Stem cells from embryo sac could heal damaged hearts

WASHINGTON - Stem cells obtained from a new non-controversial source - the amniotic membrane discarded as medical waste after childbirth - can heal damaged hearts and form heart muscle cells, results of preliminary lab tests indicate.

Investigators in Japan used the membrane - the inner lining of the sac in which an embryo develops - to obtain stem cells called human amniotic membrane-derived mesenchymal (undifferentiated) cells (hAMCs).

“The amniotic membrane is medical waste that could be collected and used after delivery,” said Shunichiro Miyoshi, study co-author and assistant professor in cardiology at the Keio University School of Medicine, Tokyo.

In lab studies, the hAMCs transformed into heart muscle cells improved function of rat hearts 34 percent to 39 percent, when injected two weeks after a heart attack, while untreated hearts continued to decline in function.

They decreased the scarred area of damaged rat hearts 13 percent to 18 percent when injected after a heart attack.

The cells also survived for more than four weeks in the rat heart without being rejected by the recipient’s immune system, even without immunosuppressive medication.

The ability of hAMCs to convert into heart muscle cells was far greater than that from mesenchymal cells derived from bone marrow or fat, Miyoshi said.

That the implanted cells were not rejected is likely because the amniotic sac is a barrier between a woman and her developing foetus. To help prevent either of their immune systems from attacking the other as foreign tissue, the amniotic membrane between them does not produce the proteins that immune systems use to identify foreign tissue.

This means the usual tissue-type matching (HLA typing) needed prior to transplantation would not be needed if hAMCs were used. Drugs to suppress the immune system also might not be needed after transplant.

The findings also suggest that hAMCs can differentiate into cells of various organs, said a release of the American Heart Association (AHA).

Much work, however, remains to be done before testing hAMCs in humans, said the researchers, who are repeating their experiments in larger animals and working to boost the number of heart cells generated by the hAMCs.

The investigators “are to be congratulated for their careful work that has brought forward a cell type that may offer the real potential for off-the-shelf cardiac myocyte [muscle cell]-based therapy,” wrote Marc S. Penn, and Maritza E. Mayorga of the Cleveland Clinic, in Circulation Research, which published these findings.