Long-term outcomes and potential safety considerations of stem cell-based therapies for spinal cord injury

Stem cell-based therapies may promote recovery after spinal cord injury through cell replacement, reconstruction of disrupted neural circuits, and remyelination. Their clinical value depends not only on early neurological improvement but also on the durability of functional benefits and absence of delayed complications. This review examines long-term efficacy and safety evidence from preclinical and clinical studies of neural stem/progenitor cell products, pluripotent stem cell-derived neural and oligodendroglial products, and mesenchymal stromal cell products for spinal cord injury. The authors address graft survival and maturation, durability of neurological recovery, tumorigenicity, graft overgrowth, aberrant differentiation, immunological complications, maladaptive connectivity, manufacturing control, and post-transplant surveillance. English-language publications were identified through a PubMed/MEDLINE search from database inception through 4 October 2026, supplemented by reference-list screening. ClinicalTrials.gov was additionally consulted through 4 October 2026, to identify corresponding clinical programs and extended follow-up reports. Clinical studies support feasibility and encouraging product-specific safety observations, but durable efficacy remains unproven. Current evidence derives from small, heterogeneous, and often uncontrolled cohorts with uneven long-term follow-up. Progress will require standardized manufacturing and potency criteria, sensitive monitoring of abnormal graft behavior, controlled efficacy studies, and coordinated long-term registries to detect rare or delayed adverse events.