Human embryonic stem cells express an immunogenic nonhuman sialic acid

Area of Science:

• Stem Cell Biology
• Immunology
• Biotechnology

Background:

• Human embryonic stem cells (HESC) hold therapeutic potential but are cultured using animal products.
• Standard HESC culture incorporates nonhuman sialic acid Neu5Gc, which is immunogenic in humans.
• Human antibodies against Neu5Gc can lead to immune rejection of HESC in vivo.

Purpose of the Study:

• To investigate the metabolic incorporation of Neu5Gc by HESC.
• To assess the immunogenicity of Neu5Gc-expressing HESC.
• To evaluate methods for reducing Neu5Gc on HESC to improve their therapeutic safety.

Main Methods:

• HESC and embryoid bodies were cultured under standard conditions and analyzed for Neu5Gc incorporation.
• Exposure of HESC to human sera containing anti-Neu5Gc antibodies was performed.
• HESC were cultured in human serum with depleted Neu5Gc and assessed for immune binding and undifferentiated state maintenance.

Main Results:

• HESC and embryoid bodies significantly incorporated Neu5Gc during standard culture.
• Exposure to anti-Neu5Gc antibodies induced immunoglobulin and complement binding, indicating potential for cell killing.
• Culture in antibody-depleted human serum reduced Neu5Gc levels and immune binding while preserving pluripotency.

Conclusions:

• Neu5Gc incorporation poses a significant immunogenic risk for HESC therapies.
• Reducing Neu5Gc levels on HESC is crucial for mitigating immune rejection.
• Future strategies should focus on xeno-free culture conditions, including human feeder layers and serum, to eliminate Neu5Gc and enhance HESC therapeutic safety.