[Relationship between ultrastructural features of endometrial-myometrial interface and pathogenesis of adenomyosis]

To explore the ultrastructural features of endometrial-myometrial interface (EMI) of adenomyosis and normal myometrium.

From May 2010 to September 2013, 102 uterine myometrial specimens were obtained from 102 patients undergoing hysterectomy. There were 56 adenomyosis patients as ADS group (including proliferative endometrium, n = 26 and secretory endometrium, n = 30) and another 46 with cervical intraepithelial neoplasis (CIN) III as control group. The myometrium underneath endometrium and the outer third of myometrium were immediately harvested after operation. And the samples were processed and observed under transmission electron microscopy.

(1) In the presence of uterine adenomyosis, the nuclei were significantly larger than controls and significantly enlarged with less prominent collagen fibrils. The cytoplasm was abundant, denoting cellular hypertrophy. The rough endoplasmic reticulum and Golgi apparatus became more prominent. But the dense patches and dense bodies appeared similar to the control; (2) EMI myocytes ultrastructure showed cyclic changes in controls. In proliferative cycle, the average nuclear size was larger than that in secretory cycle [(3.24 ± 0.41), (2.44 ± 0.27) µm, P < 0.05]. But there was not any differences from different cyclic phases in adenomyosis [(2.34 ± 0.17), (2.63 ± 0.39) µm, P > 0.05]; (3) EMI myocytes appeared significantly different than that of outer myometrium. The nuclei of EMI myocytes were much smaller than outer myometrium. And there was less prominent collagen fibrils. The dense patches, dense bodies and myofilament-cytoplasm ratio of EMI were smaller than outer myometrium. The nuclei-to-myocyte ratio was larger than outer myometrium.

Abnormal ultrastructural features of EMI may be correlated with the development of adenomyosis.