Granulosa cells (GCs) have many functions in the endocrine system. Most notably, they produce progesterone following ovulation. However, it has recently been proven that GCs can change their properties when subjected to long‑term culture. In the present study, GCs were collected from hyper‑stimulated ovarian follicles during in vitro fertilization procedures. They were grown in vitro, in a long‑term manner. RNA was collected following 1, 7, 15 and 30 days of culture. Expression microarrays were used for analysis, which allowed to identify groups of genes characteristic for particular cellular processes. In addition, reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) was performed to validate the obtained results. Two ontological groups characteristic for processes associated with the development and morphogenesis of the heart were identified during the analyses: 'Heart development' and 'heart morphogenesis'. The results of the microarrays revealed that the highest change in expression was demonstrated by the lysyl Oxidase, oxytocin receptor, nexilin F‑actin binding protein, and cysteine‑rich protein 3 genes. The lowest change was exhibited by odd‑skipped related transcription factor 1, plakophilin 2, transcription growth factor‑β receptor 1, and kinesin family member 3A. The direction of changes was confirmed by RT‑qPCR results. In the present study, it was suggested that GCs may have the potential to differentiate towards other cell types under long‑term in vitro culture conditions. Thus, genes belonging to the presented ontological groups can be considered as novel markers of proliferation and differentiation of GCs towards the heart muscle cells.