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Lohengrin A Cavieres - One of the best experts on this subject based on the ideXlab platform.
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the effects of foundation species on community assembly a global study on alpine Cushion plant communities
Ecology, 2015Co-Authors: Zaal Kikvidze, Lohengrin A Cavieres, Robin W Brooker, Bradley J Butterfield, Ragan M Callaway, Bradley J Cook, Christopher J Lortie, Richard Michalet, Francisco I Pugnaire, Sa XiaoAbstract:Foundation species can change plant community structure by modulating important ecological processes such as community assembly, yet this topic is poorly understood. In alpine systems, Cushion plants commonly act as foundation species by ameliorating local conditions. Here, we analyze diversity patterns of species' assembly within Cushions and in adjacent surrounding open substrates (83 sites across five continents) calculating floristic dissimilarity between replicate plots, and using linear models to analyze relationships between microhabitats and species diversity. Floristic dissimilarity did not change across biogeographic regions, but was consistently lower in the Cushions than in the open microhabitat. Cushion plants appear to enable recruitment of many relatively stress-intolerant species that otherwise would not establish in these communities, yet the niche space constructed by Cushion plants supports a more homogeneous composition of species than the niche space beyond the Cushion's influence. As a result, Cushion plants support higher α-diversity and a larger species pool, but harbor assemblies with lower β-diversity than open microhabitats. We conclude that habitats with and without dominant foundation species can strongly differ in the processes that drive species recruitment, and thus the relationship between local and regional species diversity.
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the best for the guest high andean nurse Cushions of azorella madreporica enhance arbuscular mycorrhizal status in associated plant species
Mycorrhiza, 2011Co-Authors: Angelica M Casanovakatny, Gustavo Torresmellado, Goetz Palfner, Lohengrin A CavieresAbstract:Positive interactions between Cushion plant and associated plants species in the high Andes of central Chile should also include the effects of fungal root symbionts. We hypothesized that higher colonization by arbuscular mycorrhizal (AM) fungi exists in Cushion-associated (nursling) plants compared with conspecific individuals growing on bare ground. We assessed the AM status of Andean plants at two sites at different altitudes (3,200 and 3,600 m a.s.l.) in 23 species, particularly in Cushions of Azorella madreporica and five associated plants; additionally, AM fungal spores were retrieved from soil outside and beneath Cushions. 18 of the 23 examined plant species presented diagnostic structures of arbuscular mycorrhiza; most of them were also colonized by dark-septate endophytes. Mycorrhization of A. madreporica Cushions showed differences between both sites (68% and 32%, respectively). In the native species Hordeum comosum, Nastanthus agglomeratus, and Phacelia secunda associated to A. madreporica, mycorrhization was six times higher than in the same species growing dispersed on bare ground at 3,600 m a.s.l., but mycorrhiza development was less Cushion dependent in the alien plants Cerastium arvense and Taraxacum officinale at both sites. The ratio of AM fungal spores beneath versus outside Cushions was also 6:1. The common and abundant presence of AM in Cushion communities at high altitudes emphasizes the importance of the fungal root symbionts in such situations where plant species benefit from the microclimatic conditions generated by the Cushion and also from well-developed mycorrhizal networks.
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positive associations between the Cushion plant arenaria polytrichoides caryophyllaceae and other alpine plant species increase with altitude in the sino himalayas
Journal of Vegetation Science, 2010Co-Authors: Yang Yang, Lohengrin A Cavieres, Yang Niu, Hang SunAbstract:Question: Does the facilitative effect of Cushion plants increase with elevation as a result of increases in environmental harshness? Does this hypothesis apply in the Sino-Himalayan Mountains? Location: Lakaka Pass on the Baima Snow Mountains (28°20′N, 99°05′E), SW China. Methods: We evaluated the spatial association of several plant species with the Cushion plant Arenaria polytrichoides (Caryophyllaceae) at two elevations (4500 m and 4700 m) in the study site and monitored temperature, moisture and nutritional status of soil beneath and outside the Cushions. Results: While 14 species grow more frequently associated with the Cushions at the higher elevation, at the lower site only three species were positively associated with Cushions. Eleven of the species that occurred at both elevations changed their spatial association from neutral or negative with Cushions at the lower site to positive at the higher elevation site. Substrate temperatures were rather similar between the Cushions and areas of bare ground. Cushions maintained higher moisture than areas of bare ground at both elevations. Soils beneath Cushions contained significantly more available nitrogen and potassium compared to open areas at the higher elevation. Conclusions: Our results show that facilitation by A. polytrichoides Cushions increases with elevation in the Sino-Himalayan region. This facilitation effect of A. polytrichoides Cushions is probably due to the improved nutrient availability provided by Cushion plants in the higher elevation, and these conditions probably permit increased plant recruitment, growth and survival.
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microclimatic modifications of Cushion plants and their consequences for seedling survival of native and non native herbaceous species in the high andes of central chile
Arctic Antarctic and Alpine Research, 2007Co-Authors: Lohengrin A Cavieres, Ernesto I Badano, Angela Sierraalmeida, Marco A MolinamontenegroAbstract:Cushion plants are one of the most common growth forms in alpine habitats. Their low stature, dense canopy, and compact form allow them to decouple their microclimate from the surrounding environment, mitigating the effect of low temperatures and drought, enhancing the survival of other species. In this study, we evaluated the modifications on soil temperature and moisture over an entire growing season by two Cushion species (Laretia acaulis and Azorella monantha) in alpine communities located at two different elevations in the central Chilean Andes. Additionally, w ep erformed seedling survival experiments with two native herbaceous species (Hordeum comosum and Erigeron andicola) and the non-native forb Cerastium arvense to assess if seedling survival is higher within Cushions than outside them. Our results indicated that Cushions ameliorated extreme low and high substrate temperatures, improved soil moisture, and enhanced seedling survival of the three herbaceous plant species evaluated. Our results suggest that microclimatic modifications associated with Cushion plant sc ould be important for the establishment and survival of other plant species, both native and non-native, in the high alpine communities of central Chile.
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assessing impacts of ecosystem engineers on community organization a general approach illustrated by effects of a high andean Cushion plant
Oikos, 2006Co-Authors: Ernesto I Badano, Clive G. Jones, Lohengrin A Cavieres, Justin P. WrightAbstract:Badano, E. I., Jones, C. G., Cavieres, L. A. and Wright, J. P. 2006. Assessing impacts of ecosystem engineers on community organization: a general approach illustrated by effects of a high-Andean Cushion plant. � Oikos 115: 369 � 385. Comparative and integrative tools are of fundamental value in ecology for understanding outcomes of biological processes, and making generalizations and predictions. Although ecosystem engineering has been shown to play a fundamental role in community organization, there are no standardized methods to measure such effects. We present a framework and methodology for assessing the impact of physical ecosystem engineers on three general features of community organization: (1) species richness and composition, (2) stability of richness over time, and (3) dominance patterns of species assemblages. We then apply the framework and methodology to assess the effects of the Cushion plant Azorella monantha on high-Andean plant communities on two mountaintops. Substrate temperatures, soil moisture and the availability of mineral nutrient resources were compared between A. monantha and surrounding open areas to ascertain whether Cushions altered abiotic environmental conditions, while community analysis assessed changes in species richness, composition and abundances at patch and landscape levels. Cushions thermally buffered temperature extremes and increased soil moisture, but had no detectable effect on soil mineral nutrients. Cushion habitat was not more species rich than surrounding areas, but Cushions added new species into the community, altering species composition and markedly enhancing landscape-level richness. Cushions also showed potential for stabilizing species richness over time, and changed patterns of species dominance. Findings were consistent across mountaintops. We evaluate the general utility of the framework and call for its application in other systems as a means to generate comparative data sets for assessing the general effects of ecosystem engineers on community organization.
David M. Brienza - One of the best experts on this subject based on the ideXlab platform.
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a randomized clinical trial on preventing pressure ulcers with wheelchair seat Cushions
Journal of the American Geriatrics Society, 2010Co-Authors: David M. Brienza, Mary Jo Geyer, Sheryl F Kelsey, Patricia Karg, Anna Allegretti, Marian B Olson, Mark R Schmeler, Jeanne M Zanca, Marybeth Kusturiss, Margo B HolmAbstract:OBJECTIVES: To determine the efficacy of skin protection wheelchair seat Cushions in preventing pressure ulcers in the elderly nursing home population. DESIGN: Clinical trial with participants assigned at random to a skin protection or segmented foam Cushion. Two hundred thirty-two participants were recruited between June 2004 and May 2008 and followed for 6 months or until pressure ulcer incidence. SETTING: Twelve nursing homes. PARTICIPANTS: Nursing home residents aged 65 and older who were using wheelchairs for 6 or more hours per day and had a Braden score of 18 or less and a combined Braden activity and mobility score of 5 or less. Participants were recruited from a referred sample. INTERVENTION: All participants were provided with a fitted wheelchair and randomized into skin protection (SPC, n=113) or segmented foam (SFC, n=119) Cushion groups. The SPC group received an air, viscous fluid and foam, or gel and foam Cushion. The SFC group received a 7.6-cm crosscut foam Cushion. MEASUREMENTS: Pressure ulcer incidence over 6 months for wounds near the ischial tuberosities (IT ulcers) were measured. Secondary analysis was performed on combined IT ulcers and ulcers over the sacrum and coccyx (sacral ulcers). RESULTS: One hundred eighty participants reached a study end point, and 42 were lost to follow-up. Ten did not receive the intervention. There were eight (6.7%) IT ulcers in the SFC group and one (0.9%) in the SPC group (P=.04). There were 21 (17.6%) combined IT and sacral ulcers in the SFC group and 12 (10.6%) in the SPC group (P=.14). CONCLUSION: Skin protection Cushions used with fitted wheelchairs lower pressure ulcer incidence for elderly nursing home residents and should be used to help prevent pressure ulcers.
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the relationship between pressure ulcer incidence and buttock seat Cushion interface pressure in at risk elderly wheelchair users
Archives of Physical Medicine and Rehabilitation, 2001Co-Authors: David M. Brienza, Mary Jo Geyer, Sheryl F Kelsey, Patricia Karg, Elaine TreflerAbstract:Abstract Brienza DM, Karg PE, Geyer MJ, Kelsey S, Trefler E. The relationship between pressure ulcer incidence and buttock-seat Cushion interface pressure in at-risk elderly wheelchair users. Arch Phys Med Rehabil 2001;82:529-33. Objective: To investigate the relation between pressure ulcer incidence and buttock-wheelchair seat Cushion interface pressure measurements. Design: Secondary analysis of data from a randomized clinical trial. Setting: Skilled nursing facility. Patients: Thirty-two elderly patients (age, ≥ 65yr), with Braden score ≤ 18 and Braden mobility and activity subscale score ≤ 5, who used wheelchairs ≥ 6hr/d, were free of existing sitting-induced pressure ulcers, and weighed ≤ 250lb. Interventions: Generic foam seat Cushion or pressure-reducing seat Cushion. Main Outcome Measures: The incidence of sitting-induced pressure ulcers over a 1- to 12-month period was compared with pressure measured between patients' buttocks and wheelchair seat Cushions. A flexible pad with a 15 × 15 pressure sensor array was used to measure interface pressure. Results: Interface pressure measured on wheelchair seat Cushions was higher ( p ≤.01 for both peak pressure and average of highest 4 pressures) for patients who developed sitting-acquired pressure ulcers compared with those patients who did not. Conclusions: Results indicated that higher interface pressure measurements are associated with a higher incidence of sitting-acquired pressure ulcers for high-risk elderly people who use wheelchairs. © 2001 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation
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seat Cushion optimization a comparison of interface pressure and tissue stiffness characteristics for spinal cord injured and elderly patients
Archives of Physical Medicine and Rehabilitation, 1998Co-Authors: David M. Brienza, Patricia KargAbstract:Abstract Objective: A method for designing tissue deformation minimizing seat surfaces was evaluated. Pressure and stiffness criteria were used to optimize surface shape. The method's efficacy for patients with spinal cord injuries (SCI) and a comparison of Cushion performance and interface characteristics with a group of 30 elderly patients are presented. Design: Repeated measures, prospective study. Setting: University medical center. Patients: SCI( n = 12), elderly (age 65+ years) ( n = 30). Interventions: One flat and two custom foam seat Cushions. Main Outcome Measures: Interface pressure measured using a pressure sensing pad; tissue stiffness and pressure recorded on a rigid programmable seat surface. Results: Pressure distributions on contoured Cushions for the SCI group contained lower values than distributions on flat Cushions. A comparison of the pressure data between the elderly and SCI showed that significant differences exist between interface characteristics. The SCI group had higher peak interface pressures for all Cushions tested. Tissue stiffness measurements were similar for each group. Conclusions: Results showed improved effectiveness of custom contoured foam seat Cushions versus flat foam Cushions. The results suggest that pressure distributions for SCI are more sensitive to support Cushion characteristics than for the elderly. Further research is needed to determine the extent of the difference between the populations represented by these groups.
Patricia Karg - One of the best experts on this subject based on the ideXlab platform.
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a randomized clinical trial on preventing pressure ulcers with wheelchair seat Cushions
Journal of the American Geriatrics Society, 2010Co-Authors: David M. Brienza, Mary Jo Geyer, Sheryl F Kelsey, Patricia Karg, Anna Allegretti, Marian B Olson, Mark R Schmeler, Jeanne M Zanca, Marybeth Kusturiss, Margo B HolmAbstract:OBJECTIVES: To determine the efficacy of skin protection wheelchair seat Cushions in preventing pressure ulcers in the elderly nursing home population. DESIGN: Clinical trial with participants assigned at random to a skin protection or segmented foam Cushion. Two hundred thirty-two participants were recruited between June 2004 and May 2008 and followed for 6 months or until pressure ulcer incidence. SETTING: Twelve nursing homes. PARTICIPANTS: Nursing home residents aged 65 and older who were using wheelchairs for 6 or more hours per day and had a Braden score of 18 or less and a combined Braden activity and mobility score of 5 or less. Participants were recruited from a referred sample. INTERVENTION: All participants were provided with a fitted wheelchair and randomized into skin protection (SPC, n=113) or segmented foam (SFC, n=119) Cushion groups. The SPC group received an air, viscous fluid and foam, or gel and foam Cushion. The SFC group received a 7.6-cm crosscut foam Cushion. MEASUREMENTS: Pressure ulcer incidence over 6 months for wounds near the ischial tuberosities (IT ulcers) were measured. Secondary analysis was performed on combined IT ulcers and ulcers over the sacrum and coccyx (sacral ulcers). RESULTS: One hundred eighty participants reached a study end point, and 42 were lost to follow-up. Ten did not receive the intervention. There were eight (6.7%) IT ulcers in the SFC group and one (0.9%) in the SPC group (P=.04). There were 21 (17.6%) combined IT and sacral ulcers in the SFC group and 12 (10.6%) in the SPC group (P=.14). CONCLUSION: Skin protection Cushions used with fitted wheelchairs lower pressure ulcer incidence for elderly nursing home residents and should be used to help prevent pressure ulcers.
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the relationship between pressure ulcer incidence and buttock seat Cushion interface pressure in at risk elderly wheelchair users
Archives of Physical Medicine and Rehabilitation, 2001Co-Authors: David M. Brienza, Mary Jo Geyer, Sheryl F Kelsey, Patricia Karg, Elaine TreflerAbstract:Abstract Brienza DM, Karg PE, Geyer MJ, Kelsey S, Trefler E. The relationship between pressure ulcer incidence and buttock-seat Cushion interface pressure in at-risk elderly wheelchair users. Arch Phys Med Rehabil 2001;82:529-33. Objective: To investigate the relation between pressure ulcer incidence and buttock-wheelchair seat Cushion interface pressure measurements. Design: Secondary analysis of data from a randomized clinical trial. Setting: Skilled nursing facility. Patients: Thirty-two elderly patients (age, ≥ 65yr), with Braden score ≤ 18 and Braden mobility and activity subscale score ≤ 5, who used wheelchairs ≥ 6hr/d, were free of existing sitting-induced pressure ulcers, and weighed ≤ 250lb. Interventions: Generic foam seat Cushion or pressure-reducing seat Cushion. Main Outcome Measures: The incidence of sitting-induced pressure ulcers over a 1- to 12-month period was compared with pressure measured between patients' buttocks and wheelchair seat Cushions. A flexible pad with a 15 × 15 pressure sensor array was used to measure interface pressure. Results: Interface pressure measured on wheelchair seat Cushions was higher ( p ≤.01 for both peak pressure and average of highest 4 pressures) for patients who developed sitting-acquired pressure ulcers compared with those patients who did not. Conclusions: Results indicated that higher interface pressure measurements are associated with a higher incidence of sitting-acquired pressure ulcers for high-risk elderly people who use wheelchairs. © 2001 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation
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seat Cushion optimization a comparison of interface pressure and tissue stiffness characteristics for spinal cord injured and elderly patients
Archives of Physical Medicine and Rehabilitation, 1998Co-Authors: David M. Brienza, Patricia KargAbstract:Abstract Objective: A method for designing tissue deformation minimizing seat surfaces was evaluated. Pressure and stiffness criteria were used to optimize surface shape. The method's efficacy for patients with spinal cord injuries (SCI) and a comparison of Cushion performance and interface characteristics with a group of 30 elderly patients are presented. Design: Repeated measures, prospective study. Setting: University medical center. Patients: SCI( n = 12), elderly (age 65+ years) ( n = 30). Interventions: One flat and two custom foam seat Cushions. Main Outcome Measures: Interface pressure measured using a pressure sensing pad; tissue stiffness and pressure recorded on a rigid programmable seat surface. Results: Pressure distributions on contoured Cushions for the SCI group contained lower values than distributions on flat Cushions. A comparison of the pressure data between the elderly and SCI showed that significant differences exist between interface characteristics. The SCI group had higher peak interface pressures for all Cushions tested. Tissue stiffness measurements were similar for each group. Conclusions: Results showed improved effectiveness of custom contoured foam seat Cushions versus flat foam Cushions. The results suggest that pressure distributions for SCI are more sensitive to support Cushion characteristics than for the elderly. Further research is needed to determine the extent of the difference between the populations represented by these groups.
Hang Sun - One of the best experts on this subject based on the ideXlab platform.
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the positive effects of the alpine Cushion plant arenaria polytrichoides on insect dynamics are determined by both physical and biotic factors
Science of The Total Environment, 2021Co-Authors: Jianguo Chen, Yazhou Zhang, Hongrui Zhang, Christian Schob, Songwei Wang, Shuai Chang, Hang SunAbstract:Abstract Cushion plants' significant role for alpine biodiversity has been demonstrated in particular through their positive effects on plant diversity. However, their effects on higher trophic levels (e.g. insects) remain largely unclear. In this study, by field sampling in the Hengduan Mountains (HDM) in southwestern China, we evaluated the effects of an alpine gynodioecious Cushion species, Arenaria polytrichoides (Carophyllaceae), on insect richness, abundance and population dynamics at two different elevations (4427 m vs. 4732 m) separately at two time periods (day vs. night) and in two growing seasons (early vs. late). The results showed that the total insect diversity decreases from low to high elevation sites. Some insect species were exclusively detected within A. polytrichoides Cushions, leading to an increase in local insect richness from 7% to 35%. The positive effects of Cushions on insect diversity could be attributed to unique biotic properties provided by Cushions. Firstly, the effects were determined by the sexual dimorphism of the Cushion with hermaphroditic Cushions supporting higher insect diversity than female Cushions. This could be because hermaphroditic Cushions provide more resources, such as nectar and pollen grains, for insects than female Cushions. Secondly, the Cushions' associated beneficiary plants can also provide extra resources for attracting more insects, but this effect was mediated by the micro-environmental conditions. Finally, the magnitude of Cushions' positive effects on insect dynamics were stronger under higher than under lower environmental stress. This study confirmed that facilitation by A. polytrichoides Cushions in HDM plays an important role in constructing the alpine insect community and further regulating its dynamics. Moreover, the positive effects of Cushions on insect dynamics increase with increasing environmental stress. Therefore, the distribution range of insects would quite possibly be expanded into higher elevation under future climate changes, which will induce new challenges for the local alpine ecosystems.
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positive associations between the Cushion plant arenaria polytrichoides caryophyllaceae and other alpine plant species increase with altitude in the sino himalayas
Journal of Vegetation Science, 2010Co-Authors: Yang Yang, Lohengrin A Cavieres, Yang Niu, Hang SunAbstract:Question: Does the facilitative effect of Cushion plants increase with elevation as a result of increases in environmental harshness? Does this hypothesis apply in the Sino-Himalayan Mountains? Location: Lakaka Pass on the Baima Snow Mountains (28°20′N, 99°05′E), SW China. Methods: We evaluated the spatial association of several plant species with the Cushion plant Arenaria polytrichoides (Caryophyllaceae) at two elevations (4500 m and 4700 m) in the study site and monitored temperature, moisture and nutritional status of soil beneath and outside the Cushions. Results: While 14 species grow more frequently associated with the Cushions at the higher elevation, at the lower site only three species were positively associated with Cushions. Eleven of the species that occurred at both elevations changed their spatial association from neutral or negative with Cushions at the lower site to positive at the higher elevation site. Substrate temperatures were rather similar between the Cushions and areas of bare ground. Cushions maintained higher moisture than areas of bare ground at both elevations. Soils beneath Cushions contained significantly more available nitrogen and potassium compared to open areas at the higher elevation. Conclusions: Our results show that facilitation by A. polytrichoides Cushions increases with elevation in the Sino-Himalayan region. This facilitation effect of A. polytrichoides Cushions is probably due to the improved nutrient availability provided by Cushion plants in the higher elevation, and these conditions probably permit increased plant recruitment, growth and survival.
Bin Zhou - One of the best experts on this subject based on the ideXlab platform.
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myocardial β catenin bmp2 signaling promotes mesenchymal cell proliferation during endocardial Cushion formation
Journal of Molecular and Cellular Cardiology, 2018Co-Authors: Bin Zhou, Yidong Wang, Dario F Riascosbernal, Nicholas E S Sibinga, Tomas Valenta, Konrad BaslerAbstract:Abnormal endocardial Cushion formation is a major cause of congenital heart valve disease, which is a common birth defect with significant morbidity and mortality. Although β-catenin and BMP2 are two well-known regulators of endocardial Cushion formation, their interaction in this process is largely unknown. Here, we report that deletion of β-catenin in myocardium results in formation of hypoplastic endocardial Cushions accompanying a decrease of mesenchymal cell proliferation. Loss of β-catenin reduced Bmp2 expression in myocardium and SMAD signaling in Cushion mesenchyme. Exogenous BMP2 recombinant proteins fully rescued the proliferation defect of mesenchymal cells in cultured heart explants from myocardial β-catenin knockout embryos. Using a canonical WNT signaling reporter mouse line, we showed that Cushion myocardium exhibited high WNT/β-catenin activities during endocardial Cushion growth. Selective disruption of the signaling function of β-catenin resulted in a Cushion growth defect similar to that caused by the complete loss of β-catenin. Together, these observations demonstrate that myocardial β-catenin signaling function promotes mesenchymal cell proliferation and endocardial Cushion expansion through inducing BMP signaling.
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bmp2 expression in the endocardial lineage is required for av endocardial Cushion maturation and remodeling
Developmental Biology, 2017Co-Authors: Jacob G Saxon, Bin Zhou, Daniel R Baer, Julie A Barton, Travis Hawkins, Thomas C Trusk, S E Harris, Yuji MishinaAbstract:Distal outgrowth, maturation and remodeling of the endocardial Cushion mesenchyme in the atrioventricular (AV) canal are the essential morphogenetic events during four-chambered heart formation. Mesenchymalized AV endocardial Cushions give rise to the AV valves and the membranous ventricular septum (VS). Failure of these processes results in several human congenital heart defects. Despite this clinical relevance, the mechanisms governing how mesenchymalized AV endocardial Cushions mature and remodel into the membranous VS and AV valves have only begun to be elucidated. The role of BMP signaling in the myocardial and secondary heart forming lineage has been well studied; however, little is known about the role of BMP2 expression in the endocardial lineage. To fill this knowledge gap, we generated Bmp2 endocardial lineage-specific conditional knockouts (referred to as Bmp2 cKOEndo) by crossing conditionally-targeted Bmp2flox/flox mice with a Cre-driver line, Nfatc1Cre, wherein Cre-mediated recombination was restricted to the endocardial cells and their mesenchymal progeny. Bmp2 cKOEndo mouse embryos did not exhibit failure or delay in the initial AV endocardial Cushion formation at embryonic day (ED) 9.5-11.5; however, significant reductions in AV Cushion size were detected in Bmp2 cKOEndo mouse embryos when compared to control embryos at ED13.5 and ED16.5. Moreover, deletion of Bmp2 from the endocardial lineage consistently resulted in membranous ventricular septal defects (VSDs), and mitral valve deficiencies, as evidenced by the absence of stratification of mitral valves at birth. Muscular VSDs were not found in Bmp2 cKOEndo mouse hearts. To understand the underlying morphogenetic mechanisms leading to a decrease in Cushion size, cell proliferation and cell death were examined for AV endocardial Cushions. Phospho-histone H3 analyses for cell proliferation and TUNEL assays for apoptotic cell death did not reveal significant differences between control and Bmp2 cKOEndo in AV endocardial Cushions. However, mRNA expression of the extracellular matrix components, versican, Has2, collagen 9a1, and periostin was significantly reduced in Bmp2 cKOEndo AV Cushions. Expression of transcription factors implicated in the cardiac valvulogenesis, Snail2, Twist1 and Sox9, was also significantly reduced in Bmp2 cKOEndo AV Cushions. These data provide evidence that BMP2 expression in the endocardial lineage is essential for the distal outgrowth, maturation and remodeling of AV endocardial Cushions into the normal membranous VS and the stratified AV valves.
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the role of cell autonomous signaling by bmp in endocardial Cushion cells in av valvuloseptal morphogenesis
2016Co-Authors: Yukiko Sugi, Yuji Mishina, Bin Zhou, Kei Inai, Jessica L. BurnsideAbstract:Distal outgrowth and fusion of the mesenchymalized AV endocardial Cushions are essential morphogenetic events in AV valvuloseptal morphogenesis. BMP-2 myocardial conditional knockout (cKO) mice die early by embryonic day (ED) 10.5 [1], hampering investigation of the role of BMP-2 in AV valvuloseptal morphogenesis after this stage. In our previous study, we localized BMP-2 and type I BMP receptors, BMPR1A and Alk2, in AV endocardial Cushions [2, 3]. Based on their expression patterns, we hypothesize that autocrine signaling by BMP-2 within mesenchymalized AV Cushions plays a critical role during AV valvuloseptal morphogenesis. To test this hypothesis, we employed recently generated endocardial/endocardial Cushion-specific cre-driver line Nfact1 Cre . Unlike a previously generated Nfatc1 enCre line whose cre-mediated recombination is restricted to AV and OT endocardium, this Nfatc1 Cre line confers cre-mediated recombination within the endocardial cells as well as their mesenchymal progeny. Using the Nfactc1 Cre driver line, we disrupted BMPR1A (Alk3) and BMP-2 specifically from AV endocardium and endocardial Cushions. BMPR1A endocardial Cushion cKO (cKO Endo ) mouse embryos died by ED 12.5 and exhibited failure of cellularization of AV Cushions (Fig. 22.1a–c) and disruption of extracellular matrix (ECM) protein deposition in the Cushion mesenchyme. On the other hand, AV Cushion formation occurred in the BMP-2 cKO Endo mice that survived beyond the AV Cushion formation stage because BMP-2 expression remained intact in the AV myocardium during AV Cushion formation. BMP-2 cKO Endo mice exhibited perimembranous ventricular septal defects (VSDs) (Fig. 22.1d, e), defective deposition of ECMs in the membranous septum, and AV mitral valve dysplasia, suggesting the cell autonomous requirement of BMP-2 in AV endocardial Cushions. BMP-2 cKO Endo did not exhibit muscular VSDs. These data strongly support our hypothesis that cell autonomous signaling by BMP-2 in the endocardial lineage plays a significant role in mesenchymalized AV Cushions during AV valvuloseptal morphogenesis.
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nfatc1 directs the endocardial progenitor cells to make heart valve primordium
Trends in Cardiovascular Medicine, 2013Co-Authors: Scott H Baldwin, Bin ZhouAbstract:Heart valves arise from the cardiac endocardial Cushions located at the atrioventricular canal (AVC) and cardiac outflow tract (OFT) during development. A subpopulation of Cushion endocardial cells undergoes endocardial to mesenchymal transformation (EMT) and generates the Cushion mesenchyme, which is then remodeled into the interstitial tissue of the mature valves. The Cushion endocardial cells that do not undertake EMT proliferate to elongate valve leaflets. During EMT and the post-EMT valve remodeling, endocardial cells at the Cushions highly express nuclear factor in activated T cell, cytoplasmic 1 (Nfatc1), a transcription factor required for valve formation in mice. In this review, we present the current knowledge of Nfatc1 roles in the ontogeny of heart valves with a focus on the fate decision of the endocardial cells in the processes of EMT and valve remodeling.
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Cell autonomous requirement of endocardial Smad4 during atrioventricular Cushion development in mouse embryos
Developmental dynamics : an official publication of the American Association of Anatomists, 2010Co-Authors: Langying Song, Bin Zhou, Mei Zhao, Qin Wang, Kai JiaoAbstract:Atrioventricular (AV) Cushions are the precursors of AV septum and valves. In this study, we examined roles of Smad4 during AV Cushion development using a conditional gene inactivation approach. We found that endothelial/endocardial inactivation of Smad4 led to the hypocellular AV Cushion defect and that both reduced cell proliferation and increased apoptosis contributed to the defect. Expression of multiple genes critical for Cushion development was down-regulated in mutant embryos. In collagen gel assays, the number of mesenchymal cells formed is significantly reduced in mutant AV explants compared to that in control explants, suggesting that the reduction of Cushion mesenchyme formation in mutants is unlikely secondary to their gross vasculature abnormalities. Using a previously developed immortal endocardial cell line, we showed that Smad4 is required for BMP signaling- stimulated upregulation of Tbx20 and Gata4. Therefore, our data collectively support the cell-autonomous requirement of endocardial Smad4 in regulating AV Cushion development.
