The reason why I enjoy reading about stem cells is because everytime an article is published on a novel application, I can think of someone who might benefit from it. In this case, its my grandfather who is presently a healthy 96 year-old (or young depending on his mood).
He is still energetic and full of enthusiasm but one of the first senses to deteriorate was his sense of hearing. He started off with just one hearing aid about ten years ago but now has one in each ear. It has become quite difficult to communicate with him now unless you can get his attention visually or by gently nudging him first (and if he turns up his hearing aid, we get the do-doo-do sounds due to the radio requencies when a nearby mobile phone rings).
Hearing Loss
Hearing loss has many causes, including genetics, aging, and infection, and may be complete or partial. Such loss may involve damage to inner ear cells called cochlear fibrocytes, which are fundamental to inner ear function.
Blind as a Bat, Deaf as a ......
Stem Cells Restore Hearing
Anyway, this article tells us of some exciting research published in the American Journal of Pathology (well, exciting to me anyway) conducted in the National Tokyo Medical Center (Japan*) by Dr. Tatsuo Matsunaga. He came up with the idea of finding out if bone marrow derived stem cells could help to restore damaged cochlear fibrocytes and thus speed up the recovery of hearing.
Dr. Matsunaga and team came up with the devastating idea of killing off these cochlear fibrocytes with a drug in mice, thus inducing an acute hearing loss. Partial recovery due to innate stem cells may occur over many weeks but these poor mice almost never regain their high-frequency hearing. Dr. Matsunaga then explored if direct administration of stem cells into the inner ear of these mice might restore the lost cell population and consequently, hearing.
The results were very interesting.
Stem cells injected into the inner ear survived in half of the injured rats, where they migrated away from the site of injection toward the injured region within the inner ear. These stem cells divided in the new environment and expressed several proteins necessary for hearing, suggesting tissue-specific differentiation. Further, transplanted cells that migrated to the damaged area of the inner ear displayed shape similar to that of cochlear fibrocytes.
Importantly, transplanted rats exhibited faster recovery from hearing loss, particularly in the high frequency range, which is difficult to restore by natural regeneration. Stem cell migration into the damaged area of the inner ear improved hearing of high frequency sound (40 kHz) by 23% compared to natural recovery in untreated animals.
So it appears that the stem cells are able to "home in" on damaged areas of the inner ear and initiate regeneration of the lost cells, and that the transplanted cells were able to adapt morphologically and functionally to their new environment.
My questions are how the stem cells are injected** into the inner ear (under X-ray guidance?), how many stem cells we'll need and whether it might work on a 96 year-old. I think this work is very exciting and I'd really like to tell my grandfather about it, but I'll wait to tell him in person, not over the phone :).
*The work was supported by grants, one of which was from the Japan Foundation of Aging and Health. It is interesting to note this as Japan as one of the most serious aging populations in the world today.
**Have a look at this interesting cochlear implant (developed by Seoul National University) which gets inserted all the way into the cochlear and connected to a speech processor. Read this page if you want an idea of how cochlear implants are surgically implanted and its risks.
On another note, I found this very interesting language company in Luxembourg. The emphasis of its founder, Dr. Alfred Tomatis, is that you have to be able to hear the language before you can speak it with the right tones. The teaching method involves the assessment of your auditory abilities before you commence the language course. Notice how English speakers are on the higher frequency whilst other european languages tend toward the lower frequencies.
Posts
2 comments:
this is really an interesting findings, and hopefully if it can be effectively used in our human, then it will be a new medical success.
anyway, i'm just a medical student. What my concern is do stem cell can regenerate any vestibularcochlear nerve (Cranial Nerve 8th)? as we know, currently we have cochler implant available around the world...but, as from what my limited knowledge is the nerve implant is still not available...so, if the regeneration of this nerve do occur, then it will be better.
2nd question is, what was the level of hearing loss that were induced in those mice? is it benefit for those profound hearing loss? again, as from my limited-knowledge is cochlear indication is for those profound hearing loss..so, do the function of this stem cell cochlear as similar as or better than the existed cochlear implant?
thanks..
Dear JC,
I have to first declare that I am no ENT expert but to my understanding of the publication, there are 2 things which we should note;
1) that the hearing was induced in cochlear fibrocytes via a chemical method, where a drug was administered to the cells which caused a permanent malfunction of the mitochondria- resulting in cell death.
2) that this experiment was performed in mice.
So with regards to your question, I don't think they actually destroyed the nerve, but they certainly did manage to cause some profound hearing loss (cochlear fibrocytes have the important function of generating the endocochlear potential essential for the transduction of sound) as shown in the auditory brainstem studies. However, I didn't see any mention of a comparison between their stem cell work and an existing cochlear implant.
What was interesting though, was that they were able to track the migration of the stem cells from the administration point (inner ear perilymph) to other parts of the auditory system, invading the lateral walls and moving to the scala tympani and even the gap junction network which was disconnected. It is known that stem cells are recruited to sites of injury by chemokines.
The authors suggest that the successful invasion of stem cells could be further improved by using cells of autologous origin (the mice stem cells were extracted from the marrow of other donor mice) and that the addition of appropriate growth factors or continuous addition of stem cells (or greater numbers) may actually enhance the rates that the stem cells invade and spread across the auditory system.
I know there's still lots more to learn and most times, answers spark more questions. But that is what science and research is all about isn't it? The seeking of knowledge to provide understanding.
Hope it helps and it would be great if you might like to contribute any interesting adult stem cell information that you might study in your medical career :)
Best regards,
Sharon
Post a Comment