Scientists Use Stem Cells to Mimic Adrenal Gland In Vitro

The adrenal gland plays a pivotal role in immunity and hormonal signaling but studying the adrenal gland in action is challenging. Regenerative medicine has long been sought out as a possible solution for primary adrenal insufficiency, where a functional adrenal gland could be regrown to synthesize hormones and cooperate with the nervous system. Researchers at the University of Pennsylvania School of Veterinary Medicine are one step closer to this reality. They found that stem cells can divide and mature in a petri dish to behave similarly to a human fetal adrenal gland.

“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 senior author Kotaro Sasaki, 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.”

The team utilized human inducible pluripotent stem cells (iPSCs) for their work, which was published in the journal Developmental Cell. These stem cells can be influenced to become numerous different cell types, so the team was able to direct them to take on the characteristics of an adrenal gland.

First, the study authors used an “organoid culture” system, where the cells could grow as a floating aggregate for three weeks before resting on a membrane exposed to air. This process fosters better survival and 3D cell proliferation. Then, the team used a growth medium to prompt the iPSCs to develop into an intermediate tissue type found in the adrenal development process, the posterior intermedia mesoderm (PIM).  

Once the team verified that they had successfully cultured PIM-like cells, they could direct those cells to transition to the next stage of development – adrenocortical progenitor-like cells. Sasaki and colleagues utilized molecular assays and transmission electron microscope analyses to check for adrenal markers.

“The process we developed was highly efficient, with around 50% of cells in organoids acquiring adrenocortical cell fate,” says lead author Michinori Mayama, a postdoc in Sasaki’s lab. “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.”

The researchers then performed numerous tests to see how closely the cells’ functionality mimicked that of a human adrenal gland. They discovered that the lab-grown cells produced steroid hormones, like DHEA, just like a human adrenal gland. “In vitro, we can produce much of the same steroids that are produced in vivo,” Mayama says.

They also revealed that the cells could respond to the hypothalamic-pituitary-adrenal (HPA) axis, an essential feedback loop for neuroendocrine signaling. “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.”

For future work, the team hopes to generate more of the gradations in tissue type that occur in a mature adult adrenal gland. “This is a first-of-its-kind study,” concludes 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.”