RÉSUMÉ
INTRODUCTION: Reticulated platelet (RP) content is increased in nonvalvular atrial fibrillation (NVAF). The purpose of this study was to determine if platelet content, morphology, and RP proportion are modulated by platelet genes. METHODS AND RESULTS: Expression of six platelet-predominate genes impacting platelet formation and release, platelet count, and RP content was assessed in NVAF patients before and 3-4 months after pulmonary veins isolation (PVI) and compared to normal sinus rhythm (NSR) controls. RNA from isolated platelets was reverse-transcribed assayed against selected genes utilizing real-time qPCR, and expressed as mean cycle threshold (ΔCt) using beta-2-microglobulin as endogenous control. RP content was assessed by flow cytometry. A fourfold lower expression of CFL1 gene coding for nonmuscle cofilin (7.8 ± 0.9 vs. 5.7 ± 1.6, P < 0.001) and twofold lower expression of four other genes were associated with similar platelet counts but fourfold higher (28.7+7.0 vs. 6.7+5.4, P < 0.001) RP content (%) in 97 NVAF cases compared to 51 NSR controls. Three to 4 months after PVI, RP decreased by 28%, while CFL1 gene expression increased over twofold but TUBA4A gene expression decreased almost twofold; NFE2 and MYL6 gene expression remained unchanged. CONCLUSIONS: NVAF is associated with notable downregulation of genes directing platelet production and size but increased RP content. PVI impacts the expression of many of these genes, implying a direct relationship between atrial fibrillation and platelet biogenesis.
Sujet(s)
Fibrillation auriculaire/chirurgie , Plaquettes/métabolisme , Ablation par cathéter , Veines pulmonaires/chirurgie , Potentiels d'action , Sujet âgé , Fibrillation auriculaire/sang , Fibrillation auriculaire/diagnostic , Fibrillation auriculaire/physiopathologie , Plaquettes/anatomopathologie , Études cas-témoins , Ablation par cathéter/effets indésirables , Cofiline-1/sang , Cofiline-1/génétique , Femelle , Régulation de l'expression des gènes , Rythme cardiaque , Humains , Mâle , Protéines membranaires/sang , Protéines membranaires/génétique , Adulte d'âge moyen , Chaînes légères de myosine/sang , Chaînes légères de myosine/génétique , Sous-unité p45 du facteur de transcription NF-E2/sang , Sous-unité p45 du facteur de transcription NF-E2/génétique , Numération des plaquettes , Veines pulmonaires/physiopathologie , Récepteurs à la progestérone/sang , Récepteurs à la progestérone/génétique , Facteurs temps , Résultat thérapeutique , Tubuline/sang , Tubuline/génétiqueRÉSUMÉ
The processes of megakaryocyte polyploidization and demarcation membrane system (DMS) formation are crucial for platelet production, but the mechanisms controlling these processes are not fully determined. Inhibition of Rho kinase (ROCK) signalling leads to increased polyploidization in umbilical cord blood-derived megakaryocytes. To extend these findings we determined the effect of ROCK inhibition on development of the DMS and on proplatelet formation. The underlying mechanisms were explored by analysing the effect of ROCK inhibition on the expression of MYC and NFE2, which encode two transcription factors critical for megakaryocyte development. ROCK inhibition promoted DMS formation, and increased proplatelet formation and platelet release. Rho kinase inhibition also downregulated MYC and NFE2 expression in mature megakaryocytes, and this down-regulation correlated with increased proplatelet formation. Our findings suggest a model whereby ROCK inhibition drives polyploidization, DMS growth and proplatelet formation late in megakaryocyte maturation through downregulation of MYC and NFE2 expression.
