The secret to growing exCEPTional stem cells

Scientists identify a drug combo that protects stem cells in culture, priming them for research and clinical applications

Picture this: The morning after working late on an important project, you reach for that hot cup of coffee-the caffeinated elixir that perks you up, gets ideas flowing, and keeps you from snapping at your colleagues.

What if, like a rejuvenating cup of joe, there was a way of boosting stem cells’ performance under stressful conditions?

Having to survive outside the body is extremely taxing on stem cells. Many don’t survive the move from human tissues to the cell culture flask, with the ones that do often ending up weak and functioning sub-optimally. Making this transition smooth for stem cells is particularly important when using them for therapeutic purposes-healthy, happy stem cells translate to safer and more effective clinical outcomes for patients.

Recently, scientists have made a breakthrough finding and identifying a unique cocktail of small molecules that supports stem cell health under laboratory conditions, potentially unlocking a whole new realm of possibilities for these cells in regenerative medicine applications.

Stalled progress on the path to the clinic

The discovery of induced pluripotent stem cells, or iPSCs, by Nobel prize-winning researcher Shinya Yamanaka in 2006, was a major turning point in research and medicine. Yamanaka and colleagues cracked the code on how to wind back the clock on adult cells, reprogramming them genetically to assume a stem cell-like state. This discovery heralded a new chapter in regenerative medicine, removing many of the ethical and technical challenges associated with the use of embryonic stem cells.

Still, while iPSCs have shone brightly in research applications such as drug discovery and disease modeling, we have yet to harness their full potential as therapeutics. One of the kinks to be ironed out is the challenge of how to multiply and cultivate iPSCs at large scales in a safe, controlled, and efficient manner. This is the first step in creating cell banks-a pharmacy of off-the-shelf cell products that can be deployed to patients. On a positive note, scientists have put together a checklist of how to gauge a “good” iPSC from a “bad” one (using molecular and cellular markers of pluripotency). However, as yet, a magic formula for expanding, storing and cloning iPSCs that maintains these viability markers has remained out of reach.

These are costly and frustrating hurdles for cell therapy developers. Flawed manufacturing processes have been identified as a root cause behind stem cells’ lackluster performance in several clinical trials over the years. Among these flops were Osiris’ Prochymal, a failed stem cell therapy for graft-versus-host disease, and Brainstorm Cell Therapeutics’ aborted approach to treating amyotrophic lateral sclerosis, a progressive disease of the nervous system.

An espresso shot for stem cells

Scientists like Ilyas Singeç, director of the Stem Cell Translation Laboratory at NIH’s National Center for Advancing Translational Sciences (NCATS), have been hunting for solutions to these long-standing stem cell culture problems. Singeç’s lab recently released a study detailing the groundbreaking discovery of a cocktail they called CEPT, which was shown to dramatically boost iPSC survival and eliminate cell culture stress.

“The small-molecule cocktail is safeguarding cells and making stem cell use more predictable and efficient. In preventing cellular stress and DNA damage that typically occur, we’re avoiding cell death and improving the quality of surviving cells,” said Singeç in an NIH news release. “The cocktail will become a broadly used staple of the stem cell field and boost stem cell applications in both research and the clinic.”

Singeç and colleagues mined over 15,000 approved pharmaceuticals and investigational small molecules using high-throughput screening assays. The targets of this intense search were molecules that could inhibit the ROCK pathway, a cellular signaling cascade that, once activated, diminishes stem cells’ chances of survival. Of this huge compound library, the team found 20 drugs that blocked ROCK, with chroman 1 being a standout molecule. Excitingly, chroman 1 beat the existing gold standard ROCK inhibitor, a widely-used compound called Y‑27632.

Could other molecules work synergistically with Chroman 1 to enhance cell survival (think of the productivity boost of coffee alone versus a coffee-donut combo)? The researchers used a matrix drug screening system to trawl for winning combinations, testing the effects of thousands of compounds in a custom-built stem cell stress test.

Eventually, they found that a cocktail of chroman 1, emricasan, polyamines, and t rans-ISRIB (or CEPT) worked best at supporting stem cell viability. CEPT was shown to vastly improve single-cell cloning, a method of creating pure colonies of cells from an individual “seed” iPSC. Single-cell cloning is an advanced culture technique used to improve the quality and homogeneity of cell products going into patients. However, current protocols are notoriously inefficient, with many cells dying as a result of the stress from being forced to multiply in isolation.

On top of that, CEPT also helped stem cells through yet another stressful experience: Being woken up from a deep freeze. Stem cells for research and clinical purposes are stored via cryopreservation but, as they are thawed out, as many as 60–70 percent don’t survive. Adding CEPT to the cell culture medium helped tremendously, raising the number of cells that bounced back from cold storage.

Singeç and colleagues also took a closer look at how CEPT treatment influenced the differentiation of iPSCs, yielding even more impressive results. iPSCs treated with CEPT formed healthier, more functional heart cells and neurons, a finding which points towards potentially more robust therapeutic outcomes in the clinic.

Research and biomanufacturing processes may have come a long way in the past two decades, but a lack of clinically approved iPSC-based therapies highlights that the journey is far from over. Breakthrough approaches to growing and harvesting iPSCs, such as with the use of CEPT, could dramatically shift the clinical landscape in years to come.

Originally published at

Cat person, PhD-qualified Cell Biologist & Science Writer. Interested in trends and emerging technologies in the biopharma industry.

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