Telomeres and oocyte maturation rate are not reduced by COVID-19 except in severe cases.

In brief: COVID-19 does not affect the telomeres or fertility outcomes in mild cases. However, in women with severe symptoms, telomeres of granulosa cells are shorter, and the oocyte maturation rate is decreased. Abstract: The coronavirus SARS-CoV-2 causes COVID-19 disease and affects primarily the lungs and also other organs, causing accelerated cell aging. One of the main pathways involved in aging is telomere attrition, which ultimately leads to defective tissue regeneration and organ dysfunction. Indeed, short telomeres in aged people aggravate the COVID-19 symptoms, and COVID-19 survivors showed shorter telomeres in blood cells. The SARS-CoV-2 has been detected in testis, but the ovaries, which express the viral entry factors, have not been fully explored. Our objective was to analyze telomeres and reproductive outcomes in women who had COVID-19 and controls. In this prospective cohort study, granulosa cells (GCs) and blood were collected from 65 women. Telomere length (TL) was measured by high-throughput in situ hybridization. Mean TL of GCs and peripheral blood mononuclear cells (PBMCs) was alike in control and mild cases. However, mean TL of GCs was lower in severe cases compared to controls (P = 0.017). Control and COVID groups had similar ovarian reserve and number of total oocytes after puncture. However, the oocyte maturation rate was lower in severe cases (P = 0.018). Interestingly, a positive correlation between the oocyte maturation rate and TL of GCs was found in the control group (P = 0.024). Our findings point to a potential impact of the coronavirus infection on telomeres and reproductive outcomes in severe cases. This might be considered upon possible new SARS-CoV threats, to favor treatments that enhance oocyte maturation in women severely affected by coronavirus undergoing ART.

The cyto-protective effects of LH on ovarian reserve and female fertility during exposure to gonadotoxic alkylating agents in an adult mouse model.

STUDY QUESTION: Does LH protect mouse oocytes and female fertility from alkylating chemotherapy? SUMMARY ANSWER: LH treatment before and during chemotherapy prevents detrimental effects on follicles and reproductive lifespan. WHAT IS KNOWN ALREADY: Chemotherapies can damage the ovary, resulting in premature ovarian failure and reduced fertility in cancer survivors. LH was recently suggested to protect prepubertal mouse follicles from chemotoxic effects of cisplatin treatment. STUDY DESIGN, SIZE, DURATION: This experimental study investigated LH effects on primordial follicles exposed to chemotherapy. Seven-week-old CD-1 female mice were randomly allocated to four experimental groups: Control (n = 13), chemotherapy (ChT, n = 15), ChT+LH-1x (n = 15), and ChT+LH-5x (n = 8). To induce primary ovarian insufficiency (POI), animals in the ChT and ChT+LH groups were intraperitoneally injected with 120 mg/kg of cyclophosphamide and 12 mg/kg of busulfan, while control mice received vehicle. For LH treatment, the ChT+LH-1x and ChT+LH-5x animals received a 1 or 5 IU LH dose, respectively, before chemotherapy, then a second LH injection administered with chemotherapy 24 h later. Then, two animals/group were euthanized at 12 and 24 h to investigate the early ovarian response to LH, while remaining mice were housed for 30 days to evaluate short- and long-term reproductive outcomes. The effects of LH and chemotherapy on growing-stage follicles were analyzed in a parallel experiment. Seven-week-old NOD-SCID female mice were allocated to control (n = 5), ChT (n = 5), and ChT+LH-1x (n = 6) groups. Animals were treated as described above, but maintained for 7 days before reproductive assessment. PARTICIPANTS/MATERIALS, SETTING, METHODS: In the first experiment, follicular damage (phosphorylated H2AX histone (γH2AX) staining and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) assay), apoptotic biomarkers (western blot), and DNA repair pathways (western blot and RT-qPCR) were assessed in ovaries collected at 12 and 24 h to determine early ovarian responses to LH. Thirty days after treatments, remaining mice were stimulated (10 IU of pregnant mare serum gonadotropin (PMSG) and 10 IU of hCG) and mated to collect ovaries, oocytes, and embryos. Histological analysis was performed on ovarian samples to investigate follicular populations and stromal status, and meiotic spindle and chromosome alignment was measured in oocytes by confocal microscopy. Long-term effects were monitored by assessing pregnancy rate and litter size during six consecutive breeding attempts. In the second experiment, mice were stimulated and mated 7 days after treatments and ovaries, oocytes, and embryos were collected. Follicular numbers, follicular protection (DNA damage and apoptosis by H2AX staining and TUNEL assay, respectively), and ovarian stroma were assessed. Oocyte quality was determined by confocal analysis. MAIN RESULTS AND THE ROLE OF CHANCE: LH treatment was sufficient to preserve ovarian reserve and follicular development, avoid atresia, and restore ovulation and meiotic spindle configuration in mature oocytes exposed at the primordial stage. LH improved the cumulative pregnancy rate and litter size in six consecutive breeding rounds, confirming the potential of LH treatment to preserve fertility. This protective effect appeared to be mediated by an enhanced early DNA repair response, via homologous recombination, and generation of anti-apoptotic signals in the ovary a few hours after injury with chemotherapy. This response ameliorated the chemotherapy-induced increase in DNA-damaged oocytes and apoptotic granulosa cells. LH treatment also protected growing follicles from chemotherapy. LH reversed the chemotherapy-induced depletion of primordial and primary follicular subpopulations, reduced oocyte DNA damage and granulosa cell apoptosis, restored mature oocyte cohort size, and improved meiotic spindle properties. LARGE SCALE DATA: N/A. LIMITATIONS, REASONS FOR CAUTION: This was a preliminary study performed with mouse ovarian samples. Therefore, preclinical research with human samples is required for validation. WIDER IMPLICATIONS OF THE FINDINGS: The current study tested if LH could protect the adult mouse ovarian reserve and reproductive lifespan from alkylating chemotherapy. These findings highlight the therapeutic potential of LH as a complementary non-surgical strategy for preserving fertility in female cancer patients. STUDY FUNDING/COMPETING INTEREST(S): This study was supported by grants from the Regional Valencian Ministry of Education (PROMETEO/2018/137), the Spanish Ministry of Science and Innovation (CP19/00141), and the Spanish Ministry of Education, Culture and Sports (FPU16/05264). The authors declare no conflict of interest.

Sildenafil citrate improves perinatal outcome in fetuses from pre-eclamptic rats.

OBJECTIVE: To evaluate perinatal outcome after sildenafil citrate (SC) administration at the onset of pregnancy in a rat pre-eclampsia model. DESIGN: In vivo animal experimental study. SETTING: Fundación IVI-Instituto Universitario IVI, Valencia, Spain. SAMPLE: Control and pre-eclampsia-induced pregnant Wistar rats exposed to chronic SC administration. METHODS: We evaluated the use of SC, which was tested as a potential therapeutic tool to maintain vasodilatation in complicated pregnancies. We have demonstrated previously that SC shows a hypotensive selective effect in normal rat pregnancies when compared with nonpregnant animals. MAIN OUTCOME MEASURES: Maternal blood pressure, weight and mortality during pre- and postnatal development, maternal blood cellularity and haemodynamic changes with maternal and fetal Doppler quantitative indices. RESULTS: SC restores normal values of blood pressure, cell count and proteinuria for maternal syndrome. In offspring, SC improves weight gain and increases survival rates without fetotoxic effects. According to the haemodynamic results, SC has a significant effect on the resistance index in the uterine artery in pre-eclamptic animals, as it restores normal values to correlate with an increase in fetal perfusion through the ductus venosus. CONCLUSIONS: These results suggest that SC administration during pregnancy may have a potential benefit for the treatment of hypertension during pregnancy by reversing the maternal effects of pre-eclampsia and by improving uteroplacental and fetal perfusion.

Toxicidad cutánea asociada a cetuximab en cáncer colorrectal metastásico / Cutaneous Toxicity Associated With Cetuximab Treatment in Metastatic Colorectal Cancer

Objetivo Evaluar la incidencia y el tipo de reacciones cutáneas secundarias al tratamiento con cetuximab y describir el protocolo terapéutico. Método Estudio retrospectivo de seguridad. Se seleccionaron los pacientes que recibieron cetuximab desde enero a diciembre de 2009. Se obtuvo la información consultando bases de datos Access y posterior revisión de historias clínicas. Se registraron los datos en una hoja de cálculo Excel. Para la gradación de la gravedad de la erupción cutánea se siguió la clasificación NCI-CTCAE. Resultados Recibieron tratamiento 43 pacientes. Presentaron erupción acneiforme 30 (69,8%): 14, grado 1 (48,3%); 13, grado 2 (44,8%), y 3, grado 3 (10,3%). La mediana de días hasta aparición de síntomas fue de 7 (4-28). Presentaron xerosis, tras una mediana de 40 (20-56) días, 10 pacientes (23,3%) y 3 (7%) manifestaron fisuras en manos y pies tras 28 (21-35) días. En dos pacientes aparecieron trastornos ungueales (como paroniquia) tras 42 (35-49) días. En cuanto a alteraciones del crecimiento del pelo: hubo dos casos de hipertricosis y un paciente experimentó un gran sobrecrecimiento de las pestañas. Se presentaron conjuntivitis importantes en cinco casos. Tuvieron lugar tres reacciones infusionales. Se aplicó a todos los pacientes un protocolo de tratamiento basado en la gravedad de la toxicidad cutánea. Conclusión El perfil de seguridad de cetuximab concuerda con el descrito en los estudios publicados. Se trata de efectos adversos cutáneos de aparición muy frecuente y de importantes consecuencias relacionadas con la efectividad de la terapia. La información al paciente y detección y tratamiento precoz de la sintomatología según un protocolo consensuado pueden favorecer el buen cumplimiento y el éxito terapéutico (AU)

Objective To evaluate the impact and type of side-effects in patients treated with cetuximab and provide a description of the general measures and treatment. Methods Retrospective safety study. We included all patients that received cetuximab from January to December 2009. All information was obtained from the Pharmacy and Oncology Department's Access databases and reviewed the patient's medical history. All data was registered in an Excel workbook. Skin toxicity was graded by the current National Cancer Institute-Common Toxicity Criteria (NCI-CTC).Results During the study period 43 patients received treatment with cetuximab. Acneiform eruption was present in 30 of the cases (69.8%): 14 patients with grade 1 (48.3%), 13 with grade 2 (44.8%) and 3 with grade 3 (10.3%). These adverse effects appeared in a median of seven (4–28) days. In a median of 40 (20–56) days, ten patients (23.3%) presented xerosis, and three (7%) suffered painful fissures in hands and feet after a median of 28 (21–35) days. Paronychia was present in two patients after a median of 42 (35–49) days. Finally, an alteration in hair growth was observed in two patients with overgrowth of facial hair and one patient with overgrowth of the eyelashes. Five patients presented important conjunctivitis. Three infusion reactions occurred. A grade-based treatment algorithm was used for all patients that presented cutaneous toxicity. Conclusions A considerable number of patients treated with cetuximab develop dermatological side-effects which left untreated could represent a threat to the efficacy of the therapy. Therefore effective management is mandatory, patient education and immediate treatment based on a grade-based algorithm to alleviate symptoms is necessary, so that patient compliance is guaranteed (AU)

[Cutaneous toxicity associated with cetuximab treatment in metastatic colorectal cancer]. / Toxicidad cutánea asociada a cetuximab en cáncer colorrectal metastásico.

OBJECTIVE: To evaluate the impact and type of side-effects in patients treated with cetuximab and provide a description of the general measures and treatment. METHODS: Retrospective safety study. We included all patients that received cetuximab from January to December 2009. All information was obtained from the Pharmacy and Oncology Department's Access databases and reviewed the patient's medical history. All data was registered in an Excel workbook. Skin toxicity was graded by the current National Cancer Institute-Common Toxicity Criteria (NCI-CTC). RESULTS: During the study period 43 patients received treatment with cetuximab. Acneiform eruption was present in 30 of the cases (69.8%): 14 patients with grade 1 (48.3%), 13 with grade 2 (44.8%) and 3 with grade 3 (10.3%). These adverse effects appeared in a median of seven (4-28) days. In a median of 40 (20-56) days, ten patients (23.3%) presented xerosis, and three (7%) suffered painful fissures in hands and feet after a median of 28 (21-35) days. Paronychia was present in two patients after a median of 42 (35-49) days. Finally, an alteration in hair growth was observed in two patients with overgrowth of facial hair and one patient with overgrowth of the eyelashes. Five patients presented important conjunctivitis. Three infusion reactions occurred. A grade-based treatment algorithm was used for all patients that presented cutaneous toxicity. CONCLUSIONS: A considerable number of patients treated with cetuximab develop dermatological side-effects which left untreated could represent a threat to the efficacy of the therapy. Therefore effective management is mandatory, patient education and immediate treatment based on a grade-based algorithm to alleviate symptoms is necessary, so that patient compliance is guaranteed.

Haemodynamic effects of long-term administration of sildenafil in normotensive pregnant and non-pregnant rats.

OBJECTIVE: To determine the effects of chronic administration of sildenafil citrate on healthy pregnant rats. DESIGN: In vivo animal experimental study. SETTING: Fundación IVI-Instituto Universitario IVI, Valencia, Spain. SAMPLE: Pregnant and non-pregnant Wistar rats exposed to chronic administration of sildenafil. METHODS: Placental cross-barrier and feto-maternal relationship levels, maternal blood pressure, and haemodymamic effects on uterine arteries were evaluated. The effect of growth on weight and fetal tissues, and on perinatal outcome, was investigated. MAIN OUTCOME MEASURES: Maternal blood pressure, blood viscosity, vascular indices of uterine arteries and fetal ductus venosus, plasmatic levels of sildenafil, embryo/fetal and litter weights, perinatal/postnatal survival rates. RESULTS: Sildenafil citrate crossed the placenta. The maternal and fetal levels of sildenafil, and its metabolite desmethyl-sildenafil, demonstrated a positive linear correlation in treated pregnant animals versus controls; a selective maternal hypotensive effect without changes in uterine vascular resistance was noted on days E8 and E11 (embryonic day). The lower pulsatility index of the ductus venosus on day E18 suggests fetal overflow at the end of the pregnancy. Effects on offspring were placental and liver enlargement, and increased fetal weight gain in the second half of pregnancy (irrespective of liver enlargement) and at birth. Perinatal and postnatal survival rates in the sildenafil group remained unaltered. No haemodynamic effects were evident in non-pregnant animals. CONCLUSIONS: In normotensive rats, sildenafil appears to have a selective effect at the onset of pregnancy, implying increased fetal blood supply, and increased fetal weight, and placental and liver enlargement, but no increased perinatal mortality.

Ultrasound bioeffects in rats: quantification of cellular damage in the fetal liver after pulsed Doppler imaging.

OBJECTIVE: To determine whether pulsed Doppler examination of the ductus venosus in rat fetuses could damage exposed tissue. METHODS: On gestational day 18, the livers of a mean of approximately five fetuses per mother (n = 5.14, SD = 1.6), in a cohort of 35 pregnant female rats, were exposed individually to pulsed Doppler and these were considered the 'exposed group'. The remaining fetuses in each pregnant rat (n = 5.16, SD = 2.1) formed the 'control group'. We tested for 600, 300, 60, 20, 15, 10 and 3 s of exposure of the fetal ductus venosus and the damage was evaluated measuring a cell death index of apoptotic activity at 7 h post-exposure (n = 16). In addition, subgroups of mothers were sacrificed at 2, 4, 5, 7, 12 and 24 h post-exposure to determine when the damage appeared and disappeared and whether this depended on the exposure time. RESULTS: After exposure of 20 s or more, we observed significant damage, as assessed by caspase 3 activity (a marker of apoptotic activity related to tissue damage), in all cases; after 15 s of exposure, some samples presented damage (P = 0.4); there was no damage after 10 s or 3 s of exposure (P = 0.87 and P = 0.3, respectively). There was a positive linear correlation between apoptotic index and pulsed Doppler exposure time, (Pearson's coefficient = 0.324, P < 0.01). No liver still showed significant damage at 12 or 24 h post-exposure (P > 0.05 and P > 0.4). CONCLUSIONS: We observed reversible damage after pulsed Doppler imaging in an in-vivo fetal liver tissue rat model and found that longer exposure times produced more tissue damage. We established that 10 s was the maximum exposure time to ensure absence of damage to tissue in this model. It would appear sensible to recommend expert supervision of pulsed Doppler imaging and to have intervals between subsequent examinations.

Treatment with sildenafil prevents impairment of learning in rats born to pre-eclamptic mothers.

Pre-eclampsia is an important hypertensive pregnancy disorder and a main cause of maternal and fetal morbidity and mortality. Children born from mothers with pre-eclampsia may present cognitive deficits. The mechanisms leading to this cognitive impairment remain unclear and no treatments to improve it have been tested. Pre-eclampsia is associated with impaired regulation of the nitric oxide-3'-5'guanosine monophosphate cyclic (cGMP) pathway, which modulates some cognitive functions. We hypothesized that alterations in the NO-cGMP pathway would be involved in the mechanisms leading to cognitive impairment in rats born to pre-eclamptic mothers and that treatment with sildenafil, an inhibitor of the phosphodiesterase that degrades cGMP, could restore their cognitive function. To test these hypotheses, we used an animal model of pre-eclampsia in rats: pregnant rats treated with l-nitro-arginine methyl ester, an inhibitor of nitric oxide synthase. Using this model, we assessed: (1) whether rats born to pre-eclamptic mothers show reduced learning ability and/or altered motor activity or coordination when they are 2 months-old; (2) whether cognitive impairment is associated with reduced function of the glutamate-NO-cGMP pathway in brain in vivo; and (3) whether treatment of the mothers with sildenafil prevents this cognitive and motor alterations. The results reported show that the ability to learn a conditional discrimination task in a Y maze is reduced in rats born to pre-eclamptic mothers. This impairment was associated with reduced function of the glutamate-NO-cGMP pathway in brain in vivo, as assessed by microdialysis in freely moving rats. Treatment with sildenafil restores the function of this pathway and learning ability.

Estudio de utilizacion de pemetrexed en el cancer de pulmon no microcitico / Study of use of pemetrexed in non-small cell lung cancer

Objetivo Estudiar la efectividad y la seguridad del pemetrexed en el cancer de pulmon no microcitico. Metodo Estudio retrospectivo (marzo 2006¨Cmayo 2008) de utilizacion de pemetrexed. Se obtuvo la informacion de bases de datos Access de los Servicios de Farmacia y Oncologia, del registro de visitas a consultas externas y de la historia clinica. Los datos se analizaron con SPSS v12.0. Las variables cuantitativas se expresaron con la mediana (minimo-maximo). Resultados Fueron 44 pacientes (61,7 años [39¨C77]) la mayoria hombres (86%), fumadores/exfumadores (80%), histologia epidermoide/escamosa (46%) o adenocarcinoma (36%), con buen estado funcional (86%) y estadio iii o superior al inicio del tratamiento con pemetrexed (93%). El tratamiento previo con taxanos y este junto con la neutropenia previa fueron los criterios de cambio a pemetrexed en el 34,4 y el 22,7% de los pacientes, respectivamente. Ningun paciente presento respuesta completa o parcial; el 18,2% mostro enfermedad estable y el 81,8% progresion de la enfermedad, siendo los principales motivos de retirada del pemetrexed la progresion de la enfermedad (54,5%) y el empeoramiento clinico (15,9%). La mediana de supervivencia desde el inicio de la quimioterapia fue de 22,2 meses (16¨C28,4) y desde el inicio con pemetrexed fue de 7,8 meses (4,4¨C11,2), siendo esta significativamente mayor en las mujeres y de aquellos con valor 0-1 en la escala Eastern Cooperative Oncology Group. Los efectos adversos mas frecuentes fueron astenia y neurotoxicidad. Conclusion Pemetrexed se ha utilizado en todos los casos como segunda linea o superior con buen perfil de seguridad. En ningun caso se alcano respuesta completa o parcial, pero la supervivencia desde el inicio de pemetrexed iguala o supera a la de otros estudios (AU)

Objective To study the effectiveness and safety of pemetrexed in non-small cell lung cancer. Method Retrospective study (March 2006¨CMay 2008) of pemetrexed use. Information was obtained from the Access database belonging to the Pharmacy and Oncology Departments, the registry of external consultations and clinical histories. Data were analysed using SPSS software version 12.0. Quantitative variables are expressed as the median (minimum-maximum).Results The study included 44 patients (61.7 [39¨C77] years old), mostly male (86%), smokers or former smokers (80%) with predominantly epidermoid/squamous disease (46%) or adenocarcinoma, in a good functional state (86%) and in stage ¡ÝIII upon beginning pemetrexed treatment (93%). Prior treatment with taxanes and taxane treatment along with a prior history of neutropoenia were the criteria for changing to pemetrexed in 34.4% and 22.7% of the patients, respectively. None of the patients presented a complete or partial response: 18.2% showed disease stability and 81.8% showed disease progression. The main reasons for discontinuing pemetrexed were progression of the disease (54.5%) and worsening of symptoms (15.9%). Median survival after beginning chemotherapy was 22.2 months (ranging from 16¨C28.4) and 7.8 months (4.4¨C11.2) after beginning pemetrexed treatment. These last figures were significantly higher in women and those with an ECOG of 0 to 1. The most common adverse effects were weakness and neurotoxicity. Conclusion In each of the cases, pemetrexed was used as a second-line treatment or higher with a good safety profile. A complete or partial response was not reached in any of the cases, but survival after beginning pemetrexed was equal to or longer than that achieved in other studies (AU)

[Study of use of pemetrexed in non-small cell lung cancer]. / Estudio de utilización de pemetrexed en el cáncer de pulmón no microcítico.

OBJECTIVE: To study the effectiveness and safety of pemetrexed in non-small cell lung cancer. METHOD: Retrospective study (March 2006-May 2008) of pemetrexed use. Information was obtained from the Access database belonging to the Pharmacy and Oncology Departments, the registry of external consultations and clinical histories. Data were analysed using SPSS software version 12.0. Quantitative variables are expressed as the median (minimum-maximum). RESULTS: The study included 44 patients (61.7 [39-77] years old), mostly male (86%), smokers or former smokers (80%) with predominantly epidermoid/squamous disease (46%) or adenocarcinoma, in a good functional state (86%) and in stage > or =III upon beginning pemetrexed treatment (93%). Prior treatment with taxanes and taxane treatment along with a prior history of neutropoenia were the criteria for changing to pemetrexed in 34.4% and 22.7% of the patients, respectively. None of the patients presented a complete or partial response: 18.2% showed disease stability and 81.8% showed disease progression. The main reasons for discontinuing pemetrexed were progression of the disease (54.5%) and worsening of symptoms (15.9%). Median survival after beginning chemotherapy was 22.2 months (ranging from 16-28.4) and 7.8 months (4.4-11.2) after beginning pemetrexed treatment. These last figures were significantly higher in women and those with an ECOG of 0 to 1. The most common adverse effects were weakness and neurotoxicity. CONCLUSION: In each of the cases, pemetrexed was used as a second-line treatment or higher with a good safety profile. A complete or partial response was not reached in any of the cases, but survival after beginning pemetrexed was equal to or longer than that achieved in other studies.

cGMP modulates stem cells differentiation to neurons in brain in vivo.

During brain development neural stem cells may differentiate to neurons or to other cell types. The aim of this work was to assess the role of cGMP (cyclic GMP) in the modulation of differentiation of neural stem cells to neurons or non-neuronal cells. cGMP in brain of fetuses was reduced to 46% of controls by treating pregnant rats with nitroarginine-methylester (L-NAME) and was restored by co-treatment with sildenafil.Reducing cGMP during brain development leads to reduced differentiation of stem cells to neurons and increased differentiation to non-neuronal cells. The number of neurons in the prefrontal cortex originated from stem cells proliferating on gestational day 14 was 715+/-14/mm(2) in control rats and was reduced to 440+/-29/mm(2) (61% of control) in rats treated with L-NAME. In rats exposed to L-NAME plus sildenafil, differentiation to neurons was completely normalized, reaching 683+/-11 neurons/mm(2). In rats exposed to sildenafil alone the number of cells labelled with bromodeoxyuridine (BrdU) and NeuN was 841+/-16/mm(2). In prefrontal cortex of control rats 48% of the neural stem cells proliferating in gestational day 14 differentiate to neurons, but only 24% in rats exposed to L-NAME. This was corrected by sildenafil, 40% of cells differentiate to neurons. Similar results were obtained for neurons proliferating during all developmental period. Treatment with L-NAME did not reduce the total number of cells labelled with BrdU, further supporting that L-NAME reduces selectively the differentiation of stem cells to neurons. Similar results were obtained in hippocampus. Treatment with L-NAME reduced the differentiation of neural stem cells to neurons, although the effect was milder than in prefrontal cortex. These results support that cGMP modulates the fate of neural stem cells in brain in vivo and suggest that high cGMP levels promote its differentiation to neurons while reduced cGMP levels promote differentiation to non-neuronal cells.