Derivation of human embryonic stem cells using a post-inner cell mass intermediate.

Area of Science:

• Developmental Biology
• Stem Cell Biology
• Human Embryology

Background:

• The precise developmental origins of human embryonic stem cells (hESCs) remain largely unknown.
• Human ESCs are derived from the inner cell mass (ICM) of the blastocyst.
• A transient epiblast-like structure, the post-ICM intermediate (PICMI), has been identified as a direct progenitor of hESCs.

Purpose of the Study:

• To establish a detailed protocol for deriving the PICMI from human preimplantation embryos.
• To describe methods for identifying, cryopreserving, and culturing PICMIs for hESC generation.
• To investigate the PICMI as a key intermediate for understanding human pluripotency.

Main Methods:

• A 7-day culture protocol for human preimplantation embryos was developed.
• Methods for the identification and cryopreservation of PICMIs were established.
• PICMIs were plated for subsequent hESC derivation and outgrowth observation.

Main Results:

• PICMI formation was observed in 21.3% of plated blastocysts with good-quality ICMs.
• The initial hESC outgrowth was visible within 2-7 days after PICMI plating.
• Eighty-six percent of PICMIs used for derivation showed successful hESC outgrowth.

Conclusions:

• The PICMI is a distinct developmental intermediate preceding hESC generation.
• The provided protocol facilitates PICMI derivation and subsequent hESC culture.
• This research offers insights into the human pluripotent state and hESC origins.