Capitalization of biological abbreviations at the beginning of a sentence

In the beginning of a sentence, should I capitalize abbreviations such as the following:

• hPSC (human pluripotent stem cell)


• mESC (mouse embryonic stem cell)


• rDNA (recombinant deoxyribonucleic acid)

I have seen both lower and upper case for the two first, while rDNA always seems to be in lower case. I'm curious which is the linguistically correct form.

Answer

Whenever you encounter a situation where a "rule" (such as begin a sentence with an upper case letter) will reduce the readability of your test (Is MESC the same as mESC?) then rewrite.
Do not try to find a loophole or a special rule that will need to be explained or justified. The meaning of your text is paramount.

There is a reason why chemistry texts do not begin a sentence about acids and bases with pH.