Abstract / Summary
Abstract Human umbilical cord mesenchymal stromal cells (UCMSCs) are multipotent stem cells with strong immunomodulatory capacity, ease of acquisition, low immunogenicity, and a non-tumorigenic nature, making them attractive candidates for tissue repair. Under standard culture conditions, cells within a population exist in various cell cycle phases. Considering the inherent rhythmicity in biological systems, we hypothesize that synchronizing the cell cycle of UCMSCs could enhance their therapeutic efficacy for specific diseases. Serum starvation was used to synchronize UCMSCs in the G0/G1 phase. The starvation-double thymidine block method was employed to achieve S-phase synchronization. Subsequently, S-phase-synchronized cells were cultured in complete medium to induce progression into the G2/M phase. We evaluated the biological characteristics of UCMSCs across these phases, including senescence, apoptosis, proliferation potential, factor secretion, and immunoregulatory capacity. An acute colitis mouse model was established using 5% dextran sulfate sodium (DSS) solution. On the first day and fifth day respectively, UCMSCs synchronized to different cell cycle phases were administered via tail vein and intraperitoneal injection. Disease Activity Index (DAI) was scored daily. On day 7, colon length was measured, and colon tissues were analyzed via H&E, PAS, and MPO staining to assess histopathology and inflammatory infiltration. The proportion of regulatory T cells (Tregs) in peripheral blood, spleen, and mesenteric lymph nodes was also measured. Serum starvation synchronized approximately 80–90% of UCMSCs to the G0/G1 phase. The starvation-double thymidine block method synchronized about 60% of cells to the S phase. Culturing S-phase-synchronized cells in complete medium for 4–8 h yielded approximately 40% enrichment to the G2/M phase. Cell cycle synchronization did not significantly affect senescence or apoptosis. G0/G1-phase cells exhibited the lowest proliferation potential, whereas S-phase and G2/M-phase cells showed increased potential. S-phase cells secreted less TGF-β, while PGE2 secretion showed an increasing trend across G0/G1, S, and G2/M phases. Synchronization-associated UCMSCs did not significantly regulate Th1/Th17 cells but demonstrated a modulatory effect on Tregs. Compared with non-synchronized UCMSCs, synchronization associated with pretreatment of UCMSCs significantly attenuated DSS-induced colon shortening, promoted histological restoration, and reduced inflammatory cell infiltration in acute colitis. Cell cycle synchronization, rather than a specific cell cycle phase, enhances the therapeutic efficacy of UCMSCs in acute colitis. This study proposes a pretreatment strategy related to UCMSCs synchronization to optimize treatment outcomes for acute colitis.