The serial cultivation of human diploid cell strains

clinical paper · 1961

type:clinical paper

year:1961

citation:Hayflick L, Moorhead PS. "The serial cultivation of human diploid cell strains." Experimental Cell Research. 1961 Dec;25:585–621. doi:10.1016/0014-4827(61)90192-6. PMID 13905658.

LINK

https://doi.org/10.1016/0014-4827(61)90192-6

SUMMARY

The foundational paper demonstrating that normal human diploid fibroblast cell strains have a finite replicative lifespan in vitro, undergoing approximately 50 divisions before ceasing to proliferate — a limit later named the Hayflick limit. Hayflick and Moorhead reported cultures of 25 independent human fetal fibroblast isolates, all of which degenerated after approximately 50 serial passages. The work directly contradicted Carrel's claim that normal cells can live indefinitely when properly cultured outside the organism. Hayflick and Moorhead proposed that the finite replicative capacity of normal cells reflects an intrinsic biological program, not environmental deterioration.

NOTES

Hayflick and Moorhead’s 1961 paper is the direct experimental refutation of Carrel’s immortal-cell thesis. By systematically culturing 25 independent human fetal fibroblast strains, they established that normal (non-cancerous) diploid cells reliably reach a phase of declining proliferation and ultimate senescence after approximately 50 population doublings. The paper proposed that cell mortality is intrinsic to normal cell biology rather than an artifact of inadequate culture conditions — reversing Carrel’s premise that the body’s degenerating “humors” are the cause of cell death and that freed cells can live forever. The phenomenon was subsequently named the Hayflick limit and is now understood mechanically through telomere shortening with each cell division.