The Effect of Mesenchymal stromal cells on macrophage immunophenotype

Abstract

Purpose : Macrophages (Mq) are a key player and regulator of inflammation and repair. Mesenchymal stromal/stem cells (MSCs) are capable of modulating the immune system through interaction with a wide range of immune cells. We evaluated the immunophenotype of Mq after co-culture with either corneal-limbal derived MSCs (CL-MSC) or bone marrow-derived MSCs (BM-MSC).

Methods : BM-MSC were isolated from healthy human donors in a GMP facility. CL-MSCs were extracted from cadaver human corneas. MSCs at passage 4 to 6 from at least 5 donors were used for all experiments. CD14+ monocytes were isolated from peripheral blood mononuclear cells and differentiated into Mqs with IMDM + 10% serum for 7 days. They were cocultured with MSCs in a 0.22 µm pore size transwell for 3 days. Cell surface and intracellular antigen expression of Mqs was investigated using fluorescence-activated cell sorting (Fortessa, BD).

Results : Median fluorescence intensity (MFI) of CD163 increased to 686.7 ± 207.4 and 662.1 ± 226.6 in Mqs that were “educated” by CL-MSCs and BM-MSCs, respectively, which was significantly higher than “uneducated” Mqs (237.1 ± 23.08) (P <0.001 for both comparisons). Likewise, CD206 MFI increased to 3583 ± 1922 and 3737 ± 975.5 compared to 1139 ± 547.5, respectively (P <0.001 for both comparisons). (CD163 and CD206 are markers of alternatively activated/anti-inflammatory Mqs). In contrast, CD86 MFI decreased to 5496 ± 493.3 and 5254 ± 497.5 compared to 8374 ± 1062, respectively (P <0.001 for both comparisons). Likewise, HLA-DR MFI decreased to 9591 ± 1652 and 10147 ± 710.7 compared to 16980 ± 3621, respectively (P <0.001 for both comparisons) (CD86 and HLA-DR are markers of classically activated/inflammatory Mqs). There was not any statistically significant difference between CL-MSC and BM-MSC educated Mqs in terms of these markers.

Conclusions : Both CL-MSCs and BM-MSCs upregulate markers associated with anti-inflammatory Mqs. This may be one of the mechanisms that MSCs confer their anti-inflammatory effects through paracrine fashion.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.