Staphylococcus aureus is the most commonly isolated pathogen from clinical bovine mastitis samples and a difficult pathogen to combat. Mesenchymal stem cells (MSC) are multipotent progenitor cells equipped with a variety of factors that inhibit bacterial growth. The aim of the present study was to evaluate the in vitro antibacterial potential against S. aureus of conditioned medium (CM) from MSC derived from fetal bovine bone marrow (BM-MSC) and adipose tissue (AT-MSC). BM-MSC, AT-MSC and fetal fibroblasts (FB) cultures were activated by infection with S. aureus. Bacterial growth was evaluated in presence of CM, concentrated CM (CCM), activated CM (ACM) and concentrated ACM (CACM) from BM-MSC, AT-MSC and FB. Gene expression of β-defensin 4A (bBD-4A), NK-lysine 1 (NK1), cathelicidin 2 (CATHL2), hepcidin (HEP) and indoleamine 2,3 dioxygenase (IDO) and protein expression of bBD-4A were determined in activated and non-activated cells. The majority of BM-MSC and AT-MSC expressed CD73, Oct4 and Nanog, and were negative for CD34. Growth of S. aureus decreased when it was exposed to CM from BM-MSC, AT-MSC and FB. Moreover, growth of S. aureus in CCM, ACM and CACM was lower compared to controls of CM from BM-MSC and AT-MSC. Activated AT-MSC increased mRNA levels of bBD4A and NK1, and protein levels of bBD4A in CM. Thus, CM from fetal bovine BM-MSC and AT-MSC has the capacity to reduce in average ~30% of S. aureus relative growth under in vitro conditions. The in vitro antibacterial effect of fetal bovine MSC may be mediated by bBD4A and NK1 activity.

Organoids are 3D-culture systems composed of tissue-specific primary cells that self-organize and self-renew, creating structures similar to those of their tissue of origin. Testicular organoids (TOs) may recreate conditions of the testicular niche in domestic and wild cattle; however, no previous TO studies have been reported in the bovine species. Thus, in the present study, we sought to generate and characterize bovine TOs derived from primary testicular cell populations including Leydig, Sertoli and peritubular myoid cells. Testicular cells were isolated from bovine testes and cultured in ultra-low attachment (ULA) plates and Matrigel. TOs were cultured in media supplemented from day 3 with 100 ng/mL of BMP4 and 10 ng/mL of FGF2 and from day 7 with 15 ng/mL of GDNF. Testicular cells were able to generate TOs after 3 days of culture. The cells positive for STAR (Leydig) and COL1A (peritubular myoid) decreased (p < 0.05), whereas cells positive for WT1 (Sertoli) increased (p < 0.05) in TOs during a 28-day culture period. The levels of testosterone in media increased (p < 0.05) at day 28 of culture. Thus, testicular cells isolated from bovine testes were able to generate TOs under in vitro conditions. These bovine TOs have steroidogenic activity characterized by the production of testosterone.

Due to their self-renewal and differentiation potentials, mesenchymal stem cells (MSCs) may be induced into germ cells (GC) differentiation under in vitro conditions. In veterinary medicine, this technology could provide an alternative method to artificial insemination, as well as potentially useful for the conservation of endangered species. Previous studies have reported the use of SCs and MSCs co-culture systems, as well as SCs conditioned medium (SCCM) to induce GC differentiation of human and murine embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs). The objective of this study was to evaluate the effect of SCCM as an inducer of in vitro GC differentiation of MSCs derived from fetal bovine adipose tissue (AT-MSCs). SCCM was collected from bovine SC cultures generated from adult bull testis. The effect of SCCM on MSCs was analyzed using quantitative PCR (Q-PCR) and flow cytometry. CD73 mRNA levels were decreased (P0.05) between treated and controls cells. DAZL gene expression was detected on day 21 of culture, as well as a proportion of AT-MSC positive for DAZL at day 21 of culture. OCT4, PIWIL2 and DAZL gene expressions were detected from day 0, 7 and 21 of culture, respectively, as well as a proportion of cells positive for each marker were detected at day 21 of culture. However, similar gene and protein expression levels (P>0,05) were detected between AT-MSCs/SCCM and control cultures. DMC1 gene expression levels were detected from day 7 of culture, and expression levels were not different (P>0,05) between treatment and control cells. Expression patterns of MSC, pluripotent, GC and meiotic markers indicate that SCCM did not induce GC differentiation of AT-MSCs.

Organoids serve as three-dimensional structures that offer spatial support and mimic cellular niches for experimental studies. The spatial and temporal association of fetal bovine adipose tissue-derived mesenchymal stem/stromal cells (AT-MSCs) with the expression of germ cell (GC) markers was evaluated in testicular organoids (TOs+AT-MSCs) under the effect of retinoic acid and testosterone (0.2, 2 and 20 µM). TOs+AT-MSCs were developed by the co-culture of Leydig, Sertoli, and peritubular myoid cells and PKH26+AT-MSCs and were analyzed for the expression of DAZL, STRA8 and UCHL1. TOs+AT-MSCs treated with 1 µM of retinoic acid and 2 or 20 µM of testosterone maintained their diameter after day 7 of culture. Pearson correlation coefficients (PCCs) of PKH26 and DAZL were higher (p < 0.05) at days 7 and 21 in TOs+AT-MSCs treated with 1 µM retinoic acid and 0.2 or 2 µM of testosterone, respectively. PCCs of PKH26 and STRA8 or UCHL1 were higher (p < 0.05) at days 14 and 21 in TOs+AT-MSCs treated with 1 µM retinoic acid and 0.2 or 2 µM of testosterone. Thus, exposure to 1 µM of retinoic acid and 2 µM of testosterone resulted in a similar diameter with respect to the control and spatial and temporal association of AT-MSCs and DAZL, STRA8 and UCHL1 markers in TOs+AT-MSCs.