2.3. Cell Culture and Bioink Preparation

Human mesenchymal endometrial cells (endMSCs) were isolated from menstrual blood of a human donor. The study was conducted in accordance with the Declaration of Helsinki and the protocol was approved by the Ethics Committee of Minimally Invasive Surgery Centre (Project identification code: SITC215). All subjects gave their written informed consent to be included in the study [38] and were seeded at a density of 5000 cells/cm² in T175 flasks incubated at 37 °C, 5% CO₂ and 95% humidity and expanded in DMEM cell culture medium supplemented with 10% FBS (Gibco), 100 U/mL penicilin, 100 µg/mL streptomicin and 10 µg/mL cyprofloxacin. After approximately an 80% confluence was reached, the cells were trypsinized and resuspended in 1 mL of cell culture medium prior to mixing with the hydrogel.

The biomaterial used in the bioprinting tests was Cellink Bioink (Cellink, Gothenburg, Sweden). The final bioink mixture was done using a Cellink Mixer with a volumetric ratio of 5:1 and a final cell concentration of 7.5 × 10⁵ cells/mL.