Biomedical subjects

Teresa K Woodruff

Publications and source records attributed to Teresa K Woodruff.

At least 19 recordsLinked to original sources

PubMed2006

The structures that underlie normal reproductive function.

The mechanisms and physiology of reproductive function have fascinated scientists throughout time. Recent cellular and molecular level structural studies have provided unprecedented insights into reproductive systems and signaling networks. This 'cutting edge' editorial provides a recent example in each of these areas, namely, the anatomical integrity of the follicle, the molecular structure of activin with its binding partners and the molecular regulation of inhibin. These three examples of structure informing function help explain reproductive health and may provide solutions to reproductive disease.

Endocrine System↗

PubMed2006

Identification of a stage-specific permissive in vitro culture environment for follicle growth and oocyte development.

The availability of viable oocytes is the limiting factor in the development of new reproductive techniques. Many attempts have been made to grow immature oocytes in vitro during recent decades. Recently, a modified alginate-based three-dimensional culture system was designed to support the growth and maturation of multilayered secondary follicles. This system was able to produce oocytes that successfully completed meiosis, fertilization, and development to the blastocyst stage. Subsequent attempts to culture two-layered secondary follicles were unsuccessful under the original conditions. Herein, we investigated the effect of alginate consistency on two-layered follicle growth and oocyte developmental competence by encapsulating follicles into alginate scaffolds of various concentrations. Although there were no significant differences in survival rates, 0.25% and 0.5% alginate supported more rapid growth of follicles and antrum formation compared with 1.5% and 1.0% alginate after 8 days of culture. Alginate scaffold concentration also affected the proliferation and differentiation of somatic cells (theca and granulosa cells), measured in terms of morphological changes, steroid profiles (androstenedione, estradiol, and progesterone), and specific molecular markers (Fshr, Lhcgr, and Gja1). Theca cell proliferation and steroid production were hindered in follicles cultured in 1.5% alginate. In vitro fertilization and embryo culture revealed that oocytes obtained from 0.25% alginate retained the highest developmental competence. Overall, the present study showed that the alginate scaffold consistency affects folliculogenesis and oocyte development in vitro and that the alginate culture system can and should be tailored to maximally support follicle growth depending on the size and stage of the follicles selected for culture.

Androstenedione↗

PubMed2006

Fate of the initial follicle pool: empirical and mathematical evidence supporting its sufficiency for adult fertility.

The importance of the initial follicle pool in fertility in female adult mammals has recently been debated. Utilizing a mathematical model of the dynamics of follicle progression (primordial to primary to secondary), we examined whether the initial follicle pool is sufficient for adult fertility through reproductive senescence in CD1 mice. Follicles in each stage were counted from postnatal day 6 through 12 months and data were fit to a series of first-order differential equations representing two mechanisms: an initial pool of primordial follicles as the only follicle source (fixed pool model), or an initial primordial follicle pool supplemented by germline stem cells (stem cell model). The fixed pool model fit the experimental data, accurately representing the maximum observed primary follicle number reached by 4-6 months of age. Although no germline stem cells could be identified by SSEA-1 immunostaining, the stem cell model was tested using a range of de novo primordial follicle production rates. The stem cell model failed to describe the observed decreases in follicles over time and did not parallel the accumulation and subsequent reduction in primary follicles during the early fertile lifespan of the mouse. Our results agree with established dogma that the initial endowment of ovarian follicles is not supplemented by an appreciable number of stem cells; rather, it is sufficient to ensure the fertility needs of the adult mouse.

Animals↗

PubMed2006

Postnatal regulation of germ cells by activin: the establishment of the initial follicle pool.

Mammalian females enter puberty with follicular reserves that exceed the number needed for ovulation during a single lifetime. Follicular depletion occurs throughout reproductive life and ends in menopause, or reproductive senescence, when the follicle pool is exhausted. The mechanisms regulating the production of a species-specific initial follicle pool are not well understood. However, the establishment of a follicular reserve is critical to defining the length of reproductive cyclicity. Here we show that activin A (rh-ActA), a known regulator of follicle formation and growth in vitro, increased the number of postnatal mouse primordial follicles by 30% when administered to neonatal animals during the time of germline cyst breakdown and follicle assembly. This expansion in the initial follicle pool was characterized by a significant increase in both germ cell and granulosa cell proliferation. However, the excess follicles formed shortly after birth did not persist into puberty and both adult rh-ActA- and vehicle-treated animals demonstrated normal fertility. A follicle atresia kinetic constant (k(A)) was modeled for the two groups of animals, and consistent with the empirical data, the k(A) for rh-ActA-treated was twice that of vehicle-treated animals. Kinetic constants for follicle formation, follicle loss and follicle expansion from birth to postnatal day 19 were also derived for vehicle and rh-ActA treatment conditions. Importantly, introduction of exogenous rh-ActA revealed an intrinsic ovarian quorum sensing mechanism that controls the number of follicles available at puberty. We propose that there is an optimal number of oocytes present at puberty, and when the follicle number is exceeded, it occurs at the expense of oocyte quality. The proposed mechanism provides a means by which the ovary eliminates excess follicles containing oocytes of poor quality prior to puberty, thus maintaining fertility in the face of abnormal hormonal stimuli in the prepubertal period.

Activin Receptors↗

PubMed2006

Distribution of extracellular matrix proteins type I collagen, type IV collagen, fibronectin, and laminin in mouse folliculogenesis.

The extracellular matrix (ECM) plays a prominent role in ovarian function by participating in processes such as cell migration, proliferation, growth, and development. Although some of these signaling processes have been characterized in the mouse, the relative quantity and distribution of ECM proteins within developing follicles of the ovary have not been characterized. This study uses immunohistochemistry and real-time PCR to characterize the ECM components type I collagen, type IV collagen, fibronectin, and laminin in the mouse ovary according to follicle stage and cellular compartment. Collagen I was present throughout the ovary, with higher concentrations in the ovarian surface epithelium and follicular compartments. Collagen IV was abundant in the theca cell compartment with low-level expression in the stroma and granulosa cells. The distribution of collagen was consistent throughout follicle maturation. Fibronectin staining in the stroma and theca cell compartment increased throughout follicle development, while staining in the granulosa cell compartment decreased. Heavy staining was also observed in the follicular fluid of antral follicles. Laminin was localized primarily to the theca cell compartment, with a defined ring at the exterior of the follicular granulosa cells marking the basement membrane. Low levels of laminin were also apparent in the stroma and granulosa cell compartment. Taken together, the ECM content of the mouse ovary changes during follicular development and reveals a distinct spatial and temporal pattern. This understanding of ECM composition and distribution can be used in the basic studies of ECM function during follicle development, and could aid in the development of in vitro systems for follicle growth.

Animals↗

PubMed2006

The expression of inhibin beta B is high in human adipocytes, reduced by weight loss, and correlates to factors implicated in metabolic disease.

Adipose tissue is an endocrine organ that produces and secretes adipokines. The aim of this study was to identify genes predominantly expressed in human subcutaneous adipocytes. For this purpose, an algorithm was developed and DNA microarray expression profiles from 33 human tissues and cell types were used to select genes. Inhibin beta B (INHBB; coding for the activin betaB subunit) was identified and high expression in adipocytes was confirmed by real-time PCR and immunohistochemistry. INHBB expression in adipose tissue was down regulated by diet-induced weight loss (p<0.001). Furthermore, INHBB expression was positively correlated to total (p<0.001) and subcutaneous (p<0.01) adipose tissue areas and serum levels of fasting insulin (p<0.01) and cholesterol (p<0.05). In conclusion, INHBB expression was high in human adipocytes, reduced by weight loss and adipose tissue INHBB mRNA levels correlated to metabolic risk factors. This suggests that activin B produced in adipocytes may play a role in the metabolic syndrome.

Adipocytes↗

PubMed2006

Folliculogenesis in the domestic cat (Felis catus).

The dynamic regulation of mammalian folliculogenesis is a key component of the reproductive process. Traditionally, the rodent had been used as a model to study ovarian function and reproductive physiology due to the availability of animals, their relatively short cycle length, high rate of fecundity and short generation interval. We maintain that much basic information can be determined using domestic cat ovaries retrieved from local veterinary clinics following routine spaying, without having the expense of maintaining a colony of laboratory cats. Studies of normal feline reproductive physiology and advances in reproductive technology may be extrapolated for use in endangered non-domestic felids. Increased understanding of feline reproduction will be beneficial to veterinary medicine, and to groups working to control feral cat populations. It is important to examine reproductive mechanisms in alternative animal models as there are a vast number of threatened and endangered species in which we lack the critical reproductive information needed to assist in preserving their long-term survival.

Animals↗

PubMed2006

Gonadotropin-induced superovulation drives ovarian surface epithelia proliferation in CD1 mice.

The ovarian surface epithelium (OSE) is a monolayer of cells that surround the ovary and accommodate repeated tear and repair in response to ovulation. OSE cells are thought to be the progenitors of 90% of ovarian cancers. Currently, the total amount of proliferation of the OSE has not been reported in response to one ovulatory event. In this study, proliferation of the OSE was quantified in response to superovulation induced by ip injection of pregnant mare serum gonadotropin (PMSG) and human chorionic gonadotropin (hCG) in immature 27-d-old CD1 mice using bromodeoxyuridine (BrdU). BrdU incorporation into the OSE cells was measured from the time of hCG injection for a total cumulative label of 12 h. BrdU incorporation was also measured from the time of PMSG injection for a total label of 60 h to correlate proliferation with specific gonadotropin stimulation. The OSE proliferation was significantly higher in superovulated animals compared with control mice at all time points. Proliferation was also analyzed in discrete anatomical sections and indicated that OSE covering antral follicles and corpora lutea proliferated more rapidly than OSE distal to follicular growth. Finally, apoptosis was assessed in response to ovulation, and virtually no cell death within the OSE was detected. These data demonstrate that the OSE, especially near antral follicles and corpora lutea, proliferates significantly in response to the gonadotropins PMSG and hCG. Therefore, ovarian surface cell division in response to ovulation could contribute to ovarian cancer by proliferation-induced DNA mutations and transformed cell progression.

Animals↗

PubMed2006

Extracellular matrix functions in follicle maturation.

The extracellular matrix (ECM) promotes and/or inhibits many cellular processes, including but not limited to proliferation, differentiation, and survival, which must occur for follicle growth and oocyte maturation. The ECM regulation of cellular processes in ovarian cells is being investigated in many animal models, including avian, rat, bovine, porcine, rabbit, sheep, human, and mouse. Granulosa cells are more frequently employed; however, the culture of intact follicles and ovaries has been developed and enables ECM functions in folliculogenesis to be studied. ECM components that have been examined are used individually (collagen, laminin, fibronectin) or collectively (Matrigel, isolated basal lamina, and ECM produced by cell lines) in both two- and three-dimensional model systems. In granulosa cell cultures, ECM affects morphology, aggregation and communication, survival, proliferation, and steroidogenesis; whereas follicle and ovary cultures demonstrate a regulation of folliculogenesis. This article describes the ECM functionality on ovarian cells throughout development, and highlights the potential of developing technologies to identify structure-function relationships in follicle maturation.

Animals↗

PubMed2006

The structural basis of TGF-beta, bone morphogenetic protein, and activin ligand binding.

The transforming growth factor-beta (TGF-beta) superfamily is a large group of structurally related growth factors that play prominent roles in a variety of cellular processes. The importance and prevalence of TGF-beta signaling are also reflected by the complex network of check points that exist along the signaling pathway, including a number of extracellular antagonists and membrane-level signaling modulators. Recently, a number of important TGF-beta crystal structures have emerged and given us an unprecedented clarity on several aspects of the signal transduction process. This review will highlight these latest advances and present our current understanding on the mechanisms of specificity and regulation on TGF-beta signaling outside the cell.

Activins↗

PubMed2006

Cell-specificity of transforming growth factor-beta response is dictated by receptor bioavailability.

Members of the transforming growth factor-beta (TGFbeta) family control diverse cellular responses including differentiation, proliferation, controlled cell death and migration. The response of a cell to an individual ligand is highly restricted yet the signaling pathways for TGFbeta, activin and bone morphogenic proteins share a limited number of receptors and activate similar intracellular cytoplasmic co-regulators, Smads. A central question in the study of this family of ligands is how cells titrate and integrate each TGFbeta-like signal in order to respond in a cell- and ligand-specific manner. This study uses the pituitary gonadotrope cell line, LbetaT2, as a model to delineate the relative contribution of TGFbeta and activin ligands to follicle-stimulating hormone (FSH) biosynthesis. It was found that pituitary gonadotrope cells do not express the TGFbeta type II (TbetaRII) receptor and are therefore not responsive to the TGFbeta ligand. Transfection of the receptor restores TGFbeta signaling capabilities and the TGFbeta-mediated stimulation of FSHbeta gene transcription in LbetaT2 cells. Consequently, we evaluated the presence of the TbetaRII in the adult mouse pituitary. TbetaRII does not co-localize with FSH-producing cells; however it is detected on the cell surface of prolactin- and growth hormone-positive cells. Taken together, these results suggest that the bioavailability of the TGFbeta-specific receptor rather than TGFbeta dictates pituitary gonadotrope selectivity to activin, which is necessary to maintain normal reproductive function. It is likely that the ligand-restricted mechanisms employed by the gonadotrope are present in other cells, which could explain the distinct control of many cellular processes by members of the TGFbeta superfamily.

Activin Receptors, Type I↗

PubMed2006

Cancer survivors and infertility: a review of a new problem and novel answers.

Improvements in cancer treatment have changed the way in which cancer is viewed and experienced. However, these same treatments have led to numerous early and late effects, including the loss of fertility. Infertility can influence the biologic and psychologic health of both male and female survivors. Reproductive science can now offer methods to address this concern and provide promising new approaches that may eliminate or mitigate this treatment-related outcome. For current and future reproductive options to serve the needs of survivors more fully, health providers must understand the complexities of infertility as well as their role in delivering answers their patients require. This review will discuss what is known about the causes and experience of infertility among cancer survivors as well as the forms of fertility preservation available.

Antineoplastic Agents↗

PubMed2005

Follicle size class contributes to distinct secretion patterns of inhibin isoforms during the rat estrous cycle.

The differential production of inhibins must be exquisitely controlled at the cellular level to ensure the secretion of the appropriate ligand at specific times during the reproductive cycle. The mechanisms underlying inhibin dimer assembly, processing and secretion are not well understood. Here we verify that the secretion of inhibin A and inhibin B from the granulosa cell is discordant during the estrous cycle: discordant production or secretion of the inhibins was not observed during the pregnant mare serum gonadotropin-induced cycle. We correlated the discordant production and secretion of inhibin A and inhibin B into the serum with distinct patterns of inhibin alpha- and beta-subunit colocalization during the cycle in granulosa cells. We determined that the discordant pattern of inhibin A and inhibin B during the rat estrous cycle is due to independent populations of antral follicles making inhibin B (small antral follicles) or inhibin A (large antral follicles).

Animals↗

PubMed2005

A steroid-conjugated contrast agent for magnetic resonance imaging of cell signaling.

We have synthesized the first steroid hormone-MR contrast agent conjugate designed to track the cell signaling process upon binding to a gene switch system. The derivative has a high relaxivity and when tested in vitro is active as a progesterone antagonist (RU-486). By combining a transcriptional system and a noninvasive imaging technology, such as MRI, it would be a powerful tool to research the cell signaling pathway in vivo.

Binding, Competitive↗

PubMed2005

Structural basis for a functional antagonist in the transforming growth factor beta superfamily.

Within the transforming growth factor beta superfamily, the agonist-antagonist relationship between activin and inhibin is unique and critical to integrated reproductive function. Activin acts in the pituitary to stimulate follicle-stimulating hormone, and is antagonized by endocrine acting, gonadally derived inhibin. We have undertaken a mutational analysis of the activin betaA subunit to determine the precise structural aspects that contribute to inhibin antagonism of activin. By substituting specific amino acid residues in the activin betaA subunit with similarly aligned amino acids from the alpha subunit, we have pinpointed the residues required for activin receptor binding and activity, as well as for inhibin antagonism of activin through its receptors. Additionally, we have identified an activin mutant with a higher affinity for the activin type I receptor that provides structural evidence for the evolution of ligand-receptor interactions within the transforming growth factor beta superfamily.

Activin Receptors↗

PubMed2005

Activin A mediates growth inhibition and cell cycle arrest through Smads in human breast cancer cells.

The transforming growth factor-beta (TGF-beta) superfamily of growth factors is responsible for a variety of physiologic actions, including cell cycle regulation. Activin is a member of the TGF-beta superfamily that inhibits the proliferation of breast cancer cells. Activin functions by interacting with its type I and type II receptors to induce phosphorylation of intracellular signaling molecules known as Smads. Smads regulate transcription of many genes in a cell- and tissue-specific manner. In this study, the role of activin A in growth regulation of breast cancer cells was investigated. Activin stimulated the Smad-responsive promoter, p3TP, 2-fold over control in T47D breast cancer cells. Activin inhibited cellular proliferation of T47D breast cancer cells after 72 hours, an effect that could be abrogated by incubation with the activin type I receptor inhibitor, SB431542. Activin arrested T47D cells in the G0-G1 cell cycle phase. Smad2 and Smad3 were phosphorylated in response to activin and accumulated in the nucleus of treated T47D cells. Infection of T47D cells with adenoviral Smad3 resulted in cell cycle arrest and activation of p3TP-luciferase, whereas a adenoviral dominant-negative Smad3 blocked activin-mediated cell cycle arrest and gene transcription. Activin maintained expression of p21 and p27 cyclin-dependent kinase inhibitors involved in cell cycle control, enhanced expression of p15, reduced cyclin A expression, and reduced phosphorylation of the retinoblastoma (Rb) protein. Smad3 overexpression recapitulated activin-induced p15 expression and repression of cyclin A and Rb phosphorylation. These data indicate that activin A inhibits breast cancer cellular proliferation and activates Smads responsible for initiating cell cycle arrest.

Activins↗

PubMed2005

The development of a mouse model of ovarian endosalpingiosis.

Pelvic pain is a common presenting ailment in women often linked to ovulation, endometriosis, early pregnancy, ovarian cancer, and cysts. Clear differential diagnosis for each condition caused by these varied etiologies is difficult and may slow the delivery of therapy that, in the case of ovarian cancer, could be fatal. Ovarian endosalpingiosis, a pelvic condition typified by the presence of cystic glandular structures lined by benign tubal/salpingeal epithelium, is also associated with pelvic pain in women. The exact cellular antecedents of these epithelial lined cystic structures are not known, nor is there a known link to ovarian cancer. A mouse model of ovarian endosalpingiosis has been developed by directing a dominant-negative version of the TGF-beta transcription factor, Smad2, to the ovary using the Müllerian-inhibiting substance promoter (MIS-Smad2-dn). Female mice develop an ovarian endosalpingeal phenotype as early as 3 months of age. Importantly, cysts continuous with the ovarian surface epithelial have been identified, indicating that these cyst cells may be derived from the highly plastic ovarian surface epithelial cell layer. A second transgenic mouse model that causes loss of activin action (inhibin alpha-subunit transgenic mice) develops similar cystic structures, supporting a TGF-beta/activin/Smad2 dependence in the onset of this disease.

Activins↗

PubMed2005

The in vitro regulation of ovarian follicle development using alginate-extracellular matrix gels.

The extracellular matrix (ECM) provides a three-dimensional structure that promotes and regulates cell adhesion and provides signals that direct the cellular processes leading to tissue development. In this report, synthetic matrices that present defined ECM components were employed to investigate these signaling effects on tissue formation using ovarian follicle maturation as a model system. In vitro systems for follicle culture are being developed to preserve fertility for women, and cultures were performed to test the hypothesis that the ECM regulates follicle maturation in a manner that is dependent on both the ECM identity and the stage of follicle development. Immature mouse follicles were cultured within alginate-based matrices that were modified with specific ECM components (e.g., laminin) or RGD peptides. The matrix maintains the in vivo like morphology of the follicle and provides an environment that supports follicle development. The ECM components signal the somatic cells of the follicle, affecting their growth and differentiation, and unexpectedly also affect the meiotic competence of the oocyte. These effects depend upon both the identity of the ECM components and the initial stage of the follicle, indicating that the ECM is a dynamic regulator of follicle development. The development of synthetic matrices that promote follicle maturation to produce meiotically competent oocytes may provide a mechanism to preserve fertility, or more generally, provide design principles for scaffold-based approaches to tissue engineering.

Alginates↗