March 24th, 2011 § § permalink
It’s a big day for sperm science. In the journal Nature today, scientists from Japan describe how they were able to mature mouse sperm in a petri dish outside of the testis.
The sperm assembly line is a complicated series of steps that takes about two months from start to finish. Sperm start off as big, round immature cells called “spermatogonia” whose main job is to multiply. At some point, cells decide to turn into full-fledged sperm, becoming cells known as “spermatocytes”. A spermatocyte splits into halves, becoming a “spermatid” in a process called meiosis, which will allow its precious genetic cargo ultimately to combine with its complementary other half waiting in an egg. The spermatid half cells finally transform their shape, growing propellers, outboard motors and egg-digesting caps in becoming “spermatozoa”.
Until now, scientists were unable to get immature sperm cells to grow outside the body into those exquisitely shaped torpedo half cells. That’s where Takuya Sato and fellow scientists have succeeded. By carefully controlling the conditions for the growing sperm’s bed, these scientists discovered how to make mature sperm outside the body.
The practical implications are enormous. Sperm can be frozen before chemotherapy to spare a man’s fertility, but only from an adult man already making mature sperm. We don’t yet have a similar way to preserve the future fertility of a boy who has yet to go through puberty, and this discovery may someday allow doctors to freeze a small piece of testis from a boy about to have chemotherapy and then mature his sperm in a petri dish later in his life. For men with “maturation arrest“, where the sperm assembly line stops midstream, it might be possible to grow their sperm to completion in a petri dish, and use the grown sperm in in-vitro fertilization.
The distance between Sato and his fellow scientists’ discovery and practical use is not small. Men are different than mice, and trying to shepherd science into the doctor’s office always brings unforeseen challenges. But this discovery is a big leap for sperm science.
March 21st, 2011 § § permalink
The horrific earthquake and tsunami in northern Japan remind us that no matter how powerful we become or careful we are, nature asserts itself in ways that we can’t imagine. The nuclear engineers and technicians working to contain the radiation leaking from the damaged power plant in Fukushima are nothing short of heroic. Radiation can cause all sorts of ills, from acute sickness to cancer and infertility.
In the testis, developing sperm cells are exquisitely sensitive to radiation. Kyodo News reported that after an explosion at the Fukushima No. 2 reactor on March 15, radiation levels measured as high as 8,217 micro sievert or 0.8217 rem per hour. (Micro sievert and rem are units of radiation dosage.)
Does that amount of radiation harm developing sperm cells? I asked Marvin Meistrich, Ph.D., Professor of Experimental Radiation Oncology and the Florence M. Thomas Professor of Cancer Research at the University of Texas M. D. Anderson Cancer Center, a world’s expert in radiation and sperm. Dr. Meistrich explained that sustained exposure to 20 rem of radiation over 4 weeks caused sperm counts to drop to 1/10th of their original amount. At doses of 40-80 rem, sperm counts fell to about 1/100th of the starting number, and in some cases were wiped out entirely. At 200 rem, that drop to zero sperm became permanent. For one-time doses, Dr. Meistrich explained that 15-20 rem caused a short-term fall in sperm count, and 400 rem or more resulted in permanent loss of sperm.
We know that radiation changes DNA, the sperm’s precious genetic cargo. What we don’t know is what dose causes a harmful DNA change that damages a developing embryo or causes disease later in life.
The radiation leakage in Fukushima seems to be in the range at which damage to sperm occurs. I can only hope that the workers at Fukushima and the people near the plants are aware of the dangers and take action to protect themselves.
March 18th, 2011 § § permalink
A writer for the NCI Cancer Bulletin interviewed me yesterday about Dr. Peter Schlegel’s recent article in the Journal of Clinical Oncology reporting success in getting sperm using microdissection testis sperm extraction from the testis of men who have had chemotherapy for cancer. Even if no sperm were found on testis biopsy, sperm could still be retrieved from a number of men using the microdissection technique. About two of every five men had a successful retrieval that had chemotherapy in the past.
That’s great news for the men who had chemotherapy for cancer who were lucky enough to have a successful sperm retrieval, and says a lot about how far we’ve come in retrieving sperm even in difficult conditions. But the best option would have been to have sperm frozen before beginning chemotherapy. Unfortunately, even today only about half of medical oncologists discuss freezing sperm with men before chemotherapy. There’s no good reason for that fact: a man can freeze sperm without delaying chemotherapy, and if he does, he can preserve his ability to have children in the future.
Medical oncologists save lives with cancer treatment. A life saved should be a full one, with a family if a man so desires. If you’re a medical oncologist, please talk about freezing sperm with men before beginning chemotherapy. If you’re a man facing the challenge of cancer and want to preserve your fertility, ask your doctor about freezing sperm.
March 12th, 2011 § § permalink
If you read Maledoc between about noon and 3 pm CST, you may have noticed a truly schizophrenic array of looks. That was me, updating the blog. I’ve tried a number of experiments now, and have settled on this clean, reader-friendly WordPress theme. If you’re curious, it’s Oulipo by Andrea Mignolo.
I also uploaded a plug-in for the iPad, which should make reading on that device even easier. I’ve had an iPhone/iPod touch-based theme for a while that automagically appears if you happen to be reading Maledoc on one of those, and this new plug-in adds that goodness for the iPad.
Let me know what you think of Maledoc’s new look. It is, after all, designed for you.
March 7th, 2011 § § permalink
The news is heating up lately over one San Franciscan’s attempts to ban circumcision in his city. Is circumcision so bad that it’s worth banning? Studies support health benefits of circumcision, including reducing the risk of human papilloma virus in men and cancer of the cervix in their female partners and lessening the chance of urinary tract infections in boys. Three large studies in Africa (Auvert, Gray and Bailey) all show that circumcision cuts by half the risk of transmission of HIV from a woman to a man.
Foreskin contains nerve endings lost during circumcision, but removing it can’t be seriously equated to clitorectomy, the practice in some cultures of removing a girl’s clitoris at birth. The equivalent of clitoretomy in the male would be to remove the entire glans penis, which would obviously have profound consequences on sexual sensation. The question is, does removing the foreskin inflict such harm to a young boy that it ought to be prohibited? LIke all medical questions, the answer comes from weighing the risks against the benefits.
The majority of circumcised men would tell you that their penises work fine without the foreskin, and so the risk of circumcision, while there, is small. The benefits, lessening the chance of infection and cancer, are real. It seems to me that parents choosing to circumcise their newborn boys are balancing the benefits against the risks and making a sensible choice. If the voters in San Francisco do get a chance to vote on a ban on circumcision, I hope that they preserve that choice for parents.