## 2 Results and Discussion
### Discussion
However, with respect to the aMSCs, the effect is due to the contribution of culture expanded MSCs, which have the capacity for regeneration and differentiation into the various tissues involved, that is, new cells are provided that differentiate into cells at the injury site allowing for greater improvement in the area treated [70]. These types of cells express the potential to differentiate into multiple tissue lineages such as osteogenic and chondrogenic phenotypes [71, 72] and have the ability to localize and participate in the repair of damaged joint structures, including cruciate ligaments, menisci, and cartilage lesions [21]. Additionally, aMSCs are known for their anti-inflammatory and immunomodulatory properties and for being a safe therapy without adverse effects [52, 60]. In this study both groups increased ROM from baseline; although aMSCs had worse scores at the beginning of the study, dogs treated with aMSCs reported increased ROM at 6 months after treatment. Thus based on the findings in this study, the therapeutic use of both PRGF and aMSCs are novel treatments that report goods results for overcoming the difficulties in regeneration of articular cartilage in OA while maintaining or improving the structure and joint function without the need for more aggressive techniques that can cause further damage to the organism. Mesenchymal cells are cell populations with molecular mechanisms capable of self-renewal and differentiation into various cell types in damaged tissue, repairing and supplying physiological functions in the affected joint, reducing pain, restoring joint function and delaying the onset of cartilage degradation [73, 74, 75]. In the case of PRGF, the proteins they contain have the ability to increase the proteoglycan and collagen synthesis by chondrocytes and regulate homeostasis and proper functioning of cartilage [75, 76]. Notably, both PRGF and aMSCs improved the pathology at an articular level, with improvement to clinical signs and symptoms as well as to the structural damage caused by the disease [53, 77]. Given that the animals in the current study showed significant improvement in all parameters studied but without obvious radiographic changes, it could be deduced that radiology may not be a sufficiently sensitive technique to assess the evolution of OA at the particular time points studied by the team of researchers in this parallel study [78]. In addition to OA, the beneficial effects of both treatments have also been described in Achilles tendon in a murine animal model and in facial nerve injury in a porcine experimental model, finding a synergistic effect on healing when PRP was used in combination with adult stem cells [79, 80]. However, this synergistic effect was not demonstrated in a study on flexor tendons in sheep, where the group treated with MSCs showed an improvement in the composition and organization of the structural matrix, with increased expression of collagen I and cartilage oligomeric matrix protein, along with a decreased expression of collagen III, compared to the groups treated with PRP alone or in combination with MSC. The authors attributed the absence of the synergistic effect between the treatments to the possibility that the behavior and action exerted by each take completely different routes, or that protocols were not optimal for stimulation of this synergistic action [81]. Having demonstrated the therapeutic benefit of both treatments, one must take the advantages and disadvantages of each treatment's clinical application into account. Although PRGF demonstrated a shorter duration of effect, it has the advantage of being substantially more affordable and far less invasive, and therefore simpler for ambulatory use. And it is important to highlight that PRGF treatment can be optimized with serial injections over time to obtain better results with respect to the duration of the effect [77].