Otolaryngology researchers in Bejing have recently published their remarkable findings, showcasing methodology to track implanted stem cells, in a paper entitled, “Transplantation and Tracking of the Human Umbilical Cord Mesenchymal Stem Cell Labeled with Superparamagnetic Iron Oxide in Deaf Pigs.”
By attaching a tracer to stem cells, a team of scientists led by L. Xu were able to follow stem cell progression after transplantation into deaf minipigs. Xu et al. conclusively demonstrated their methods to be both safe and effective, with no adverse effect seen from the nanoparticle tracer itself. These findings support broadening the application of stem cells derived from cord blood into use for experimentation with larger mammals, and for further stem cell therapies in general.
By attaching a tracer to stem cells, a team of scientists led by L. Xu were able to follow stem cell progression after transplantation into deaf minipigs.
There has been much research in the past few decades investigating the possibilities (and limits) of stem cell therapy. Valued for their ability to be multipotent and self-renewable, many exciting therapeutic applications are pursued in laboratories worldwide. Stem cells are comprised of a number of different forms, and are categorized according to their source. These include:
- embryonic stem cells, considered pluripotent because of their ability to form any type of cell in the body
- tissue-specific stem cells, also referred to adult stem cells, which can give rise only to one organ or cell type, such as liver or blood cells
- induced pluripotent stem cells (iPS), which are lab-manufactured and used primarily for the development of new therapies
- mesenchymal stem cells, which can be derived from bone marrow, fat and cord blood and whose application has been vigorously debated in the scientific community.
The power of Mesenchymal Stem Cells (MSCs)
First discovered in bone marrow, MSCs are still traditionally isolated from this source. However, recent studies, like the one being discussed, have shown the promise of harvesting them from human umbilical cord blood, as well. Researchers often work with this cell type because of its ability to travel to areas of injured tissue and exert immunomodulatory and regenerative benefits. Human Umbilical Cord Mesenchymal Stem Cells (UC-MSCs) have a particular allure due to the fact that they are easily sourced and expanded in the laboratory setting.
Advances in biotechnology have led to frequent use of MSCs for connective tissue disorders. However, bone marrow is not easily obtained without significantly impacting the source. Comparatively, UC-MSCs can be obtained without difficulty and from a substance historically treated as medical waste—cord blood. Furthermore, evidence suggests that UC-MSCs can indeed be isolated and expanded within culture for broader application, including the ability to cross germ layers in the body.
Applications for UC-MSCs for Sensorineural Hearing Loss
For the purposes of this study, Xu et al. aimed to apply a tracer to UC-MSCs in order to assess their therapeutic range within the scope of sensorineural hearing loss (SNHL). SNHL can occur from injury or disease processes to the inner ear and is the cause of 90% of diagnosed hearing loss cases. One of the most common causes is damage incurred from environmental exposure, such as bomb blasts or even prolonged exposure to loud music. The minipigs used for this study were treated with UC-MSCs one week following noise exposure.
After one week, Xu et al. had positive confirmation of the efficacy of UC-MSC treatment by measuring the auditory brainstem response of the minipigs. This finding was expected; what the researchers were more interested in, was where exactly the cells had traveled to.
Use of nanoparticle tracers to assess the therapeutic range of UC-MSCs
The lack of cytotoxicity found in superparamagnetic iron oxide (SPIO) nanoparticles demonstrated their safety as a cell tracer. From there, Xu et al. used transmission electron microscopy (TEM) to assess the therapeutic range of the UC-MSCs within the minipigs’ auditory system. Cells were found in the following locations: “cochlear blood vessels, the bony wall of scala tympani, and spiral ganglion nerve fibers…in the stem cell recipients’ cochlea.”
Additionally, “TEM found SPIO in the medulla oblongata and the cerebrum in the SNHL minipigs after stem cell transplantation.” This finding is remarkable because it speaks to the ability of MSCs—particularly, UC-MSCs—to cross germ layers, a feat previously disbelieved.
Currently, there is debate within the scientific community as to exact capabilities of MSCs. Indeed, marked differences in behavior of these cells are seen depending on their source origin and culture technique. One of the major gray areas is understanding the MSCs’ ability for “homing,” or finding the site of injury. Thus, the conclusive visualization of where the nanoparticle-traced cells had migrated to—in addition to their positive therapeutic influence on the injury site—offers a tremendous advantage for further study.