Figure 3. Effects of mouse embryonic stem cells (OG2 cells expressing the GFP-transgene) on cord formation of rat testicular cells.

3A) Micrographs showing immunofluorescence of GFP-signal (upper panels) and merged images (phase contrast plus immunofluorescence) of primary rat (7-day-old) Sertoli cells and peritubular cells seeded at an initial density of 10⁶ cells/cm² on flat PDMS substrates after culture for one day (upper two panels), three days (middle two panels) and six days (lower two panels) in DMEM. A variable number of OG2 cells (10, 10², 10³, 10⁴, 10⁵ cells/cm²) was added to the primary cells at the initiation of cell cultures. No OG2 cells were added to controls. No obvious change of cellular arrangements was observed at day 1. On days 3 and 6 of culture cord-like structure formation is observed which intensified with increasing numbers of OG2 cells. OG2 cells formed expanding colonies in contact with the cord-like structures. 3B) Analysis of the size of cord-like structures at day 6 of culture. Cord-like structures were significantly larger compared to all other experimental groups depending on the initial density of OG2 cells on flat PDMS substrates at day 6. In the control group and after addition of only 10 OG2 cells no cord like structures were encountered.