Mode of Action of Mouse Epidermal Growth Factor on the Wool Follicles of Merino Sheep: An Ultrastructural Study

The study investigated the effects of mouse epidermal growth factor (mEGF) on wool follicles of Merino sheep, focusing on its potential for biological wool harvesting. Three main follicular responses to mEGF were identified: (i) a catagenic regression lasting 4 days, characterized by reduced cellular proliferation and protein synthesis, leading to tapered fibre ends and eventual follicle regeneration; (ii) formation of disruptive lesions in the inner root sheath and fibre cells, involving abnormal fluid transport; and (iii) transient hyperplasia of sebaceous glands with glycogen deposition, normalizing by 4-6 days. These responses indicated mEGF's dual action: a quasi-physiological inhibition of fibre growth and a pathological effect on cell differentiation.