations seems high.

Despite the hurdles, this research should proceed. We are way past the luxury of questioning if human intervention is necessary or acceptable. According to greenhouse gas emission and temperature predictions by the Intergovernmental Panel on Climate Change, corals will face annual mass bleaching and mortality events by 2050. The current methods of coral conservation are simply not enough, and we need to be more effective in our efforts if we are going to save the coral reefs we rely upon and love. Stem cell therapy could be the answer.

Grace Snyder is a graduate student at the University of Miami Rosenstiel School of Marine, Atmospheric, and Earth Science, studying the capability of coral stem cell transplantations.