Scientists at Cambridge University in the laboratory Amer Ahmed Rana have used blood samples to isolate cells from which patient-specific stem cells were made. Because blood samples are far more routine than tissue or organ biopsies, they can provide a much more patient-friendly way to secure material for the production of patient-specific stem cells.
Induced pluripotent stem cells (iPSCs) are made from adult cells by genetic engineering techniques that introduce four specific genes into them. The adult cells then de-differentiate to a more developmentally primitive state and if these cells survive and are successfully cultured, they will form an iPSC line.
Rana and his co-workers cultured blood drawn from several heart patients to isolate a blood cells known as a “late outgrowth endothelial progenitor cell” or L-EPC. Endothelial cells are those cells that compose blood vessels, and endothelial progenitor cells or EPCs are the stem cell population that make endothelial cells. EPCs are found in bone marrow, but some are also found in the peripheral circulation.
There are two main types of EPCs: early-outgrowth and late-outgrowth EPCs. Early-outgrowth EPCs are among the first cells to form spindle-shaped clusters of cells only a few days after being placed in culture. Early-outgrowth EPCs secrete high levels of blood vessel-inducing molecules, but they have only a limited ability to proliferate. They also are able to ingest bacteria, like other white blood cells. Late outgrowth EPCs are much rarer and they grow very well in culture, but are unable to ingest bacteria. They also can form capillaries and repair damaged blood vessels when injected into laboratory animals. There is a debate as to whether or not these cells come from the bone marrow or are dislodged from blood vessels.
Rana and his colleagues have designed a protocol for converting L-EPCs into iPSCs that can then be differentiated into heart, or blood vessel cells rather easily. This practical and rather efficient method does not require tissue biopsies, which are painful and impractical in very young or very old patients, and only requires the cells available from a single, routine blood sample.
Also, because blood samples can be efficiently and safely frozen, the cells from the blood sample can be locked in time for later use, when the patient needs regenerative treatments. The ease of this procedure should, Rana hopes, push it further toward human clinical trials in the near future.