Here are some stem cell stories that caught our eye this past week. Some are groundbreaking science, others are of personal interest to us, and still others are just fun.
Good news from sickle cell clinical trial. It is always satisfying to report positive results from human clinical trials using stem cells even when we don’t fund the work. Bluebird Bio released the first data on a patient treated for sickle cell anemia using the same procedure the company had earlier used to get good outcomes for two patients with beta thalassemia.
Both diseases result from defects—though different defects—in the gene for hemoglobin, the protein our red blood cells use to carry needed oxygen. So, in both cases they use a modified, deactivated virus to carry a correct version of the gene into patients’ own blood-forming stem cells in the lab. They then re-infused those cells into the patients to provide a ready supply of cells able to make the needed protein.
In the sickle cell patient, after the transplant a third of his red cells were making the right protein and that was enough to wean him off blood transfusions that had been keeping him alive and prevented any further hospitalizations due to the disease. The company also announced that the two previously reported patients treated for beta thalassemia had continued to improve. Reuters ran a story on the new data.
CIRM funds a similar project about to begin treating patients for sickle cell disease (link to video), also using a viral vector but a somewhat different one, so it is reassuring to see viral gene carriers working without side effects.
Another reason to vaccinate, prevent leukemia. While it has been known for some time that infant vaccination seems to have driven down the rate of childhood leukemia, no one has known why. A CIRM-funded team at the University of California, San Francisco, thinks they have figured it out. Viral infections trigger inflammation and the production of enzymes in cells that cause genetic mutations that lead to the cancer.
They worked with Haemophilus influenza Type b (Hib) vaccine but suggest a similar mechanism probably applies to other viral infections, and correspondingly, protection from other vaccines. The senior author on the paper, Marcus Muschen, explained the process in a university press release posted at Press-News.org
“These experiments help explain why the incidence of leukemia has been dramatically reduced since the advent of regular vaccinations during infancy. Hib and other childhood infections can cause recurrent and vehement immune responses, which we have found could lead to leukemia, but infants that have received vaccines are largely protected and acquire long-term immunity through very mild immune reactions.”
Barcoding individual cells. Our skin cells all pretty much look the same, but in the palm of your hand there are actually several different types of cells, even a tiny scratch of the fingernail. As scientist work to better understand how cells function, and in particular how stem cells mature, they increasingly need to know precisely what genes are turned on in individual cells.
Until recently, all this type of analysis blended up a bunch of cells and asked what is in the collective soup. And this did not get the fine-tuned answers today’s scientists are seeking. Numerous teams over the past couple years have reported on tools to get down to single-cell gene analysis. Now, two teams at Harvard have independently developed ways to make this easier. They both use a type of DNA barcode on tiny beads that gets incorporated into individual cells before analysis.
Allan Klein, part of one team based at the Harvard Medical School’s main campus, described why the work is needed in a detailed narrative story released by the school:
“Does a population of cells that we initially think is uniform actually have some substructure. What is the nature of an early developing stem cell? . . . How is [a cell’s] fate determined? “
Even Macosko who worked with the other team centered at the Broad Institute of Harvard and MIT, noted the considerable increase in ease and decrease in cost with the new methods compared to some of the early methods of single cell gene analysis:
“If you’re a biologist with an interesting question in mind, this approach could shine a light on the problem without bankrupting you. It finally makes gene expression profiling on a cell-by-cell level tractable and accessible. I think it’s something biologists in a lot of fields will want to use.”
The narrative provides a good example of what we called the “bump rate” when I was at Harvard Med. Good science often moves forward when scientists bump into each other, and with Harvard Medical faculty scattered at 17 affiliated hospitals and research institutes scattered across Boston and Cambridge we were always looking for ways to increase the bump rate with conferences and cross department events. Macosko and Klein found out they were both working on similar systems at a conference.