Development of a xeno-free non-contact co- culture system for derivation and maintenance of embryonic stem cells using a novel human endometrial cell line

Mouse embryonic fibroblast feeder layers (MEF) have conventionally been used to culture and maintain the pluripotency of embryonic stem cells (ESC). This study explores the potential of using a novel human endometrial cell line to develop a non-xeno, non-contact co-culture system for ESC propagation and derivation. Such xeno-free systems may prove essential for the establishment of clinical grade human ESC lines suitable for therapeutic application. A novel line of human endometrial cells were seeded in a 6-well dish. Filter inserts containing mouse ESCs were placed on these wells and passaged 2-3 times per week. Inner cell masses derived from mouse blastocysts were also cultured on transwells in the presence of the feeder layer. In both cases, staining for SSEA-1, SOX-2, OCT-4 and alkaline phosphatase were used to monitor the retention of stem cells. ESC colonies retained their stem cell morphology and attributes for over 120 days in culture and 44 passages to date. Inner cell mass derived ESC cultures were maintained in a pluripotent state for 45 days, through 6 passages with retention of all stem cell characteristics. The stem cell colonies expressed stem cell specific markers SSEA-1, Sox 2, Oct-4 and alkaline phosphatase. Upon removal of the human feeder layer, there was a distinct change in cell morphology within the colonies and evidence of ESC differentiation. Human feeder layers offer a simple path away from the use of MEF feeder cells or MEF conditioned medium for ESC culture. Furthermore, indirect co-culture using porous membranes to separate the two cell types can prevent contamination of stem cell preparations with feeder cells during passaging.