Dynamic Study On The Change Of RGCs And The Expression Of GFAP After Optic Nerve Crush Of Rat

【Background】Optic nerve crush is one of usual kinds of eye injuries for clinical forensic medicine and ophthalmology. It often results in serious optic dysfunction. So recognizing and evaluating the affection of this injury is one of the important tasks of forensic expertise. Glial fibrillary acid protein is a major component of cytoskeletal intermediate filament, primarily in the horizontal cell of central nervous system. After nervous system injury, glial cell functional changes are often immune reactive changes. In many neurodegenerative diseases GFAP immune reactive changes are found, GFAP is considered as sensitive indicator of central nervous damage. Meanwhile, a series of studies in animal models are confirmed, after optic nerve injury pathomechanism of the decrease of visual function is predominant because retinal ganglion cells (RGCs) are lossed. So correctly understanding the characteristics of the pathological changes after optic nerve injury has important value for this study.【Objective】: In this study, models of rat optic nerve contund are established, morphologic changes of RGCs after optic nerve and GFAP in Müller cells are investigated. This study will provide molecular pathology foundation to forensic expertise after optic nerve injury.【Method】: 45 adult Wistar rats are divided into seven groups, each include 5 animals. Refering to methods of other literature, rat optic nerve contend models are established, after optic nerve contend rats in each group are raised, respectively 1d,3d,5d,7d,9d,14d,21d,at the same time optic nerve is perfused to fix, eye globes are exsected and was made pathological sections, pathological changes of RGCs are observated, GFAP of RGCs are detected by immunohistochemical method. To investigate the relationships between GFAP express of RGCs and nerve injury time.【Results】: Optic nerve injury induct loss of RGCs, 1d after optic nerve injury several RGCs degenerate to death, 3d after optic nerve injury number of RGCs decrease more than 1d, 7d after optic nerve injury RGCs reduce ca. 36%,14d after optic nerve injury RGCs reduce ca. 44%, 21d after optic nerve injury RGCs reduce ca. 52%. In 7 days after optic nerve injury RGCs reduce rapidly, 14d after optic nerve injury RGCs reduce slower, from 14d to 21d after optic nerve injury RGCs reduce ca. 7.43%, however RGCs in normal tissue change never. 1d after optic nerve injury staining of GFAP in retina is similar in normal retina. 3d after injury staining positive of GFAP increase in fibrage and nodal cell of retina, in inner plexiform layer,inner nuclear layer,outer plexiform layer staining positive of GFAP is filiform. 7d after injury staining positive of GFAP in nodal cell of retina, between internal limiting membrane and external limiting membrane deepen, concentrate and achieve peak. 9d after injury expression of GFAP decrease, but reduce slowly, trend to reduce mildly. 14d after injury expression of GFAP decrease to near normal level.【Conclusion】:In the study 3d after optic nerve injury RGCs start to loss much, within 7d after optic nerve injury RGCs decrease rapidly, to 14d after optic nerve injury RGCs decrease ca. 44%,after 14d after optic nerve injury decrease of RGCs become slow obviously, 21dafter optic nerve injury decrease of RGCs change never. This demonstrate that after optic nerve injury loss of RGCs correlate to time of injury obviously, this is same to the conclusion of Berkelaar`s study. 3d after optic nerve contend immunological reaction of GFAP in retina increase, and achieve the peak in 7d, this demonstrate that optic nerve injury results reactive increase of retinal colloid cells. Follow the time after optic nerve injury retinal colloid cells reduce little by little, to normal level after 14d after optic nerve injury. This is accordant to degeneration and increasing mortality of injured RGCs. Then expression location of GFAP dominating center the cell membrane of RGCs and periphery of its fiber. Thus GFAP correlate to number of living RGCs obviously, as injured RGCs degenerate and die, expression of GFAP reduce correspondingly. Altogether after optic nerve injury direct mechanical injury result in rapid descend of ocular function, secondary loss of RGCs and degeneration of neuraxis result in aggravation of ocular function. And this manifest relationships with time. Also expression level of GFAP considerably correlate to time, and to number of living RGCs obviously. It provide important molecular evidences to understand pathology factors and evaluate prognosticly visual function after optic nerve injury, and new clue for concluding injury time.