Govindappa Prem Kumar, Ellur Govindaraj, Hegarty John P, Gupta Akash, Rahul V G, Elfar John C
Department of Orthopaedics and Sports Medicine, University of Arizona College of Medicine, Tucson, AZ 85724, USA.
Department of Cellular and Molecular Physiology, The Pennsylvania State University College of Medicine, Hershey, PA, 17033, USA.
bioRxiv. 2025 Jan 23:2025.01.22.634402. doi: 10.1101/2025.01.22.634402.
After peripheral nerve trauma, insufficient clearance of phagocytic debris significantly hinders nerve regeneration. Without sufficient myelin debris clearance, Schwann cells (SCs) undergo increased apoptosis, impairing functional recovery. There is no treatment for peripheral nerve crush injury (PNCI). Erythropoietin (EPO) is an FDA-approved drug for anemia, which may help in the treatment of PNCI by transdifferentiating resident SCs into repair SCs (rSCs) and enhancing phagocytosis to facilitate the removal of cellular debris. For the first time, we conducted bulk RNA sequencing on mice with calibrated sciatic nerve crush injuries (SNCIs) on days 3, 5, and 7 post-SNCI to uncover transcriptomic changes with and without EPO treatment. We found EPO altered several biological pathways and associated genes, particularly those involved in cell apoptosis, differentiation, proliferation, phagocytosis, myelination, and neurogenesis. We validated the effects of EPO on SNCI on early (days 3/5) and intermediate (day 7) post-SNCI, and found EPO treatment reduced apoptosis (TUNEL), and enhanced SC repair (c-Jun and p75-NTR), proliferation (Ki67), and the phagocytosis of myelin debris by rSCs at crush injury sites. This improvement corresponded with an enhanced sciatic functional index (SFI). We also confirmed these findings . EPO significantly enhanced SC repair during early de-differentiation, marked by high c-Jun and p75-NTR protein levels, and later re-differentiation with high EGR2 and low c-Jun and p75-NTR levels. These changes occurred under lipopolysaccharide (LPS) stress at 24 and 72h, respectively, compared to LPS treatment alone. Under LPS stress, EPO also significantly increased rSCs proliferation and phagocytosis of myelin or dead SCs. In conclusion, our findings support EPO may enhance the function of rSCs in debris clearance as a basis for its possible use in treating nerve trauma.
周围神经损伤后，吞噬性碎片清除不足会显著阻碍神经再生。如果没有足够的髓磷脂碎片清除，雪旺细胞（SCs）会经历更多凋亡，从而损害功能恢复。目前尚无治疗周围神经挤压伤（PNCI）的方法。促红细胞生成素（EPO）是一种经美国食品药品监督管理局（FDA）批准用于治疗贫血的药物，它可能通过将驻留的雪旺细胞转分化为修复性雪旺细胞（rSCs）并增强吞噬作用以促进细胞碎片清除，来帮助治疗PNCI。我们首次对坐骨神经挤压伤（SNCI）后第3、5和7天的校准坐骨神经挤压伤小鼠进行了批量RNA测序，以揭示有无EPO治疗时的转录组变化。我们发现EPO改变了几个生物学途径和相关基因，特别是那些参与细胞凋亡、分化、增殖、吞噬作用、髓鞘形成和神经发生的基因。我们验证了EPO对SNCI后早期（第3/5天）和中期（第7天）的影响，发现EPO治疗减少了凋亡（TUNEL），并增强了雪旺细胞修复（c-Jun和p75-NTR）、增殖（Ki67）以及rSCs在挤压伤部位对髓磷脂碎片的吞噬作用。这种改善与坐骨神经功能指数（SFI）的提高相对应。我们还证实了这些发现。EPO在早期去分化过程中显著增强了雪旺细胞修复，其标志是c-Jun和p75-NTR蛋白水平较高，而在后期再分化过程中，EGR2水平较高，c-Jun和p75-NTR水平较低。与单独的脂多糖（LPS）处理相比，这些变化分别发生在LPS应激后24小时和72小时。在LPS应激下，EPO还显著增加了rSCs的增殖以及对髓磷脂或死亡雪旺细胞的吞噬作用。总之，我们的研究结果支持EPO可能增强rSCs在碎片清除中的功能，这是其可能用于治疗神经创伤的基础。
