Responses of EpCs after SCI. Post SCI, 95% of the EpCs differentiated into astrocytes, accounting for 53% of newly generated astrocytes (GFAP-), with the remaining 47% of new astrocytes being derived from the proliferation of resident astrocytes (GFAP+). These cells promote glial scar formation which can prevent secondary injury but restrict neural regeneration. Less than 5% of the activated EpCs differentiated into myelin-forming oligodendrocytes, accounting for 3% of newly generated oligodendrocytes, with the remaining 97% of newly generated oligodendrocytes being derived from the differentiation of OPCs. Unfortunately, almost none of the EpCs differentiated into neurons which leads to the lossof neural circuit regeneration.