Introduction:
Long non-coding RNAs (lncRNAs) are implicated in endometriosis development. The aim of the study was to analyse the expression of lncRNA HOTAIR in the context of the risk of developing endometriosis.

Material and methods:
The presented study determined lncRNA HOTAIR expression in patients with endometriosis (n = 100) compared with a healthy control group (n = 100). Histological examination was performed by pathologists using a digital slide scanner and slide viewer software (Case Viewer 2.3, 3DHistech, Budapest, Hungary). The gene expression was measured by the reverse-transcription polymerase chain reaction (RT-PCR) technique. Two-step qRT-PCR was used to analyse the expression of the HOTAIR gene in normal tissue and in endometriosis samples. The total RNA was used for cDNA synthesis. Ct values were used for subsequent analysis, and GADPH was used as the endogenous control.

Results:
Statistically significantly higher HOTAIR expression was found in endometriosis samples compared to the expression in the control material (p < 0.0001). Regarding the classification of endometriosis (stage I–IV), there was a statistically significant increase in HOTAIR expression in stage IV (p < 0.05). There was no relationship between the age of the patients, the number of deliveries, the number of spontaneous abortions and BMI and the expression of HOTAIR.

Conclusions:
The reported studies suggest a significant role of lncRNA HOTAIR expression in the pathogenesis of endometriosis.