Heart stem cell patches not as strong as ‘real’

Once flagged as a miracle treatment, stem cell transplants have successfully patched up damaged heart tissue. But it’s less clear if the patches help the repaired heart beat as strongly as a healthy one. Clinical trials have returned mixed results.

Now, a study published in The Journal of Cell Biology has delivered a possible explanation, suggesting that stem cells, inherently, just don’t pack enough punch.

A group at Harvard University’s Wyss Institute of Biologically Inspired Engineering put the beating power of stem-cell-derived heart cells to the test.

The researchers used two batches of heart cells: some derived from stem cells and others harvested from mice.

They then fused stem-cell-derived heart cells to those from a mouse, which they called “muscles-on-a-chip” – two-celled versions of the junction between a stem cell-derived patch and the normal cardiac cells in a patient’s heart.

When prompted to start contracting, both muscle cells beat to the same rhythm – but the stem-cell-derived heart cells contracted less strongly then the “real” mouse heart cells.

The team used computer models to predict how this power imbalance may affect a contraction as it pulses through heart tissue. They found that, for stem-cell-derived heart cells, the contraction’s force dissipated to the cell’s surroundings, instead of moving from cell to cell.

This could be the reason hearts repaired with stem cells don’t perform as well as the real thing.

But it’s not all bad news.

The authors plan to develop their muscle on-a-chip as a screening platform. Different stem cells and gene or drug therapies could craft more powerful heart cells, letting all cells in a mended heart beat as one.