RESPONSE OF BASIC FIBROBLAST GROWTH FACTOR TO RAT BRAIN STAB WOUND AND INFLUENCE OF 5′ METHYLTHIOADENOSINE ON REACTIVE ASTROGLIOSIS in vivo

This study is aimed to determine: 1. the cell types, after rat brain stab wound, which dynamically express bFGF, FGFR and GFAP, and interaction of these cells; 2. the interference of 5′ methylthioadenosine (5′ MTA), an inhibitor of FGFR, with the reactive astrogliosis of rat brain. This study was divided into 2 parts. Ⅰ. Seventy five SD rats (male, 200～250 g) were divided into 15 groups (average 5). One group accepted sham operation as control, and the other 14 groups were punctured and sacrificed at designed time points (0 5 h～30 d). Ⅱ. Twenty Wistar rats (male 200～250 g) were divided into 2 groups (average 10). Five rats of one group had brain injury and administered 5′ MTA for 3 days, while the other 5 rats with same insult had 5′ MTA for 7 days. The other 10 rats only had brain injury as control. HE, immunohistochemistry of bFGF, FGFR and GFAP with frozen and paraffin sections were stained and determined with morphometry. The main findings were as follows: Swelling of astocytic nuclei is the earliest changes appeared at 0 5 hour after insult and red neurons appeared at 1st hour. Neuronal loss occurred at 4th hour. From 4th day the injured tissue was gradually filled with hypertrophic astrocytes. At the same time astrogliosis was sharply marked by GFAP stain. Astrocytes firstly enhanced its expression of bFGF at 4th hour, 2 hours prior to increased expression of bFGF in neurons. bFGF reaction appeared robust around 2nd day and astrocytes were the main source of bFGF, simultaneously bFGF positive stained area also existed in extracellular matrix with undefined shape, and internalization of bFGF was also found in nucleoli of both neurons and astrocytes. Astrocytes and neurons exhibit their FGFR positive stain from 12 hours after injury, enhanced slightly around one day and quickly declined. 5′ MTA administration decreased the cell number adjacent to the injury and weakened the reaction of bFGF and GFAP compared with those of the control at 4th day; eight days later, the lesion width interfered with 5′ MTA was apparently wider than that of the control. The above results strongly suggested: (1) Reactive increase of bFGF expression is firstly observed in astrocytes at 4th hour after injury, followed by neurons' at 6th hour. bFGF autocrine is the main initiation mechanism of astrogliosis. (2) bFGF could be internalized into nucleoli of both astrocytes and neurons in the area where cells were actively expressing bFGF. (3) Reactive expression of FGFR is a transient event with mild degree, thus may inhibit neurotrophic effect of the bFGF system. (5) 5′ MTA could partly block the reactive astrogliosis.