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Decoding muscle-resident Schwann cell dynamics during neuromuscular junction remodeling
Steve D. Guzman, Ahmad Abu-Mahfouz, Carol S. Davis, Lloyd P. Ruiz, Peter C.D. Macpherson, Susan V. Brooks
Steve D. Guzman, Ahmad Abu-Mahfouz, Carol S. Davis, Lloyd P. Ruiz, Peter C.D. Macpherson, Susan V. Brooks
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Research Article Cell biology Muscle biology

Decoding muscle-resident Schwann cell dynamics during neuromuscular junction remodeling

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Abstract

In this study, we used single-cell RNA sequencing to delineate the contributions of muscle-resident Schwann cells to neuromuscular junction (NMJ) remodeling by comparing a model of stable innervation with models of reinnervation following partial or complete denervation. We discovered multiple distinct Schwann cell subtypes, including a terminal Schwann cell subtype integral to the denervation-reinnervation cycle, identified by a transcriptomic signature indicative of cell migration and polarization. The data also characterize 3 myelin Schwann cell subtypes, which are distinguished based on enrichment of genes associated with myelin production, mesenchymal differentiation, or collagen synthesis. Importantly, SPP1 signaling emerged as a pivotal regulator of NMJ dynamics, promoting Schwann cell proliferation and muscle reinnervation across nerve injury models. These findings advance our understanding of NMJ maintenance and regeneration and underscore the therapeutic potential of targeting specific molecular pathways to treat neuromuscular and neurodegenerative disorders.

Authors

Steve D. Guzman, Ahmad Abu-Mahfouz, Carol S. Davis, Lloyd P. Ruiz, Peter C.D. Macpherson, Susan V. Brooks

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Figure 5

SPP1 signaling promotes tSC proliferation and muscle fiber reinnervation after nerve injury.

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SPP1 signaling promotes tSC proliferation and muscle fiber reinnervation...
(A) Following sciatic nerve crush injuries, gastrocnemius (GTN) muscles from C57BL/6J mice were collected at 0 (control), 7, 14, and 28 days postinjury (dpi). mRNA expression levels of denervation markers (Chrna1), components of SPP1 signaling (Spp1, Cd44, Itgav, Tgfb1, Tgfbr2), genes linked to SC-mediated nerve regeneration (Ngfr, Gdnf), and cell proliferation (Ccnd1) at each time point are presented. (B) Peroneal nerve injuries were induced, and tibialis anterior (TA) muscles were intramuscularly injected with either SPP1-nAb or IgG at time of injury and every 2 days thereafter. (C) Data are shown for force (mN) evoked by direct muscle stimulation, with nerve stimulation, and ratio of force elicited by nerve and direct muscle stimulation at 7 dpi for IgG- (gray) and SPP1-nAb–treated (blue) groups. (D) Representative immunofluorescence images of NMJs at 7 dpi stained for S100B (green), nuclei (DAPI, blue), AChRs (BTX, red), and NF/SV2 (cyan). (E) Quantification of NMJ nerve terminal area and perimeter, synaptic area, percentage of denervated (>10% overlap) NMJs, tSC number and area. Open circles indicate values for individual mice and bars represent the mean across animals ± SEM. Scale bars: 25 μm. *P ≤ 0.05, **P ≤ 0.01, ***P ≤ 0.001, ****P ≤ 0.0001 by 2-tailed unpaired t test (IgG vs. SPP1-nAb) or 1-way ANOVA with Dunnett’s test; comparison against the single control uninjured group (7, 14, 28 dpi vs. control) for multiple comparisons. In A, n = 4/group; C, n = 8/group; E, n = 4–5/group.

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ISSN 2379-3708

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