Scientists used human pluripotent stem cells to generate human embryonic colons in a laboratory that function much like natural human tissues when transplanted into mice, according to research published June 22 in the journal Cell Stem Cell.

The technology allows diseases of the colon to be studied in unprecedented detail in a human modeling system. It also comes with the potential to one day generate human gastrointestinal (GI) tract tissues for transplant into patients, according to James Wells, PhD, senior study investigator and director of the Cincinnati Children’s Pluripotent Stem Cell Center.

“Diseases affecting this region of the GI tract are quite prevalent and include ailments like colitis, colon cancer, Irritable Bowel Syndrome, Hirschsprung’s disease and polyposis syndromes,” Wells said. “We’ve been limited in how we can study these diseases, including the fact that animal models like mice don’t precisely recreate human disease processes in the gastrointestinal tract. This system allows us to very effectively model human diseases and human development.”

The researchers – including Jorge Munera, PhD, first author and postdoctoral fellow in the Wells laboratory – note in their current paper the colon has been more difficult to generate than other parts of the GI tract.

Part of the challenge to identifying the correct genetic and molecular programming to coax hPSCs in to colonic organoids has been a lack of data about embryonic development of the organ, according to the authors.

They also mined public databases (GNCPro, TiGER, Human Protein Atlas) to identify molecular markers of the hindgut in the adult colon.

To develop a model for generating the human colon, scientists first identified SATB2 (special AT–rich sequence–binding protein 2) as a definitive molecular marker for hindgut in frogs, mice and in humans.

SATB2 is a DNA–binding protein that facilitates structural organization of chromosomes in the nucleus of cells.

The protein sequence of SATB2 is remarkably similar between frogs, mice and humans. This led the authors to the hypothesis that molecular signals regulating SATB2 in frogs and mice could be used to make human colon organoids that express the protein.

The authors also noticed that signaling from the growth factor BMP (bone morphogenetic protein) was highly active in the SATB2–expressing region of the gut tube. The researchers learned during their analysis of frog, mouse and human stem–cell derived intestine that signaling by BMP is needed to establish SATB2 in the developing hindgut. With SABT2 as a marker, the researchers show BMP signaling is required for development of tissues specific to the posterior gut region of frogs and mice where the colon develops.

When BMP protein was added for three days in human pluripotent stem cell–derived gut tube cultures, it induced a posterior HOX code. HOX includes a critical set of genes that help control the embryo’s development plan from head to toe. Researchers report the posterior HOX helps control the formation of SATB2–expressing human colon organoids. To see how human GI tissues perform in a living organism – and to test their future therapeutic potential – the research team included collaborators from the Division of Surgery, led by Michael Helmrath, MD, a pediatric surgeon and director of the Surgical Research program. The tissue–engineered colonic organoids were transplanted into the kidney capsules of immunocompromised mice for six to 10 weeks. During observation and analysis of the now in vivo organoids, study authors looked for signs of posterior region enteroendocrine cells, which make hormones found in naturally developed human colon.