OBJECTIVE

To investigate the possibility and effect of chitosan porous scaffolds combined with bone marrow mesenchymal stem cells (BMSCs) in repair of neurological deficit after traumatic brain injury (TBI) in rats.

METHODS

BMSCs were isolated, cultured, and passaged by the method of bone marrow adherent culture. The 3rd generation BMSCs were identified by the CD29 and CD45 surface antigens and marked by 5-bromo-2-deoxyuridine (BrdU). The chitosan porous scaffolds were produced by the method of freeze-drying. The BrdU-labelled BMSCs were co-cultured with chitosan porous scaffolds, and were observed by scanning electron microscopy. MTT assay was used to observe the cell growth within the scaffold. Fifty adult Sprague Dawley rats were randomly divided into 5 groups with 10 rats in each group. The rat TBI model was made in groups A, B, C, and D according to the principle of Feeney's free fall combat injury. Orthotopic transplantation was carried out at 72 hours after TBI. Group A was the BMSCs and chitosan porous scaffolds transplantation group; group B was the BMSCs transplantation group; group C was the chitosan porous scaffolds transplantation group; group D was the complete medium transplantation group; and group E was only treated with scalp incision and skull window as sham-operation group. Before TBI and at 1, 7, 14, and 35 days after TBI, the modified neurological severity scores (mNSS) was used to measure the rats' neurological function. The Morris water maze tests were used after TBI, including the positioning voyage test (the incubation period was detected at 31-35 days after TBI, once a day) and the space exploration test (the number of crossing detection platform was detected at 35 days after TBI). At 36 days after TBI, HE staining and immunohistochemistry double staining [BrdU and neurofilament triplet H (NF-H) immunohistochemistry double staining, and BrdU and glial fibrillary acidic protein (GFAP) immunohistochemistry double staining] were carried out to observe the transplanted BMSCs' migration and differentiation in the damaged brain areas.

RESULTS

Flow cytometry test showed that the positive rate of CD29 of the 3rd generation BMSCs was 98.49%, and the positive rate of CD45 was only 0.85%. After co-cultured with chitosan porous scaffolds for 48 hours, BMSCs were spindle-shaped and secreted extracellular matrix to adhere in the scaffolds. MTT assay testing showed that chitosan porous scaffolds had no adverse effects on the BMSCs' proliferation. At 35 days after TBI, the mNSS scores and the incubation period of positioning voyage test in group A were lower than those in groups B, C, and D, and the number of crossing detection platform of space exploration test in group A was higher than those in groups B, C, and D, all showing significant differences ( <0.05); but no significant difference was found between groups A and E in above indexes ( >0.05). HE staining showed that the chitosan porous scaffolds had partially degraded, and they integrated with brain tissue well in group A; the degree of repair in groups B, C, and D were worse than that of group A. Immunohistochemical double staining showed that the transplanted BMSCs could survive and differentiate into neurons and glial cells, some differentiated neural cells had relocated at the normal brain tissue; the degree of repair in groups B, C, and D were worse than that of group A.

CONCLUSION

The transplantation of chitosan porous scaffolds combined with BMSCs can improve the neurological deficit of rats following TBI obviously, and also inhabit the glial scar's formation in the brain damage zone, and can make BMSCs survive, proliferate, and differentiate into nerve cells in the brain damage zone.