Increased levels of circulating granulocytic myeloid‑derived suppressor cells in lumbar disc herniation.

Myeloid-derived suppressor cells (MDSCs) expand when the body undergoes inflammatory diseases and chronic diseases. However, its role in intervertebral disc degeneration remains unclear. The present study aimed to characterize specific subsets of MDSCs as potential indicators of disease progression in patients with lumbar disc herniation (LDH). The Gene Expression Omnibus (GEO) database was used to analyze the changes in granulocyte MDSCs (G-MDSCs). Peripheral blood samples were collected from 40 patients with LDH and 15 healthy controls, and flow cytometry was used to characterize different subsets of MDSCs. All subjects underwent lumbar spine magnetic resonance imaging. Then, t-distributed stochastic neighborhood embedding and FlowSOM were used to analyze the data obtained by CytoFlex. The correlation between circulating MDSCs and the clinicopathological stage of LDH was then further analyzed. The GEO database predicted that G-MDSCs were highly expressed in patients with LDH. The frequency of circulating G-MDSCs increased with Pfirrmann stage III and IV, while the percentage of mononuclear MDSCs (M-MDSCs) only increased. Patient age and sex did not correlate with the frequency of circulating G-MDSCs and M-MDSCs. The results of the computer algorithm analysis were consistent with those of our manual gating. The present study showed that the occurrence of LDH led to changes in the MDSC subpopulation in the circulating peripheral blood of patients, and the frequency of circulating G-MDSCs in patients with clinical stage III and IV LDH increased with the degree of degeneration. The determination of G-MDSCs can be used as an auxiliary examination item for LDH.