Cellular metabolites: woven together like a rug
Call me a nerd, but I have to admit that I am pretty excited about metabolomic technology. Uh, what? Metabolomics is the study of the chemical fingerprints that cells leave behind. It does not look at genes, DNA, RNA or proteins, but is a peek into the products or metabolites that result from all this genetic orchestration. It is a “physiological snapshot” of a living cell.
This past week, we published a study that applies metabolomics to male infertility. If you have been reading this column, you are well aware of my interest in helping sterile men become fathers. Over the last decade, it has become clear that many men with azoospermia (no ejaculated sperm) may have small pockets of sperm in the testicle. The question is how to safely find that sperm without causing undo harm to the testicle. Current methods for evaluating whether sperm are present include somewhat invasive techniques such as testicular biopsy and microdissection and less invasive ones such as FNA Sperm Mapping that I invented 13 years ago. However, as I always say, there is always room for improvement.
Wouldn’t it be nice to find the “pockets” of sperm in the testis through a simple scan and avoid a biopsy? Maybe even a scan that involves no radiation exposure, like an MRI? Well, that is precisely what we have developed in this study.
We showed that magnetic resonance (MR) spectroscopy can measure metabolic activity in the testis. And given that most metabolic activity in the testis is concentrated on building sperm (remember, normally men produce 1200 sperm/heartbeat!), metabolic measurements in the testis generally reflect sperm production. The study showed that the metabolomic scanning is as accurate as a more invasive testis biopsy in reading several abnormal patterns of sperm production typically associated with infertility. It also showed that testes that contain sperm carry a distinct chemical “signature” that can be distinguished by MR Spectroscopy.
How does it work? Essentially, the scan looks for chemicals in the testis that are the building blocks for sperm production. The theory is if you see a pile of bricks in the yard, then there is a good chance that a house is being built. In the study, phosphocholine was observed as one of the building-block chemicals in the testis. The more there is, the more likely sperm are being made.
Not only that, MR Spectroscopy can evaluate for sperm in as many as 100-200 areas within the testis, significantly increasing the ability to sample for sperm well beyond any of the more invasive techniques commonly used today.
Are we ready to replace a testis biopsy with an MRI scan? Not yet, but give me some time to tweak the system a bit and perform clinical trials comparing it to current approaches. My motivation runs deep, as I know that men would rather have their picture taken than have a surgical procedure to understand whether they can be fathers.
