Paclitaxel-mediated Cytoskeletal Stabilization Improves Blastocyst Developmental Competence of Bovine Embryos in Vitro.

Our previous study has suggested that paclitaxel-induced F-actin stabilization enhances the developmental competence of porcine in vitro fertilization (IVF) embryos; however, its role in bovine embryos remains unclear. Herein, we analyzed the embryo cleavage stages 48 h post-IVF to assess their correlation with blastocyst development and investigated the impact of paclitaxel-induced cytoskeletal stabilization. After IVF, bovine embryos were classified into two groups based on cleavage stage: LCG and ECG (late cleaved group; LCG, < 8-cell and early cleaved group; ECG, ≥ 8-cell). Bovine embryos cultured in the ECG developed to the blastocyst stage at a significantly higher rate (35.9 ± 9.5%, p < 0.01), whereas most embryos in the LCG underwent apoptosis owing to low developmental competence (4.5 ± 4.9%). Additionally, the intensities of F-actin and vimentin at the junctional adhesion sites among blastomeres in blastocysts were higher in the ECG. Paclitaxel (10 nM) significantly improved the blastocyst development rate of in vitro fertilized embryos (Control: 21.7 ± 1.7% vs. Paclitaxel: 31.8 ± 8.5%, p < 0.05), and the fluorescence intensity of F-actin was increased by more than 1.2-fold in the paclitaxel-treated group (p < 0.01). Then, the mRNA expression levels of transcription factors associated with the 8-cell stage (H2AZ1, SALL4, TBX3, and KLF4) and cytoskeleton factors related to blastomere division E-cadherin and β-cadherin, were significantly upregulated (p < 0.05) in bovine embryos exposed to 10 nM paclitaxel on day 2 after IVF. Our findings indicate that paclitaxel promotes early cleavage progression and enhances blastocyst development by stabilizing F-actin and maintaining cytoskeletal integrity.