Knowledge Base Prototype Creating with Using Interdisciplinary Metathesaurus.

This article presents our experience in development an ontological model can be used in clinical decision support systems (CDSS) creating. We have used the largest international biomedical terminological metathesaurus the Unified Medical Language System (UMLS) as the basis of our model. This metathesaurus has been adapted into Russian using an automated hybrid translation system with expert control. The product we have created was named as the National Unified Terminological System (NUTS). We have added more than 33 million scientific and clinical relationships between NUTS terms, extracted from the texts of scientific articles and electronic health records. We have also computed weights for each relationship, standardized their values and created symptom checker in preliminary diagnostics based on this. We expect, that the NUTS allow solving task of named entity recognition (NER) and increasing terms interoperability in different CDSS.

Mechanisms of antiviral action and toxicities of ipecac alkaloids: Emetine and dehydroemetine exhibit anti-coronaviral activities at non-cardiotoxic concentrations.

The emergence of highly infectious pathogens with their potential for triggering global pandemics necessitate the development of effective treatment strategies, including broad-spectrum antiviral therapies to safeguard human health. This study investigates the antiviral activity of emetine, dehydroemetine (DHE), and congeneric compounds against SARS-CoV-2 and HCoV-OC43, and evaluates their impact on the host cell. Concurrently, we assess the potential cardiotoxicity of these ipecac alkaloids. Significantly, our data reveal that emetine and the (-)-R,S isomer of 2,3-dehydroemetine (designated in this paper as DHE4) reduce viral growth at nanomolar concentrations (i.e., IC50 ∼ 50-100 nM), paralleling those required for inhibition of protein synthesis, while calcium channel blocking activity occurs at elevated concentrations (i.e., IC50 ∼ 40-60 µM). Our findings suggest that the antiviral mechanisms primarily involve disruption of host cell protein synthesis and is demonstrably stereoisomer specific. The prospect of a therapeutic window in which emetine or DHE4 inhibit viral propagation without cardiotoxicity renders these alkaloids viable candidates in strategies worthy of clinical investigation.

Assimilation Results Comparison of Educational Material by Senior Students of a Medical University in Distance and Face-to-Face Form Education.

Despite the fact that many researchers and teachers reported that distance education can be equated with traditional face-to-face form education, the question of analyzing the quality of knowledge gained in distance education is open. This study was conducted on the basis of the Department of Medical Cybernetics and Informatics named after S.A. Gasparyan of Russian National Research Medical University. N.I. Pirogov for the period from September 1, 2021 to March 14, 2023 and included results of answers of two variance of test on the same topic. The responses of students who missed the lectures were not included in the processing. For 556 students with distance education, the lesson was held remotely using https://meet.google.com and for 846 students the lesson was performed in face-to-face form education. Students' answers to test tasks were collected using the Google form https://docs.google.com/forms/…The data base statistical assessment and statistical description were made in Microsoft Excel 2010 and IBM SPSS Statistics programs version 23. In this study, it was shown that the results of the learned material assessment for distance education and traditional face-to-face form education are statistically significantly different (p<0.001). The topic studied in face-to-face format was assimilated by 0.85 points better (the difference was five percent of the correct answers received).

Word-final complexity in speech sound intervention: two case studies.

In speech sound intervention, consonant clusters promote generalisation (i.e. improvement in untreated sounds and words), ostensibly due to their relative complexity compared to other phonological targets. However, our understanding of clusters as intervention targets is largely restricted to those in word-initial position (e.g. [fl-], flip). The present study extends available work to consider the effects of word-final consonant cluster targets (e.g. [-ks]). Phonologically complex word-final clusters may be morphologically simple (e.g. mix) or morphologically complex (e.g. packs, inflected with third-person singular) - yet this cross-domain complexity remains an understudied phenomenon. Presently, two case studies provide an initial investigation of word-final cluster intervention targets for children with phonologically based speech sound disorders. Intervention targets for both Anna (3;7 [years;months]) and David (4;1) featured the phonologically complex word-final cluster [-ks], with Anna's target being morphologically simple and David's being morphologically complex. Intervention was provided in 45-minute, individual sessions three times per week for a maximum of 18 sessions. Both children demonstrated high target accuracy by intervention's end. Following intervention, both children demonstrated progress in intelligibility and ability to produce word-final consonant clusters; David further demonstrated generalisation across multiple measures. Results are interpreted with consideration of individual differences and existing research on complexity in phonological intervention. Overall, present findings motivate continued research, as manipulation of word-final complexity allows for emphasis on a context that is relevant for children with speech sound disorders, for peers with difficulties in morphology (including word-final grammatical morphemes) and for the substantial proportion of children demonstrating weaknesses in both domains.

Understanding (un)grammaticality in context: Evidence from young Spanish-English bilinguals over time.

PURPOSE: Percent grammatical utterances (PGU) provides clinicians and researchers with meaningful information on young children's grammatical abilities (Eisenberg & Guo, 2016). However, work is still needed to place PGU within the context of conventional language sample measures and understand how PGU reflects grammatical development in bilingual populations. The current study focuses on Spanish-English bilingual preschoolers to examine: 1) change in Spanish and English PGU over one year of preschool English instruction, 2) associations between PGU and other language sample measures within each language and across time, and 3) the types and frequency of error patterns in each language. METHOD: Play-based language samples were elicited in English and Spanish from bilingual children (n = 19) at the beginning and end of an instructional preschool year in English. PGU was derived from each sample along with other language sample measures (e.g., mean length of utterance). We examined change in PGU from Time 1 to Time 2, and correlations between Time 1 PGU and Time 2 PGU for each language. Specific grammatical errors were described in terms of their frequency in each language and stability across time. RESULTS: Average English PGU increased from Time 1 to Time 2, and correlated with other language sample measures. Conversely, average Spanish PGU did not increase from Time 1 to Time 2, nor did PGU correlate with any other Spanish measure. Error patterns in each language reflected grammatical differences across English and Spanish. CONCLUSIONS: Our results revealed distinct developmental patterns in bilingual children's first and second languages. Associations between time points and measures in English contrasted with disassociations in Spanish. Error patterns revealed more detailed information as to how bilingual children begin to acquire grammatical structures in each of their languages. We provide a case example to illustrate how grammaticality and error patterns can be used to characterize children's language abilities. We conclude with clinical implications of grammaticality in Spanish-English bilingual children.

Language dominance predicts cognate effects and metalinguistic awareness in preschool bilinguals.

The current work investigates whether language dominance predicts transfer of skills across cognitive-linguistic levels from the native language (Spanish) to the second language (English) in bilingual preschoolers. Sensitivity to cognates (elephant/elefante in English/Spanish) and metalinguistic awareness (MLA) have both been shown to transfer from the dominant to the nondominant language. Examining these types of transfer together using a continuous measure of language dominance may allow us to better understand the effect of the home language in children learning a majority language in preschool. Forty-six preschool-aged, Spanish-English bilinguals completed English receptive vocabulary and metalinguistic tasks indexing cognate effects and MLA. Language dominance was found to predict crosslinguistic (cognate) facilitation from Spanish to English. In addition, MLA skills also transferred from Spanish to English for children with lower English proficiency, and no transfer of MLA was evident for children with higher English proficiency. Altogether, findings suggest that transfer from a dominant first language to a nondominant second language happens at linguistic and cognitive-linguistic levels in preschoolers, although possibly influenced by second language proficiency. The current study has implications for supporting the home language for holistic cognitive-linguistic development.

Grammatical Characteristics of Vietnamese and English in Developing Bilingual Children.

Purpose Defining parameters for typical development in bilingual children's first and second languages can serve as the basis for accurate language assessment. This is the first study to characterize Vietnamese and English grammatical development in a sample of bilingual children. Method Participants were 89 Vietnamese-English bilingual children, aged 3-8 years. Children completed story retell tasks in Vietnamese and English. Stories were transcribed and analyzed for grammaticality, error patterns, subordination index, and types of subordinating clauses. Of key interest were associations with age and identifying developmental patterns that were shared across languages or unique to a given language. Results Age correlated with more measures in English than in Vietnamese, suggesting that older children had higher grammaticality and greater syntactic complexity in English than younger children. Children also produced greater syntactic complexity with age in Vietnamese, but not higher grammaticality. There were a set of error patterns shared across languages (e.g., object omission) and patterns specific to each language (e.g., classifier errors in Vietnamese, tense errors in English). While children produced nominal, adverbial, and relative clauses in Vietnamese and English, the proportion of each clause type differed by language. Conclusions Results from this typically developing sample provide a reference point to improve clinical practice. Characterizing developmental patterns in sentence structure in Vietnamese and English lays the groundwork for investigations of language disorders in this bilingual population.

Towards understanding the bilingual profile in typical and atypical language development: A tutorial.

Purpose: The purpose of this tutorial is to inform assessment, treatment and research approaches that are uniquely tailored to bilingual children with and without developmental language disorder (DLD), a communication disorder characterised by weaknesses in language production and comprehension.Method: A review is presented on what is known about joint language activation in adult and child bilinguals. This supports a discussion of the bilingual profile, which includes cross-language interactions and associations with broader cognitive functions. This is followed by consideration on how these bilingual phenomena may manifest in the context of relatively weak language skills, as is the case with DLD.Result: In addition to exploring the bilingual profile, guidelines are provided for incorporating cognates - a type of translation equivalent with distinct overlap in form and meaning that enhances cross-linguistic interactions - in language assessment, therapy and research.Conclusion: The field of speech-language pathology would benefit from more tools specifically designed for bilingual children. Already, there is interest in clinical applications of cognates, as they may support transfer and generalisation across languages. Future research is needed to better explore this potential in child bilinguals, particularly those with DLD. Such work would help establish a developmental bilingual language processing model with clinical relevance.

Spanish-English Bilingual Children's Relative Use of English Tense and Agreement Morphemes.

Best practice for bilingual speakers involves considering performance in each language the client uses. To support this practice for young clients, a comprehensive understanding of how bilingual children develop skills in each language is needed. To that end, the present work investigates relative use of English tense and agreement (T/A) morphemes - a skill frequently considered as part of a complete language assessment - in Spanish-English developing bilingual preschoolers with varying levels of language ability. Results indicate that developing bilingual children with both typical and weak language skills demonstrate greater use of copula and auxiliary BE relative to third person singular, past tense and auxiliary DO. Findings thus reveal a relative ranking of T/A morphemes in developing bilingual children that differs from that of English monolingual children, who demonstrate relatively later emergence and productivity of auxiliary BE. In turn, findings demonstrate the importance of utilizing appropriate comparisons in clinical practice.

Evaluating English Morpheme Accuracy, Diversity, and Productivity Measures in Language Samples of Developing Bilinguals.

Purpose: This work explores the clinical relevance of three measures of morpheme use for preschool-age Spanish-English bilingual children with varying language skills. The 3 measures reflect accuracy, diversity (the tense marker total), and productivity (the tense and agreement productivity score [TAP score]) of the English tense and agreement system. Method: Measures were generated from language samples collected at the beginning and end of the participants' preschool year. Participants included 74 typically developing Spanish-English bilinguals and 19 peers with low language skills. The morpheme measures were evaluated with regard to their relationships with other language sample measures, their ability to reflect group differences, and their potential for capturing morphological development at group and individual levels. Results: Across both groups, the tense marker total and TAP scores were associated with other language measures and demonstrated both group differences and growth over time. The accuracy measure met few of these benchmarks. Conclusion: The tense marker total and TAP score, which were designed to capture emerging morphological abilities, contribute valuable information to a comprehensive language assessment of young bilinguals developing English. Case examples are provided to illustrate the clinical significance of including these measures in assessment.

Influences of Phonological Context on Tense Marking in Spanish-English Dual Language Learners.

Purpose: The emergence of tense-morpheme marking during language acquisition is highly variable, which confounds the use of tense marking as a diagnostic indicator of language impairment in linguistically diverse populations. In this study, we seek to better understand tense-marking patterns in young bilingual children by comparing phonological influences on marking of 2 word-final tense morphemes. Method: In spontaneous connected speech samples from 10 Spanish-English dual language learners aged 56-66 months (M = 61.7, SD = 3.4), we examined marking rates of past tense -ed and third person singular -s morphemes in different environments, using multiple measures of phonological context. Results: Both morphemes were found to exhibit notably contrastive marking patterns in some contexts. Each was most sensitive to a different combination of phonological influences in the verb stem and the following word. Conclusions: These findings extend existing evidence from monolingual speakers for the influence of word-final phonological context on morpheme production to a bilingual population. Further, novel findings not yet attested in previous research support an expanded consideration of phonological context in clinical decision making and future research related to word-final morphology.

Induced Pluripotent Stem Cell-Derived Cardiomyocytes Provide In Vivo Biological Pacemaker Function.

BACKGROUND: Although multiple approaches have been used to create biological pacemakers in animal models, induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) have not been investigated for this purpose. We now report pacemaker function of iPSC-CMs in a canine model. METHODS AND RESULTS: Embryoid bodies were derived from human keratinocytes, their action potential characteristics determined, and their gene expression profiles and markers of differentiation identified. Atrioventricular blocked dogs were immunosuppressed, instrumented with VVI pacemakers, and injected subepicardially into the anterobasal left ventricle with 40 to 75 rhythmically contracting embryoid bodies (totaling 1.3-2×106 cells). ECG and 24-hour Holter monitoring were performed biweekly. After 4 to 13 weeks, epinephrine (1 µg kg-1 min-1) was infused, and the heart removed for histological or electrophysiological study. iPSC-CMs largely lost the markers of pluripotency, became positive for cardiac-specific markers. and manifested If-dependent automaticity. Epicardial pacing of the injection site identified matching beats arising from that site by week 1 after implantation. By week 4, 20% of beats were electronically paced, 60% to 80% of beats were matching, and mean and maximal biological pacemaker rates were 45 and 75 beats per minute. Maximum night and day rates of matching beats were 53±6.9 and 69±10.4 beats per minute, respectively, at 4 weeks. Epinephrine increased rate of matching beats from 35±4.3 to 65±4.0 beats per minute. Incubation of embryoid bodies with the vital dye, Dil, revealed the persistence of injected cells at the site of administration. CONCLUSIONS: iPSC-CMs can integrate into host myocardium and create a biological pacemaker. Although this is a promising development, rate and rhythm of the iPSC-CMs pacemakers remain to be optimized.

Cognate identification methods: Impacts on the cognate advantage in adult and child Spanish-English bilinguals.

OBJECTIVES: The purpose of this study was to determine whether four different cognate identification methods resulted in notably different classifications of cognate status for Peabody Picture Vocabulary Test-Third Edition (PPVT-III) test items and to investigate whether differences across criteria would impact findings of cognate effects in adult and preschool-aged Spanish-English bilingual speakers. METHODOLOGY: We compared four cognate identification methods: an objective criterion based on phonological overlap; two subjective criteria based on a translation elicitation task; and a hybrid criterion integrating objective and subjective standards. We then used each criterion to investigate cognate effects on the PPVT-III in 26 adult and 73 child Spanish-English bilinguals. DATA AND ANALYSIS: The test items identified as cognates by each criterion were compared (Experiment 1). Then, cognate advantage magnitudes, cognate accuracy rates, non-cognate accuracy rates, and number of individuals demonstrating the cognate advantage were investigated in both adult (Experiment 2) and child bilinguals (Experiment 3). CONCLUSIONS: Objective and subjective cognate identification methods were found to select notably different subsets of test items as cognates. Further, the methods led to differences in cognate effects, as well as in cognate and non-cognate accuracy rates, for both child and adult bilinguals. ORIGINALITY: Although the cognate advantage has been widely studied in adult bilinguals, research on the cognate advantage in child bilinguals is limited and methods of identifying cognates are inconsistent across studies. The present study provides information about cognate effects in a young population and is the first comparison of objective and subjective approaches to cognate identification. IMPLICATIONS: This study extends previous work on cognate word processing in both child and adult bilinguals. Further, results offer an evaluation of methodologies that are critical for investigating the cognate advantage. This both facilitates interpretation of previous findings and can be used to guide methodological decisions in future research.

Autocrine A2 in the T-system of ventricular myocytes creates transmural gradients in ion transport: a mechanism to match contraction with load?

Transmural heterogeneities in Na/K pump current (IP), transient outward K(+)-current (Ito), and Ca(2+)-current (ICaL) play an important role in regulating electrical and contractile activities in the ventricular myocardium. Prior studies indicated angiotensin II (A2) may determine the transmural gradient in Ito, but the effects of A2 on IP and ICaL were unknown. In this study, myocytes were isolated from five muscle layers between epicardium and endocardium. We found a monotonic gradient in both Ip and Ito, with the lowest currents in ENDO. When AT1Rs were inhibited, EPI currents were unaffected, but ENDO currents increased, suggesting endogenous extracellular A2 inhibits both currents in ENDO. IP- and Ito-inhibition by A2 yielded essentially the same K0.5 values, so they may both be regulated by the same mechanism. A2/AT1R-mediated inhibition of IP or Ito or stimulation of ICaL persisted for hours in isolated myocytes, suggesting continuous autocrine secretion of A2 into a restricted diffusion compartment, like the T-system. Detubulation brought EPI IP to its low ENDO value and eliminated A2 sensitivity, so the T-system lumen may indeed be the restricted diffusion compartment. These studies showed that 33-50% of IP, 57-65% of Ito, and a significant fraction of ICaL reside in T-tubule membranes where they are transmurally regulated by autocrine secretion of A2 into the T-system lumen and activation of AT1Rs. Increased AT1R activation regulates each of these currents in a direction expected to increase contractility. Endogenous A2 activation of AT1Rs increases monotonically from EPI to ENDO in a manner similar to reported increases in passive tension when the ventricular chamber fills with blood. We therefore hypothesize load is the signal that regulates A2-activation of AT1Rs, which create a contractile gradient that matches the gradient in load.

Caspases and p38 MAPK regulate endothelial cell adhesiveness for mesenchymal stem cells.

Mesenchymal stem cells natively circulating or delivered into the blood stream home to sites of injury. The mechanism of mesenchymal stem cell homing to sites of injury is poorly understood. We have shown that the development of apoptosis in endothelial cells stimulates endothelial cell adhesiveness for mesenchymal stem cells. Adhesion of mesenchymal stem cells to apoptotic endothelial cells depends on the activation of endothelial caspases and p38 MAPK. Activation of p38 MAPK in endothelial cells has a primary effect while the activation of caspases potentiates the mesenchymal stem cell adhesion. Overall, our study of the mesenchymal stem cell interaction with endothelial cells indicates that mesenchymal stem cells recognize and specifically adhere to distressed/apoptotic endothelial cells.

Von willebrand factor increases endothelial cell adhesiveness for human mesenchymal stem cells by activating p38 mitogen-activated protein kinase.

INTRODUCTION: Delivered systemically or natively circulating mesenchymal stem cells accumulate in injured tissues. During homing mesenchymal stem cells adhere to endothelial cells and infiltrate underlying tissue. Previously we have shown that adhesiveness of endothelial cells for mesenchymal stem cells correlates with the inhibition of mitochondrial function of endothelial cells and secretion of von Willebrand factor. We hypothesized that von Willebrand factor is an auto/paracrine regulator of endothelial cell adhesiveness and studied the effect of von Willebrand factor on adhesion of mesenchymal stem cells to endothelial cells. METHODS: We used Affymetrix DNA microarrays, human protein phospho-MAPK array, Western blot, cell-based ELISA and flow cytometry analysis to study the activation of endothelial cells by von Willebrand factor. Cell adhesion assay and protein kinase inhibitors were used to evaluate the role of mitogen-activated protein kinases in the regulation of endothelial cell adhesiveness for mesenchymal stem cell. RESULTS: Treatment of endothelial cells with von Willebrand factor stimulated the mesenchymal stem cell adhesion in a time- and concentration-dependent manner. Mesenchymal stem cells did not adhere to immobilized von Willebrand factor and did not express receptors for von Willebrand factor suggesting that the stimulation of the mesenchymal stem cell adhesion is a result of endothelial cell activation with von Willebrand factor. Treatment of endothelial cells with von Willebrand factor activated ERK-1,2 and p38 MAPK without an effect on gene or cell surface expression of E-selectin, P-selectin, VCAM1 and ICAM1. Inhibition of p38 MAPK, but not ERK-1,2, in endothelial cells completely abrogated the stimulation of the mesenchymal stem cell adhesion by von Willebrand factor. CONCLUSIONS: Von Willebrand factor is an auto/paracrine regulator of endothelial cells. Activation of p38 MAPK in endothelial cells by von Willebrand factor is responsible for the regulation of endothelial cell adhesiveness for mesenchymal stem cells.

Increased myocyte content and mechanical function within a tissue-engineered myocardial patch following implantation.

During the past few years, studies involving the implantation of stem cells, chemical factors, and scaffolds have demonstrated the ability to augment the mammalian heart's native regenerative capacity. Scaffolds comprised of extracellular matrix (ECM) have been used to repair myocardial defects. These scaffolds become populated with myocytes and provide regional contractile function, but quantification of the myocyte population has not yet been conducted. The purpose of this study was to quantitate the myocyte content within the ECM bioscaffold and to correlate this cell population with the regional mechanical function over time. Xenogenic ECM scaffolds derived from porcine urinary bladder were implanted into a full-thickness, surgically induced, right ventricular-free wall defect in a dog model. Zero, 2, and 8 weeks following implantation, regional function and myocyte content were determined in each patch region. Regional function did not significantly increase from 0 to 2 weeks. At 8 weeks, however, regional stroke work increased to 3.7 +/- 0.7% and systolic contraction increased to 4.4 +/- 1.2%. The myocyte content also significantly increased during that period generating a linear relationship between regional function and myocyte content. In conclusion, ECM used as a myocardial patch increases both the regional function and the myocyte content over time. The mechanical function generated in the patch region is correlated with the quantity of local tissue myocytes.

Apoptotic endothelial cells demonstrate increased adhesiveness for human mesenchymal stem cells.

Mesenchymal stem cells (MSCs) participate in the wound healing process in mammalians. Adhesion of MSCs to endothelium is a key step in the homing of MSCs circulating in the bloodstream to the sites of injury and inflammation. Because endothelial cells (ECs) may become apoptotic under certain pro-inflammatory conditions, we investigated the effects of pro-inflammatory, TNF-alpha and IL-1 beta, and pro-apoptotic agents, actinomycin D, cycloheximide, okadaic acid, wortmannin, and staurosporine, on human MSCs (hMSCs) adhesion to ECs. Treatment of ECs with pro-apoptotic agents markedly increased adhesion of hMSCs to ECs. This adhesion correlated with reduction of mitochondrial membrane potential, inhibition of NADH dehydrogenases, and release of von Willebrand factor (vWF) by ECs. Treatment of ECs with exogenous vWF also stimulated hMSC adhesion. These data provide evidence that apoptosis of ECs may regulate homing of hMSCs to the sites of tissue injury. These results are consistent with the hypothesis that activation of apoptotic signaling pathways in ECs releases vWF which regulates hMSC adhesion to ECs.

Enhanced recovery of mechanical function in the canine heart by seeding an extracellular matrix patch with mesenchymal stem cells committed to a cardiac lineage.

The need to regenerate tissue is paramount, especially for the heart that lacks the ability to regenerate after injury. The urinary bladder extracellular matrix (ECM), when used to repair a right ventricular defect, successfully regenerated some mechanical function. The objective of the current study was to determine whether the regenerative effect of ECM could be improved by seeding the patch with human mesenchymal stem cells (hMSCs) enhanced to differentiate down a cardiac linage. hMSCs were used to form three-dimensional spheroids. The expression of cardiac proteins was determined in cells exposed to the spheroid formation and compared with nonmanipulated hMSCs. To determine whether functional calcium channels were present, the cells were patch clamped. To evaluate the ability of these cells to regenerate mechanical function, the spheroids were seeded on ECM and then implanted into the canine heart to repair a full-thickness right ventricular defect. As a result, many of the cells spreading from the spheroids expressed cardiac-specific proteins, including sarcomeric alpha-actinin, cardiotin, and atrial natriuretic peptide, as well as the cell cycle markers cyclin D1 and proliferating cell nuclear antigen. A calcium current similar in amplitude to that of ventricular myocytes was present in 16% of the cells. The cardiogenic cell-seeded scaffolds increased the regional mechanical function in the canine heart compared with the unmanipulated hMSC-seeded scaffolds. In addition, the cells prelabeled with fluorescent markers demonstrated myocyte-specific actinin staining with sarcomere spacing similar to that of normal myocytes. In conclusion, the spheroid-derived cells express cardiac-specific proteins and demonstrate a calcium current similar to adult ventricular myocytes. When these cells are implanted into the canine heart, some of these cells appear striated and mechanical function is improved compared with the unmanipulated hMSCs. Further investigation will be required to determine whether the increased mechanical function is due to a differentiation of the cardiogenic cells to myocytes or to other effects.

Culturing of human mesenchymal stem cells as three-dimensional aggregates induces functional expression of CXCR4 that regulates adhesion to endothelial cells.

Culture-expanded human mesenchymal stem cells (hMSCs) are increasingly used in a variety of preclinical and clinical studies. However, these cells have a low rate of engraftment to bone marrow or damaged tissues. Several laboratories have shown that during isolation and subculturing mesenchymal stem cells quickly lose the expression of CXCR4, the key receptor responsible for lymphocytes and hematopoietic stem cell homing. Here we show that culturing of hMSCs as three-dimensional aggregates (hMSC spheroids) restores CXCR4 functional expression. Expression of CXCR4 inversely correlates with the secretion of SDF-1 by hMSCs. Cells from hMSC spheroids up-regulate expression of CD49b, the alpha2 integrin subunit, and suppress the expression of CD49d, the alpha4 integrin subunit. Transfer of cells from the spheroids back to a monolayer suppresses the expression of CXCR4 and CD49b and restores the expression of CD49d. Treatment of cells from the spheroids with SDF-1 leads to CXCR4 internalization and activation of ERK-1,2. Adhesion of hMSCs to human umbilical vein endothelial cells (HUVECs) was investigated. SDF-1, AMD-3100, or exposure of HUVECs to hypoxia did not affect adhesion of hMSCs from a monolayer to HUVECs. Adhesion of cells from hMSC spheroids to HUVECs was stimulated by SDF-1, AMD-3100, or by exposure of HUVECs to hypoxia. Stimulatory effects of hypoxia and addition of SDF-1 or AMD-3100 were not additive. Overall, our data indicate that the expression of CXCR4 by hMSCs regulates hMSC adhesion to endothelial cells.