Histological Characteristics of the Regression of Corpora Lutea in Wistar Hannover Rats: the Comparisons with Sprague-Dawley Rats

Abstract

We examined the ovaries of 44 Wistar Hannover (RccHanTM:WIST) (WH) and 30 Sprague-Dawley (SD) rats at 32-weeks of age to determine whether the ovarian structure and formation/regression of the corpora lutea (CLs) differ between the two strains. The average ovary weight was higher in WH rats. The average number of all CLs, including currently formed and previously formed CLs, was higher in WH rats in all cycles; however, no appreciable difference was detected in the number of newly or currently formed CLs between the two strains. CLs regression characterized by degeneration and necrosis of luteal cells began to appear in diestrus in both strains; however, the distribution of degenerated/necrotic cells in CLs differed. Necrotic cells were scattered in SD rats but were focally observed in the center of the CL in WH rats. The reduction in size of previously formed CLs accompanied by regression started about 2 or more stages later in WH rats than in those of SD rats. In conclusion, the higher number of CLs in WH rats is considered to be due to slow CL regression compared with in SD rats.

Historical control data on developmental toxicity studies in rats

“…The incidence of supernumerary ribs was higher in Wistar Hannover rats than that in Crl:CD(SD) rats, in agreement with previous findings. [7][8][9][10][11] The types and incidence of skeletal variation in both Crl:CD (SD) rats (Tables S15A and S15B) and Wistar Hannover rats (Table S16) did not differ between this and the previous surveys.…”

“…These results are in good agreement with those of previous studies. 3,7,[9][10][11]14 Fetal weights varied among laboratories and were dependent on the gestational day of cesarean section.…”

“…2 Historical control data in Japan on reproductive and developmental toxicity studies in laboratory animals, such as rats, mice, guinea pigs, and rabbits, performed from 1998 to 2010, were reported by Ema et al 3 Three previous studies reported histological control data of laboratory animals in Japan Kameyama et al, 4 Morita et al, 5 and Nakatsuka et al 6 Wistar Hannover rats have become more widely used in toxicological studies because of their characteristics, including a lower body weight but comparable reproductive performance when compared with Sprague-Dawley (SD) rats. [7][8][9][10][11][12] Rat breeders in Japan publish in-house reproductive and developmental findings on their websites (CLEA Japan; www.cleajapan.co/index. Charles River Japan; http://www.crj.co.jp/product/ domestic/detail/2), but not on a regular basis.…”

Noradrenaline modulates the presence of gonadotropin-releasing hormone in ovary. The importance of its interrelation on the ovarian steroidogenesis and apoptosis on dioestrus II in rat.

“…On DII, the functional CL, the CLs in various states of apoptosis/ necrosis [46] and atresic and non atresic follicles are present. The non atresic follicles might be responsible for the steroidogenic activity, which might explain the high levels of E 2 found at short incubation times (120 min) in our experimental scheme.…”

PGRMC1/2 promote luteal vascularization and maintain the primordial follicles of mice

“…While the CL of pseudopregnant mice is functional, histological analysis of the CL of pseudopregnant mice is complicated because CLs from the current cycle as well as previous cycles are present. The CLs derived in previous cycles are approximately 40-50% smaller than those formed during the current cycle, possess numerous necrotic areas and found in the medullary region (Sato et al 2014). CL possessing these characteristics were not assessed and only fully developed CL as indicated by having diameters greater than 300 µm and without necrotic areas were analyzed.…”