domingo, 11 de septiembre de 2011

The Spleen and Ovulation

At the start of my college education while taking Biology, I was briefly introduced into a very light "view" of what goes on in a woman's body during the ovulation and menstruation period and it may seem corny, but the ability to give life that women posses is just incredible right from the start and lately, I have been reminded of this awesome capacity by some recent births (wich hands down, I'm sure will be some kick ass babies in no time!). A couple of years ago during our Physiology courses, we entered the world of Endocrinology wich included the Female Sex Hormones and that became a pretty exciting topic for me since this time around I had the chance to get a more in depth view on this subject, however the same way that it happens with a bunch of stuff in the Medicine world, a lot of things still go unanswered when it comes to the ovulation phase.

So a couple of days ago, I was "wasting time" jumping through some medical news headlines and I ended up in an Endocrinology journal since we are taking that subjec this semester ( from the specialty point of view now), And I ended up finding a review article relating the Ovulation period with the Spleen and Leukocytes, (yes, feel free to read that again). I know that this may not be news to some of you, since this research has been going on for the last decade but I really wanted to share this approach.

It turns out that there seems to be another key element in order for ovulation to take place other than the hormonal changes and that's where Inflammation comes in. There's actually a lot of info out there about pathological inflammation but it's the opposite when it comes to physiological scenarios of inflammation, wich means the details of how it works on the ovary are a little blurry. There is a breaktrough approach that has allowed advances in this field, and that's flow cytometry, wich now allows us to see exactly wich cell types are located on an specific site of the body, that's how researches ended up finding leukocytes inside the ovary prior and during the ovulation period.

Taking this into consideration, when I say inflammation I'm taking about the whole package: neutrophils, mast cells,  eosinophils, macrophages, NK cells and lymphocites. But they've already gone farther by discovering specific functions for these guys with neutrophils and lymphocites having a role in luteal formation, neutrophils also play part in follicle maturation and ovulation and mast cells, eosinophils and neutrophils dealing with ECM degradation. Meanwhile, NK cells are relevant for angiogensis and macrophages secret IL-8 enhancing chemotaxis.

But how does this happen and where do these guys come from? The current hypothesis is that it happens via the same Hypothalamous-Pituitary-Ovarian axis that we should be familiar with but there's a twist to it and that's where the Spleen comes in. And isn't the spleen supposed to be some non functional purple organ that functions as a cell cementery in our bodies? Well, for females the answer now seems to be NO.

Recent studies, using the above mentioned flow cytometry have demostrated that after a heart attack, the spleen starts sending out armies of leukocytes to deal with the inflammation inside the heart. The same approach was used to asses the procedence of leukocytes arriving at the ovary during the  pre-ovulatory and ovulation period and they ended up seeing that as the ovarian vessels start filling up with these inflammatory cells, the spleen's population of leukocytes starts decreasing. Up to this point, it is thought that the LH hormone is the one responsible for going up to the hypothalamous and triggering the send me some white cells!!! signal moments prior to the start of ovulation and even if the above has been tested, it is in the triggering mechanism of this physiological inflammation where most questions remain.

There is a simple question that should arise from this: then does this mean that women who go trough splenectomy should be considered infertile? The problem is that along with splenectomy comes a process of radiotherapy and chimiotherapy wich could alone be harmful to the female reproductive abilities and it's difficult to measure this effect on humans. However, studies in animals who have gone trough splenectomy show that  the ovulatory becomes irregular and some of them actually stop ovulating all together. Another intriguin fact is that, considerably large leukocytes populations have been spotted in other female reproductive organs such as the uterus and flow cytometry shows that not all of the leukocytes coming out from the spleen end up in the ovary wich could also mean that at the same time they end up somewhere else in the reproductive tract.

Seems like we'll have to start thinking of ovulation as an important inflammatory event in no time and that's where the bridge between immunology and reproductive sciences will have to keep being crossed. This promises to be an interesting ride!