Effect of L-serine on apoptosis of nerve cells and proliferation of endogenous neural stem cells in rats after spinal cord injury

Abstract

Objective To observe the role of L-serine (L-Ser) in neuronal apoptosis and proliferation of endogenous neural stem cells in rats after spinal cord injury (SCI).Methods A total of 100normal adult SD rats were randomly divided into 5 even groups (n =20) to receive different operations and treatments:sham operation group (only the vertebral lamina was excided without SCI),only SCI group (intraperitoneal injection of only physiological saline was performed after SCI modeling),L-serine treatment group (intraperitoneal injection of L-Ser after SCI modeling),D-cycloserine (DCS) treatment group (intraperitoneal injection of DCS after SCI modeling),and DCS antagonism group (intraperitoneal injection of DCS plus L-Ser after SCI modeling).In the tihboard tests,the angle of slope and the Basso,Beattie,Bresnahan (BBB) locomotor rating score were observed and recorded for each rat in the 3 groups on days 1,3,5and 7.The sample of spinal cord 5 mm from the center of damaged region received Nissle staining; in situ end labeling (TUNEL) was used to detect apoptosis and immunofluorescence to measure the expressions of double-labeled positive cells of Brdu/Nestin in each group.Results Three days postoperation,the angle of slope and BBB score in the L-serine treatment group were significantly higher than those in the only SCI group,DCS treatment group and DCS antagonism group (P ＜ 0.05).The angle of slope tended to increase with days of treatment.The Brdu positive cells,Nestin positive cells and Brdu/Nestin double labeled cells were significantly more in the L-serine treatment group than in the only SCI group,DCS treatment group and DCS antagonism group while TUNEL-positive cells in the injured spinal cord parenchyma decreased significantly as compared to the other 3 groups (P ＜0.05).There were no significant differences between the only SCI group,DCS treatment group and DCS antagonism group regarding the angle of slope,BBB score,Brdu positive cells,Nestin positive cells or Brdu/Nestin double labeled cells (P ＞ 0.05).Conclusion L-serine can inhibit neuronal apoptosis and promote the proliferation of endogenous neural stem cells after acute spinal cord injury in rats. Key words: Apoptosis; Cell proliferation; Spinal cord injuries; Serine; Endogenous neural stem cells