Intrarectal delivery of chitosan hydrogel-encapsulated mesenchymal stem cell-conditioned media attenuates disease severity in experimental ulcerative colitis.

BACKGROUND

Ulcerative colitis (UC) is a chronic inflammatory disease characterized by mucosal immune dysregulation and epithelial injury. While mesenchymal stem cells (MSCs) hold regenerative and immunomodulatory promise, their use entails safety and logistical challenges. MSC-derived conditioned medium (MSC-CM) may offer a safer, cell-free alternative. Here, we present a novel intrarectal delivery strategy that pairs MSC-CM with a mucoadhesive chitosan hydrogel (Cs-Hyd), aiming for localized mucosal therapy in colitis.

METHODS

Experimental colitis was induced in mice via DSS exposure. Human MSCs were cultured under standardized conditions to generate CM enriched in immunoregulatory factors. This CM was loaded into a chitosan hydrogel, validated for mucoadhesion and release kinetics, and administered intrarectally. Clinical metrics (weight loss, stool consistency, fecal blood), colon length, histopathology, cytokine profiles, and myeloperoxidase (MPO) activity were assessed. Data were analyzed via ANOVA with post hoc Tukey correction; significance was set at p < 0.05.

RESULTS

In the DSS model, 60% mortality was observed by day 10, whereas the Cs-Hyd containing MSC-CM (Cs-Hyd-CM) group achieved 100% survival (n = 4-6, log-rank p = 0.034). Cs-Hyd-CM-treated mice exhibited substantially less weight loss (- 5.2 ± 1.3% vs. - 15.1 ± 2.2%; repeated-measures ANOVA, p = 0.008), lower Disease Activity Index (DAI: 2.1 ± 0.6 vs. 8.0 ± 0.9; p = 3.2 × 10-4), and preserved colon length (7.5 ± 0.4 cm vs. 6.0 ± 0.3 cm; p = 6.2 × 10-3). Histology scores decreased by ~ 70% (4.0 ± 0.7 vs. 12.1 ± 0.8; p = 3.1 × 10-6), confirming mitigation of ulceration and inflammation. Treatment with Cs-Hyd-CM reduced TNF-α by ~ 40% vs DSS-only (104.5 ± 6.8 → 63.8 ± 8.7 pg/mg; p = 4.6 × 10-4) while restoring IL-10 toward normal levels (p = 3.0 × 10-3). MPO activity dropped ~ 52% (76.5 ± 3.4 → 36.8 ± 5.3 U/mg; p = 8.4 × 10-4). Collectively, Cs-Hyd-CM significantly attenuated disease severity and promoted mucosal healing in DSS colitis.

CONCLUSIONS

Local intrarectal delivery of MSC-CM via chitosan hydrogel substantially alleviates experimental UC. This cell-free platform leverages MSC secretome functions, immunomodulation, barrier restoration, and controlled retention, while avoiding the complexities and risks of cell transplantation.