At GenePro, we do not include the percent acrosomal damage in the viability calculation, the reason being is that we can’t determine if the cell was or is alive or dead.
We base this on the fact that living sperm cells are theoretically acrosomally okay. We are associating acrosomal damage with cell destabilization and preeminent death some time shortly there after. From a viability standpoint we do not want to count a dead cell and an acrosomal damaged cell twice. Doing that would be a falsely negative representation of number of actual viable cells. That is why we simply state that NAR was conducted on non-living cells and is not included in viability estimates.
It is a widely held scientific belief that the capacitation process which leads to an acrosome reaction is considered to be a controlled destabilization process which reduces the life span of sperm (Harrison, 1996.) No one knows exactly how the life span is affected, but we do know from frozen semen experiments (frozen-thawed sperm are generally capacitated or in the process) that this lifespan is between three and 12 hours-approximately after capacitation has occurred.
We don’t have a very good way to determine if a living cell has acrosome damage or not. The only way to theoretically do this is with a live dead stain and then one has to question if the staining or the smear had anything to do with the damage?
Long story short, we don’t put a lot of weight in acrosome evaluation of sperm cells and prefer sperm membrane viability assessment with stains because it is better, however a bit more costly. A number of years back I tested PNA stain (acrosome stain) with SYBR 14 and PI to see if I could find any “green” (living) cells with acrosome damage (these cells would be green with an orange cap) and there wasn’t a single cell that showed this in fresh pig semen. However, we did see it occur in frozen thawed samples (small amount). The bull guys are the ones who discovered this triple stain technique with frozen-thawed bull sperm.
If I took three people and showed them what a lifted or ruffled acrosome was, variation should be very small when one has great optics and the same sample. Variation can occur if you asked each individual to prepare a stained smear, or if they each had a different microscope. The key to looking at acrosomes is microsope optical quality. If you don’t have phase contrast and infinity corrected objectives you can’t see acrosomes very well, or at all. The other wild card is what some people call “pitted” acrosomes. This is difficult to see and can be quite often miss-read and would result in a large technician variance because of the interpretation involved. This is why membrane viability staining is better.
A lifted or ruffled acrosome is pretty obvious with good optics, and this is why there should be very little variance from one tech to another if evaluated correctly.