Local administration of mesenchymal stromal cells is safe and modulates the immune compartment in ulcerative proctitis

Abstract

BACKGROUNDDue to their immunoregulatory and tissue regenerative features, mesenchymal stromal cells (MSCs) are a promising novel tool for the management of ulcerative proctitis (UP). Here we report on a phase IIa clinical study that evaluated the impact of local MSC therapy on UP.METHODSThirteen refractory UP patients, with an endoscopic Mayo score (EMS) of 2 or 3, were included. Seven patients received 20-40 million allogeneic MSCs (cohort 1), while 6 patients received 40-80 million MSCs (cohort 2). Adverse events (AEs) were assessed at baseline and on weeks 2, 6, 12, and 24. Clinical, endoscopic, and biochemical parameters were assessed at baseline and on weeks 2 and 6. Furthermore, we evaluated the engraftment of MSCs, the presence of donor-specific human leukocyte antigen (HLA) antibodies (DSAs), and we determined the impact of MSC therapy on the local immune compartment.RESULTSNo serious AEs were observed. The clinical Mayo score was significantly improved on weeks 2 and 6, and the EMS was significantly improved on week 6, compared with baseline. On week 6, donor MSCs were still detectable in rectal biopsies from 4 of 9 patients and DSAs against both HLA class I and class II were found. Mass cytometry showed a reduction in activated CD8+ T cells and CD16+ monocytes and an enrichment in mononuclear phagocytes and natural killer cells in biopsies after local MSC therapy.CONCLUSIONLocal administration of allogeneic MSCs is safe, tolerable, and feasible for treatment of refractory UP and shows encouraging signs of clinical efficacy and modulation of local immune responses. This sets the stage for larger clinical trials.TRIAL REGISTRATIONEU Clinical Trials Register (EudraCT, 2017-003524-75) and the Dutch Trial Register (NTR7205).FUNDINGECCO grant 2020.

Keywords: Clinical Trials; Inflammation; Inflammatory bowel disease.

Figure 1. Study design.

Time points are indicated in weeks (w) or years (y). AE, adverse events; CMS, clinical Mayo score; EMS, endoscopic Mayo score; FCP, fecal calprotectin; CRP, C-reactive protein; GS, Geboes score; QoL, Quality of Life; PROMs, patient-reported outcome measures; sIBDQ, Short Inflammatory Bowel Disease Questionnaire; SF-36, Short Form-36; mHI, mobile Health Index (56).

Figure 2. Mean full Mayo score with corresponding subscores at baseline and on weeks 2 and 6.

Data are presented as mean ± SD. Wilcoxon’s signed-rank test was performed.

Figure 3. MSCs persist in the rectal mucosa after 6 weeks.

A representative image is displayed of a rectal biopsy from a male patient that received allogeneic MSCs from a female donor. In multiple regions, 2 X chromosomes (in green) were detected in close proximity in the nucleus of a cell (red arrow). Probes detect the presence of chromosome Y (in red) and chromosome X (in green). DAPI (4′-6′-diamidino-2-phenylindole, in blue) was used to stain the DNA. Scale bars: 200 μm (left) and 10 μm (right).

Figure 4. Local MSC therapy is associated with modulation of the inflammatory proteins in rectal biopsies.

A volcano plot showing the statistical significance and fold change in protein levels 6 weeks after MSC injection compared with baseline. Decreased levels of proteins are indicated in blue and increased levels of proteins in red. Gray points indicate no significant change. Wilcoxon’s signed-rank test was performed.

Figure 5. CD8⁺ T cells, γδ T cells and, innate lymphoid cells are decreased in case biopsies compared with control biopsies but do not change significantly upon local MSC injection.

(A) HSNE embedding showing 1.6 × 10⁴ landmarks representing immune cells (3.4 × 10⁶ cells) isolated from control biopsies at baseline (n = 12) and on week 6 (n = 7) and from case biopsies at baseline (n = 13) and on week 6 (n = 12). Colors represent the biopsies at different time points (left) and the other immune lineage clusters (right). (B) Frequencies of CD66b⁺ granulocyte cluster in control biopsies at baseline (n = 12), case biopsies at baseline (n = 13), and after 6 weeks (n = 12) as a percentage of total CD45⁺ cells. (C) Composition of the major immune lineages, CD66b⁺ granulocytes excluded, in individual patients (n = 13) in control biopsies (left), case biopsies (middle) at baseline, and case biopsies on week 6 (right), represented as vertical bars. The size of the colored segments represents the proportion of the cells as a percentage of total CD45⁺ cells in the samples. Colors are as in A. (D) Frequencies of the CD8⁺ T cells, γδ T cells, ILCs, and CD45⁺Lineage^– cells from individual samples (n = 12) (control biopsies and case biopsies at baseline and case biopsies on week 6). Each dot represents an individual sample. Red dots are biopsies with mild endoscopic inflammation. NS, not significant. Wilcoxon’s signed-rank test was performed.

Figure 6. Reduction in activated CD8⁺ T cells and CD16⁺ monocytes and increased CD127⁺ monocytes/macrophages and tissue-resident NK cells after local MSC therapy.

(A) t-SNE embedding of memory CD8⁺ T cell compartment (in total 1.7 × 10⁵ cells), CD66b^– mononuclear phagocyte (MNP) compartment (in total 4.2 × 10⁵ cells), and ILC compartment (in total 4.6 × 10⁴ cells). Colors represent the biopsies at different time points (left) and the different clusters (right). (B–D) Heatmaps of the memory CD8⁺ T cell compartment (B), MNP (CD66b^–) compartment (C), and ILC compartment (D) showing median marker expression values (top). (E–G) Frequencies of selected clusters within the CD8⁺ T cell compartment (E), MNP compartment (F), and ILC compartment (G) in biopsies from control biopsies at baseline (n = 12), case biopsies at baseline (n = 12), and after 6 weeks (n = 12) as a percentage of the corresponding major lineages. Each dot represents an individual sample. Red dots are biopsies with mild endoscopic inflammation. NS, not significant. Wilcoxon’s signed-rank test was performed.