Heat shock transcription factor-1 and heat shock protein 90: insights into post-insemination endometritis

In mares, post-breeding endometritis is a major cause of embryo mortality. In other species, endometrial function and pathology seem to involve heat shock protein-90 (HSP90), a factor regulated by heat shock transcription factor-1 (HSF-1).

To study the relationships between HSP90 and HSF-1 and post-insemination endometritis.

Endometrium was sampled at oestrus without artificial insemination (AI) and at 2 h and 4 h after AI. Immunohistochemistry and image analysis were used to localise and quantify HSP90 and HSF-1 in luminal and glandular epithelium; in stroma, immuno-positive leucocytes and fibroblasts were counted.

Both HSP90 and HSF-1 were expressed in the cytoplasm and the nucleus of luminal epithelial and stromal cells. In the glandular epithelium, HSP90 immunoexpression increased above the control (no AI) values, 2 h and 4 h after AI. In contrast, HSF-1 immunoexpression decreased 2 h and 4 h after AI. At 2 and 4 h after AI, the numbers of HSP90- and HSF-1-positive leucocytes and fibroblasts exceeded control values.

Changes in HSP90 and HSF-1 expression in endometrium after AI are associated with endometrial inflammation. Their presence in the cytoplasm and nucleus (luminal and glandular epithelial cells, fibroblasts, leucocytes) suggests roles in cytosolic protein interactions and DNA regulation. Their expression in luminal and glandular epithelium, and in stromal cells, suggests roles in the regulation of endometrial repair and remodelling.

The relationships between HSP90 and HSF-1 and the development of post-insemination endometritis suggest that these proteins can be targets for prevention or treatment of persistent endometritis.