What Is a Stem Cell? What Are Its Applications in Veterinary Medicine?

Stem cells are undifferentiated cells with a high capacity for self-renewal and the potential to transform into various cell types. Unlike other cells in the body, which are specialized to perform specific functions—such as red blood cells transporting oxygen, liver cells storing glycogen or intestinal epithelial cells facilitating nutrient absorption—stem cells can transform into nearly any type of cell in the body. This transformation potential is what makes stem cell research so promising in the medical field.

The specialization of stem cells into particular cell groups depends on the active or inactive states of the genes in their nuclei.

At the same time, stem cells are found in many tissues and are responsible for regenerating, or repairing, damaged cells within the tissue they reside in. Although stem cells are present in various tissues, they can be sourced from specific areas of the body. They can be obtained through methods such as extracting fat from the abdominal region, drawing blood from a vein, surgically retrieving marrow from the hip bone, or collecting blood from the umbilical cord.

How do stem cells have such a high capacity for division?

The high division potential of stem cells is due to the length of their telomeres and the high activity of the enzyme telomerase. Telomeres are repetitive DNA sequences located at the ends of chromosomes. High telomerase activity extends telomere length, which allows stem cells to divide almost indefinitely.

Types of Stem Cells

Stem cells are primarily divided into two main groups:

Embryonic Stem Cells (ESCs): These include the dividing cells called blastomeres formed after the zygote stage and are totipotent. The differentiation potential of these stem cells is much higher than that of adult stem cells, due to their longer telomere length.

Adult Stem Cells (ASCs): These are stem cells derived from differentiated tissue in the body and are responsible for renewing or repairing tissue when damage occurs. They can transform into nerve, muscle, and liver cells. The types of these cells include:

• Hematopoietic Stem Cells (HSCs): Capable of differentiating into all blood cells, these stem cells can be obtained from bone marrow, peripheral blood, and cord blood.

• Mesenchymal Stem Cells (MSCs): These stem cells can differentiate into cells such as fat, bone, cartilage, muscle, tendon, and ligament. They can be obtained from muscle tissue, dental pulp, cord blood, amniotic fluid, synovial fluid, and peripheral blood.

Differentiation of Stem Cells

The process by which stem cells differentiate into various cell types under appropriate conditions and stimuli is called “plasticity” (transdifferentiation). Stem cells can transform into multiple types of cells based on their potential.

Generally, there are three types of stem cells:

• Totipotent Stem Cells: Found in the zygote (fertilized egg) and early morula stage, the term “totipotent” means “having the potential to become anything.” Totipotent stem cells can, on their own, create a new organism. Identical twins, who share the same genetic makeup, are formed in this way.

• Pluripotent Stem Cells: These are embryonic stem cells. Unlike totipotent stem cells, pluripotent cells cannot create a new organism. They form cells within the embryonic layers (endoderm, mesoderm, and ectoderm). All other specialized cells in the body develop from these layers. The table below shows the structures specialized from each of these layers.

• Multipotent Stem Cells: Found in tissues such as the umbilical cord, bone marrow, adipose (fat) tissue, and various other tissues.

Applications of Stem Cells

Certain organs in the body, such as the brain and heart, cannot regenerate when they suffer severe damage. In such cases, stem cell therapy may be introduced. Due to their high capacity for division and differentiation, stem cells can be used to repair damaged organs.

Stem cell therapy can treat a variety of conditions, including bone marrow cancers, lymphoma, leukemia, anemia, organ cancers, plasma cell diseases, hereditary blood disorders, and immune deficiency-related diseases.

In veterinary medicine, the therapeutic use of stem cells was first introduced in 1995 by Herthel to treat ligament issues in horses. In this application, pure bone marrow from the sternum was directly applied to the damaged ligament, and it was reported that this approach led to functional recovery.

Since then, stem cell therapy has become more widespread and is used in cats and dogs for conditions such as heart disease, eye disorders, orthopedic lesions, type 1 and type 2 diabetes, central nervous system diseases, tumors, and cartilage defects. In dogs, stem cells are obtained from the proximal humerus or femur.

In horses, stem cells are used to treat tendinitis, ligament injuries, joint damage, and cartilage damage. As mentioned earlier, stem cells in horses are typically obtained from the sternum.

In cattle, stem cells are used for orthopedic injuries, joint diseases, and skin lesions.

Research on stem cell therapy, which could potentially replace organ transplantation in the future, continues today.

Stem cell treatment is used in conditions such as heart muscle regeneration, diabetes, rheumatism, Parkinson’s, Alzheimer’s, nervous system and spinal cord injuries, and liver damage. Clinically, stem cell therapy is also increasingly being applied in the treatment of orthopedic defects, infertility, and skin diseases.

–Hakan SAĞSÖZ, M. Aydın KETANİ. Sağsöz ve Ark. Kök Hücreler Dicle Üniversitesi Vet. Fak. Dergi 2008: 1 (2): 29 – 33 syf. 32 Kök Hücrelerin Kullanım Alanları

Stem cell therapies offer hope for currently incurable diseases such as Parkinson’s and Alzheimer’s, which develop due to the death or dysfunction of numerous cells.

Did you know? Every year, on the third Saturday of September, “World Marrow Donor Day” is celebrated to thank voluntary bone marrow donors.

-Anadolu Ajansı

SOURCES

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Murat AVCI, Kök Hücre; Tanımı ve Genel Özellikleri, Kullanım Alanları, Tarihi, Yüzey Belirteçleri, Arşiv Kaynak Tarama Dergisi. Erişim tarihi: 14.09.2023
Orçun CANNAZİK, Bülent POLAT, Kök Hücre ve Veteriner Hekimlikte Uygulama Alanları, Atatürk Üniversitesi Vet. Bil. Derg. 2014; 9(3): 198-205. Erişim tarihi: 14.09.2023
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