PSII-13 - Size and abundance of extracellular vesicles in cattle during early to mid-gestation consuming control or restricted diets

Abstract: Extracellular vesicles (EVs) are known to be present in cattle blood, and have been shown to contain miRNA; however, little information is available describing the abundance or size of circulating EVs in cattle during gestion. Our objective was to determine EVs size and abundance in maternal circulation during early and mid-gestation. Cattle were blocked by body condition score (BCS) and body weight (BW), synchronized and bred to the same AI sire using male-sexed semen (n = 23). At day 30 post-AI, pregnancy was determined and cattle were allotted to 1 of 3 groups and received a control diet (CON) from d30 to d190 of gestation (n =8), a CON diet from d30 to d110 and nutrient-restricted (NR) diet from d 110 to d190 (CON/NR; n= 8), or an NR diet from d30 to d110 and CON diet from d110 to d190 (NR/CON; n = 7). BW and BCS were recorded weekly or biweekly, respectively. Blood samples were collected via the coccygeal vein, samples allowed to clot, stored at 4 ^oC overnight and processed for serum. Serum was stored at -20 ^oC until used for EVs isolation. Six serum samples were utilized for each diet within each day of gestation. Two samples within each group were pooled giving 3 biological replicates for each group by day combination. EVs were isolated using differential centrifugation procedures, resuspended in 1X PBS and then subjected to nanoparticle tracking analysis (NTA; NanoSight NS300, Malvern Panalytical, UK). NTA established a size range across all samples of 31 to over 400 nm indicating the presence of exosomes and larger EVs. NTA data were subjected to ANOVA where day of gestation, diet treatment, and their interaction were the main effects. Student’s t-test among LS means for particle EVs concentration and size were used to determine significance (P < 0.05). Day of gestation affected EVs concentration with 3.9 x 10⁹ ± 2.1 x 10⁸ particles per ml, 1.4 x 10⁹ ± 2.1 x 10⁸ particles per ml and 2.6 x 10⁹ ± 2.2 x 10⁸ particles per ml, at day 30, 110 and 190 of gestation, respectively (P < 0.05). There was a day of gestation by diet effect for the size of EVs with the largest sizes observed for CON, NR and CON/NR group at day 30 and for NR/CON at day 190 (P < 0.05). The smallest EVs were detected on day 110 of gestation for the NR/CON and the CON groups (P < 0.05). These data indicate that EVs size in maternal circulation can be impacted by diet and day of gestation and this observation is most likely linked to the observations of differential abundance of miRNA previously reported.