Monthly Archives: June 2012

Rudimentary liver grown in vitro

 Japanese scientists have used induced stem cells to create a liver-like tissue in a dish.

Although they have yet to publish their results and much work remains to be done, the achievement could have big clinical implications. If the results bear out, they would also constitute a significant advance in the ability to coax stem cells to self-organize into organs.

The work was presented by Takanori Takebe, a stem-cell biologist at Yokohama City University in Japan, at the annual meeting of the International Society for Stem Cell Research in Yokohama last week. “It blew my mind,” said George Daley, director of the stem-cell transplantation programme at the Boston Children’s Hospital in Massachusetts, who chaired the session.

“It sounds like a genuine advance,” says Stuart Forbes, who studies liver regeneration at the University of Edinburgh, UK. Forbes, who also works as a consultant for Scotland’s liver-transplantation unit, says that the advance could one day help to avoid the “bleak outcome” currently experienced by the many patients who don’t survive long enough to get a new liver.

But the liver described by Takebe has a long way to go before that. Takebe told how his team grew the organ using induced pluripotent stem cells (iPS), created by reprogramming human skin cells to an embryo-like state. The researchers placed the cells on growth plates in a specially designed medium; after nine days, analysis showed that they contained a biochemical marker of maturing liver cells, called hepatocytes.

At that key point, Takebe added two more types of cell known to help to recreate organ-like function in animals: endothelial cells, which line blood vessels, taken from an umbilical cord; and mesenchymal cells, which can differentiate into bone, cartilage or fat, taken from bone marrow. Two days later, the cells assembled into a 5-millimetre-long, three-dimensional tissue that the researchers labelled a liver bud — an early stage of liver development. 

The tissue lacks bile ducts, and the hepatocytes do not form neat plates as they do in a real liver. In that sense, while it does to some degree recapitulate embryonic growth, it does not match the process as faithfully as the optic cup recently reported by another Japanese researcher. But the tissue does have blood vessels that proved functional when it was transplanted under the skin of a mouse. Genetic tests show that the tissue expresses many of the genes expressed in real liver. And, when transferred to the mouse, the tissue was able to metabolize some drugs that human livers metabolize but mouse livers normally cannot. The team claims that its work is “the first report demonstrating the creation of a human functional organ with vascular networks from pluripotent stem cells”.

Takebe says the success depended on properly timing the addition of the other two cell types. “It took over a year and hundreds of trials,” says Takebe.

The team says that the tissue’s three dimensions will give it advantages over simple cell-replacement therapies. It could be used for long-term replacement or short-term graft while the recipient waits for a suitable liver donor, or in cases in which doctors anticipate that the native liver will eventually regain its function. But such applications would require extensive development, including making sure that the tissue contains the proper arrangement of lobules.

It won’t be easy, says Forbes. To treat the commonest reason for liver transplants, chronic liver disease, the cells would have to be stable, potentially for many years, in the patient. But it is not clear whether that would be possible, especially considering that they would be exposed to many toxins and pathogens. Furthermore, the organ would need to stay the right size, without atrophying or developing cancerous growth. “Any deviation from the mature phenotype could be catastrophic for the graft,” says Forbes.

Other researchers have developed competing technologies using scaffolds to build three-dimensional liver-like structures.  Sangeeta Bhatia, a bioengineer at the Massachusetts Institute of Technology in Cambridge, for example, has produced a scaffold-based graft that doesn’t try to recapitulate development but has proved to be functional and transplantable in mice. Bhatia is now working on increasing the number of hepatocytes present on the two-centimetre graft, to ensure that it is useful in the clinic. “One billion cells is the next frontier,” she says.

In the meantime, Takebe and the rest of the team, led by Hideki Taniguchi, also a stem-cell biologist at Yokohama City University — who are collaborating on the project with researchers at Sekisui Medical, a biotechnology firm based in Tokyo — hope that his liver bud could be useful for toxicity testing in drug screening, for which bile ducts are not needed. Many conventional hepatocyte cells that are transplanted to mice for in vivo testing last for only two or three days, but the drug and its various metabolites might take weeks to metabolize, so toxic effects might not be apparent in such testing. Takebe says his graft has the necessary staying power.

Many researchers are already growing hepatocyte-like cells: Bhatia, for example, has already commercialized a device that uses bioengineered cells for drug testing. However, Takebe’s liver bud has the advantage of being grown from iPS cells, rather than, for example, the primary human hepatocytes used in Bhatia’s graft, which could make it useful in modelling rare diseases or examining the specific genetic backgrounds of the iPS cell donors.

Markus Grompe, who studies liver disease at the Oregon Health and Science University in Portland, says that Takebe’s team is “on the right track”. Still, he says, the liver cells need to function much more efficiently than they do at present. On the basis of a cursory inspection of Takebe’s data presented at the meeting, Grompe says that the liver bud was producing only a small fraction of the albumin — a plasma protein that is a key marker of liver function — that it should. But Takebe says that since his group generated the data presented at the Yokohama meeting, procedural improvements have already led to higher levels of albumin.

The next step for the team is to try to make the liver bud more liver-like, by including structures such as bile ducts.

 

Source: David Cyranoski, Nature

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Ten-year-old girl gets vein grown from her stem cells

A 10-year-old girl has had a major blood vessel in her body replaced with one grown with her own stem cells, Swedish doctors report. 

She had poor blood flow between her intestines and liver.

A vein was taken from a dead man, stripped of its own cells and then bathed in stem cells from the girl, according to a study published in the Lancet.

Surgeons said there was a “striking” improvement in her quality of life.

This is the latest is a series of body parts grown, or engineered, to match the tissue of the patient.

Last year, scientists created a synthetic windpipe and then coated it with a patient’s stem cells.

A blockage in the major blood vessel linking the intestines and the liver can cause serious health problems including internal bleeding and even death.

In this case, other options such as using artificial grafts to bypass the blockage, had failed.

Doctors at the University of Gothenburg and Shalgrenska University Hospital tried to make a vein out of the patient’s own cells.

It used a process known as “decellularisation”.

It starts with a donor vein which is then effectively put through a washing machine in which repeated cycles of enzymes and detergents break down and wash away the person’s cells.

It leaves behind a scaffold. This is then bathed in stem cells from the 10-year-old’s bone marrow. The end product is a vein made from the girl’s own cells.

The doctors said: “The new stem-cell derived graft resulted not only in good blood flow rates, but also in strikingly improved quality of life for the patient.”

Profs Martin Birchall and George Hamilton, from University College London, said: “The young girl was spared the trauma of having veins harvested from the deep neck or leg with the associated risk of lower limb disorders.”

They said this one-off procedure needed “to be converted into full clinical trials… if regenerative medicine solutions are to become widely used”.

Source: James Gallagher, BBC News


A better way to make bone: Fresh, purified fat stem cells grow bone faster, better

 UCLA stem cell scientists who purified a subset of stem cells from fat tissue and used the stem cells to grow bone discovered that the bone formed faster and was of higher quality than bone grown using traditional methods.
The finding may one day eliminate the need for painful bone grafts that use material taken from patients during invasive procedures.
Adipose, or fat, tissue is thought to be an ideal source of mesenchymal stem cells — cells capable of developing into bone, cartilage, muscle and other tissues — because such cells are plentiful in the tissue and easily obtained through procedures like liposuction, said Dr. Chia Soo, vice chair of research for the UCLA Division of Plastic and Reconstructive Surgery.
Soo and Bruno Péault, the co-senior authors on the project, are members of the Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research at UCLA.
Traditionally, cells taken from fat had to be cultured for weeks to isolate the stem cells which could become bone, and their expansion increases the risk of infection and genetic instability. A fresh, non-cultured cell composition called stromal vascular fraction (SVF) also is used to grow bone. However, SVF cells taken from adipose tissue are a highly heterogeneous population that includes cells that aren’t capable of becoming bone.
Péault and Soo’s team used a cell-sorting machine to isolate and purify human perivascular stem cells (hPSC) from adipose tissue and showed that those cells worked far better than SVF cells in creating bone. They also showed that a growth factor called NELL-1, discovered by Dr. Kang Ting of the UCLA School of Dentistry, enhanced bone formation in their animal model.
“People have shown that culture-derived cells could grow bone, but ours are a fresh cell population, and we didn’t have to go through the culture process, which can take weeks,” Soo said. “The best bone graft is still your own bone, but that is in limited supply and sometimes not of good quality. What we show here is a faster and better way to create bone that could have clinical applications.”
The study was published June 11 in the early online edition of Stem Cells Translational Medicine, a new peer-reviewed journal that seeks to bridge stem cell research and clinical trials.
In the animal model, Soo and Péault’s team put the hPSCs with NELL-1 in a muscle pouch, a place where bone is not normally grown. They then used X-rays to determine that the cells did indeed become bone.
“The purified human hPSCs formed significantly more bone in comparison to the SVF by all parameters,” Soo said. “And these cells are plentiful enough that patients with not much excess body fat can donate their own fat tissue.”
Soo said that if everything goes well, patients may one day have rapid access to high-quality bone graft material: Doctors will get their fat tissue, purify that into hPSCs, and replace the patient’s own stem cells with hPSCs and NELL-1 in the area where bone is required.
The hPSCs with NELL-1 could grow into bone inside the patient, eliminating the need for painful bone-graft harvestings. The goal is for the process to isolate the hPSCs and add the NELL-1 with a matrix or scaffold to aid cell adhesion in less than an hour, Soo said.
“Excitingly, recent studies have already demonstrated the utility of perivascular stem cells for regeneration of disparate tissue types, including skeletal muscle, lung and even myocardium,” said Péault, a UCLA professor of orthopedic surgery “Further studies will extend our findings and apply the robust osteogenic potential of hPSCs to the healing of bone defects.”
The study was funded in part by the California Institute of Regenerative Medicine’s Early Translational Research Award and Training Grant Research Fellowship; a University of California Discovery Grant; and the National Institute of Dental and Craniofacial Research Center at the National Institutes of Health (R21-DE0177711 and RO1-DE01607).
Source: Kim Irwin, UCLA Newsroom

Doctors turn to cord blood transplants in hopes of curing patients with HIV

 Timothy Brown made medical history when he became the first patient who was essentially cured of HIV, after receiving a stem cell transplant from a person who was genetically resistant to the infection.  Now, doctors are hoping to build on Brown’s success by treating HIV patients using cord blood units that have the same HIV-resistant gene.

Brown, 46, was a student living in Berlin in 1995 when he tested positive for HIV.  He responded well to therapies for the disease until 2006, when doctors also diagnosed him with acute myeloid leukemia.

The doctor who treated Brown, Dr. Gero Hütter from Berlin’s University Hospital, proposed to tackle his leukemia by using chemotherapy to wipe out his immune system, and then rebuild the immune system with a bone marrow transplant.

However, when searching for an appropriate match, Hütter kept his eyes out for a specific donor: one who carried a genetic mutation called delta 32, which disables the CCR5 receptor on immune system cells.  The CCR5 receptor is the one HIV uses to infect its victims – meaning people who carry the mutation are essentially immune to the disease.  Approximately one percent of Europeans carry the mutation, but it is rarer people of African, Asian, or South American descent.

Out of 232 potential donors, Hütter found a match for Brown, who also carried the delta 32 mutation, on the 67th try.  The doctors performed the transplant, repopulating Brown’s bone marrow cells with the donor cells.  Months later, Brown was in remission for leukemia and had no trace of HIV in his body.

And while Brown’s leukemia eventually recurred a year later, necessitating another transplant, his HIV never did.

“I still have some disabilities due to the treatments – it’s not perfect,” Brown told FoxNews.com, explaining that he suffered from speech and balance issues following the procedure.  “But it is my life, and I’m very happy not to have to worry about HIV anymore.”

However, Brown’s stem cell transplant isn’t feasible as a widespread treatment for HIV patients, according to doctors.  It can be highly difficult to find a matching bone marrow donor – let alone one who also carries the HIV-resistant gene.

“The cord blood idea came about later because of the success with my transplant,” Brown said.  “…In my case, using stem cells, they had to find a perfect match for me.  With cord blood, you don’t have to use donors that are  an exact match, so it means doctors are more likely to find a donor who will work.”

Dr. Lawrence Petz, a stem cell transplantation specialist, as well as chief medical officer for StemCyte and president of the Cord Blood Forum, explained cord blood essentially gives doctors more leeway in regards to matching patients with donors and opens the possibility of treating many more people.

“At the present time, I feel there’s no other way to cure a reasonable number of patients other than using cord blood,” Petz said.

Two weeks ago, a patient in the Netherlands was the first to undergo this potentially revolutionary treatment.  As was the case with Brown, the transplant was primarily done to address another disease, but doctors specifically selected a unit of cord blood that contained the HIV-resistant gene in hopes of curing that as well.   Another similar surgery is scheduled for a patient in Madrid within the month.

“We don’t know the final outcome yet, but we’re very optimistic that the transplant will be of significant benefit to the patient,” Petz said.  “Usually it takes some months after the procedure to determine the outcome [while the recipient’s cells are being repopulated with the donor cells], so we’re keeping an eye on it very closely because it could be of historic interest.”

Petz explained that as of now, the treatment isn’t meant for all HIV patients.  The inventory of cord blood units that carry the HIV-resistant gene – 100 out of 17,000 tested so far – needs to be built up over time.

Petz said he believes HIV patients with other hemolytic disorders, such as Brown and the Netherlands patient, and AIDS patients who do not respond well to current drugs on the market, should be considered for the transplants.

Source: Alex Crees, Fox News


Stem Cells Restore Sight in India

 Ashok Chakravarti remembers the moment he went blind.

It was on February 18, 2002. He was at work, at a chemical plant, when a pipe carrying sodium hydroxide (caustic soda) started to leak.

“I was fixing the leak when the chemical splashed into my eyes,” he says. The accident damaged the outermost layer of his eyes, the cornea.

Chakravarti is among thousands of Indians who lose their sight in chemical accidents each year.

Today, some of those people can see again, thanks to scientists at the L.V. Prasad Eye Institute, in Hyderabad.

The institute is treating patients with stem cells – not the controversial embryonic stem cells, but adult stem cells.

Inside the lab where the cells are grown, Savitri Maddileti shows me two petri dishes. Each dish contains a tiny piece of eye tissue from a patient.

“One is [from a] 15-year-old female, and the other is [from a] five-year-old male,” she says.

Both children had accidents with household chemicals and became blind in one eye.

What scientists here aim to do is fix the damaged eye with stem cells taken from the good eye. (In patients who have suffered damage to both eyes, the stem cells are taken from the eye of a close relative.)

Maddileti and her team don’t isolate the stem cells from the eye tissue, but under the right conditions, those cells start growing on their own. 

“Can you see these bright cells coming out?” she says, showing me an image through a microscope.

The cells look shiny, and they are starting to form a thin transparent layer. This is the new corneal tissue that will be transplanted into the patient’s damaged eye.

Pathologist Geeta Vemuganti, who heads the team that grows these stem cells, says the process is much like gardening.

“It’s akin to putting seeds, or a little sapling along with a little bit of soil, or the roots,” she says – the stem cells being the seeds or saplings, and the rest of the eye tissue being the soil or roots.

Vemuganti’s team is not the first to repair damaged corneas with stem cells. This technique was developed by a group of Italian scientists.

But Vemuganti modified that technique, making it simpler and faster.

“Instead of three to four weeks, we made it 10 days,” she says.

This also made the process less expensive, which is important in a hospital that treats all patients, including those who can’t afford to pay.

Vemuganti and her colleagues have treated hundreds of patients from all over India.

One of them is Ashok Chakravarti, the man who lost his sight back in 2002 while fixing a pipe at work. Three months and a few surgeries later, he was able to see again.

“It was like being given a second life,” he says.

But after several years of normal vision, Chakravarti started having eye problems again. So he has returned to the institute to see Virender Sangwan, the surgeon who spearheaded the stem cell initiative.

Sangwan examines Chakravarti’s eyes.

“Your body has rejected the right cornea,” Sangwan tells Chakravarti.

That’s because Chakravarti wasn’t just given the stem cell transplant; he also received corneal tissue from a dead donor, because his injury was especially severe.

Sangwan says the stem cell transplant worked just fine, but the corneal graft is starting to fail.

“That’s a normal graft rejection, like any other transplant rejection,” says Sangwan. “So we are going to replace that cornea and see if that will work.”

Many of his patients return with post-surgical complications. Treating them is an ongoing process.

But Sangwan says any success is important because when poor people in India go blind, they lose more than their sight.

“Once you don’t have the eyesight, then the society doesn’t respect you,” he says. “Socially [you’re] not productive, so everybody starts neglecting [you].”

By restoring sight, Sangwan says he is restoring his patients’ self esteem and, as he puts it, their “faith in life.”

Source: Rhitu Chatterjee via theworld.org