In short
Cell culture expands cells under controlled temperature, gas, medium and sterility conditions. The quality of this step directly affects cell safety and properties, which is why manufacturing must follow GMP standards.
Key steps
Cells are isolated from tissue, cultured in controlled vessels with periodic medium changes, passaged when confluent, then quality tested before release for viability, cell count, surface markers, microbial contamination and endotoxin.
Why passage number matters
Excessive passaging drives cells toward senescence and may cause loss of original properties, so defining a maximum passage number and checking chromosomal stability are part of the quality system.