The safety profile of mesenchymal stem cell therapy administered through intrathecal injections for treating neurological disorders: a systematic review and meta-analysis of randomised controlled trials.

Background: Based on previous in vivo studies and human trials, intrathecal cell delivery is a safe and relevant therapeutic tool for improving patient's quality of life with neurological conditions. We aimed to characterise the safety profile of intrathecally delivered Mesenchymal stem cells (MSCs).

Methods: Ovid MEDLINE, Embase, Scopus, Cochrane Library, KCI-Korean Journal Database, and Web of Science. Databases were searched from their inception until April 13, 2023. Randomised Controlled Trials (RCTs) that compared intrathecal delivery of MSCs to controls in adult populations were included. Adverse events (AEs) were pooled and meta-analysed using DerSimonian-Laird random effects models with a correction factor 0.5 added to studies with zero count cells. Pooled AEs were described using Risk ratio (RR) and 95% confidence intervals (95% CI). Then, a random-effects meta-regress model on study-level summary data was performed to explore the relationship between the occurrence of AEs and covariates thought to modify the overall effect estimate. Finally, publication bias was assessed.

Results: 303 records were reviewed, and nine RCTs met the inclusion criteria and were included in the quantitative synthesis (n = 540 patients). MSCs delivered intrathecally, as compared to controls, were associated with an increased probability of AEs of musculoskeletal and connective tissue disorders (categorised by Common Terminology Criteria for Adverse Events-CTCAE version 5.0) (RR: 1.61, 95% CI 1.19-2.19, I = 0%). The random-effects meta-regress model suggested that fresh MSCs increased the probability of occurrence of AEs compared to cryopreserved MSCs (RR: 1.554; p-value = 0.048; 95% CI 1.004-2.404), and the multiple-dose, decreased the probability of AEs by 36% compared to single doses (RR: 0.644; p-value = 0.048; 95% CI 0.416-0.996); however, univariate random effects meta-regression models revealed a not significant association between the occurrence of AEs from MSCs intrathecal delivery and each covariate.

Conclusions: Intrathecal delivery of MSCs was associated with a slight increase in AEs associated with musculoskeletal and connective tissue disorders, albeit without serious AEs. We conclude that intrathecal MSCs delivery is safe for patients with neurological conditions. However, further high-quality, large-scale RCTs are needed to confirm these findings.