*4.5. RNA Isolation*

Frozen tissue samples were homogenized with a Precellys 24 homogenizer (PEQLAB, Erlangen, Germany). Subsequently, total RNA was isolated from eutopic and ectopic endometrium using the Agilent Absolutely RNA kit in accordance with the manufacturer's instructions (DNase I treatment included), and total RNA from the 12Z cell line was isolated using the RNeasy mini kit (Qiagen). To remove DNA contamination the RNA samples were subsequently treated with DNAseI using RapidOut DNA removal Kit (Thermo Fisher Scientific, Waltham, MA, USA). RNA concentration and purity were determined by measuring optical density using a NanoDrop ND-1000 spectrophotometer (NanoDrop Technologies, Wilmington, DE, USA). We defined the quality of the RNA samples to be sufficient when the ratios of OD260/280 and OD260/230 were around 2.00. Additionally, for RNA-sequencing we confirmed that RNA integrity was RIN > 7 on a Bio Analyzer (Agilent Technologies, Santa Clara, CA, USA).
