Scientists have demonstrated the ability of human cord blood stem cells to regenerate damaged liver tissue in mice. Led by Dr. Ping Zhou, the study was conducted by researchers at the UC-Davis Medical Center in Sacramento in collaboration with scientists at the Washington University School of Medicine in St. Louis and the Krembil Center for Stem Cell Biology at the Robarts Research Institute in Ontario, Canada.

Human cord blood stem cells (hCBSCs) are already known to generate hepatocyte-like cells, and human patients who receive autologous bone marrow transplants as a treatment for liver failure have been found to exhibit clinical improvement in pilot trials. It had not been previously demonstrated, however, whether the hCBSC-derived cells are capable of transdifferentiating directly into hepatocytes, or if other mechanisms are at work that merely allow for the fusion of the cells with recipient hepatocytes.

In the current study, Dr. Zhou and his colleagues investigated the action of hCBSCs with beta-glucoronidase-deficient nonobese diabetic/severe combined immunodeficient/ mucopolysaccharidosis type VII (NOD/SCID/MPSVII) mice to whom carbon tetrachloride had been administered to induce liver damage. Using human umbilical cord blood stem cells that had been selected for aldehyde dehydrogenase activity, which correlates with high stem cell activity, the scientists found that the human progenitor cells with high aldehyde dehydrogenase activity engrafted into the damaged liver tissue with an efficiency rate of 3% to 14.2%, while actual fusion of the human cells to the mouse cells was found to be very rare. Additionally, it was observed that the cells in the target mouse tissue expressed a number of human hepatic markers such as albumin, hepatocyte nuclear factor 1 protein, and liver-specific alpha 1-antitrypsin messenger RNA, and the majority of the albumin-expressing cells of human origin also contained mouse genetic material, thereby further indicating engraftment of the human cells to the mouse tissue. As the researchers noted, the procedure thereby "improved recovery of the mice from toxic insult".

As the authors concluded, "hCBSCs or their progeny may home to the injured liver and release trophic factors that hasten tissue repair, whereas fusion of these cells with hepatocytes may occur rarely and contribute to a lesser extent to liver repair."

One reviewer of the study, in StemCellPatents.com, further suggests the supplemental administration of G-CSF (granulocyte-colony stimulating factor), a known stem cell mobilizer which was already shown by Piscaglia et al. in Italy to accelerate liver regeneration. Also recommended is the continued investigation of CD34+ adult stem cells, found in abundance in umbilical cord blood, which have already yielded positive results in the treatment of liver failure as demonstrated by Pai et al. in London in 2008.

In 2007, when Marsh Mayfly suffered a tendon injury, it seemed as though her career was over. But after receiving adult stem cell therapy and taking some time off to have a foal, the 12-year-old horse returned to the circuit with renewed strength and vigor. Last month she won the Burnham Market CIC and then took third place in the advanced section at the Belton Trials.

It was after finishing in 4th place at the Chatsworth International in 2007 that Marsh Mayfly, also known as "Flower", began developing inflammation in her right foreleg. According to the horse’s owner and breeder, Ann Lawson, "Flower is a brave horse with a wonderful temperament. Show jumping is her weak point but she jumped beautifully at Chatsworth only to pull up lame. We were understandably devastated but our vet Andrew Miller remained optimistic and recommended stem cell therapy. We duly proceeded with the treatment and also decided to put Flower in foal."

According to Dr. Miller, equine veterinarian from the Ark Vet Centre in Lockerbie, "Scans showed fiber damage in the mare’s off fore superficial digital flexor tendon. Stem cell therapy offers a good prognosis for this type of injury and was the ideal treatment protocol in the circumstances. Ann’s desire to put Flower in foal also tied in well with the required rehabilitation program following treatment."

The company VetCell Bioscience developed the equine autologous adult stem cell procedure in the U.K., where such therapy is routine practice at most equine veterinary locations, and is even covered by most equine insurance policies. Unlike other companies such Vet-Stem in the U.S., which uses mesenchymal stem cells (MSCs) derived from the adipose (fat) tissue of animals, VetCell uses MSCs that are derived from the animal’s own bone marrow which is extracted from the horse’s sternum. The MSCs are then isolated, expanded to more than 10 million cells, re-suspended in bone marrow supernatant which is rich in growth factors and other chemical nutrients, and then the cells are injected directly into the site of the injury where the cells regenerate the tendon tissue and also prevent the formation of scar tissue, which is often a main hindrance to healing and the cause of future reinjury. Physical rehabilitation and a controlled exercise program are also important to the recovery of the horse, and periodic MRI (magnetic resonance imaging) scans are taken to monitor the healing. As Ann Lawson describes, "We adhered to the rehabilitation program religiously until it came to the cantering when Flower was just too large for any faster work. On June 3rd she gave birth to Perry, a colt foal by the dressage stallion Pro Set. After weaning we started exercise again, including a weekly workout in our local equine pool at Pine Lodge."

The horse began competing again in April. According to Marsh Mayfly’s rider, Ruth Edge, "She gave me wonderful rides at Burnham Market and at Belton and felt fit, keen and full of power. She’s such a generous horse and it’s great to be back on board. Luhmuhlen is next on the calendar and I’m looking forward to it."

VetCell Bioscience specializes in the development and commercialization of new biotechnologies for veterinarian musculoskeletal regeneration. VetCell was formed in partnership with the Royal Veterinary College and the Institute for Orthopaedic and Musculoskeletal Science, and is a trading company within MedCell Bioscience, its parent company, which develops musculoskeletal regenerative therapeutics for human clinical treatment. As stated on their website, "VetCell has rapidly commercialised a technique for the multiplication of equine stem cells which can be used in the treatment of tendon and ligament injury. This service is now available to veterinary surgeons in the U.K. and internationally. VetCell has also developed a simple method for separating and storing stem cells from the umbilical cords of foals." Although VetCell specializes in the treatment of horse injuries, they are also expanding their services and products to therapeutic applications for dogs, cats and other domestic species. Headquartered in Cambridge, England with laboratories in Edinburgh, Scotland, MedCell and VetCell also have offices in Germany, Spain, China, Australia, South America, Canada and the United States.

In Louisiana, the State Legislature has made it a crime to create human-animal hybrids. Under the newly approved legislation, the crime would be punishable by up to ten years in prison.

Promoted by State Senator Danny Martiny, the bill passed without objection by members of the State Senate Judiciary Committee, before going to the full State Senate.

Specifically, the bill prohibits the combination of human sperm with a nonhuman egg, and nonhuman sperm with a human egg, and the development of human neural tissue within a nonhuman animal. The bill does not prohibit some common medical practices such as the use of pig valves in human heart surgery.

The creation of human-animal hybrid embryos is a common procedure in many types of experimental embryonic stem cell research, although outside of the embryonic stem cell world such practices remain highly controversial, primarily for the ethical can of worms that is unleashed by such research. Hybrid experimentation was the topic of widespread debate last year in Britain when funding for such procedures was abruptly halted, despite the fact that Parliament had passed the Human Fertilisation and Embryology Bill, which legalized the creation of human-animal hybrid embryos, in May of 2008. (Please see the related news article on this website entitled, “Human-Animal Hybrid Experimentation in the U.K. is Halted”, dated January 13, 2009). Although such hybrids are usually destroyed during the process of embryonic stem cell experimentation, the possibility of such an embryo surviving past the embryonic stage and growing to adulthood would be a bioethical nightmare, if not also a scientific one as well. Despite the immense biological interest that such hybrids present, the ability to create entire new species in the laboratory is usually a cause for grave concern within the legal and religious communities if not the scientific community.

Earlier this year, research conducted by the company Advanced Cell Technology in Worcester, Massachusetts yielded disappointing results regarding the effectiveness of hybrid techniques. When human DNA was combined with nonhuman ova (eggs) to create hybrid embryos, researchers found that the human DNA did not reprogram effectively and therefore failed to generate stem cells.

The adult stem cell storage company Neostem announced today that it has signed an exclusive licensing agreement with Regenerative Sciences for the commercialization of proprietary adult stem cell technology. The territory to which the licensing agreement applies is all of Asia.

Regenerative Sciences developed the technology, known as Regenexx, specifically for the treatment of orthopedic conditions. Regenexx is a minimally invasive outpatient procedure in which adult stem cells are extracted from a patient’s own bone marrow, cultured in a medium containing important growth factors from the patient’s own blood, expanded to millions of stem cells over a period of 2 to 3 weeks, and then readministered to the patient. Specifically, mesenchymal stem cells are derived from each patient’s own bone marrow, and after processing the cells are injected directly into the patient’s afflicted joints. Since the stem cells are autologous (in which the donor and recipient are the same person), there is no risk of immune rejection. The procedure has already been used to treat hundreds of patients, for whom the procedure has eliminated the need for surgery.

Regenerative Sciences will serve as a consultant to NeoStem throughout their commercialization of the technology in Asia. According to Dr. Robin Smith, CEO of NeoStem, "We are very pleased to obtain the exclusive license in Asia to Regenerative Sciences’ unique technology, and we’re delighted to establish this relationship with Dr. Centeno. The minimally invasive Regenexx procedure complements NeoStem’s established in-office stem cell collection procedures and expands our expertise into a new area. Restoring joints, bone, muscle and cartilage and combating orthopedic diseases complements our growth in the anti-aging and regenerative medicine arena. Recently, we announced acquisition of an exclusive worldwide license for innovative stem cell technology and applications for cosmetic facial expansion procedures and skin rejuvenation. With Dr. Centeno’s assistance we will be adding his stem cell expansion procedure for orthopedic regeneration to the services we are offering in Asia through prominent medical institutions with which we are partnering that we expect to come to market by the end of this year."

According to Dr. Christopher Centeno, founding CEO of Regenerative Sciences, "I look forward to working with Dr. Smith and her team at NeoStem to bring Regenerative Sciences’ important stem cell innovations to a worldwide audience of doctors and patients. I’m especially excited about NeoStem’s relationships and its expanding presence in China."

With their corporate headquarters in New York City and their laboratory banking facility in Los Angeles, NeoStem specializes in the collection, processing and long-term storage of adult stem cells for therapeutic use at a later time in the future, if and when such a therapy might be needed. NeoStem was the first company to provide adult stem cell collection and banking services to the general public.

Headquartered in Colorado, Regenerative Sciences first began performing the Regenexx joint and bone stem cell procedure in 2005. Since then, hundreds of patients have been able to avoid surgeries of the shoulder, knee and hip through the use of their own autologous adult stem cells. As stated on their website, Regenexx is "a non-surgical treatment option for people suffering from moderate to severe joint or bone pain due to injury or other conditions."

Regenerative Sciences found itself at the center of an important controversy when, in July of 2008, Dr. Centeno received a letter from the U.S. FDA (Food and Drug Administration) stating that the autologous adult mesenchymal stem cells processed with Regenexx are considered to be "drugs" since they are intended for therapeutic use. According to the FDA letter, "These cells are considered drugs because the therapeutic claims shown on your website demonstrate that they are intended for use in the diagnosis, cure mitigation, treatment or prevention of disease in man." The letter concluded by stating, "Please be advised that in order to introduce or deliver for introduction a drug that is also a biological product into interstate commerce, a valid biologics license must be in effect. Such licenses are issued only after a showing of safety and efficacy for the product’s intended use. While in the development stage, such products may be distributed for clinical use in humans only if the sponsor has an investigational new drug (IND) application in effect as specified by FDA regulations… The mesenchymal stem cells utilized in your Regenexx procedure are not the subject of an approved biologics license application (BLA) nor is there an investigational new drug application (IND) in effect. Therefore, your implantation of the mesenchymal stem cells for which a valid license or IND is not in effect appears to violate the Act and the PHS Act and may result in the FDA seeking relief as provided by law."

Regenerative Sciences responded by posting the following notice on their website, which was most recently updated on March 31, 2009: "Last summer we got a letter from the FDA stating that they felt that our Regenexx medical procedure was actually the manufacturing of a new drug. The letter made no sense, as what we’re doing is practicing medicine. We kindly wrote back stating our position and then we didn’t hear back for more than half a year. Recently, the FDA has again asserted that they believe we are manufacturing a drug. They haven’t given any credible rationale for why they believe this, as what we’re doing with adult stem cells is no different than the average fertility clinic that grows embryos in culture for re-implantation. The fertility clinic is not regulated as a drug manufacture facility. The fertility specialists fought that fight and won."

This is a critically important issue, since it illustrates the frustration that many, if not all, adult stem cell scientists in the U.S. feel, as it this stance by the FDA which poses an insurmountable, not to mention entirely illogical, hindrance to adult stem cell therapies in the United States. For anyone who has ever wondered why it is that adult stem cell therapies are available in ordinary clinics in most countries outside of the U.S., but only in a limited number of FDA-approved clinical trials within the U.S., here’s your answer: the FDA considers each person’s own autolgous adult stem cells to be a "drug", and therefore those stem cells are subject to the same multi-year, multi-million-dollar clinical trial process through which all pharmaceutically produced drugs must pass before being considered legally marketable within the United States.

The statement on the website of Regenerative Sciences continues: "ASCTA (American Stem Cell Therapy Association) is a physician organization that was formed in opposition to the FDA’s position that adult stem cells are drugs. This group heralds a much bigger movement than what we’re doing here with the Regenexx procedure. We’ve found literally an outcry by patients with chronic diseases that the FDA would stand in their way of getting safe stem cell work performed by their doctors. We agree that there are hundreds of likely unsafe stem cell outfits around the globe injecting God-knows-what into whoever has the will to pay. All the more reason for an organization to step to the forefront to establish physician-run guidelines for safe lab practices and clinical oversight… The pre-clinical research on adult stem cells is much stronger than embryonic stem cells… When I’ve posed the question to numerous doctors and experts in the field, are your own stem cells drugs? They look at me like I’m crazy, and often reply ‘Of course my stem cells aren’t drugs!’ Why would the FDA take the position that your cells are drugs… The ASCTA physician group will be getting out its lab practices guidelines meant to hold new adult stem cell practices to the highest standards to protect patients. Our goal is clear and it’s worth fighting for: Safe Stem Cells Now!"

Likewise, the ASCTA has posted the following statement on their website: "The American Stem Cell Therapy Association (ASCTA) announced today the online publication of its mission statements and charter. The organization was formed in response to the Food and Drug Administration’s (FDA) recent position that the adult stem cells found in everyone’s body are drugs, a position the ASCTA opposes. This physician organization is establishing laboratory guidelines that will allow doctors to bring adult stem cell therapy to their patients more quickly. These guidelines will be similar to those used by fertility specialists in in-vitro fertilization (IVF) labs, where many of the same cell culture techniques are used."

Dr. Centeno, one of the founding members of the ASCTA, is quoted on the ASCTA’s website where he states, "Many patients are dying or suffering daily with incurable diseases or problems that require major surgery. These patients should have access to basic adult stem cell therapy now. ASCTA is establishing guidelines which will allow the safe use of the patient’s own adult stem cells under the supervision of doctors." According to Dr. Frank Falco, another ASCTA founding member who is also quoted on the ASCTA’s website, "The FDA’s position against someone using their own stem cells is taking it too far. We are talking about a person using their own tissue to treat a degenerative disorder or process safely without the use of medications or surgery. Although we agree that oversight and standards are necessary, this should be provided through a physician organization such as ASCTA rather than by a government agency."

Not all stem cells are created equal, of course, and it is vitally important that the FDA make distinctions between embryonic, fetal and adult stem cells. In this regard, the ASCTA website continues, "Adult stem cells are different than embryonic stem cells. Adult stem cells are found in the patient’s body in various tissues. In order to obtain enough stem cells for treatment, they often need to be cultured, similar to today’s fertility treatments. Adult stem cells have undergone much more research than embryonic stem cells and therefore are closer to real world treatments. These adult stem cells are taken from the patient’s own body (autologous) and ASCTA believes that they are therefore the safest for use in treating patients." To this Dr. Centeno adds, "While the Obama administration seems to have opened the embryonic stem cell door, their FDA seems to want to slam the adult stem cell door shut."

As also stated on their website, "The ASCTA is a physician group comprised of various medical and surgical specialists whose goal is to bring safe stem cell therapy to patients by establishing laboratory and clinical guidelines." More information is available at www.stemcelldocs.org.

Additionally, in April of 2009 a patient movement called "Safe Stem Cells Now!" was formed in response to the FDA’s unfounded position that a person’s own adult stem cells are "drugs" and therefore should be regulated in the same manner. More information is available at www.safestemcells.org.

As Barbara Hanson, cofounder of www.stemcellpioneers.com, states, "Adult stem cells are cells from our own body. They are very safe. There are no moral or ethical issues. They are safer than taking aspirin and yet the FDA has classified our own stem cells as drugs that require regulation. This means that prolonged investigations, including lengthy clinical trials, will be required for each and every disease and application that adult stem cells could be used for. This could take years and years. It smells of big pharma to me and many others."

Indeed, many people feel that this stance by the FDA is purely politically and economically motivated. At the very least, it is an entirely unscientific stance, and it is merely one example of the numerous ways in which the FDA needs to update its regulations so that these regulations are relevant and applicable to stem cells, which do not fall into any of the previously existing categories for which the FDA has ever had to formulate national law in the past. Such outdated laws are precisely what is driving many of the best and most accomplished adult stem cell physicians and scientists "off-shore", to set up their laboratories and clinics anywhere at all in the world, just as long as it is outside the borders of the United States. In the end, it is the U.S. patient who suffers, since the researchers and clinicians themselves are not stopped but are merely forced to relocate to other countries. Until the FDA is able to recognize the numerous and vast differences between an autologous adult stem cell and a pharmaceutically manufactured drug, it is no wonder that adult stem cell companies such as NeoStem and Regenerative Sciences are able to form licensing agreements throughout all of Asia, but not in their own home country, the United States.

Today the biotech company Genzyme announced updates on anticipated near-term regulatory milestones, new clinical data and plans for continued sustainable growth across each of its businesses. The company reaffirmed its estimated goal of $7 billion in annual revenue by 2011, as growth continues to be driven by an increase in sales of existing products as well as by the launch of new treatments and "continued operating leverage from the company’s global infrastructure." According to Henri A. Termeer, Genzyme’s chairman and CEO, "We are modifying our earnings presentation to provide a simpler picture for investors. We continue to meet our financial commitments, increasing the profitability of the company while investing in new therapies and bringing them to the market."

Genzyme measures its financial activities not just by earnings but also by a number of other parameters and metrics which include cash flow, return on equity, return on assets and return on invested capital, all of which are expected to increase through 2011. Return on invested capital is estimated to be approximately 13% in 2011, with approximately $5.6 billion in cash from operations through the end of 2011. Additionally, the company plans to invest approximately $1.9 billion of this projected total in the expansion and maintenance of its global infrastructure, with approximately $1 billion allocated for repurchasing shares and approximately $700 million designated for potential milestone payments that are scheduled to be made to partners.

The company reported that pipeline as well as business developments have exceeded expectations. According to the report, "The launch of Myozyme (alglucosidase alfa) has been more rapid than the launch of any of Genzyme’s other treatments for lysosomal storage disorders, driven by faster-than-expected adoption by physicians and patients and consistent support from health authorities in more than 40 countries." Genzyme also presented new data from a Phase II clinical trial of GENZ-112638, which is an oral therapy currently in development for patients with Gaucher disease type 1. Data at the end of the first year indicate that the compound either improved or stabilized the bone disease that is caused by Gaucher disease.

In the product portfolio for the hematologic oncology field, the company estimates revenue of $1 billion by 2011. In oncology and bone marrow transplant, a recently announced transaction with Bayer HealthCare extends Genzyme’s commercial presence to more than 90 countries. Cardiometabolic and renal proprietary products are currently in Phase II/III clinical trials in which 315 hyperphosphatemic dialysis patients are enrolled. Results for the primary endpoint of serum phosphorus changes are expected during the first half of next year, and the core patent estate for sevelamer will not expire until 2014.

Additionally, in December of last year Genzyme received approval from the U.S. FDA for the marketing of its proprietary adult stem cell stimulating product, Mozobil, which is a novel, proprietary small-molecule CXCR4 chemokine receptor agonist. When used in combination with G-CSF (granulocyte-colony stimulating factor), Mozobil has been shown to increase the number of stem cells circulating in the peripheral blood by mobilizing hematopoietic stem cells in the bone marrow and stimulating the cells to migrate into the bloodstream for easier collection and subsequent autologous transplantation. According to John DiPersio, M.D., Ph.D., a professor at Washington University in St. Louis, "Mozobil is an important advancement in the treatment of patients with certain types of cancer who require a stem cell transplant. This product should become an integral part of the treatment regimen for transplantation because of the benefits it offers to patients, physicians and transplant centers." Approximately 55,000 hematopoietic stem cell transplants are performed each year globally for multiple myeloma, Hodgkin’s and non-Hodgkin’s lymphoma, for which Mozobil is expected to be used in the majority of such cases. Peak annual sales of Mozobil are projected to reach $400 million. Genzyme has also submitted applications to the respective regulatory agencies in Europe, Australia and Brazil for marketing approval of Mozobil, and additional applications in up to 60 countries are planned.

In November of 2008, Genzyme announced a strategic alliance with Osiris Therapeutics for the commercialization of two adult stem cell products. According to the agreement, Osiris will commercialize the proprietary products Prochymal and Chondrogen in the U.S. and Canada, while Genzyme will commercialize the products throughout the rest of the world. Genzyme made an upfront payment of $130 million to Osiris in additon to milestone and royalty payments that will be made in the future and which are estimated to be worth approximately $1.3 billion. Prochymal and Chondrogen are therapies that use allogeneic (in which the donor and recipient are different people) adult mesenchymal stem cells derived from bone marrow. Both of the products are late-stage treatments for a wide variety of diseases.

Genzyme, the world’s largest maker of drugs for rare genetic disorders, is well known for commercializing first-in-class biotechnologies. In addition to its large orthopedic franchise, Genzyme’s products are focused on rare genetic disorders, kidney disease, cancer, transplant and immune disease, diagnostic testing, cardiovascular disease, neurodegenrative diseases, endocrinology and other medical specializations in which patient needs are not adequately met. Genzyme’s strategic alliance with Osiris marks a major expansion by Genzyme into the field of cell transplant therapies. Founded in 1981, Genzyme now has more than 10,000 employees around the world with revenues in 2007 of $3.8 billion. Its products and services are available in nearly 90 countries worldwide. In 2007, Genzyme was awarded the National Medal of Technology, the highest honor awarded by the President of the United States for technological innovation.

Genzyme’s stock closed at $60.85 today.

Cytori Therapeutics has announced that GE Healthcare, a division of the General Electric Company, will market Cytori’s stem cell extraction products in the U.S., Canada and Mexico for 18 months, beginning in the second quarter of 2009. This agreement follows a similar arrangement that the two companies made in January and which applied to ten European countries.

Known as StemSource, the proprietary technology is used to extract adult stem cells from adipoes (fat) tissue, after which the cells are then either cryogenically preserved or made available for research purposes. The processing system would make the stem cells available for cell banking and research markets.

The agreement does not include Cytori’s Celution System, which is still being reviewed by the U.S. FDA (Food and Drug Administration) for marketing approval.

According to Christopher Calhoun, CEO for Cytori Therapeutics, "Expanding our commercialization partnership into North America will allow us to take advantage of GE Healthcare’s established stem cell banking and research customer base. Both organizations recognize there is an existing demand in the United States for these products and we look forward to making the StemSource technology available in the U.S. in the first half of 2009."

According to Konstantin Fiedler, general manager of Cell Technologies at GE Healthcare, "This agreement between GE Healthcare and Cytori is important for our growing life sciences business. Our U.S. sales team, like that in Europe, is seeing growing customer demand for adipose-related cell technology, both from our existing stem cell banking customers as well as our research customers involved in the development of cell therapies. An expanded partnership with Cytori gives our U.S. sales team access to these first-in-class products for these markets in the United States."

Founded in 1878 by Thomas Edison, the multinational conglomerate General Electric ranks as the tenth largest company in the world in terms of market capitalization, with reported revenue in 2008 of $182.5 billion. The GE Healthcare division alone employs more than 47,000 people in more than 100 countries.

Founded in 1996 and headquartered in San Diego, Cytori Therapeutics develops technology for reconstructive and aesthetic surgical procedures.

Researchers at the University of Sheffield have announced that they have differentiated fetal stem cells into the sensory hair cells of the ear, which could then be surgically inserted into the ear to restore lost hearing, at least theoretically.

According to Dr. Marcelo Rivolta, who led the study, "It will take several years before we are in a position to start doing human trials." He and his colleagues caution that the research is still in the preclinical, animal model phase, and has not yet advanced to a level where it could be performed safely and effectively in humans.

In the past, whenever auditory hair cells were damaged, permanent hearing loss would result since it was not possible to repair the damaged cells. Now, however, stem cells could be differentiated into auditory cells, thereby restoring lost hearing.

According to Dr. Ralph Holme, director of biomedical research at the Royal National Institute for Deaf People, which helped fund the research, "This research is incredibly promising and opens up exciting possibilities by bringing us closer to restoring hearing in the future."

Although the scientists used fetal stem cells, they are also investigating the ability of embryonic and adult stem cells to differentiate into auditory hair cells. Fetal stem cells have a number of inherent problems and risks, not the least of which is the formation of tumors. (Please see the related news article on this website, entitled "Fetal Stem Cell Therapy Could Prove Fatal", dated February 17, 2009). Presumably this is also the reason why iPS (induced pluripotent stem) cells were not differentiated into auditory neurons, which iPS cells are certainly capable of doing, but scientists have not yet been able to create a completely safe iPS cell which is free of cancer-causing genes and which also lacks the strong tendency to form teratomas (a type of tumor with cells and tissue from all 3 germ layers).

The auditory hair cells of the cochlea, or cochlear hair cells, function as the sensory receptors of both the auditory system and the vestibular system, not only in humans but in all vertebrates. In the past, damage to any part of the cochlear apparatus would often result in decreased hearing sensitivity, which was always considered to be irreversible. These fine hair cells are “bundled” in two sections, known as outer and inner hair cells, each of which performs a specialized function. The outer hair cells provide a purely mechanical amplification of sound, in a similar way as an acoustic preamplifier. The inner hair cells act as a more complex transducer, converting the mechanical vibrations into electrical signals that travel via the auditory nerve to both the auditory brainstem and the auditory cortex of the brain. Although the normal human hearing range is considered to be from 20 Hz to 20,000 Hz, some degree of sensorineural hearing loss is normal with advanced age.

Since all aspects of the auditory system were originally formed from stem cells, then at least in principle it should be possible to regenerate all aspects of the auditory system, given the right type of stem cell. At least conceptually, it should be possible to regenerate not only the auditory sensory receptors of the cochlear hair cells but also auditory neurons as well, regardless of where, exactly, the anatomical damage is located.