Regenerating organs: using teeth

After spending weeks listening and watching news of the rise of incident cases of COVID-19  in Pakistan, we tend to overlook other diseases, like Cancer, which are still fatal. In fact, during this condition, our lifestyle has changed. Spending about two months under lockdown have made us depressed, and thereby, we tend to overeat. From the other way around, binge-watching, episodes after episodes on Netflix. Not just that it put us into the risk of getting diseases, like Diabetes, but chewing excessive foods could affect our teeth, as well.  Yes, COVID-19 is not the only problem, currently.  Diseases, like cardiovascular disorders, diabetes, and some others, still exist among us, which further increases the risk of our mortality. Such illness requires organs and many studies have reported the significance of regenerative medicine and ongoing research has turned their attention towards deriving stem cell therapy from a tooth.

Most of us are familiar with Hematopoietic Stem cells, extracted from bone marrow. Such stem cells are characterized as Adult Stem Cells (Bluteau et. al, 2008). Despite various stem cells being found from different parts of the body, the one that stands out is Dental Stem cells.  Five types of stem cells have been discovered from our teeth, out of which Dental Pulp Stem Cells (DPSC)  are being discussed.

DPSC are mesenchymal stem cells that are originated from the neural crest region of an embryo and like BMSC It is a multipotent stem cell, meaning, having an ability to differentiate into multiple specialized cells, from fats (adipocytes) to brain (Neuronal cells), to muscles (myocytes), to the bone, and to its own, the tooth  (Nuti et. al., 2016). 

The benefit of using such cells for therapy is of its accessibility plus it’s easily managed and not much of ethical concern. With respect to Bone Marrow Stem Cells (BMSC) , it has similarities with some of the biomarkers being expressed, morphology, and functionality (Bluteau et. al, 2008). On the contrary, Dental Stem Cells, especially of deciduous teeth, have a higher proliferation rate than BMSC. And, due to its origin, DPSC has additional biomarkers that are similar to neurons  (Nuti et. al., 2016). In addition, Dental Stem Cells are much more rigid than Bone Marrow Stem Cells because a tooth doesn’t have to go for continuous remodeling, unlike bone. (Nuti et. al., 2016)

A typical a tooth consists of enamel, dentin, dental pulp, cementum, periodontal ligament, and root. With the exception of enamel, all are originated from the neural crest region of the embryo. Enamel is derived from epithelial-like stem cells, deriving from the ectoderm of an embryo.

Due to the origin of DPSC, it can be used to treat certain neurological diseases. The harm caused by Spinal Cord Injury, resulting in the inflammation from secreted cytokines by necrotic cells inside the injured spinal cord. The stem cells implanted, induces its secreted growth factors to restore the number of cells and thereby, its function  (Chalisserry et. al, 2017). Also, the secretion of neuronal factors by DPSC upon co-culture with neurons, weakens toxicity, induced by MPP+ and rotenone, further strengthen the use of DPSC in stem cell therapy to cure degenerative disorders  (Chalisserry et. al, 2017). Furthermore, based on lab studies, Dental Stem Cells proved to be effective against Alzheimer's Disease (Chalisserry et. al, 2017). And furthermore, DNSC stimulates angiogenesis and reduces infarction, thereby, relieving symptoms of Myocardial Infarction. In addition, such stem cells cure Glaucoma and corneal blindness, secreting growth factors to revive retinal cells and further, developing and elongating their axons  (Chalisserry et. al, 2017). Moreover, a study stated of regenerated Insulin secreting islets for Diabetic patients (Chalisserry et. al, 2017).

To know Regenerative medicine, in brief, before going further.

 

To simplify,...

       Being familiar with a famous show, ‘House’, reminds us of an episode about a patient suffering from liver disease and requires a donor for a portion of the liver.  As of searching, Dr. James Wilson was found to be a perfect donor. Being anxious, his friend, Dr. House was with him and due to support, he donated his liver. A technique, namely ‘Hepatic Resection’.

 So, in brief,  ‘Regenerative medicine’ is a technique of replacing or repairing cells of an organ with healthy cells.

If we talk about extracting Hepatic Stem Cells, it’s an invasion procedure, as compared to DPSCs.

So, if we were to reconstruct a tissue, using stem cells from the tooth, Then:

 

1. Transport: Obtaining a tooth, through dentist appointments or plucking from our mouth, it’s essential to maintain a protocol to transport a tooth for stem cell research. Otherwise, it may affect its function. A paper reviews ways of handling teeth for either a research or clinical purpose. Two methods have been mentioned: 1) Containment of teeth in cold temperature to preserve its functionality (Rodas -Junco & Villicana, 2017), and; 2) Transporting teeth in fresh pasteurized milk, for its antimicrobial properties (Rodas -Junco & Villicana, 2017).
2. Isolation: To isolate mesenchymal stem cells from dental pulp, the surrounding hardcover: the Enamel and Cementum, should be removed. A paper reviews two common methods to isolate stem cells: 1) Tearing up the pulp through Enzyme activities to separate individual cells for culture. The mixture of enzymes of mainly collagenase, helps to tear down extracellular matrices (Rodas -Junco & Villicana, 2017). Although, it’s efficient but no exact composition of enzyme cocktails have been reported for its effective activity, and; 2) Outgrowth of cells through culture. The pulp is directly cultured in media and further subcultures of cells are performed to obtain a pure colony of DPSCs (Rodas -Junco & Villicana, 2017). The media is prepared with specific constituents for selective growth of particular cells. In contrast to enzyme degradation, it’s time consuming although much effective for isolation (Rodas -Junco & Villicana, 2017). Despite certain differences, no significant variation has been found with regards to expression of Biomarkers on the surface of DPSCs.
3. Culture: Certain factors, together,  affect the proliferation and differentiation of DNSCs: 1) Media: Based on two types: i) Complex media: For instance, bovine serum, composed of different combinations of various compounds, of which we don’t have any idea of it’s composition, plus, it’s susceptible to contamination. The complexity of such media could affect our results, either by inducing apoptosis of Dental stem cells, or differentiating cells into other kinds of specialized cells. ii) Chemical media: On contrary, it’s measurable and thereby, controls the process for results. 2) Growth Factors: To channelize DPSCs for self renewal and differentiation to certain cells, growth factors are added in media. These chemicals regulates i) Cell multiplication, ii) Differentiation, and; iii) Survival (Rodas -Junco & Villicana, 2017); 3) Additional chemicals:  For instance, Glucose, facilitating cell division of Stem Cells but adding excessively could affect metabolism of DPSC and hence, accumulating oxidative compounds (Rodas -Junco & Villicana, 2017). The precise amount of adding Glucose, providing certain physical parameters, could optimize DPSC activity, and;4) Physical parameter: Culturing DPSC in 21% Oxygen can deteriorate  the activity of Dental stem cells. By adjusting Glucose amount and Oxygen concentration, DPSC can have optimum activity (Rodas -Junco & Villicana, 2017), 5) Anchoring stem cells: Unlike Cancer cells, DPSC or most normal stem cells depends on anchorage to bind for its proliferation (Rodas -Junco & Villicana, 2017). Certain animal cell culture bottles or dishes have anchorage molecules on their inner surface. Such appendages include collagen, as in the case of DPSC, they grow within their microenvironment, containing collagen. In short, maintaining cultural parameters doesn’t require adjustment of each factor, separately. The combination of such parameters gives rise to optimal growth.
4. Preservation: Two methods to preserve DPSCs: 1) Traditional Cryopreservation: DPSCs are stored in liquid Nitrogen in 10% Dimethyl Sulfoxide (Rodas -Junco & Villicana, 2017), and; 2) Magnetic Cryopreservation: The method uses magnetic field around DPSCs, lowering  temperature by 6 to 7 Celsius, preventing cells from being damaged by ice expansion and nutrient drainage (Rodas -Junco & Villicana, 2017).

 

In short, using Mesenchymal Stem Cells from teeth do have a promising future for creating options for therapy, with regards to being easily accessible, easy to manage, and having a potency to differentiate in multiple cell types. As mentioned, in comparison to BMSCs, Dental Stem cells have a higher rate of multiplication. Nonetheless, due to its similarity with BMSCs, it can differentiate into osteoblast, forming bone.

 And,...

     Due to the current situation, we have been panicking and tend to overlook other diseases and despite fear, we don’t even maintain SOPs for precautions. Also, despite knowing that COVID-19 increases the risk of mortality among Diabetes patients. Here’s another fact, patients with Diabetes Mellitus and severe Periodontal disease have 3.2 times higher chance to die, compared to patients who have no or mild Periodontal disorder (Nazir, 2017).

 

References

1. Bluteau, G., Luder, H. U., De Bari, C., & Mitsiadis, T. A. (2008). Stem cells for tooth engineering. European Cells and Materials, 16, 1-9.
2. Chalisserry, E. P., Nam, S. Y., Park, S. H., & Anil, S. (2017). Therapeutic potential of dental stem cells. Journal of tissue engineering, 8, 2041731417702531.
3. Nazir, M. A. (2017). Prevalence of periodontal disease, its association with systemic diseases and prevention. International journal of health sciences, 11(2), 72.
4. Nuti, N., Corallo, C., Chan, B. M. F., Ferrari, M., & Gerami-Naini, B. (2016). Multipotent differentiation of human dental pulp stem cells: a literature review. Stem Cell Reviews and Reports, 12(5), 511-523.
5. Rodas-Junco, B. A., & Villicana, C. (2017). Dental pulp stem cells: current advances in isolation, expansion, and preservation. Tissue engineering and regenerative medicine, 14(4), 333-347.

By: Mohammad Irtaza Tafheem