Rescuing macrophage normal function in spinal cord injury with embryonic stem cell conditioned media.

Macrophages play an important role in the inflammatory responses involved with spinal cord injury (SCI). We have previously demonstrated that infiltrated bone marrow-derived macrophages (BMDMs) engulf myelin debris, forming myelin-laden macrophages (mye-Mϕ). These mye-Mϕ promote disease progression through their pro-inflammatory phenotype, enhanced neurotoxicity, and impaired phagocytic capacity for apoptotic cells. We thus hypothesize that the excessive accumulation of mye-Mϕ is the root of secondary injury, and that targeting mye-Mϕ represents an efficient strategy to improve the local inflammatory microenvironment in injured spinal cords and to further motor neuron function recovery. In this study, we administer murine embryonic stem cell conditioned media (ESC-M) as a cell-free stem cell based therapy to treat a mouse model of SCI. We showed that BMDMs, but not microglial cells, engulf myelin debris generated at the injury site. Phagocytosis of myelin debris leads to the formation of mye-Mϕ in the injured spinal cord, which are surrounded by activated microglia cells. These mye-Mϕ are pro-inflammatory and lose the normal macrophage phagocytic capacity for apoptotic cells. We therefore focus on how to trigger lipid efflux from mye-Mϕ and thus restore their function. Using ESC-M as an immune modulating treatment for inflammatory damage after SCI, we rescued mye-Mϕ function and improved functional locomotor recovery. ESC-M treatment on mye-Mϕ resulted in improved exocytosis of internalized lipids and a normal capacity for apoptotic cell phagocytosis. Furthermore, when ESC-M was administered intraperitoneally after SCI, animals exhibited significant improvements in locomotor recovery. Examination of spinal cords of the ESC-M treated mice revealed similar improvements in macrophage function as well as a shift towards a more anti-inflammatory environment at the lesion and parenchyma. The embryonic stem cell conditioned media can be used as an effective treatment for SCI to resolve inflammation and improve functional recovery while circumventing the complications involved in whole cell transplantation.

巨噬细胞在脊髓损伤（SCI）相关的炎症反应中起重要作用。我们先前已证明，浸润的骨髓来源巨噬细胞（BMDMs）吞噬髓鞘碎片，形成富含髓鞘的巨噬细胞（mye - Mϕ）。这些mye - Mϕ通过其促炎表型、增强的神经毒性以及对凋亡细胞吞噬能力的受损促进疾病进展。因此我们假设mye - Mϕ的过度积累是继发性损伤的根源，并且靶向mye - Mϕ是改善受损脊髓局部炎症微环境以及进一步促进运动神经元功能恢复的有效策略。在这项研究中，我们使用小鼠胚胎干细胞条件培养基（ESC - M）作为一种无细胞的干细胞疗法来治疗脊髓损伤小鼠模型。 我们发现BMDMs而非小胶质细胞吞噬损伤部位产生的髓鞘碎片。髓鞘碎片的吞噬导致在受损脊髓中形成mye - Mϕ，其周围是活化的小胶质细胞。这些mye - Mϕ具有促炎作用，并丧失了正常巨噬细胞对凋亡细胞的吞噬能力。因此我们关注如何触发mye - Mϕ的脂质外流从而恢复其功能。使用ESC - M作为脊髓损伤后炎症损伤的免疫调节治疗方法，我们恢复了mye - Mϕ的功能并改善了运动功能的恢复。ESC - M对mye - Mϕ的处理导致内化脂质的胞吐作用改善以及对凋亡细胞吞噬的正常能力恢复。此外，当脊髓损伤后腹腔注射ESC - M时，动物在运动功能恢复方面表现出显著改善。对接受ESC - M治疗的小鼠脊髓进行检查发现，巨噬细胞功能有类似的改善，并且在损伤部位和实质中向更抗炎的环境转变。 胚胎干细胞条件培养基可作为一种有效的脊髓损伤治疗方法，用于解决炎症并改善功能恢复，同时避免全细胞移植所涉及的并发症。