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.

A new sexual identity crisis—in our organs. With the transition from Mr. to Ms. Jenner and other transsexual news this year, it seems inevitable that a research paper would come out suggesting we may all have some mosaic sexual identity. A team in the U.K. found that the stem cells that develop our organs can have varying sexual identities and that can impact the function of the organ.

The organ in question in this case, intestines in fruit flies, is smaller in males than in females. By turning on and off certain genes the researchers at the Medical Research Council’s Clinical Science Centre found that making stem cells in the gut more masculine reduced their ability to multiply and produced smaller intestines. They also found that female intestines were more prone to tumors, just as many diseases are more common in one sex than the other.

In an interview with Medical News Today, Bruno Hudry, the first author on the paper, which is published in Nature, talked about the likelihood that we all have some adult cells in us with genes of the opposite sex.

 “This study shows that there is a wider spectrum than just two sexes. You can be chromosomally, hormonally or phenotypically female but still having some specific adult stem cells (here the stem cells of the intestine) acting like male. So it is hard to say if someone is “really” male or female. Some people are simply a mosaic of male and female cells within a phenotypically ‘male’ or ‘female’ body.”

Hurdry speculated that if the results are duplicated in humans it could provide a window into other sex-linked differences in diseases and could be a matching factor added to the standard protocol for blood and organ donations.

Reprogramming stomach to produce insulin.  The stem cells in our gut show an efficiency not seen in most of our organs. They produce a new lining for our stomach and intestine every few days. On the opposite end of the spectrum, the insulin-producing cells in our pancreas rank poorly in self renewal. So, what if you could get some of those vigorous gut stem cells to make insulin producing beta cells? Turns out you can and they can produce enough insulin to allow a diabetic mouse to survive.

A mini-gut with insulin-producing cells (red) and stem cells (green).

A team at the Harvard Stem Cell Institute manipulated three genes known to be associated with beta cell development and tested the ability of many different tissues—from tail to snout—to produce beta cells. A portion of the stomach near the intestine, which naturally produces other hormones, easily reprogrammed into insulin producing cells. More important, if the first batch of those cells was destroyed by the team, the remaining stem cells in the tissue quickly regenerated more beta cells. Since a misbehaving immune system causes type 1 diabetes, this renewal ability could be key to preventing a return of the disease after a transplant of these cells.

In the lab the researchers pushed the tissue from the pylorous region of the stomach to self-organize into mini-stomachs along with the three genetic factors that drive beta cell production.  When transplanted under the skin of mice that had previously had their beta cells destroyed, the mice survived. The genetic manipulations used in this research could not be used in people, but the team is working on a system that could.

 “What is potentially really great about this approach is that one can biopsy from an individual person, grow the cells in vitro and reprogram them to beta cells, and then transplant them to create a patient-specific therapy,” said Qiao Zhou, the senior author. “That’s what we’re working on now. We’re very excited.”

Medicalxpress ran a story about the work published in Cell Stem Cell.

Muscle stem cells generate new muscle (green) in a mouse.

Better way to build muscle.  Stem cells behave differently depending on what environment they find themselves in, but they are not passive about their environment. They can actively change it. A CIRM-funded team at Sanford Burnham Prebys Medical Discovery Institute (SBP) found that fetal muscle stem cells and adult muscle stem cells make very different changes in the micro-environment around them.

Fetal muscle stem cells become very good at generating large quantities of new muscle, while the adult stem cells take the role of maintaining themselves for emergencies. As a result, when major repair is needed like in muscular dystrophies and aging, they easily get overwhelmed. So the SBP team looked for ways to make the adult stem cells behave more like their fetal predecessors.

 “We found that fetal MuSCs remodel their microenvironment by secreting specific proteins, and then examined whether that same microenvironment can encourage adult MuSCs to more efficiently generate new muscle. It does, which means that how adult MuSCs normally support muscle growth is not an intrinsic characteristic, but can be changed,” said Matthew Tierney, first author of the study in an institute press release distributed by Newswise.

The results point to paths for developing therapies for a number of muscle wasting conditions.