Galactic Cosmic Radiation Negatively Affects Rat Ovarian Follicles
Poster #: 135
Session/Time: B
Author:
Mitch Chad Warren Jr, BS
Mentor:
Diane M Duffy, PhD
Research Type: Basic Science
Abstract
INTRODUCTION:
Galactic cosmic radiation (GCR), the radiation found in space, is 3-100 times more potent than X-rays and poses a significant risk to astronauts. NASA will send female astronauts on Mars missions, but we currently have little information on the effects that space radiation has on female reproductive health. After birth, women do not generate new oocytes. As they age, progression through follicular stages and depletion of oocyte reserves leads to menopause. By assessing the four stages of follicular growth in the ovary, we can identify which stages are most vulnerable to GCR. Decreased follicle numbers could lead to operational issues, early menopause, and fertility issues. There may also be long-term health implications like osteoporosis and cardiovascular disease. We hypothesize that exposure to GCR will damage ovarian health by reducing the number of ovarian follicles and decreasing overall ovarian volume.
METHODS:
Female Wistar rats (7-months old) were exposed to space radiation (SR) at Brookhaven National Laboratory. After cognitive testing, the rats were euthanized (~4 months post exposure). Ovaries were recovered and fixed in 10% formalin. Sham rats travelled to and from Brookhaven but were not exposed to radiation. Ovaries from sham (n=4) and ovaries exposed to two types of SR (10 cGy of GCR/GCR (n=4) or 10 cGy of He/GCR (n=4)), were embedded in paraffin wax and sectioned at 5 µm. Every fifth slide was stained with hematoxylin and eosin. Follicles with a visible oocyte nucleus were counted, and counts were multiplied by five to account for assessing every fifth section. Antral follicles are larger than the other follicles and were counted without adjustment. Ovarian volume was calculated using the ellipsoid formula: V = 4/3*π*rh*rl*rw.
RESULTS:
Ovaries from sham animals contained all four follicle classes. Primordial follicles were present in large numbers, with smaller numbers of primary and secondary follicles, and fewer antral follicles. When compared to sham animals, irradiated animal ovaries contained similar numbers of primordial, primary, and antral follicles. Our preliminary data suggests that SR reduces the abundance of secondary follicles compared to that observed in sham rats. There were 95±21 secondary follicles in the sham group, whereas GCR/GCR had 61±18 secondary follicles, and He/GCR had 56±4 (ANOVA p=0.2280, n=4/group). There was also a trend towards decreased ovarian volume following radiation, with sham measuring 17.2±5.3 μL, GCR/GCR measuring 12.4±2.2 μL, and He/GCR measuring 13.2±3.8 μL.
CONCLUSION:
These preliminary data support our hypothesis that space radiation negatively affects the ovary. Secondary follicle numbers were decreased by both types of radiation, and irradiated ovaries were smaller than the sham ovaries. The diminished secondary follicle counts could explain the difference in ovary size between radiation and sham groups, as larger ovaries are thought to be more active. Future studies could compare the size of antral follicles between irradiated and sham ovaries to assess whether the follicles are growing to adequate size for ovulation after radiation exposure. Moving forward, studies like this will help inform the need for protective measures against GCR exposure to prevent negative health consequences for female astronauts.
Galactic cosmic radiation (GCR), the radiation found in space, is 3-100 times more potent than X-rays and poses a significant risk to astronauts. NASA will send female astronauts on Mars missions, but we currently have little information on the effects that space radiation has on female reproductive health. After birth, women do not generate new oocytes. As they age, progression through follicular stages and depletion of oocyte reserves leads to menopause. By assessing the four stages of follicular growth in the ovary, we can identify which stages are most vulnerable to GCR. Decreased follicle numbers could lead to operational issues, early menopause, and fertility issues. There may also be long-term health implications like osteoporosis and cardiovascular disease. We hypothesize that exposure to GCR will damage ovarian health by reducing the number of ovarian follicles and decreasing overall ovarian volume.
METHODS:
Female Wistar rats (7-months old) were exposed to space radiation (SR) at Brookhaven National Laboratory. After cognitive testing, the rats were euthanized (~4 months post exposure). Ovaries were recovered and fixed in 10% formalin. Sham rats travelled to and from Brookhaven but were not exposed to radiation. Ovaries from sham (n=4) and ovaries exposed to two types of SR (10 cGy of GCR/GCR (n=4) or 10 cGy of He/GCR (n=4)), were embedded in paraffin wax and sectioned at 5 µm. Every fifth slide was stained with hematoxylin and eosin. Follicles with a visible oocyte nucleus were counted, and counts were multiplied by five to account for assessing every fifth section. Antral follicles are larger than the other follicles and were counted without adjustment. Ovarian volume was calculated using the ellipsoid formula: V = 4/3*π*rh*rl*rw.
RESULTS:
Ovaries from sham animals contained all four follicle classes. Primordial follicles were present in large numbers, with smaller numbers of primary and secondary follicles, and fewer antral follicles. When compared to sham animals, irradiated animal ovaries contained similar numbers of primordial, primary, and antral follicles. Our preliminary data suggests that SR reduces the abundance of secondary follicles compared to that observed in sham rats. There were 95±21 secondary follicles in the sham group, whereas GCR/GCR had 61±18 secondary follicles, and He/GCR had 56±4 (ANOVA p=0.2280, n=4/group). There was also a trend towards decreased ovarian volume following radiation, with sham measuring 17.2±5.3 μL, GCR/GCR measuring 12.4±2.2 μL, and He/GCR measuring 13.2±3.8 μL.
CONCLUSION:
These preliminary data support our hypothesis that space radiation negatively affects the ovary. Secondary follicle numbers were decreased by both types of radiation, and irradiated ovaries were smaller than the sham ovaries. The diminished secondary follicle counts could explain the difference in ovary size between radiation and sham groups, as larger ovaries are thought to be more active. Future studies could compare the size of antral follicles between irradiated and sham ovaries to assess whether the follicles are growing to adequate size for ovulation after radiation exposure. Moving forward, studies like this will help inform the need for protective measures against GCR exposure to prevent negative health consequences for female astronauts.