KIT-KIT Ligand in the Growth of Porcine Oocytes in Primordial Follicles

Moniruzzaman, Mohammad; Miyano, Takashi

doi:10.1262/jrd.19107

Cited by 27 publications

(16 citation statements)

References 27 publications

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“…However, in similar conditions, primordial follicles from prepubertal pigs had not started to develop even after 4 months. Similarly, our previous reports revealed that the primordial follicles from cows (Senbon et al 2003) and prepubertal pigs (Moniruzzaman & Miyano 2007) survived without initiating development at 6-8 weeks after xenografting.…”

Section: Discussionsupporting

confidence: 69%

“…Primordial follicles developed to the antral stage at 45-75 days after xenografting of the ovarian tissues from 20-day-old piglets (Kaneko et al 2003). On the other hand, the development of primordial follicles from cows (Senbon et al 2003) and prepubertal pigs (Moniruzzaman & Miyano 2007) was not initiated at 6-8 weeks after xenografting. Primordial oocytes, therefore, are thought to differ between infant and prepubertal/adult animals.…”

Section: Introductionmentioning

confidence: 95%

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Knockdown of FOXO3 induces primordial oocyte activation in pigs

Moniruzzaman¹,

Lee²,

Zengyo³

et al. 2010

Reproduction

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Mammalian ovaries are endowed with a large number of primordial follicles, each containing a nongrowing oocyte. Only a small population of primordial oocytes (oocytes in primordial follicles) is activated to enter the growth phase throughout a female's reproductive life. Little is known about the mechanism regulating the activation of primordial oocytes. Here, we found that the primordial oocytes from infant pigs (10-to 20-day-old) grew to full size at 2 months after xenografting to immunodeficient mice, whereas those from prepubertal pigs (6-month-old) survived without initiation of their growth even after 4 months; thereafter, they started to grow and reached full size after 6 months. These results suggest that the mechanism regulating the activation of primordial oocytes in prepubertal pigs is different from that in infant pigs. In this regard, the involvement of FOXO3, a forkhead transcription factor, was studied. In prepubertal pigs, FOXO3 was detected in almost all (94G2%) primordial oocyte nuclei, and in infant pigs, 42G7% primordial oocytes were FOXO3 positive. At 4 months after xenografting, the percentage of FOXO3-positive primordial oocytes from prepubertal pigs had decreased to the infant level. Further, siRNA was designed to knock down porcine FOXO3. FOXO3-knockdown primordial follicles from prepubertal pigs developed to the antral stage accompanied by oocyte growth at 2 months after xenografting. These results suggest that primordial oocytes are dormant in prepubertal pigs by a FOXO3-related mechanism to establish a nongrowing oocyte pool in the ovary, and that a transient knockdown of the FOXO3 activates the primordial oocytes to enter the growth phase.

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Section: Discussionsupporting

confidence: 69%

Section: Introductionmentioning

confidence: 95%

Knockdown of FOXO3 induces primordial oocyte activation in pigs

Moniruzzaman¹,

Lee²,

Zengyo³

et al. 2010

Reproduction

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“…The mRNA encoding KIT and KL was detected in the porcine ovary, in which KL mRNA was localized in granulosa cells and KIT mRNA was detected in oocytes [34,35]. In our study [24], KIT was expressed in all primordial oocytes from both neonatal and prepubertal pigs. This result agreed with the expression pattern in sheep [36] and humans [37], in which KIT expression was similarly found in primordial oocytes from fetal and postnatal ovaries.…”

supporting

confidence: 61%

“…They xenografted ovarian tissues containing mainly primordial follicles and a few primary follicles and found antral follicles at 45-75 days after xenografting. Similarly, we found that primordial follicles from neonatal (10-to 20-day-old) piglets developed to the antral stage along with enlargement of oocytes at 2 months after xenografting in SCID mice [24]. …”

supporting

confidence: 58%

Growth of Primordial Oocytes in Neonatal and Adult Mammals

Moniruzzaman

Miyano

2010

J. Reprod. Dev.

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Abstract. Mammalian ovaries are endowed with a huge number of small oocytes (primordial oocytes) in primordial follicles. A small number of primordial oocytes start to grow, while others remain quiescent. Little is known about the mechanism regulating the activation of primordial oocytes. Recently, we found that primordial follicles in mature cows and prepubertal pigs took longer to initiate growth in xenografts compared with those in neonatal animals. We think that primordial oocytes in adult mammals are different from those in neonatal mammals. In this review, we summarize the results regarding the activation of primordial oocytes in neonatal and adult ovaries of different species and propose a model in which ovaries of neonatal mammals contain a mixed population of both quiescent and activated primordial oocytes, while almost all primordial oocytes are quiescent in adult females. The dormancy of primordial oocytes may be required to reserve the non-growing oocyte pool for the long reproductive life in mammals. FOXO3 is considered one of the molecules responsible for the dormancy of primordial oocytes in adult ovaries. These quiescent primordial oocytes are activated, perhaps by certain mechanisms involving the interaction between stimulatory and inhibitory factors, to enter the growth phase. Key words: Adult, Neonatal, Oocyte growth, Ovary, Primordial follicle (J. Reprod. Dev. 56: [559][560][561][562][563][564][565][566] 2010) n fetal ovaries, germ cells known as oogonia proliferate mitotically and become oocytes that enter the meiotic cell cycle, and the oocytes then become arrested at prophase I. At around birth in rodents and during mid-gestation in humans and pigs, oocytes (15-20 μm in diameter in rodents and 30 μm in diameter in humans and pigs) are enclosed by a single layer of flattened follicular epithelial cells (granulosa cells; Fig. 1). This unit consisting of an oocyte and granulosa cells is called the primordial follicle. The oocytes in primordial follicles are called "primordial oocytes" [1]. After formation of primordial follicles, some of the primordial oocytes begin to grow, although most spend months or years in the quiescent state. Activation of primordial oocytes causes the transformation of their surrounding granulosa cells to a cuboidal shape [2]. The follicles at this stage are called primary follicles that contain growing oocytes. The granulosa cells proliferate and become multilayered to form secondary follicles. As follicles develop through the primary, secondary and tertiary (antral) stages, they gain successive layers of granulosa cells, oocytes increase in size towards 70-75 μm in rodents and 120-125 μm in humans, cows and pigs and theca cell layers surround the follicles. Finally, a large fluid-filled antral cavity (follicular antrum) is formed, and the follicle is called a tertiary or antral follicle.The time point at which first activation of primordial oocytes occurs depends on the species. In mice, growth of a portion of oocytes begins within several days after birth [3,4]...

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“…Thus, the present experiments suggest that primordial oocytes entered the growth phase in vitro by the knockdown of Foxo3. In previous experiments, we found that primordial follicles from neonatal pigs developed to the antral stage along with oocyte growth at 2 months after xenografting, whereas those from prepubertal pigs survived without initiation of development [17]. After knockdown of FOXO3, a proportion of primordial oocytes from prepubertal pigs became activated and entered the growth phase in the xenografts [9].…”

Section: Discussionmentioning

confidence: 89%

Foxo3 negatively regulates the activation of mouse primordial oocytes

Kashiwagi

Moniruzzaman

Miyano

2012

Reprod Medicine & Biology

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Purpose The objective of this study is to know the role of Foxo3, a forkhead transcription factor, in the growth initiation of primordial oocytes in neonatal mice. Methods We studied the expression of Foxo3 in 0-, 1-, 2-, 7-and 21-day-old mouse ovaries by immunohistochemistry. Ovaries from 1-day-old mice were treated with Foxo3 siRNAs (small interfering RNAs) and subsequently organcultured for 6 days, and the oocyte growth was examined histologically. Results Expression of Foxo3 was low in newborn mouse ovaries. In 1-day-old ovaries, Foxo3 was expressed in the nuclei of 20 ± 7 % primordial oocytes. The percentage of Foxo3-positive primordial oocytes was increased to 48 ± 8, 37 ± 2 and 47 ± 4 in 2-, 7-and 21-day-old mice, respectively. After treatment of ovaries with Foxo3 siRNAs, higher proportion of oocytes entered the growth phase in cultured ovaries than that in control. Conclusions These results suggest that Foxo3 negatively regulates the growth initiation of primordial oocytes and knockdown of Foxo3 leads primordial oocytes to the growth phase in vitro.

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KIT-KIT Ligand in the Growth of Porcine Oocytes in Primordial Follicles

Cited by 27 publications

References 27 publications

Knockdown of FOXO3 induces primordial oocyte activation in pigs

Knockdown of FOXO3 induces primordial oocyte activation in pigs

Growth of Primordial Oocytes in Neonatal and Adult Mammals

Foxo3 negatively regulates the activation of mouse primordial oocytes

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