ISSCR Review

Along with 3500 other scientists, I spent the last week of June at the annual ISSCR (International Society for Stem Cell Research) conference in Stockholm, Sweden.  Among other things, the ISSCR has been at the forefront of advocating for patient education when it comes to stem cell therapies.  I highly recommend that anyone considering a stem cell treatment, especially those occurring outside of the US, read the ISSCR website and the guides provided there.

The meeting was very exciting, filled with dozens of talks and hundreds of posters describing the most recent advances in stem cell research.  Here are some of my highlights:

  • Masayo Takahashi (RIKEN, Japan), the lead scientist on the iPSC-derived RPE clinical trial for macular degeneration described the years of work leading up to the trial and the current results of the first patient (no problems reported and an overall stabilization of vision).  However, days after the meeting, the trial was put on hold when cells that were planned to be injected into a second patient were found to bear mutations that could lead to cancer.
  • Hans Clevers (Hubrecht Institute, Netherlands) described their use of gut cancer organoids to screen for drugs that would specifically work for individual patients, based on the specific mutation that led to their cancer.  They are expanding their work to also screen for cystic fibrosis drugs.  This is a fine example of the immediate impact that personalized medicine can have on treatment.
  • Organoids – there were many talks from various researchers on the use of organoids to understand normal organ development and disease processes, including an update on brain organoids
  • Genome Editing – I have been remiss on blogging about this topic–stay tuned, as it has and will continue to be a game-changer in regenerative medicine

I’m optimistic that there will continue to be exciting advances in regenerative medicine in the second half of 2015, but researchers need to careful to ensure that everything is done to ensure that potential treatments undergo rigorous safety checks before moving into human clinical trials.

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I can see clearly now

I aim to make this blog as broadly about regenerative medicine as I can, and not let my personal biases about topics influence what I write about–if I’m not careful, the whole blog could be about treatments for blinding disorders.  However, I couldn’t keep from posting the latest news about an approved treatment for blindness due to clouding of cornea.  The treatment, Holoclar [1], has been approved by the European Commission and the European Medicines Agency, the European Union equivalent of the US FDA (Food and Drug Administration).  This is the first time a stem cell treatment, apart from those using bone marrow or cord blood, has been approved commercially by any regulatory agency worldwide [2].  This is a huge step forward for treating this form of blindness, but also for regenerative medicine as a whole.

The cornea, limbal stem cells, and blindness

The cornea is the clear covering of your eye, which serves critical functions in preventing infection and refracting light to the back of the eye (See Figure 1).  You can think of the cornea like the cover on the face of a watch–it protects what’s inside, while still allowing you to see what’s behind it.  Just as your skin is currently being sloughed off, every time you blink, cells of the cornea are wiped away.  In order to maintain the cornea, new cells have to be generated, which is where stem cells come in.  At the boundary of the cornea and the rest of the covering of the eye is a region called the limbus, which is where corneal stem cells live (See Figure 1).

250px-Limbus
Figure 1: The Human Eye                       From Wikipedia

Normally corneal stem cells continue to function throughout your lifetime, but sometimes they are damaged or lost, as is the case in a chemical (e.g. acid) burn to the eye.  There are also genetic defects that can lead to disfunction or loss of corneal stem cells.  In patients with corneal stem cell deficits, the “white” of the eye grows over the pupil in place of the cornea, which keeps light from getting to the retina, and causes significant vision loss and pain (See Figure 2).

limbus
Figure 2: Corneal opacity as a result of a chemical burn. From Secker and Daniels, Stembook, http://www.stembook.org/node/588

Over the past several decades, researchers have looked for ways to replace missing corneal stem cells.  This is where Holoclar comes in.  In this treatment, a small piece of limbus from the patient’s other eye (which is unaffected) is cut out and taken to the lab.  The cells from the tissue grow, and the normal corneal stem cells are expanded on a support system , until they form a sheet of cornea (See Figure 3).

cornea graft
Figure 3: Sheet of corneal tissue ready to be transplanted. http://www.chiesisgroup.com

Once there sheet has grown large enough, the cloudy corneal tissue is removed from the patient’s affected eye, and the graft is transplanted in its place (See Figure 4).

CornealTransplant
Figure 4: Schematic of corneal replacement surgery.

The researchers behind this technique recently reported their success with 112 patients.  77% of these grafts were deemed to be successful, and many of the patients have been stable for years following their transplant [3].  See Figure 5 for some of their outstanding results.

treatment.001
Figure 5, [3]

These results, and the regulatory success of this treatment, are a big step in the right direction for regenerative medicine.   While it took them many years to get approval, their success will pave the way for the approval of other treatments.

[1] Holostem, http://www.holostem.com/en/Homepage.html

[2] Abbott.  Nature, 2015.

[3] Rama et al. NEJM, 363:147-55, 2010.

The (Bloody) Fountain of Youth

With the rise in popularity of movies and books about vampires and zombies, blood transfusions to reverse aging may sound like another fictional tale.  But whether it is life imitating art, or the other way around, California-based Alkahest is testing the premise that young blood may be able to reverse cognitive decline in older Alzheimer’s patients.

The scientific foundation for this clinical trial is the idea of heterochronic parabiosis (hetero = different, chronic = time, para = alongside, bios = life), in which the circulatory systems of two living organisms, typically mice, are sewn together (See Figure 1).  Though it may sound like science fiction, studies investigating heterochronic parabiosis have roots as far back as the 1880s, when Paul Bert found that a fluid injected into one of the paired animals (in this case, rats) passed into the second rat through their connected blood vessels.  In the 1950s Clive McCay of Cornell University applied this idea to the study of aging, by joining rats of different ages and found that older rats joined to younger rats lived longer that old:old pairs [1].

Figure 1
Figure 1 Nik Spencer/Nature; Chart Data: A. Eggel & T. Wyss-Coray Swiss Med. Wkly 144, W13914 (2014)

Recently, heterochronic parabiosis has experienced a rebirth, with a number of groups investigating the specific effects of young blood on the organs of old mice, and vice versa.  Work led by Tom Rando of Stanford University demonstrated that the blood of young mice can rejuvenate the muscles and livers of old mice.  It is well known that the regenerative capacity of stem cells present in muscle (and many other tissues) declines with age.  What Rando’s study demonstrated, was that the blood of young mice was able to restore the inherent regenerative potential of old muscle and liver stem cells.  Similar experiments have investigated the effects of young blood on many organs, including the spinal cord, brain, and heart [3-6] with similar results.  Significantly, young blood can reverse cognitive decline in aged mice and increase the function of brain stem cells [6].  Interestingly, the general effects go both ways–old blood causes premature tissue aging in young mice [7].

Scientists are now trying to determine which factors present in young blood restore stem cell function in old mice.  Tony Wyss-Coray, Stanford University professor and founder of Alkahest, has determined that plasma alone is sufficient to restore tissue function [6]. Two candidate molecules have been proposed: one called GDF11 (Growth Differentiation Factor 11) [5] and oxytocin [8], the so-called ‘cuddle hormone’.  Both molecules decline with age, and injections of either GDF11 or oxytocin lead to improved stem cell function in old mice.  However, there are likely to be many other factors that are contributing to the rejuvenating abilities of young blood.

As I alluded to earlier, Wyss-Coray is banking on the potency of young blood.  A clinical trial is under way, in which 18 male patients over 50 years old with Alzheimer’s disease are receiving blood transfusions from healthy males under the age of 30. This trial moved forward very quickly based on the known safety of countless blood transfusions.  There are many caveats, however.  For one thing, there may be nothing specific in young blood that will have an effect on Alzheimer’s disease.  Secondly, how many blood transfusions would be required to sustain any effect?  Clearly there are more critical needs for donated blood than to slow degenerative diseases.  Perhaps it is time to consider synthetic blood, a la Tru Blood?  Whatever the case, it will be interesting to see how this trial plays out.

[1] Scudellari.  Nature, 517:426-9, 2015.

[2] Conboy et al.  Nature, 433:760-4, 2005.

[3] Ruckh et al. Cell Stem Cell, 10:96103, 2012.

[4] Katsimpardi et al. Science, 344:6304, 2014.

[5] Loffredo et al. Cell, 153:82839, 2013.

[6] Villeda et al.  Nature Medicine, 20:659-63, 2014.

[7] Thomson.  New Scientist, 2983, 2014.

[8] Elabd et al. Nature Commun. 5:4082, 2014.

One small step for science, one giant leap for diabetes

Diabetes is a growing health concern in the United States and worldwide.  In 2012, nearly 10% of the US population was diagnosed with diabetes, and diabetes was the 7th leading cause of deaths in the US [1].  Worldwide, nearly 400 million people are diagnosed with diabetes [2].

What is diabetes?

Diabetes comes in two main forms: Type 1 and Type 2.  Type 2 is the more common form of diabetes, and results from the body not properly using and responding to insulin, which is called insulin resistance.  Type 1 diabetes is typically diagnosed in children and young adults and is caused by a person’s body attacking their own cells that produce insulin.  As a result, these patients do not make enough insulin.  Insulin is a key hormone that is needed to convert sugar and starches into energy.  Insulin is made in the pancreas, by a specific cell type called ß-cells.  Typically, diabetes is treated with daily insulin injections, to restore missing function.

http://transplant.surgery.ucsf.edu/conditions--procedures/islet-cell-transplantation.aspx
http://transplant.surgery.ucsf.edu/conditions–procedures/islet-cell-transplantation.aspx

Stem Cell Therapy for Diabetes

Stem cell therapy has long been envisioned for the treatment of diabetes, especially Type 1.  Scientists believe that if they transplant working ß-cells into diabetic patients, these cells will work properly and produce insulin.  This idea is supported by the fact that when ß-cells from cadavers are implanted into patients, the patients no longer need daily insulin injections, for 5 years and longer.  Unfortunately, there is a limited supply of high quality cadaver-isolated cells, making the promise of this treatment limited.  However, stem cells may offer a solution.  Using embryonic stem cells or induced pluripotent stem cells (together termed PSCs), scientist could make an unlimited supply of ß-cells to be transplanted into diabetic patients.  But how do we make pluripotent stem cells into functioning ß-cells?

Recently, scientists at Harvard have generated PSC-derived ß-cells in the lab for the first time.  They exposed PSCs to different combinations of factors that are expressed when our ß-cells are normally created during development.  Excitingly, the resulting cells look and behave like native ß-cells in the lab.  More importantly, when the scientists transplanted these cells into mice with diabetes, their symptoms were reduced. The mice who received the stem cell-derived ß-cells also lived longer than diabetic mice who did not receive ß-cells [3].

abstract

In addition to developing these cells for transplantation therapy, scientists can also use these cells in the lab to test the function of potential diabetes drugs.

Visit these sites to learn more about diabetes and treatments.

American Diabetes Association

International Diabetes Federation

Diabetes Center, Washington University School of Medicine

[1] http://www.diabetes.org/diabetes-basics/statistics/?loc=db-slabnav

[2] http://www.idf.org/worlddiabetesday/toolkit/gp/facts-figures

[3] Pagiluca et al, Cell, 159:428-39, 2014.

Paper Highlight

A calcium-dependent protease as a potential therapeutic target for Wolfram Syndrome.  PNAS, Early Edition, 2014.

Simin LuKohsuke KanekuraTakashi HaraJana MahadevanLarry D. SpearsChristine M. OslowskiRita MartinezMayu Yamazaki-InoueMasashi ToyodaAmber NeilsonPatrick BlannerCris M. BrownClay F. SemenkovichBess A. MarshallTamara HersheyAkihiro UmezawaPeter A. Greer, and Fumihiko Urano.

Wolfram syndrome is an rare disorder characterized by juvenile diabetes and blindness, which is usually diagnosed in children around age 10, and typically results in death by age 40.  New research has identified a potential therapy to prevent the death of insulin-producing cells, which, when unchecked, leads to diabetes.

Led by Dr. Fumihiko Urano, researchers isolated skin cells from Wolfram Patients and then converted these cells into induced pluripotent stem cells (iPSCs).  Once they had these Wolfram-iPSCs, they differentiated them into insulin-producing beta cells in a dish.  They noticed that these beta cells had increased levels of a particular protein, called calpain 2, which can instruct cells to commit suicide.

When researchers  treated these dying cells with an FDA-approved muscle relaxant (dantrolene), they were able to keep insulin-producing beta-cells from committing suicide, with no adverse affects on normal cells.  Though Wolfram Syndrome results in a unique form of diabetes, researchers are hopeful that dantrolene may be an effective therapy for more common forms.  Additionally, they are looking into the potential of dantrolene to block other parts of Wolfram Syndrome, including degeneration of the optic nerve, which leads to blindness.

Dr. Fumihiko Urano is the Samuel E. Schechter Professor of Medicine in the Division of Endocrinology at Washington University in St. Louis.  He runs the Wolfram Syndrome International Registry and is very active in the Wolfram Syndrome community.  His work is supported, in part, by the Jack and J.T. Snow Scientific Research Foundation, which seeks to raise awareness and fund research for Wolfram Syndrome.

Paper Highlight

Generation of human striatal neurons by microRNA-dependent direct conversion of fibroblasts.  Neuron, 84:311-23, 2014.

Matheus B. Victor, Michelle Richner, Tracey O. Hermanstyne, Joseph L. Ransdell, Courtney Sobieski, Pan-Yue Deng, Vitaly A. Klyatchko, Jeanne M. Nerbonne, Andrew S. Yoo.

One of the major promises of regenerative medicine is the ability to produce large quantities of any cell type, either to model biological processes and diseases or for transplantation, to restore function.  This is particularly needed for the human brain, as there are thousands of different cell types, and disease processes cannot be easily studied in humans.  In 2007, researchers took one step closer to this goal with the discovery that differentiated human cells (such as skin fibroblasts) could be reprogrammed into an embryonic stem cell-state [1].  These induced pluripotent stem cells (iPSCs) can theoretically be differentiated into any cell type, but progress has been limited.

An alternative strategy adopted by a number of researchers is to directly turn skin fibroblasts into neurons (the cells that transmit information in the brain), without first turning them into iPSCs [2, 3].  One set of studies, pioneered by Dr. Andrew Yoo at WUSTL, relies on a special genetic element–termed microRNAs–to cause this profound switch to neurons.  microRNAs are very small pieces of genetic material that can serve as guides to silence other genes.  Dr. Yoo has studied the role of two microRNAs, miR9/9* and miR124, in converting skin cells into neurons [3]. In essence, these microRNAs ‘re-wire’ the identity of the cells into which they are placed.

Now, the Yoo lab, led by graduate student Mat Victor, has generated a very specific kind of neuron from human skin samples (4, shown below).  The neuronal type they generated–striatal medium spiny neurons (MSNs)–is the cell type that is affected in Huntington’s Disease.  Huntington’s Disease is a neurodegenerative disease that affects cognitive function and muscle function.  By combining the previously used microRNAs with specific factors that are normally expressed in human MSNs, they were able to generate MSNs in a dish.  When transplanted into mice, these lab-made neurons incorporated into the brain and functioned properly.


Slide1

These studies represent an important advance in regenerative medicine.  On one hand, they provide a method for generating cells to study and potentially treat Huntington’s Disease.  From a much broader perspective, they demonstrate a general strategy for generating large amounts of specific cell types, which may be applied to other disorders and conditions.

Dr. Andrew Yoo is an assistant professor in the Department of Developmental Biology, and a member of the Hope Center for Neurological Disorders and the Center of Regenerative Medicine at WUSTL.  Read more about the research in the Yoo lab.

[1] Takahashi et al, 2007.  Cell 131:1-12.

[2] Vierbuchen et al, 2010.  Nature 463:1035-41.

[3] Yoo et al, 2011.  Nature 476:228-31.

[4] Victor et al, 2014.  Neuron 84:311-23.

Growing organs in a dish

While it may sound like science fiction, researchers are continuing to move closer to the goal of being able to grow human organs in a dish, in the lab.  In recent years, scientists have grown “organoids” or “microtissues” of multiple organs, including eye, brain, pituitary, and gut [1-4].  Most recently, scientists in Germany reported the growth of organoids mimicking the neural tube, the precursor to the spinal cord [5].

Researchers are harnessing the power of human Embryonic Stem Cells (hESCs) or human induced Pluripotent Stem Cells (hiPSCs), together referred to as human pluripotent stem cells (hPSCs) .  These cells, when grown in the presence of specific combinations of growth factors and proteins–mimicking those present during normal development–differentiate into organized structures that replicate various aspects of human organs.  For example, a protocol for generating human brain tissue is described below [3].

brain organoid

Shown below on the left [3] is a picture of the “brain” that resulted when the steps described above were followed.   On the right is a picture of a mouse brain [6].  Can you see the similarities between the two?

brain orgallenbrain

Here is a comparison of eyes grown in a dish (left) and a mouse eye (right) [1].

eye comparison

These studies represent significant advances, both in our understanding of the developmental processes that occur to generate specific human organs, as well as our hope of developing novel therapies to combat degenerative diseases and injuries.  Another important aspect of these studies is the fact that, though researchers have learned much from studying mouse organs, there are distinct differences between animals and humans.  These differences, and ethical concerns, have limited our understanding of specific aspects of human organs.  However, being able to grow human organs in a dish will allow researchers to more fully understand their complex biology, and hopefully begin to understand various diseases that affect humans.

[1] Eiraku et al.  Nature 472:51-6, 2011

[2] Suga et al.  Nature 480:57-62, 2011

[3] Lancaster et al.  Nature 501:373-9, 2013

[4] Sato et al.  Nature 459:262-5, 2009

[5] Meinhardt et al.  Stem Cell Reports, 2014

[6] Allen Brain Atlas, Developing Mouse Brain Reference Atlas