Falco María Victoria, Fabbiani Gabriela, Maciel Cecilia, Valdivia Spring, Vitureira Nathalia, Russo Raúl E
Departamento de Neurofisiología Celular y Molecular, Instituto de Investigaciones Biológicas Clemente Estable, Montevideo, Uruguay.
Departamento de Fisiología, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay.
Front Cell Neurosci. 2023 Dec 18;17:1288676. doi: 10.3389/fncel.2023.1288676. eCollection 2023.
The ependyma of the spinal cord is a latent stem cell niche that is reactivated by injury, generating new cells that migrate to the lesion site to limit the damage. The mechanisms by which ependymal cells are reactivated after injury remain poorly understood. ATP has been proposed to act as a diffusible "danger signal" to alert about damage and start repair. Indeed, spinal cord injury (SCI) generates an increase in extracellular ATP around the lesion epicenter that lasts for several hours and affects the functional outcome after the damage. The P2X7 receptor (P2X7r) has functional properties (e.g., low sensitivity for ATP, high permeability for Ca) that makes it a suitable candidate to act as a detector of tissue damage. Because ependymal cells express functional P2X7r that generate an inward current and regenerative Ca waves, we hypothesize that the P2X7r has a main role in the mechanisms by which progenitor-like cells in the ependyma react to tissue damage. To test this possibility, we simulated the P2X7r activation that occurs after SCI by intraspinal injection of the selective agonist BzATP nearby the central canal. We found that BzATP rescued ependymal cells from quiescence by triggering a proliferative response similar to that generated by injury. In addition, P2X7r activation by BzATP induced a shift of ependymal cells to a glial fibrillary acidic protein (GFAP) phenotype similar to that induced by injury. However, P2X7r activation did not trigger the migration of ependyma-derived cells as occurs after tissue damage. Injection of BzATP induced the expression of connexin 26 (Cx26) in ependymal cells, an event needed for the proliferative reaction after injury. BzATP did not induce these changes in ependymal cells of P2X7 mice supporting a specific action on P2X7r. blockade of P2X7r with the potent antagonist AZ10606120 reduced significantly the injury-induced proliferation of ependymal cells. Our data indicate that P2X7r has a key role in the "awakening" of the ependymal stem cell niche after injury and suggest purinergic signaling is an interesting target to improve the contribution of endogenous progenitors to repair.
脊髓室管膜是一个潜在的干细胞微环境，在损伤后被重新激活，产生新的细胞迁移到损伤部位以限制损伤。损伤后室管膜细胞被重新激活的机制仍知之甚少。ATP被认为是一种可扩散的“危险信号”，用于警示损伤并启动修复。事实上，脊髓损伤（SCI）会使损伤中心周围的细胞外ATP增加，这种增加会持续数小时，并影响损伤后的功能结果。P2X7受体（P2X7r）具有一些功能特性（例如，对ATP敏感性低，对Ca通透性高），这使其成为充当组织损伤探测器的合适候选者。由于室管膜细胞表达功能性P2X7r，可产生内向电流和再生性Ca波，我们推测P2X7r在室管膜中祖细胞样细胞对组织损伤作出反应的机制中起主要作用。为了验证这种可能性，我们通过在脊髓中央管附近注射选择性激动剂BzATP来模拟SCI后发生的P2X7r激活。我们发现BzATP通过触发类似于损伤产生的增殖反应，使室管膜细胞从静止状态中恢复。此外，BzATP激活P2X7r会使室管膜细胞转变为类似于损伤诱导的胶质纤维酸性蛋白（GFAP）表型。然而，P2X7r激活并未触发组织损伤后发生的室管膜来源细胞的迁移。注射BzATP会诱导室管膜细胞中连接蛋白26（Cx26）的表达，这是损伤后增殖反应所需的事件。BzATP不会在P2X7基因敲除小鼠的室管膜细胞中诱导这些变化，这支持了其对P2X7r的特异性作用。用强效拮抗剂AZ10606120阻断P2X7r可显著降低损伤诱导的室管膜细胞增殖。我们的数据表明，P2X7r在损伤后室管膜干细胞微环境的“唤醒”中起关键作用，并提示嘌呤能信号传导是改善内源性祖细胞对修复贡献的一个有趣靶点。
