Intravital microscopy of satellite cell dynamics and their interaction with myeloid cells during skeletal muscle regeneration

Abstract

Skeletal muscle regeneration requires the highly coordinated cooperation of muscle satellite cells (MuSCs) with other cellular components. Upon injury, myeloid cells populate the wound site, concomitant with MuSC activation. However, detailed analysis of MuSC–myeloid cell interaction is hindered by the lack of suitable live animal imaging technology. Here, we developed a dual-laser multimodal nonlinear optical microscope platform to study the dynamics of MuSCs and their interaction with nonmyogenic cells during muscle regeneration. Using three-dimensional time-lapse imaging on live reporter mice and taking advantages of the autofluorescence of reduced nicotinamide adenine dinucleotide (NADH), we studied the spatiotemporal interaction between nonmyogenic cells and muscle stem/progenitor cells during MuSC activation and proliferation. We discovered that their cell-cell contact was transient in nature. Moreover, MuSCs could activate with notably reduced infiltration of neutrophils and macrophages, and their proliferation, although dependent on macrophages, did not require constant contact with them. These findings provide a fresh perspective on myeloid cells’ role during muscle regeneration.

Chronological Management of Adjuvant Effect for Optimized mRNA Vaccine Inspired by Natural Virus Infection

“…Alterations in the vaccination site immune microenvironment (VSIM) during successive intramuscular injections may potentially account for the differences in safety profile. , The introduction of exogenous pharmacologic agents or physical trauma cause by injection triggers the recruitment of immune cells, including neutrophils, monocytes, and dendritic cells, to converge at the vaccine administration site . After intramuscular injection, neutrophils will rapidly infiltrate the site of inflammation and reach a peak within 3 to 6 h. In the Follow strategy, a predominant recruitment of neutrophil-based immune cell was happened due to the 6 h earlier administration of CNE.…”