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defects Animal model Table 1: Donors, sources and types of stem cells used in veterinary medicine with most common treated diseases. Arch Vet Sci Med 2020; 3 (2):40-50 DOI: 10.26502/avsm.014 Archives of Veterinary Science and Medicine 44 There are many disorders in veterinary medicine where MSCs can be indicated, but many others still remain under research (Table 1). The most common diseases treated with MSCs are musculoskeletal, cardiovascular, ophthalmological, neurological and urological disorders. Companion animals such as dogs and cats may present with bone problems, mainly with hereditary background or caused by malformation due to inappropriate diet. Horses subjected to high-impact sports often struggle with injuries to their soft tissues, tendons, cartilages and bones. Other animals such as mice, rats or pigs are still used as small or large experimental animal models for human medicine [40]. 4.1 Musculoskeletal disorders Musculoskeletal disorders such as tendonitis, osteoarthritis, muscular dystrophy or bone defects caused by trauma, cancer or inflammation are the most common indications for UC MSC administration [17, 41-44]. The repair of bone defects caused by injury, chronic inflammation and tumor presents a challenge in veterinary regenerative medicine [45]. Newly-developed biocompatible bone-forming scaffolds seeded with MSCs seem to be a promising form of therapy [41]. Although the differentiation potential of MSCs varies with respect to the tissue source, UC MSCs have shown higher osteogenic potential than bone marrow MSCs in vitro [42]. Recent studies indicate that regeneration of fractures can be achieved by injection of UC MSCs with betatricalcium phosphate (β-TCP) included as a supportive implant [41]. By means of this therapy, enhanced bone remodelling leading to accelerated fracture healing was found after just six weeks [41]. Furthermore, the paracrine effect of UC MSCs may play a role in bone regeneration as well [46]. The curative properties of UC MSCs have also been documented in the case of canine osteoarthritis, with the regeneration of cartilages and surrounding tissues being observed [44]. Impressive results have been attained in the treatment of superficial digital flexor tendinitis, which is the most common disorder in race horses [23]. UC MSC injection in combination with regular physical therapy demonstrated locomotor improvement just one month after the initiation of treatment [23]. Spontaneously-occurring muscular dystrophy in golden retriever dogs is an excellent model for studying the progressive muscle weakness and atrophy in humans known as Duchenne muscular dystrophy (DMD). Recently-developed pharmacological, genetic and UC MSC-based therapies may partially improve the muscle function of those affected by muscular dystrophy. However, after single administration of UC-MSCs in a dog clinical study, no dystrophin was detected in the affected muscles [17]. Therapy including multiple injections is therefore now being considered. 4.2 Neurological disorders Neurological disorders are usually associated with irreversible processes due to the limited regeneration capability in the central nervous system. They can be classified into traumatic injuries of the brain (TBI) and spinal cord (SCI) and age-related degenerations. Recent findings indicate that MSCs derived from different sources are able to survive and migrate towards injury sites and contribute to axonal survival, thus promoting functional recovery after SCI and TBI [47-51]. Moreover, UC MSCs have been associated with more neuroprotection, nerve regeneration and less inflammation than other MSCs following SCI [52]. Surprisingly, no enhanced sparing of spinal cord tissue was demonstrated in a study using MRI [50]. Arch Vet Sci Med 2020; 3 (2):40-50 DOI: 10.26502/avsm.014 Archives of Veterinary Science and Medicine 45 Preclinical studies have shown possibilities of treating neurodegenerative disorders such as Parkinson's and Alzheimer's disease, multiple sclerosis, or stroke and brain tumours [53]. Both MSCs and NPCs seem to have promising therapeutic impact, as they decrease neuroinflammation, support neurogenesis, synaptogenesis and differentiation of neural cells [54]. Furthermore, they are able to suppress cell death caused by tau protein and Aβ deposit accumulation [54]. Thus their biological activity seems to consist in neuroprotection and the ability to release immune modulatory factors [54]. MSC-based therapy may decrease depression states in rats with subarachnoid haemorrhage, although the mechanism is not yet clear. Because MSCs are able to cross the blood-brain barrier [54], the administration of MSCs can be provided intravenously, intra-arterially or intranasally, which are easy procedures that can be carried out on awake animals. Although this treatment appears promising, there is a need for further research also in the field of veterinary medicine [53]. 4.3 Myocardial disorders and wound healing Several stem-cell populations, including adult MSCs from various organs and tissues, have been tested for cardiac repair potential with encouraging pre-clinical and clinical results [55]. For a long time the heart has been considered a post-mitotic organ, although this view has recently changed with the identification of stem/progenitor cells