Effects of neural stem cells in combination with nerve neurotrophic factor 3 gene modified olfactory ensheathing cell co-transplants on functional recovery after traumatic brain injury in the adult rats

Abstract

Objective To observe the effects of neural stem cells (NSCs) combined with neurotrophin-3 gene modified olfactory ensheathing cells (OECs-NT-3) co-transplants on functional recovery after traumatic brain injury in the adult rats. Methods NSCs and OECs were cultured from hippocampus and olfactory bulb of neonatal rats and then identified. OECs-NT-3 was constructed by lentiviral vector containing NT-3 gene. Male SD rats weighing (200±20) g were randomly divided into sham group, model group, OECs-NT-3 transplantation group, NSCs transplantation group and OECs-NT-3 combined NSCs transplantation group. The rat brain injury model was established. The corresponding cells were transplanted. At day 1, 7, 14 and 28 after transplantation, the modified neurological severity score (mNSS) was used to evaluate neurological function, and brain tissues were taken at each time point for paraffin sections. Hematoxylin-eosin staining was performed. Cell apoptosis was detected by terminal-deoxynucleotidyl transferase mediated nick end labeling (TUNEL) method. Immunohistochemical staining of BrdU and p75 was done. Results At day 28 of transplantation, the mNSS scores in rats in the combined group (4.00±1.05) were significantly different from those in the model group (8.50±1.43), the OECs-NT-3 group (5.50±1.35) and the NSCs group (6.00±1.49) (t=-7.997, -2.764, -3.464, P 0.05). Hematoxylin and eosin (HE) staining revealed that the cell density in the sham group, model group, OECs-NT-3 group, NSCs group and the combined group was (220±22), (299±47), (347±35), (390±72) and (523±55) cells, respectively. As compared with the model group, OECs-NT-3 group and NSCs group, the cell density in the combined group was significantly increased (t=7.246, 5.996, 3.373, P<0.05), and the tissue structure was relatively regular. The p75 and BrdU immunohistochemistry showed that the two kinds of transplanted cells could survive continuously and were widely distributed around the lesion. At day 7 after transplantation, the apoptotic index in the sham group, model group, OECs-NT-3 group, NSCs group and combined group was (1.67±0.17)%, (47.49±7.92)%, (31.22±3.97)%, (34.48±4.69)% and (18.17±3.13)% respectively. The apoptosis rate in the combined transplantation group was significantly lower than that in the model group, OECs-NT-3 group and NSCs group (t=5.963, 4.470, 5.012, P<0.05). Conclusion Transplantation of NSCs combined with OECs-NT-3 can alleviate neuronal apoptosis after brain injury in rats, repair tissue defects, and promote the recovery of nerve function. Key words: Neural stem cell; Neurotrophin-3 gene; Gene modify; Olfactory ensheathing cells; Combined transplantation; Traumatic brain injury