The sense of smell is something that most human beings take for granted. While the general population is aware that people can lose their sense of sight or hearing, smell seems like a sense that everyone can rely upon throughout their lifetimes. However, the sense of smell can be lost, sometimes permanently, in what is called “anosmia”.
Anosmia can occur temporarily for a number of reasons; people often temporarily lose their senses of smell due to sinus conditions or allergies. The sense of smell can also be temporarily lost because of a change in hormone levels or malnutrition. Unfortunately, permanent anosmia is also an issue that some have to contend with, if relatively rarely. Often, permanent anosmia is linked to neurological conditions, such as brain tumors or epilepsy, or even a specific traumatic brain injury. However, specific medical conditions, including Cushing’s syndrome, Turner’s syndrome, or Kallmann’s syndrome can cause permanent anosmia. With that being said, more common medical problems can also lead to the problem, even diabetes.
The Impact of Anosmia
Permanent anosmia can be devastating, as the loss of any sense would be. The sense of smell allows an individual to participate in life’s simple pleasures. For that matter, the loss of smell can also be linked to the loss or weakening of taste, as the two senses are closely connected.
Restoring the sense of smell is not necessary to sustain life, but it can be necessary to sustain a patient’s quality of life. Due to the former issue, research on the topic has been somewhat limited, and anosmia can often be concerned incurable, depending on the root of the problem. Fortunately, stem cell treatments have produced recent promising results related to the restoration of the sense of smell.
Why Stem Cells?
Stem cells may seem only tangentially related to anosmia, particularly as stem cells are often harvested from umbilical cord blood or embryos. In fact, stem cells are most often related to the most common type of stem cell treatment today, bone marrow transplants. However, a unique quality of stem cells is their ability to differentiate; that is, they can take on specialized cellular traits, and can be manipulated into becoming functional specialized cells. A stem cell will essentially “transform” into other types of cells.
What Researchers Are Doing
Currently, researchers are studying how stem cells can be used to treat neurological conditions, which would naturally link to the treatment of issues linked to brain, such as anosmia. For that matter, the structure responsible for the sense of smell is particularly linked to the potential use of stem cells.
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The lining of the nasal cavity, a layer of neurons and supporting cells, is called the olfactory epithelium. It actually possesses two different types of stem cells, called globose basal cells (GBCs) and horizontal basal cells (HBCs). GBCs are actually responsible for renewing nasal cells. This means that, should an individual lose his or her sense of smell, that sense could potentially be “regrown” through the manipulation of GBCs. The fact that HBCs and GBCs are stem cells at all means that scientists can potentially use them to create therapies that will restore, or at least strengthen, a person’s sense of smell.
What Has Research Shown So Far?
Even stem cells can be limited in their scope; therefore, it is easy to understand why some might treat them with skepticism, especially when considering their application to anosmia. However, the research that has been done thus far indicates that there is much potential in stem cells. GBCs have already been cultured successfully, though HBCs are more limited in this sense, they cannot be activated unless tissue is damaged.
The Tufts University of Medicine has actually made progress in researching these types of cells. Prompting stem cells to differentiate into olfactory epithelium cells, they grafted the new cells onto injured tissue. The though process is that these cells can potentially “awaken” dormant cells within the nose, which would then lead to the recovery of the olfactory system.
How Has Stem Cell Research Progressed?
Of course, the prospect of grafting new cells onto damaged tissue seems to be a far cry from any easily accessible treatment. However, the above mentioned researchers are not alone in their efforts. Recently, mice have also been used to study the potential for stem cell therapies in treating anosmia. When experimenting with a mouse that lacked the sense of smell, scientists, including Bradley Goldstein at the University of Miami Miller School of Medicine, discovered that a stem cell therapy delivered directly into the nose may be able to restore the sense of smell.
Goldstein hypothesized that the failure to replace neurons in the olfactory system accounted for the loss of smell in some, perhaps many, cases. Therefore, stem cell therapy, which would replace or trigger the replacement of these neurons, could be a logical treatment in the future. The mouse subject was treated with a nasal spray containing GBCs, which then produced functional olfactory sensory neurons in the olfactory epithelium. Not only did the mouse subject regain its sense of smell; it did not develop any tumors, a side effect which would be a concern with this type of treatment.
One of the most interested outcomes of this experiment is the revelation that such a simple delivery method could produce such positive results. If such a treatment could be developed for humans and delivered through a nasal spray, it would be a far fry from many other types of potential treatments, some of which would be surgical. A nasal spray is minimally invasive and far less traumatic, but it could be a long time before such a treatment would be approved for human use. A potential standing in the way of a stem cell therapy is that it is, at this time, difficult to understanding what exactly a stem cell therapy would treat. Anosmia can be linked to an injury or illness; it is unclear at this time if a stem cell therapy would be able to anosmia resulting from any cause, or merely a specific cause.
Is Stem Cell Therapy Right For Treating Anosmia?
The fact is that, as previously mentioned, anosmia is a condition that can result from a number of different problems. It can be difficult to diagnose, let alone treat. While stem cell therapy can and should be studied in relation to more life-threatening conditions, anosmia cannot fall to the wayside. Research has shown that stem cell therapy is perhaps the future of treating anosmia, and that should not be ignored.
The potential for stem cell therapy as a minimally invasive treatment for anosmia presents new options for not only those who have lost the sense of smell, but even the rare cases in which a patient was born without the sense of smell. It should be followed through, and hopefully will open the door for a new focus on treating anosmia in general.
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