A researchers persuaded stem cells to mimic the traits and activities of a human adrenal gland, paving the way for new therapeutics for adrenal insufficiencies and a better understanding of the genetics of such illnesses.
Adrenal gland diseases, such as primary adrenal insufficiency, in which the gland fails to produce enough hormones, can cause exhaustion, dangerously low blood pressure, coma, and even death if left untreated.
There is no treatment for primary adrenal insufficiency, and the lifelong hormone replacement medication used to treat it has serious negative effects. A better option would be a regenerative medicine strategy that involves regrowing a functioning adrenal gland capable of manufacturing hormones and correctly releasing them in response to brain signals.
Researchers at the University of Pennsylvania School of Veterinary Medicine induced stem cells in a petri dish to divide, develop, and take on some of the characteristics of a human embryonic adrenal gland in a recent study published in the journal Developmental Cell, bringing that objective one step closer.
“This is a proof-of-principle that we can create a system grown in a dish that functions nearly identically to a human adrenal gland in the early stages of development,” says Kotaro Sasaki, senior author and an assistant professor at Penn Vet. “A platform like this could be used to better understand the genetics of adrenal insufficiency and even for drug screening to identify better therapies for people with these disorders.”
According to Sasaki, his team’s goal was to simulate the stages of normal human adrenal development using human inducible pluripotent stem cells (iPSCs), which may give birth to a variety of different cell types. The cells would be instructed to take on the features of the adrenal gland throughout this process.
To begin, the researchers utilised a “organoid culture” technique, in which cells develop for three weeks as a floating aggregate, then on a membrane exposed to air on one side, boosting greater survival and allowing them to multiply in three dimensions. They induced an intermediate tissue type in the adrenal development process, the posterior intermediate mesoderm, in iPSCs using a carefully designed growth medium (PIM).
After confirming that they had cultivated PIM-like cells, the researchers proceeded to drive those cells to the next step, adrenocortical progenitor-like cells, during which cells turn on markers suggesting that they had “committed” to become adrenal gland cells.
Molecular tests for adrenal markers, as well as transmission electron microscopy investigations, all indicated that Sasaki and colleagues were on the correct route toward generating a tissue that resembled the early adrenal gland.
“The process we developed was highly efficient, with around 50% of cells in organoids acquiring adrenocortical cell fate,” says Michinori Mayama, a postdoc in Sasaki’s lab and a lead author on the study. “The ovoid cells with voluminous pink cytoplasm and relatively small nuclei that we saw in our cultures are very characteristic of human adrenal cells at that stage.”
Sasaki, Mayama, and the rest of the study team ran a series of experiments to see how closely the cells’ functioning matched that of a human adrenal gland. They discovered that the lab-grown cells generated steroid hormones like DHEA much like the “real-life” equivalent.
“In vitro, we can produce much of the same steroids that are produced in vivo,” Mayama says.
They also demonstrated that the cells they created could respond to the hypothalamic-pituitary-adrenal axis, a feedback loop that directs communication from the brain to the adrenal gland and back.
“We used drugs that normally suppress adrenal DHEA production and showed that our iPSC-derived adrenal cells respond similarly to these drugs, with a marked reduction of hormone production,” says Sasaki.
“This means that you can use this system for screening drugs that target adrenal hormone production, which could benefit patients with excessive adrenal hormone production or with a prostate cancer that exploits adrenal hormones for their growth.”
As the researchers perfect their technology, they aim to be able to replicate more of the tissue type gradations seen in a mature adult adrenal gland. A platform like this provides opportunity to learn a lot more about the still-mysterious adrenal gland. Sasaki, in particular, adds that it might be used to investigate the genetic basis of adrenal insufficiencies as well as other disorders such as adrenal carcinomas. Finally, the method employed to produce this gland-in-a-dish might one day be utilised to recreate a working brain-adrenal gland feedback loop in persons with adrenal gland problems.
“This is a first-of-its kind study,” says Sasaki. “The field of cell therapy holds so much promise for treating not just adrenal insufficiencies but other hormone-driven diseases: hypertension, Cushing syndrome, polycystic ovary syndrome, and more.”
