Leptomeninges: a novel stem cell niche with neurogenic potential
The meninges are composed of three membranous layers referred to as the dura mater, arachnoid mater, and pia mater. The arachnoid mater and pia mater are connected together and form the leptomeninges. The meninges not only protect the central nervous system (CNS), including the brain and spinal cord, directly with their thick outer layers but also indirectly by cushioning through the cerebrospinal fluid filled in the subarachnoid space. In addition, a previous study demonstrated that removing the meninges causes impaired cortical development (1). This suggests that the meninges have functions other than protection. In support of this idea, it is reported that the meninges modulate cortical neuron generation during early brain development by producing trophic factors such as retinoic acid (2). Thus, it is likely that they play pivotal roles in cortical neurogenesis by regulating embryonic neural stem/progenitor cells (NSPCs) (3).