Jian-Da Lin | PubMed Health

PubMed2026

Contact hypersensitivity promotes hair regeneration through SPP1-secreting macrophages.

Allergic contact dermatitis, or contact hypersensitivity (CHS), is a pathological adaptive immune response that paradoxically induces hair regeneration, yet its underlying mechanisms remain unclear. We integrated high-resolution spatial transcriptomics and single-cell RNA sequencing to map the intricate interactions between immune cells, stroma, and hair follicles during CHS-induced hair growth in mice. Among all immunocytes, macrophages underwent the most prominent compositional and functional remodeling. We resolved five transcriptionally distinct macrophage subsets, with contact hypersensitivity driving a shift from homeostatic antigen-presenting cells toward a pro-inflammatory CD14+SPP1+ population. Trajectory analysis revealed divergent differentiation paths under homeostatic versus allergic conditions, highlighting the plasticity of skin macrophages. Mechanistically, CD14+SPP1+ macrophages secreted SPP1 (osteopontin), which engaged CD44 on hair follicle stem cells to activate PI3K-AKT signaling and trigger their proliferation. Notably, canonical pro-inflammatory cytokine signaling through TNF-α and IL-1 was dispensable for this process, underscoring the specificity of the SPP1-CD44 axis in immune-mediated hair regeneration. These findings reveal a macrophage-dependent mechanism of immune-mediated hair regeneration, offering therapeutic insights into immune-stem cell crosstalk.

Journal Article↗

PubMed2025

Parabacteroides goldsteinii mitigates parkinsonism in LRRK2 mutant mice by reducing neuroinflammation through Gut-Brain axis.

INTRODUCTION: Alterations in the gut microbiota accompanied by intestinal inflammation are early features of Parkinson's disease (PD). Mutations in the leucine-rich repeat kinase 2 (LRRK2) gene represent a common genetic risk factor for PD and inflammatory bowel disease. Parabacteroides goldsteinii has been reported to alleviate intestinal and systemic inflammation. However, whether modulation of the gut microenvironment at early disease stage can attenuate PD progression remains unclear. OBJECTIVE: To investigate the impact of P. goldsteinii colonization prior to the onset of motor dysfunction on PD progression. METHODS: We established a germ-free PD mouse model carrying the LRRK2 G2019S mutation and administered P. goldsteinii orally at the pre-symptomatic stage to evaluate its effects on motor performance and PD-related neuropathology. Spatial and bulk RNA transcriptomic analyses of brain tissue, together with cytokine profiling, were conducted to assess central changes. To investigate gut immunomodulatory mechanisms, we performed intestinal bulk and single-cell RNA sequencing, spectral flow cytometry as well as cellular bioenergetic analyses. RESULTS: Germ-free conditions partially alleviated PD-like phenotypes in LRRK2 G2019S mice. Colonization with P. goldsteinii at 5-months of age, prior to motor symptom onset, further improved locomotor performance, reduced neuronal α-synuclein aggregations, and mitigated microglial activation and dopaminergic neurodegeneration. Neuroprotection was mediated through enhanced noncanonical neuronal IL-12 receptor-dependent neurotrophic support without activating the canonical STAT4 phosphorylation pathway, along with suppression of microglial activation and downregulation of LRRK2 kinase activity. At the intestinal level, P. goldsteinii suppressed TLR4-driven inflammation, expanded anti-inflammatory intraepithelial CD4+CD8αα+ T cells, promoted dendritic cell and macrophage differentiation, upregulated epithelial tight-junction genes, and improved mitochondrial bioenergetics in intestinal cells. CONCLUSION: P. goldsteinii colonization attenuates the progression of LRRK2-associated parkinsonism by restoring intestinal homeostasis and reducing neuroinflammation. These findings underscore the therapeutic potential of modulating the gut-immune-brain axis during the prodromal stage of PD.

Animals↗