Why does PromoCell only guarantee 15 population doublings (PDs) for dermal fibroblasts, while higher passage numbers are sometimes possible?

PromoCell guarantees at least 15 population doublings (PDs) for Normal Human Dermal Fibroblasts (NHDF). This guarantee is based on internal quality control testing, during which fibroblasts are routinely cultured for 15 PDs.
This corresponds to approximately 6–8 passages, depending on the split ratio used.

What the guarantee means - and what it does not

• The guarantee ensures that the cells can be reliably expanded for a minimum of 15 PDs.
• It does not mean that the cells will senesce immediately after reaching 15 PDs.
• PromoCell does not determine or claim a maximum number of population doublings or passages.

Practical experience
In practice, most NHDF lots can achieve well beyond the guaranteed minimum, and more than 20 passages are commonly possible, depending on:

• culture conditions
• handling
• split ratios
• donor‑specific characteristics