To investigate the mechanisms underlying changes in CSF biomarkers in response to intrathecal mesenchymal stem cell-neural progenitor (MSC-NP) treatment in patients with progressive multiple sclerosis (MS).

MSC-NPs are a bone marrow-derived population of cells enriched in cell signaling molecules that exhibit trophic and immunomodulatory therapeutic properties. A recent phase II randomized, double blind, placebo-controlled clinical trial demonstrated safety and efficacy of multiple intrathecal injections of autologous MSC-NPs in patients with progressive MS. Biomarker screening of CSF from trial subjects revealed changes in multiple protein biomarkers associated with MSC-NP treatment. Newly identified biomarkers included the chemokine CCL-2, matrix metalloproteinase MMP-9, chitotriosidase-2 (CHIT-1) and adhesion receptor ICAM-1.

We utilized human iPSC-derived cell lines to model microglia and astrocyte activity and polarization in response to pro-inflammatory and pro-regenerative signals. Expression of CCL-2, MMP-9, CHIT-1 and ICAM-1 along with polarization controls were measured by quantitative PCR, and protein levels were determined by ELISA. The paracrine effect of MSC-NPs on candidate biomarker expression was tested by culturing activated microglia or astrocytes with MSC-NP conditioned media derived from multiple MS donors.

Microglia polarized to a pro-inflammatory phenotype exhibited significantly increased CCL-2 and ICAM-1, and decreased MMP-9 and CHIT-1 expression that was reversed in the presence of MSC-NP conditioned media. These changes correlated with decreased CCL-2/ICAM-1 and increased MMP-9/CHIT-1 protein biomarker levels in CSF from patients following MSC-NP treatment. In addition, CCL-2 and ICAM-1 were upregulated in activated astrocytes which was significantly inhibited by paracrine factors from MSC-NPs. MMP-9 and CHIT-1 expression were not regulated in activated astrocytes, suggesting microglia-specific expression.

These results demonstrate that CSF biomarker changes in response to intrathecal MSC-NP treatment reflect changes in the pro-inflammatory phenotype of microglia and astrocytes, suggesting that microglia and/or astrocytes are a possible therapeutic target of MSC-NP cell therapy in MS.