Scientists generate “mini-kidney” structures from human stem cells.


Diseases affecting the kidneys represent a major and unsolved health issue worldwide. The kidneys rarely recover function once they are damaged by disease, highlighting the urgent need for better knowledge of kidney development and physiology.

Now, a team of researchers led by scientists at the Salk Institute for Biological Studies has developed a novel platform to study  diseases, opening new avenues for the future application of regenerative medicine strategies to help restore kidney function.

Salk scientists generate “mini-kidney” structures from human stem cells

For the first time, the Salk researchers have generated three-dimensional kidney structures from human stem cells, opening new avenues for studying the development and diseases of the kidneys and to the discovery of new drugs that target human . The findings were reported November 17 in Nature Cell Biology.

Scientists had created precursors of kidney cells using stem cells as recently as this past summer, but the Salk team was the first to coax human stem cells into forming three-dimensional cellular structures similar to those found in our kidneys.

“Attempts to differentiate human stem cells into renal cells have had limited success,” says senior study author Juan Carlos Izpisua Belmonte, a professor in Salk’s Gene Expression Laboratory and holder of the Roger Guillemin Chair. “We have developed a simple and efficient method that allows for the differentiation of human stem cells into well-organized 3D structures of the ureteric bud (UB), which later develops into the collecting duct system.”

The Salk findings demonstrate for the first time that pluripotent stem cells (PSCs)—cells capable of differentiating into the many cells and tissue types that make up the body—can made to develop into cells similar to those found in the ureteric bud, an early developmental structure of the kidneys, and then be further differentiated into three-dimensional structures in organ cultures. UB cells form the early stages of the human urinary and reproductive organs during development and later develop into a conduit for urine drainage from the kidneys. The scientists accomplished this with both human  and induced  (iPSCs),  from the skin that have been reprogrammed into their pluripotent state.

After generating iPSCs that demonstrated pluripotent properties and were able to differentiate into mesoderm, a germ cell layer from which the kidneys develop, the researchers made use of growth factors known to be essential during the natural development of our kidneys for the culturing of both iPSCs and embryonic stem cells. The combination of signals from these growth factors, molecules that guide the differentiation of stem cells into specific tissues, was sufficient to commit the cells toward progenitors that exhibit clear characteristics of renal cells in only four days.

The researchers then guided these cells to further differentiated into organ structures similar to those found in the ureteric bud by culturing them with kidney cells from mice. This demonstrated that the mouse cells were able to provide the appropriate developmental cues to allow human  to form three-dimensional structures of the kidney.

In addition, Izpisua Belmonte’s team tested their protocol on iPSCs from a patient clinically diagnosed with polycystic  (PKD), a genetic disorder characterized by multiple, fluid-filled cysts that can lead to decreased  and kidney failure. They found that their methodology could produce kidney structures from patient-derived iPSCs.

Because of the many clinical manifestations of the disease, neither gene- nor antibody-based therapies are realistic approaches for treating PKD. The Salk team’s technique might help circumvent this obstacle and provide a reliable platform for pharmaceutical companies and other investigators studying drug-based therapeutics for PKD and other kidney diseases.

“Our differentiation strategies represent the cornerstone of disease modeling and drug discovery studies,” says lead study author Ignacio Sancho-Martinez, a research associate in Izpisua Belmonte’s laboratory. “Our observations will help guide future studies on the precise cellular implications that PKD might play in the context of .”

Hans-Peter Kiem genetically manipulates stem cells to treat HIV, genetic diseases and cancers.


Fred Hutch oncologist, stem cell and gene therapy researcher

Imagine if we could treat deadly diseases by generating healthier versions of the very building blocks of our bodies—blood stem cells. That’s the vision of Dr. Hans-Peter Kiem, whose Hutchinson Center laboratory is working to make such therapies a reality.

“Not long ago, this was science fiction,” he said.

Kiem’s cutting edge research reflects his longstanding interest in blood stem cell transplantation, now one of the standard treatments for many blood cancers, in which the patient receives an infusion of blood stem cells, either from a donor or from the patient’s own multiplied cells. The idea is that the new stem cells will grow into disease-free blood cells—a concept that Kiem’s research takes a step further.

“Stem cells can do everything,” said Kiem, who first came to the Hutchinson Center as a fellow in 1992 and joined the faculty five years later. “If we can correct defective stem cells, we can cure diseases.”

Kiem and his colleagues investigate how stem cells can be extracted from sick patients, manipulated at a genetic level and then delivered back to them to treat a range of diseases, from infections like HIV to genetic diseases to aggressive cancers.

One ongoing research effort confronts a major challenge in cancer treatment: Patients can receive only so much chemotherapy at a time, or else their blood cell counts may drop to a level that invites infections, anemia, excessive bleeding and other serious health complications. In such a scenario, the patient must stop receiving chemotherapy until the cell counts recover to healthy levels—but meanwhile, the cancer can worsen.

Kiem’s lab has developed a way to extract a patient’s blood stem cells and insert a special “resistance” gene that is designed to protect the cells from damage by common chemotherapy drugs such as temozolomide and BCNU. An infusion of these enhanced cells could give new hope to patients with the most aggressive form of brain cancer—glioblastoma—which is very difficult to treat. A small study for glioblastoma patients that Kiem started in fall 2009 is showing promising initial results and continuing to expand.

Kiem is also planning a study of patients with AIDS and lymphoma, who would receive blood stem cells with two inserted genes: one that counteracts the HIV infection and one that protects the patient from chemotherapy’s effects.

More recently Kiem has extended his work to derive blood stem cells from a new class of stem cells called induced pluripotent stem cells. What makes pluripotent stem cells promising for new treatments is that they can be derived from readily accessible adult tissues, such as skin cells, and can mature into many other types of tissues and cells, including blood stem cells. These blood stem cells could in turn be expanded and used for blood stem cell transplantations, offering a new treatment option for patients with defective marrow or immune function.

Kiem’s groundbreaking work led to his selection in 2009 as the recipient of the first José Carreras/E. Donnall Thomas Endowed Chair for Cancer Research. The award is named for internationally known tenor and leukemia survivor Carreras and Thomas, who developed bone marrow transplantation.

Don Thomas was pursuing something that was at that time viewed as very difficult,” Kiem said. “It’s a bit of the same thing right now for gene therapy in stem cells. I hope that in 10 or 20 years it will be like what Don has achieved.”

Source: Fred Hutchinson Cancer Research Center

 

 

 

Highly potent human haemopoietic stem cells first emerge in the intraembryonic aorta-gonad-mesonephros region.


Abstract

Background

Haemopoietic stem cells (HSCs) are used in the clinic to treat various haematological disorders. These cells emerge during early embryogenesis and maintain haemopoiesis in the adult organism. In the vertebrate embryo, HSCs develop in multiple locations. Little is known about the embryonic development of human HSCs.

Methods

Human embryonic and fetal tissues were obtained after elective termination of pregnancy. Preconditioned immunodeficient mice were used as recipients for human HSCs. Transplanted mice were bled every 1—2 months to assess human HSC contribution.

Findings

We have found that human HSCs emerge first in the aorta-gonad-mesonephros (AGM) region and only later appear in the yolk sac, liver, and placenta. Transplantation of human AGM region cells into immunodeficient mice provides long-term high-level multilineage haemopoietic repopulation. We have shown that, despite the low number of HSCs in the human AGM region, their self-renewal potential is enormous. A single HSC derived from the AGM region generates around 600 daughter HSCs in primary recipients, which disseminate throughout the entire recipient bone marrow and are retransplantable.

Interpretation

We provide a systematic spatiotemporal analysis of HSC emergence in the early human embryo and identify the AGM region as the primary source of powerful HSCs with enormous self-renewal capacity. This high potency of the first HSCs sets a new standard for in-vitro generation of HSCs from pluripotent stem cells for the purpose of regenerative medicine.

Source: Lancet