Pets and stem cells
There is a growing interest in the use of stem cells for treating domestic animals with various ailments.
Research development
In 1996 Dolly the sheep was produced at the Roslin Institute (Scotland) as part of research into producing medicines in the milk of farm animals. Researchers have managed to transfer human genes that produce useful proteins into sheep and cows, so that they can produce, for instance, the blood clotting agent to treat haemophilia.
Several clones had been produced in the lab before Dolly, e.g. frogs and mice which had all been cloned from the DNA from embryos, but Dolly was the first mammal to be cloned from an adult cell. This was a major scientific achievement as it demonstrated that the DNA from adult cells, despite having specialised as one particular type of cell, can be used to create an entire organism. Dolly became infamous and the world suddenly realised the potential for the manipulation of biological cells.
Whilst work was progressing on cloning, research started in 1981 on deriving embryonic stem cells from animals and in 1998 from humans. Stem cells are important for living organisms for many reasons. In the 3- to 5-day-old embryo, the inner cells give rise to the entire body of the organism, including all of the many specialized cell types and organs such as the heart, lungs, skin, sperm, eggs and other tissues. In some adult tissues, such as bone marrow, muscle, and brain, discrete populations of adult stem cells generate replacements for cells that are lost through normal wear and tear, injury, or disease.
Cell types and function
Stem cells possess two unique properties and are able to both maintain an undifferentiated state by self-renewing (i.e. generating identical daughter stem cells) and differentiate into mature cell types (i.e. generating more specialised daughter cells capable of forming distinct tissue types).
Stem cells have been categorised by their characteristics into three groups; embryonic stem cells (ESCs), adult stem cells and induced pluripotent stem cells (iPSCs). ESCs and iPSCs possess pluripotency properties and are able to differentiate into all cells of all three germ layers: ectoderm, endoderm and mesoderm. Whereas, adult stem cells possess more restricted differentiation capabilities and may possess multipotent, oligopotent and unipotent properties.
Adult stem cells are only able to differentiate into a limited number of different cell types. For example, mesenchymal stem cells (MSCs) are multipotent and are able to differentiate multiple cell types of mesoderm origin including chondrocytes, osteoblasts and adipocytes. There is a shift of conducting research into using adult derived stem cells as they alleviate ethical and practical issues associated with ESCs and iPSCs. Adult stem cells, especially MSCs, were among the first stem cells used in cell transplantation therapies in animals. This is because MSCs also possess immunomodulatory properties where they respond to both the adaptive and innate immune systems by supressing T cells and dendritic cell (DC) maturation, decreasing B cell activation and proliferation. MSCs are found in various tissues and organs including bone, skeletal muscle, cartilage and adipose tissue but the cells are mostly isolated from bone marrow.
Opportunities for pet treatment
The unique properties of stem cells allow the opportunities to be used in tissue regeneration for treating numerous animals with various ailments. Over the past 15 years there has been great interest in the field of regenerative medicine with the focus on regenerating and replacing cells, tissues and organs to restore functionality, using the body’s own repair mechanisms. Cell and tissue regeneration may be achieved by using the combination of engineered scaffolds, cells and biomolecules, to stimulate regeneration of the defective area with a view to producing functional tissues.
This explosion of research into regenerative medicine has allowed vast improvements and advancements in their use within biomedical science. The potential use of MSCs in cell therapies for treating animals has been steadily gaining momentum, due to their diverse range of properties.