Esther J. Kim

Leukemia inhibitory factor inhibits neuronal terminal differentiation through STAT3 activation

The discovery of stem cells in the adult central nervous system raises questions concerning the neurotrophic factors that regulate postnatal neuronal development. Olfactory receptor neurons (ORNs) are a useful model, because they are capable of robust neurogenesis throughout adulthood. We have investigated the role of leukemia inhibitory factor (LIF) in postnatal neuronal development by using ORNs as a model. LIF is a multifunctional cytokine implicated in various aspects of neuronal development, including phenotype determination, survival, and in response to nerve injury. LIF-deficient mice display significant increases, both in the absolute amount and in the number of cells expressing olfactory marker protein, a marker of mature ORNs. The maturation of ORNs was significantly inhibited by LIF in vitro. LIF activated the STAT3 pathway in ORNs, and transfection of ORNs with a dominant negative form of STAT3 abolished the effect of LIF. These findings demonstrate that LIF negatively regulates ORN maturation via the STAT3 pathway. Thus, LIF plays a critical role in controlling the transition of ORNs to maturity. Consequently, a population of ORNs is maintained in an immature state to facilitate the rapid repopulation of the olfactory epithelium with mature neurons during normal cell turnover or after injury.

Leukemia inhibitory factor promotes olfactory sensory neuronal survival via phosphoinositide 3-kinase pathway activation and Bcl-2

Leukemia inhibitory factor (LIF), a neuropoietic cytokine, has been implicated in the control of neuronal development. We previously reported that LIF plays a critical role in regulating the terminal differentiation of olfactory sensory neurons (OSNs). Here, we demonstrate that LIF plays a complementary role in supporting the survival of immature OSNs. Mature OSNs express LIF, which may be elaborated in a paracrine manner to influence adjacent neurons. LIF null mice display more apoptotic immature neurons than do their wild‐type littermates. LIF treatment of dissociated OSNs in vitro significantly reduces the apoptosis of immature OSNs. Double immunocytochemical analysis indicates that the survival of immature OSNs is dependent on the presence of LIF. LIF activates the phosphoinositide 3‐kinase (PI3K) pathways and induces the expression of the antiapoptotic molecule Bcl‐2 in OSNs, whereas inhibition of the PI3K pathway blocks LIF‐dependent OSN survival and Bcl‐2 induction. Thus, LIF plays a central role in maintaining the size and integrity of the population of immature neurons within the olfactory epithelium; this population is critical to the rapid recovery of olfactory function after injury. LIF may play a similar role elsewhere in the CNS and thus be important for manipulation of stem cell populations for therapeutic interventions.

Combined oral contraceptive use increases HPV persistence but not new HPV detection in a cohort of women from Thailand.

BACKGROUND Women diagnosed with cervical cancer report longer duration and more recent use of combined oral contraceptives (COCs). It is unclear how COC use impacts risk of cervical carcinogenesis. METHODS We estimated the risk of new human papillomavirus (HPV) DNA detection and persistence among 1135 human immunodeficiency virus (HIV)-negative women aged 20-37 years from Thailand who were followed for 18 months at 6-month intervals. Type-specific HPV DNA, demographic information, hormonal contraceptive use, sexual behavior, genital tract coinfection, and Papanicolaou test results were assessed at baseline and each follow-up. RESULTS Women who reported current COC use during follow-up were less likely to clear HPV infection compared with nonusers, independent of sexual behavior, and Papanicolaou test diagnosis (AHR: 0.67 [95% CI: .49-.93]). Similar associations were not observed among women reporting current use of depomedroxyprogesterone acetate (DMPA). Neither COC nor DMPA use was significantly associated with new HPV DNA detection. CONCLUSIONS These data do not support the hypothesis that contraceptive use is associated with cervical cancer risk via increased risk of HPV acquisition. The increased risk of HPV persistence observed among current COC users suggests a possible influence of female sex hormones on host response to HPV infection.

The association of hormonal contraceptive use and HPV prevalence.

Women diagnosed with cervical cancer report longer duration and more recent use of combined oral contraceptives (COCs). It is unclear whether COC use is associated with upstream events of human papillomavirus (HPV) infection prior to development of clinical disease. The objective of our study was to assess the association of contraceptive use on the risk for prevalent HPV infection in a cohort of long‐term hormonal contraceptive (HC) users. One thousand and seventy (n = 1,070) HIV‐negative women aged 20–37 from Thailand enrolled in a prospective study of the natural history of HPV. Baseline HPV genotype information, recency and duration of HC use, sexual behavior, other sexually transmitted infection (STI) information and cervical cytology and histology were assessed. At enrollment, 19.8% and 11.5% of women were infected with any HPV or any high‐risk (HR)‐HPV, respectively. After adjustment for age, current and past sexual risk behaviors, STI history and cytology, the use of COCs for >6 years was found to be associated with an increased risk of infection with any HPV [prevalence ratio (PR): 1.88 (1.21, 2.90)] and any HR‐HPV [PR: 2.68 (1.47, 4.88)] as compared to never users. Recent, long‐term COC use was associated with an increased risk for prevalent HPV infection independent of sexual behavior and cervical abnormalities. No similar association was observed for recent or long duration use of progestin‐only contraceptives (i.e., depomedroxyprogesterone acetate). These data suggest that COC use may impact early upstream events in the natural history of HPV infection.

Leukemia inhibitory factor is a proliferative factor for olfactory sensory neurons.

Neuropoietic cytokines are known to play crucial roles in neuronal development. Among them, leukemia inhibitory factor (LIF) has been implicated in various processes of neuronal development, such as neuronal differentiation, survival and neurogenesis. Moreover, LIF is highly expressed in regions of the central nervous system where adult neurogenesis occurs. LIF was tested for its efficacy in promoting postnatal neurogenesis using LIF-null mice and dissociated cultures of early postnatal rat olfactory sensory neurons. Our results indicate that LIF promoted proliferation of olfactory sensory neuron precursors both in vivo and in vitro. In addition, LIF did not affect proliferation of non-neuronal cells. LIF may therefore be useful when developing stem cell therapy to replace damaged olfactory sensory neurons as well as a therapeutic agent to treat some anosmic symptoms.

Prevalence and correlates of HPV among women attending family-planning clinics in Thailand

BackgroundCervical cancer is the most common cancer among women of reproductive age in Thailand. However, information on the prevalence and correlates of anogenital HPV infection in Thailand is sparse.MethodsHPV genotype information, reproductive factors, sexual behavior, other STI and clinical information, and cervical cytology and histology were assessed at enrollment among one thousand two hundred and fifty-six (n = 1,256) HIV negative women aged 20–37 from Thailand enrolled in a prospective study of the natural history of HPV. The type-specific prevalence of HPV was estimated using cervical swab specimens from healthy women and women with a diagnosis of CIN 2/3 at baseline. Prevalence ratios (95% CI) were estimated using Poisson regression to quantify the association of demographic, behavioral, and clinical correlates with prevalent HPV infection.ResultsOverall, 307 (24.6%) and 175 (14.0%) of women were positive for any HPV type and any HR-HPV type, respectively; the most common types were 72, 52, 62, and 16. Among women diagnosed with CIN 2/3 at enrollment (n = 11), the most prevalent HPV types were 52 and 16. In multivariate analysis, HPV prevalence at enrollment was higher among women with: long-term combined oral contraceptive use, a higher number of lifetime sexual partners, a prior Chlamydia infection, and a current diagnosis of Bacterial Vaginosis.ConclusionThe study findings provide important information that can be used in the evaluation of primary and secondary interventions designed to reduce the burden of cervical cancer in Thailand.

Confirmation and quantitation of human papillomavirus type 52 by Roche Linear Array using HPV52-specific TaqMan E6/E7 quantitative real-time PCR.

Human papillomavirus type 52 is highly prevalent in Asia and Africa and accounts for 2-3% of total cervical cancer burden worldwide. The Roche Molecular Systems HPV Linear Array (RMS-LA uses multiple type (i.e. mixed) probes to detect DNA from HPV 52 infection which limits the assays ability to determine HPV 52 status in the presence of HPV 33, 35, or 58 infection. This report presents a simple to use and highly reproducible HPV 52 type-specific quantitative real-time PCR (RT-PCR) assay based on Taqman chemistry for detection and quantification of HPV 52 DNA from cervical swab specimens. Mixed probe positive cervical swab specimens collected from rural and urban women in Thailand (n=68) were used to determine assay agreement and differences in HPV 52 DNA viral load across cytological diagnosis. Forty-eight specimens were determined to be HPV 52 positive by RMS-LA with 94% (n=45) confirmed positive by Taqman assay (kappa: 0.86, 95% CI: 0.74, 0.99). Higher median viral load was observed among women with a Pap diagnosis of >=ASCUS vs. normal/inflammation (8510 copies/1000 cell equivalents vs. 279 copies/1000 cell equivalents, p<0.05). Accurate ascertainment of infection status is important in understanding HPV 52s role in the etiology of cervical cancer as well as for the development of type-specific vaccines.

Kinetics of DNA load predict HPV 16 viral clearance

INTRODUCTION While high HPV 16 viral load measured at a single time point is associated with cervical disease outcomes, few studies have assessed changes in HPV 16 viral load on viral clearance. OBJECTIVE To measure the association between changes in HPV 16 viral load and viral clearance in a cohort of Thai women infected with HPV 16. STUDY DESIGN Fifty women (n=50) between the ages of 18-35 years enrolled in a prospective cohort study were followed up every three months for two years. Women positive for HPV 16 DNA by multiplex TaqMan assay at two or more study visits were selected for viral load quantitation using a type-specific TaqMan based real-time PCR assay. The strength of the association of change in viral load between two visits and viral clearance at the subsequent visit was assessed using a GEE model for binary outcomes. RESULTS At study entry, HPV 16 viral load did not vary by infection outcome. A >2 log decline in viral load across two study visits was found to be strongly associated with viral clearance (AOR: 5.5, 95% CI: 1.4-21.3). HPV 16 viral load measured at a single time point was not associated with viral clearance. CONCLUSIONS These results demonstrate that repeated measurement of HPV 16 viral load may be a useful predictor in determining the outcome of early endpoints of viral infection.

Simulating complicated human birth for research and training

We report on the design, testing and implementation of a novel birthing simulator developed specifically to research the delivery process and improve clinical training in uncommon but inevitable complicated human births. The simulator consists of a maternal model and an instrumented fetal model, used in conjunction with an existing force-sensing system and a data-acquisition system. The maternal model includes a bony, rotatable pelvis, flexible legs, and a uterine expulsive system. The fetal model, which can be delivered repeatedly through the maternal model, is instrumented with potentiometers to measure neck extension, rotation and flexion during delivery. Simulation of the brachial plexus within the model fetal neck allows measurement of stretch in those nerves at risk for injury during difficult deliveries. Wooden elements mimic the properties of neonatal bone and can break either spontaneously or purposely. Two methods for measuring clinician-applied force during simulated deliveries provide trainees with real-time assessment of their own traction force and allow researchers to correlate fetal neck motion and nerve stretch parameters with clinician-applied traction. Preliminary testing indicates the system is biofidelic for the final stages of the birthing process, and can be used for training and research in obstetrics.