Malgorzata E. Skaznik-Wikiel

Oocyte Generation in Adult Mammalian Ovaries by Putative Germ Cells in Bone Marrow and Peripheral Blood

It has been suggested that germline stem cells maintain oogenesis in postnatal mouse ovaries. Here we show that adult mouse ovaries rapidly generate hundreds of oocytes, despite a small premeiotic germ cell pool. In considering the possibility of an extragonadal source of germ cells, we show expression of germline markers in bone marrow (BM). Further, BM transplantation restores oocyte production in wild-type mice sterilized by chemotherapy, as well as in ataxia telangiectasia-mutated gene-deficient mice, which are otherwise incapable of making oocytes. Donor-derived oocytes are also observed in female mice following peripheral blood transplantation. Although the fertilizability and developmental competency of the BM and peripheral blood-derived oocytes remain to be established, their morphology, enclosure within follicles, and expression of germ-cell- and oocyte-specific markers collectively support that these cells are bona fide oocytes. These results identify BM as a potential source of germ cells that could sustain oocyte production in adulthood.

Setting the record straight on data supporting postnatal oogenesis in female mammals

Of all the ‘certainties’ in mammalian female reproductive biology, the concept that a non-renewing oocyte reserve is set forth in the ovaries at birth may be the most longstanding and widely held. However, when data from our studies of oocyte apoptosis unintentionally began to contradict this theory in the latter part of 2002, we embarked on an investigation, unbiased by any pre-conceived dogmas, to determine if oocyte production persists in adult female mice. In 2004, we presented our first experimental findings in the journal Nature, which indicated that oogenesis indeed continues in adulthood. Amidst widespread skepticism, we moved forward with our studies and this year published our follow-up experiments in the journal Cell. Results from this latter body of work not only reinforced our earlier conclusions but also identified bone marrow as a surprising source of oocyte-producing germ cells in adults. Although this study has also been met with skepticism, doubts raised in commentaries on our work are largely based on inaccurate or incomplete assessments of our experimental models and results. Here we have attempted to clarify published misperceptions and misinterpretations of our data, and offer additional insights that challenge the idea of fixed endowment of oocytes at birth.

Sphingosine-1-Phosphate Receptor Expression and Signaling Correlate with Uterine Prostaglandin-Endoperoxide Synthase 2 Expression and Angiogenesis During Early Pregnancy

Abstract Signaling mechanisms coordinating uterine angiogenesis and tissue remodeling during decidualization are not completely understood. Prostanoid signaling is thought to play a functionally important role in each of these events. In the present study, we demonstrate that the subfamily of G-protein-coupled receptors that binds and becomes activated by the terminal signaling lipid in the sphingolipid pathway, sphingosine-1-phosphate (S1P), were expressed during uterine decidualization. Three of the five known S1P receptors, termed endothelial differentiation genes (Edg; Edg1, Edg3, and Edg5) were upregulated in the uterine deciduum from Day of Pregnancy (DOP) 4.5 to 7.5, while Edg6 and Edg8 expression remained unchanged. Consistent with angiogenesis in general during decidualization, we believe EDG1 and EDG5 to be regulated by the embryo because no microvascular expression for these receptors was observed in oil-induced deciduomas. Observed expression of EDG1 and EDG5 showed a similar expression pattern to that previously reported for prostaglandin-endoperoxide synthase 2 (PTGS2), transitioning from the sublumenal stromal compartment in the antimesometrial pole (DOP 5) to the microvasculature of the mesometrial pole (DOP 7). Furthermore, these two receptors colocalized with PTGS2 at three additional sites at the maternal:fetal interface throughout pregnancy. Treatment of cultured predecidualized stromal cells with S1P resulted in upregulation of Ptgs2 mRNA and PTGS2 protein, but not the downstream enzyme prostacyclin synthase. These combined results suggest the existence of a link between the sphingolipid and prostanoid signaling pathways in uterine physiology, and that, based on their expression pattern, S1P receptors function to coordinate uterine mesometrial angiogenesis during the implantation phase of early gestation.

Granulocyte colony-stimulating factor with or without stem cell factor extends time to premature ovarian insufficiency in female mice treated with alkylating chemotherapy

OBJECTIVE To examine gonadal protective properties of granulocyte colony-stimulating factor (G-CSF) alone or in combination with stem cell factor (SCF) in female mice treated with high-dose alkylating chemotherapy. DESIGN Experimental laboratory animal study. SETTING Tertiary care academic hospital and research institute. ANIMAL(S) Six- and 8-week-old C57Bl/6 female mice. INTERVENTION(S) Adult female mice were treated with [1] cyclophosphamide and busulfan (CTx), [2] CTx + G-CSF/SCF, [3] CTx + G-CSF, or [4] normal saline and dimethyl sulfoxide (DMSO; vehicle control). MAIN OUTCOME MEASURE(S) Follicle counts, microvessel density, cellular response to DNA damage, and litter production. RESULT(S) G-CSF ± SCF increased microvessel density and decreased follicle loss in CTx-treated female mice compared with CTx-only treated female mice. Mice administered CTx alone exhibited premature ovarian insufficiency, with only 28% of mice producing two litters. However, 100% of mice receiving CTx with G-CSF + SCF, and 80% of mice receiving CTx + G-CSF alone produced at least three litters and 20% of mice in each group produced five litters. CONCLUSION(S) Treatment of mice with G-CSF decreases chemotherapy-induced ovarian follicle loss and extends time to premature ovarian insufficiency in female mice. Further studies are needed to validate these preclinical results in humans and compare efficacy with the established GnRH analogue treatments.

Loss of CABLES1, a Cyclin-dependent Kinase-interacting Protein that Inhibits Cell Cycle Progression, Results in Germline Expansion at the Expense of Oocyte Quality in Adult Female Mice

Recent studies have shown that cell cycle inhibitors encoded by the Ink4a gene locus constrain the self-renewing activity of adult stem cells of the hematopoietic and nervous systems. Here we report that knockout (KO) of the Cables1 [cyclin-dependent kinase (CDK)-5 and ABL enzyme substrate 1] cell cycle-regulatory gene in mice has minimal to no effect on hematopoietic stem cell (HSC) dynamics. However, female Cables1-null mice exhibit a significant expansion of germ cell (oocyte) numbers throughout adulthood. This is accompanied by a dramatic elevation in the number of atretic immature oocytes within the ovaries and an increase in the incidence of degenerating oocytes retrieved following superovulation of CABLES1-deficient females. These outcomes are not observed in mice lacking p16INK4a alone or both p16INK4a and p19ARF. These data support recent reports that adult female mice can generate new oocytes and follicles but the enhancement of postnatal oogenesis by Cables1 KO appears offset by a reduction in oocyte quality, as reflected by increased elimination of these additional germ cells via apoptosis. This work also reveals cell lineage specificity with respect to the role that specific CDK-interacting proteins play in restraining the activity of adult germline versus somatic stem cells.

Granulocyte colony-stimulating factor in conjunction with vascular endothelial growth factor maintains primordial follicle numbers in transplanted mouse ovaries

OBJECTIVE To determine whether granulocyte colony-stimulating factor (G-CSF), stem cell factor (SCF), or vascular endothelial growth factor (VEGF) improve the outcome of ovarian grafting. DESIGN Experimental animal study. SETTING Tertiary care hospital, animal facilities. ANIMAL(S) Young adult (6- to 8-week-old) C57BL/6 female mice. INTERVENTION(S) Orthotopic transplantation of the frozen-thawed ovary. Group 1 (n = 6) received VEGF (8 g/kg/day); group 2 (n = 6) received VEGF and G-CSF (50 g/kg/day), group 3 (n = 6) received G-CSF and SCF (100 g/kg/day), and group 4 (n = 5) received saline (vehicle controls). All injections were given once daily for 5 days starting the day after surgery. Ovaries were collected 2 weeks after transplantation. MAIN OUTCOME MEASURE(S) Number of nonatretic immature (primordial, primary, and small preantral) follicles. RESULT(S) Transplanted ovaries in mice injected with VEGF concurrently with G-CSF maintained a statistically significantly larger pool of primordial follicles compared with transplanted ovaries in saline-injected controls. Follicle numbers (total immature and primordial) in transplanted ovaries showed no statistically significant difference in mice injected with VEGF alone or G-CSF plus SCF compared with saline-injected controls. CONCLUSION(S) After ovarian transplantation, mice treated with VEGF and G-CSF maintain a significantly greater number of primordial follicles compared with the transplanted ovaries in control animals, suggesting that the combination of G-CSF and VEGF minimizes ischemic damage and thus improves the viability and function of the ovarian graft.

High-Fat Diet Causes Subfertility and Compromised Ovarian Function Independent of Obesity in Mice

ABSTRACT Excess calorie consumption, particularly of a diet high in fat, is a risk factor for both obesity and reproductive disorders. Animal model studies indicate that elevated dietary fat can influence some reproductive functions independent of obesity. In the current study we sought to determine whether a high-fat diet (HFD) impacts ovarian function, long-term fertility, and local and systemic markers of inflammation independent of obesity. Five-week-old mice were fed either low-fat diet (control group-LF-Ln) or HFD for 10 wk and were divided based on body weight into high-fat obese (HF-Ob: >25 g) and high-fat lean (HF-Ln: <22 g). Ovaries were collected to assess ovarian follicles and to determine the degree of local inflammation. Serum proinflammatory cytokines were also measured. A group of animals was followed for breeding trials for 5 mo while being exposed to LFD or HFD. We found that both 10-wk and 32-wk exposure to HFD resulted in depleted primordial follicles regardless of obesity phenotype. Macrophage counts revealed increased tissue inflammation in the ovary independent of obesity. In addition, serum proinflammatory cytokines were increased in HF-Ln and HF-Ob in comparison to LF-Ln mice. Moreover, HFD had a sustained effect on litter production rate and number of pups per litter regardless of obese phenotype. This study describes for the first time that exposure to HFD causes significant reduction in primordial follicles, compromised fertility, produced higher proinflammatory cytokine levels, and increased ovarian macrophage infiltration, independent of obesity. The negative effects of HFD on primordial follicles may be mediated by increased tissue inflammation.

High-Fat Diet and Female Fertility

The prevalence of obesity is high among reproductive-age women and is associated with impaired reproductive function. Obesity is multifactorial in origin, yet many cases of obesity result from overconsumption of a diet high in fat. Excess dietary fat increases both adipose and nonadipose tissue lipid content and, through lipotoxicity, leads to cell dysfunction and death. High dietary fat intake, with or without the development of obesity, impairs female hypothalamic-pituitary-ovarian (HPO) axis functionality and fertility. Based on the current evidence, it appears the reproductive dysfunction involves increased leptin and insulin signaling at the various levels of the HPO axis, as well as changes in peroxisome proliferator-activated receptor γ actions and increased inflammation, yet other mechanisms may also be involved. This review summarizes the current body of knowledge on impaired female reproductive function after high-fat diet exposure, as well as discusses proposed mechanisms through which this may occur.

Accuracy of endometrial thickness in detecting benign endometrial pathology in postmenopausal women

Objective: The aim of this study was to determine whether an endometrial thickness less than 5 mm on transvaginal ultrasound (TVUS) is sufficient to exclude benign endometrial lesions in postmenopausal women with bleeding and to determine a cutoff value below which benign endometrial pathology could be ruled out. Methods: Electronic medical records of consecutive postmenopausal women presenting with vaginal bleeding suspicious for benign pathology were reviewed between September 2002 and December 2007. All women underwent TVUS with endometrial stripe measurement followed by saline infusion sonography (SIS). Accuracy of endometrial echo thickness for detecting intracavitary masses was compared with the reference standard of SIS. A receiver operating characteristic curve was constructed to calculate whether other cutoff values would be more accurate than 5 mm in detecting benign endometrial masses. Results: A total of 1,097 women were referred during the study period; 135 met the inclusion criteria and underwent TVUS followed by SIS. The endometrial echo was less than 5 mm in 43% and 5 mm or greater in 57%. The overall prevalence of polyps or fibroids was 50%. Using an endometrial echo cutoff less than 5 mm, sensitivity was 76% (95% CI, 65-85), specificity was 63% (95% CI, 51-73), positive predictive value was 67%, and negative predictive value was 72%. The area under the receiver operating characteristic curve for detection of benign masses was 0.79 (95% CI, 0.72-0.87). We were unable to determine a cutoff value below which benign endometrial pathology could be excluded. Conclusions: With an endometrial thickness cutoff of 5 mm a considerable amount of benign endometrial pathology in postmenopausal women with bleeding is missed, and SIS or hysteroscopy may be warranted.

Intraperitoneal chemotherapy for recurrent epithelial ovarian cancer is feasible with high completion rates, low complications, and acceptable patient outcomes.

Objectives Three large randomized clinical trials have shown a survival benefit for patients treated with intraperitoneal (IP) compared with intravenous chemotherapy for advanced stage epithelial ovarian cancer (EOC). However, the use of IP chemotherapy in recurrent EOC is controversial. The purpose of this study was to determine outcomes, completion rates, and frequency of complications in patients with platinum-sensitive recurrent EOC treated with IP chemotherapy. Methods A retrospective, single-institution analysis of women who received IP chemotherapy for recurrent EOC from January 2003 to April 2010 was conducted. Study patients were identified from the Tumor Registry and office records. Demographic factors, stage, histology, surgical findings, cytoreduction status, and subsequent therapies were abstracted. Progression-free (PFS) and overall survival (OS) were estimated by Kaplan-Meier methods. Results Fifty-six women who received IP chemotherapy for their first EOC recurrence were identified. The mean age of patients was 56.7 years (range, 40–79 y). Fifty-five patients (98.3%) had previously completed at least 6 cycles of intravenous chemotherapy. Of all patients, 87.5% were initially diagnosed with advanced stage disease (stage IIA–IV). All patients underwent secondary cytoreduction at the time of IP port placement. Moreover, 67.9% of patients were considered optimally cytoreduced (<1 cm residual disease) at the end of the secondary debulking surgery. Forty-two patients (75%) were able to successfully complete at least 6 cycles of IP chemotherapy. Reasons for noncompletion were disease progression, allergic reaction, renal failure, pain, severe nausea and vomiting, death, and patient refusal. Six patients (10.7%) developed port complications including pain around port site, port malfunction, and port erosion into small bowel. Median PFS since the initiation of IP chemotherapy was 10.5 months (95% confidence interval, 7.5–16.4 months) and median OS was 51 months (95% confidence interval, 40.8–61.1 months). Conclusions Intraperitoneal chemotherapy is a feasible option for patients with recurrent EOC, with high completion rates, low frequency of complications, and acceptable PFS and OS.