Histological evaluation of the influence of oestrogen deficient state in the epidural fibrosis formation after lumbar laminectomy in the rats

The purpose of this study was to evaluate whether epidural fibrosis formation around the spinal cord was affected by endogenous oestrogen deficient state after lumbar laminectomy in the rats. Thirty-six 12-month-old adult female Sprague-Dawley rats were used in this study. Bilaterally ooferectomy were done in 18 rats. Rats were divided into two groups: oophrectomised (oestrogen deficient) group and sham operated (oestrogen maintained) group. Three weeks after the ooferectomy each rat underwent complete bilaterally laminectomy at the L2 and L3 vertebral levels (two sides per rat). The rats were randomly divided into three equal groups (12 rats in each group). The rats were sacrificed at four, eight, and twelve weeks postoperatively and the lumbar spine excised en bloc, fixed and decalcified. Section stained with hematoxylin and eosin and Masson's trichrome were used to evaluate epidural fibrosis, acute inflammatory cells, chronic inflammatory cells and vascular proliferation. Sections were analyzed by investigator blinded to the study and graded on a five-point grading system. Statistic were performed using Mann-Whitney U test when compare two variable and Kruskal-Wallis test when compare more than two variables. Compared with the oopherectomised group, the sham operated group showed decreased rate of epidural fibrosis and higher acute and chronic inflammatory cells response at four and eight weeks which was no statistically significant (p>0.05). The results of this study revealed that endogenous oestrogen may decrease epidural fibrosis formation after lumbar laminectomy in the rats. Key Words: Epidural fibrosis, laminectomy, estrogen, histological comparison, rat