Rich innervation of deep infiltrating endometriosis

Deep infiltrating endometriosis (DIE) is a specific type of endometriosis, which can be associated with more severe pelvic pain than other forms of endometriotic lesions. However, the mechanisms by which pain is generated are not well understood.

DIE (n = 31) and peritoneal endometriotic (n = 40) lesions were sectioned and stained immunohistochemically with antibodies against protein gene product 9.5, neurofilament, nerve growth factor (NGF), NGF receptors tyrosine kinase receptor-A (Trk-A) and p75, substance P, calcitonin gene-related peptide, vesicular acetylcholine transporter, neuropeptide Y, vasoactive intestinal peptide and tyrosine hydroxylase to demonstrate myelinated, unmyelinated, sensory and autonomic nerve fibres.

There were significantly more nerve fibres in DIE (67.6 +/- 65.1/mm(2)) than in peritoneal endometriotic lesions (16.3 +/- 10.0/mm(2)) (P < 0.01). DIE was innervated abundantly by sensory Adelta, sensory C, cholinergic and adrenergic nerve fibres; NGF, Trk-A and p75 were strongly expressed in endometriotic glands and stroma of DIE.

The rich innervation of DIE may help to explain why patients with this type of lesion have severe pelvic pain.