Abstract
Vertebral body has marrow cavities where hematopoiesis takes place. There are pluripotent stem cells in vertebral bone marrow and they may be recruited into the bone cells of the vertebra, form chondrocytes orcells of annulus fibrosus. Injury to vertebral disc is a common occurrence in both sexes; however, Estrogen has been reported to have beneficial effects in the postmenopausal women receiving hormone replacement therapy. An experimental study was designed to see the effects of estrogen on cell population of the bone marrow five days after the injury to intervertebral disc, using rabbit as an experimental model. Animals were divided into a control and experimental group of 15 each. Both groups received injury to the annulus fibrosus. Experimental group was given a calculated dose of estrogen after the injury. Animals were sacrificed and intervertebral discs along with marrow spaces were obtained 5 days after injury to the annulus fibrosus. The sections were stained with hematoxylin and eosin. Cells of the myelocyte series were found to be increasing in population in response to hormone therapy. It was concluded that estrogen may lead to recruitment of cells from bone marrow to the cell population of the annulus fibrosus and this maybe beneficial for its healing.