Mesenchymal stem cells are used for different therapeutic approaches, e.g. for osteoarthritis, lesions of the tendon as well as for bone defects. Current research on the mechanism of stem cells on the repair of damaged tissue suggest an important role of a cell-to-cell communication through secreted extracellular vesicles, mainly represented by exosomes. To enhance the scarce knowledge on the functional role of exosomes we compared as a first step different techniques to isolate and identify exosomes from the supernatant of equine adipose derived mesenchymal stem cells for further characterization and usage in functional assays. It was possible to obtain exosomes secreted from equine adipose derived mesenchymal stem cells with three common techniques: a stepwise ultracentrifugation at 100.000 g, an ultrafiltration with 3 kDa exclusion membranes and a charge-based precipitation method. The mean sizes and amounts of exosomes isolated with the different techniques were measured by the nanoparticle tracking analysis. The diameter ranged between 116.2 nm (ultracentrifugation), 453.1 nm (precipitation) and 178.7 nm (ultrafiltration), the counts of particles / ml ranged between 9.6 × 108 (ultracentrifugation), 2.02 × 109 (precipitation) and 52.5 × 109 (ultrafiltration). Relevant marker for exosomes, tetraspanins CD9, CD63 and CD81 were detectable by immunofluorescence staining of the investigated exosomes secreting mesenchymal stem cells. In addition, transmission electron microscopy and immunogold labeling with CD9 and CD90 was performed to display the morphological shape of exosomes and existence of marker relevant for exosomes (CD9) and mesenchymal stem cells (CD90). Western blot analysis of CD9 and CD90 of exosomes ensured the specificity of the rare available respectively cross reacting antibodies against equine antigens. Exosomes generated by equine mesenchymal stem cells can be obtained by ultrafiltration and ultracentrifugation in an equal quality for in vitro experiments. Especially for later therapeutic usage we recommend ultrafiltration due to a higher concentration without aggregation of extracellular vesicles in comparison to exosomes obtained by ultracentrifugation.

Skeletal muscle plays a pivotal role in physical activity, protein storage and energy utilization. Skeletal muscle wasting due to immobilization, aging, muscular dystrophy and cancer cachexia has negative impacts on the quality of life. The deletion of myostatin, a growth and differentiation factor-8 (GDF-8) augments muscle mass through hyperplasia and hypertrophy of muscle fibers. The present study examines the impact of myostatin deletion using CRISPR/Cas9 editing on the myogenic differentiation (MD) of C2C12 muscle stem cells. A total of five myostatin loci were targeted using guided RNAs that had been previously cloned into a vector. The clones were transfected in C2C12 cells via electroporation. The cell viability and MD of myostatin-edited clones (Mstn^−/−) were compared with C2C12 (Mstn^+/+) using a series of assays, including MTT, sulforhodamine B, immunocytochemistry, morphometric analysis and RT-qPCR. The clones sequenced showed evidence of nucleotides deletion in Mstn^−/− cells. Mstn^−/− cells demonstrated a normal physiological performance and lack of cytotoxicity. Myostatin depletion promoted the myogenic commitment as evidenced by upregulated MyoD and myogenin expression. The number of MyoD-positive cells was increased in the differentiated Mstn^−/− clones. The Mstn^−/− editing upregulates both mTOR and MyH expression, as well as increasing the size of myotubes. The differentiation of Mstn^−/− cells upregulates ActRIIb; in contrast, it downregulates decorin expression. The data provide evidence of successful CRISPR/Cas9-mediated myostatin deletion. In addition, targeting myostatin could be a beneficial therapeutic strategy to promote MD and to restore muscle loss. In conclusion, the data suggest that myostatin editing using CRISPR/Cas9 could be a potential therapeutic manipulation to improve the regenerative capacity of muscle stem cells before in vivo application.

The investigation of adipose tissue-derived mesenchymal stem cells (ASCs) has received considerable interest in regenerative medicine. A nontoxic adipogenic induction protocol valid for cells of different mammalian species has not been described. This study aims to establish an adipogenic differentiation protocol suitable for horses, sheep, dogs, murines, and human cells. An optimized rosiglitazone protocol, consisting of 5% fetal calf serum in Dulbecco’s Modified Eagle’s Medium, 10 μg/mL insulin, 0.55 μg/mL transferrin, 6.8 ng sodium selenite, 1 μM dexamethasone, and 1–5 μM of rosiglitazone, is compared to the 3-isobutyl-1-methylxantine (IBMX) protocol, where rosiglitazone was replaced with 0.5 mM IBMX and 0.2 mM indomethacin. Cell viability, cytotoxicity, a morphometric analysis of the lipid, and the expression of adipogenic markers for 14 days were assessed. The data revealed that using 5 µM of rosiglitazone promotes the adipogenic differentiation capacity in horse, sheep, and dog cells compared to IBMX induction. Meanwhile, marked reductions in the cell viability and cell number with the IBMX protocol were detected, and rosiglitazone increased the cell number and lipid droplet size, prevented apoptosis, and upregulated FABP-4 and Leptin expression in the cells of most of the species. Our data revealed that the rosiglitazone protocol improves the adipogenesis of ASCs, together with having less toxicity, and should be considered for cell reproducibility and clinical applications targeting obesity.

The impact of donor age on Adipose-derived mesenchymal stem cell (ASC) functionality and safety remains insufficiently characterized, particularly in equine models. This study investigates the influence of age on ASCs proliferation dynamics and the expression of tumorigenic and apoptosis-related markers. Equine ASCs were isolated from juvenile (15 years) horses and assayed across multiple passages. The relative mRNA expressions of pluripotency (Oct4), tumorigenic (CA9), and apoptosis-related (Bax and Bcl 2) markers were evaluated. The Gompertz growth model, population doubling time (PDT), and tissue non-specific ALP activity also followed. The expression of pluripotency and tumorigenic markers showed passage-dependent up-regulation, raising concerns about prolonged culture expansion. Apoptotic regulation displayed a shift with aging, as evidenced by alterations in the Bax/Bcl2 ratio, suggesting compromised cell survival in older ASCs. An age-associated decline in proliferation rates was established, as evidenced by declining alkaline phosphatase (ALP) activity. These findings underscore the necessity for stringent age-based selection criteria in equine stem cell therapies and the challenges associated with using autologous stem cells for regenerative therapies in aged horses. Future research should focus on molecular interventions to mitigate age-related functional decline, ensuring the safety and efficacy of ASCs-based regenerative medicine in equine practice.

Extracellular vesicles (EVs) have become a key area of research, as scientists study their role in various biological processes. These vesicles appear to play a key role in the use of mesenchymal signaling cells (MSCs, formerly known as mesenchymal stem cells) to treat various diseases, such as osteoarthritis (OA), and other degenerative conditions. In our experiments, we examined EVs formed by canine mesenchymal signaling cells (MSCs) to identify them according to current guidelines and define their content, particularly the microRNA (miRNA) they contain, for future research projects. After obtaining the EVs, we demonstrated via Western blotting and transmission electron microscopy that the nanoparticles visible in the nanotracking analysis were positive for CD9 and ALIX and positive for CD9 and CD81, respectively. Markers for nanoparticles that do not represent extracellular particles—tested here as cytochrome C for mitochondrial particles and histones for nuclear particles—were negative. Finally, we detected a total of 85 different miRNAs in the negative controls. To determine the potential influence of various cell stimulations intended to induce osteoarthritis (e.g., interleukin-1β stimulation) or a possible treatment (e.g., shockwave therapy), or the influence of ITS prior to extracellular vesicle extraction, we detected a total of 208 different miRNAs. These results demonstrate how canine EVs from MSCs can be detected in vitro and how the EVs’ miRNA profile changes after stimulation of the producing cells. This information may provide valuable insight into the understanding and treatment of osteoarthritis. Additionally, we demonstrated that using ITS instead of FCS to produce EVs should be reconsidered due to the significant change in miRNA expression levels.