Time-dependent changes in monocyte subsets and gene expression patterns are associated with long-term recovery in patients with ischemic stroke

Background Post-stroke inflammation is increasingly recognized as a dynamic process that influences neurological recovery. However, how circulating monocyte subsets and their transcriptional programs evolve in relation to long-term functional outcomes in humans remains poorly defined. The objective of this study was to characterize the temporal dynamics of circulating monocyte subsets and their gene-expression profiles after ischemic stroke, and to identify immune signatures associated with neurological recovery, as assessed by longitudinal changes in the NIH Stroke Scale (NIHSS). Main text Blood samples were collected from 37 patients with ischemic stroke at four time points: 24 hours, 3-5 days, 1 and 3 months after stroke, and from 37 age- and gender-matched control subjects. Monocyte subsets were quantified by flow cytometry. Gene expression profiling of isolated monocytes was performed using Fluidigm, with quantitative transcriptional analysis of immune-related genes. Longitudinal changes in monocyte subtype frequencies and gene expression were assessed, along with associations among immune parameters, sex, and neurological outcomes, to identify recovery-linked immune trajectories. Total circulating monocyte levels increased during the acute and early subacute phases, with outcome- and sex-dependent differences. Classical monocytes declined at 3 months, whereas intermediate monocytes increased at 3-5 days in patients with favorable recovery. Gene expression analyses showed early attenuation of inflammatory and costimulatory signaling. Low TSPO expression at 24 hours was associated with greater neurological deficit, as indicated by higher NIHSS, and reduced CD86 and IL-1β expression at 3-5 days was observed in patients with more severe neurological impairment. At 3 months, increased CCR2 expression suggested ongoing monocyte recruitment and persistent immune activity. Increased expression of CD91, CD36, and TGM2 was associated with favorable outcomes, whereas higher expression of CD11c, CCR2, and CX3CR1 was associated with a poorer prognosis. CD91 emerged as a marker associated with greater longitudinal improvement in NIHSS, and CD36 expression in intermediate monocytes revealed a previously unrecognized immune signature linked to recovery in human stroke. Conclusions These findings demonstrate that stroke recovery is associated with coordinated, time-dependent reprogramming of circulating monocytes rather than persistent inflammatory activation. Identification of monocyte-based transcriptional signatures associated with functional outcomes supports the potential of immune profiling to improve prognostic stratification and inform future immune-targeted strategies for stroke recovery.