What a growth recordshows you.

When a biopsy is turned into a growing cell line, our laboratory keeps a running log of what happened to it: the date it arrived, when cells first appeared migrating out of the tissue, how many days each passage took, how many cells were present at each stage, and how many survived a test freeze and thaw. This is the growth record. It is not a prediction about the animal, and it is not a genetic report – it is closer to a nursing chart, documenting the health and behaviour of the culture itself as it grew.

We keep this record for every line we bank, and we share a summary of it with clients as part of the documentation issued alongside a vault certificate, described more fully in what a vault certificate certifies. Understanding a few of its terms is useful even for owners who never plan to look at it closely, because it explains why some lines take two weeks to bank and others take four.

A passage is one round of a culture growing to fill its dish and then being split into new dishes to keep growing. The passage number simply counts how many times this has happened since the original biopsy. We bank cells at a low passage, typically two or three, because ordinary cells have a finite number of times they can divide before they slow down and stop – a limit described in the founding cell biology literature and discussed at length in what a cell line is. A lower passage number at the time of freezing means more of that capacity is preserved in the vial.

Doubling time is how long, on average, it takes a culture to double in cell number. For healthy fibroblasts, the cells almost always used for this kind of banking, that is typically one to three days, though it varies by species, by the individual animal, and by the age of the animal at biopsy. A doubling time that is unusually long is one of the first signs our laboratory watches for, because it can indicate the culture is under stress, contaminated, or simply from tissue that was compromised before it reached us.

A strong record shows steady, unremarkable numbers: consistent doubling times passage over passage, viability at freezing above roughly 90 percent, and post-thaw viability close to that figure. Nothing about a good record is exciting to read, and that is the point. Cell culture is one of the few areas where boring is the outcome you want.

It is also worth noting what a growth record looks like when something has gone wrong, since most owners only ever see the clean version. A troubled culture might show a doubling time that lengthens rather than holds steady across passages, cells that round up and detach from the dish before reaching confluence, or a viability figure at freezing that comes in below the roughly 90 percent threshold we consider reliable for long-term storage. When we see this pattern, we do not bank the line as though nothing were wrong; we investigate, and in some cases recommend a second biopsy rather than freezing cells we are not confident will still be dividing when they are needed.

A growth record describes the culture, not the animal's health, temperament, or genetics. A line can grow beautifully from an animal that had an unrelated illness, and a line can be slow to establish from an animal that was, in every other respect, healthy. It also says nothing about outcomes from any later use of the cells. A well-documented growth record supports confidence that a line was banked competently; it is not a forecast for genetic testing results, for how stem cells or PRP prepared from the line might perform in treatment, or for a cloning attempt years afterward.

We are careful about this distinction because it is easy, understandably, for an owner reading a clean set of numbers to feel reassured about more than the numbers actually cover. A growth record is evidence that a specific, narrow job was done well: turning a biopsy into a viable, tested, bankable line. Everything after that – whether the line is ever thawed, and for what – is a separate decision with its own separate uncertainties.

Some laboratories treat internal culture records as proprietary detail an owner does not need. We take the opposite view, for the same reason we publish prices in full rather than quoting case by case: an owner who is trusting a laboratory with something irreplaceable should be able to see the evidence that the work was done carefully, not only be told that it was. A summary growth record, alongside the identity profile and viability testing described in what a cell line is, is part of that evidence.

This is also why we test a spare vial before it ever counts toward the twelve held in two cities: the growth record from that test is the last check before a deposit is considered complete, and it is the figure we point to when a client asks, years later, how confident they should be in a line that has sat untouched since it was banked.