Combined fecal microbiota transplantation and adipose-derived stem cells protect the blood-spinal cord barrier after spinal cord injury

Background Blood–spinal cord barrier (BSCB) disruption and neuroinflammation contribute to secondary injury after spinal cord injury (SCI). Fecal microbiota transplantation (FMT) and human adipose-derived stem cells (hADSCs) each show therapeutic potential, but the effects of combined treatment and the influence of fecal soluble components on hADSCs secretory activity remain unclear. Methods A T9 forceps-crush SCI model was established in C57BL/6J mice to compare FMT, intralesional hADSCs transplantation, and their combination. Functional recovery, BSCB permeability, neuroinflammation, lesion pathology, and neural tissue preservation were evaluated. Exploratory 16S rRNA sequencing was performed at 35 days post-injury. In vitro , hADSCs were exposed to filtered fecal material from healthy donor mice, and their conditioned medium was applied to oxygen–glucose deprivation/reoxygenation-injured bEnd.3 endothelial cells. Results Combined FMT and hADSCs treatment improved locomotor recovery, attenuated BSCB leakage and neuroinflammatory responses, and preserved neural tissue, with several outcomes greater than either monotherapy. Exploratory 16S analysis identified treatment-associated differences in microbial richness and overall community composition. Fecal-filtrate preconditioning increased hADSCs secretion of VEGF, HGF, and IL-10 by 2.3-, 2.2-, and 1.8-fold, respectively. Conditioned medium from preconditioned hADSCs improved wound closure, preserved ZO-1 and Claudin-5 signals, and reduced endothelial monolayer permeability after OGD/R. IL-10 silencing partially attenuated these protective effects. Conclusions Combined FMT and hADSCs treatment was associated with greater BSCB preservation, reduced neuroinflammation, and improved functional recovery after SCI. In vitro , soluble components of healthy-donor fecal filtrate modulated hADSCs secretory activity and enhanced endothelial protection. These findings do not establish that oral FMT reprograms transplanted hADSCs in vivo or that microbiota alterations mediate the combined therapeutic effect.