CDK8/19 inhibition triggers a switch from mitosis to endomitosis in cord blood megakaryocytes.

Neonatal and adult megakaryocytes differ in proliferative capacity and ploidy levels, and neonatal and adult platelets differ in function, gene expression, and protein content. The mechanisms underlying these differences are incompletely understood. CDK8 and CDK19 are transcriptional kinases part of the CDK-mediator complex, which regulates gene transcription in a cell-specific manner. We discovered that cortistatin A, a potent highly selective inhibitor of CDK8/CDK19, significantly reduced cell expansion and increased ploidy in cord blood-derived megakaryocytes. These phenotypic changes were associated with gene expression changes that partially overlapped developmentally regulated genes. These findings might have relevance for the management of developmental megakaryocyte disorders.

Fetal vs adult megakaryopoiesis.

Fetal and neonatal megakaryocyte progenitors are hyperproliferative compared with adult progenitors and generate a large number of small, low-ploidy megakaryocytes. Historically, these developmental differences have been interpreted as "immaturity." However, more recent studies have demonstrated that the small, low-ploidy fetal and neonatal megakaryocytes have all the characteristics of adult polyploid megakaryocytes, including the presence of granules, a well-developed demarcation membrane system, and proplatelet formation. Thus, rather than immaturity, the features of fetal and neonatal megakaryopoiesis reflect a developmentally unique uncoupling of proliferation, polyploidization, and cytoplasmic maturation, which allows fetuses and neonates to populate their rapidly expanding bone marrow and blood volume. At the molecular level, the features of fetal and neonatal megakaryopoiesis are the result of a complex interplay of developmentally regulated pathways and environmental signals from the different hematopoietic niches. Over the past few years, studies have challenged traditional paradigms about the origin of the megakaryocyte lineage in both fetal and adult life, and the application of single-cell RNA sequencing has led to a better characterization of embryonic, fetal, and adult megakaryocytes. In particular, a growing body of data suggests that at all stages of development, the various functions of megakaryocytes are not fulfilled by the megakaryocyte population as a whole, but rather by distinct megakaryocyte subpopulations with dedicated roles. Finally, recent studies have provided novel insights into the mechanisms underlying developmental disorders of megakaryopoiesis, which either uniquely affect fetuses and neonates or have different clinical presentations in neonatal compared with adult life.

Pooling, room temperature, and extended storage time increase the release of adult-specific biologic response modifiers in platelet concentrates: a hidden transfusion risk for neonates?

BACKGROUND: Adult donor platelets (PLTs) are frequently transfused to prevent or stop bleeding in neonates with thrombocytopenia. There is evidence for PLT transfusion-related morbidity and mortality, leading to the hypothesis on immunomodulatory effects of transfusing adult PLTs into neonates. Candidate factors are biologic response modifiers (BRMs) that are expressed at higher rates in adult than in neonatal PLTs. This study investigated whether storage conditions or preparation methods impact on the release of those differentially expressed BRMs. STUDY DESIGN AND METHODS: Pooled PLT concentrates (PCs) and apheresis PCs (APCs) were stored under agitation for up to 7 days at room temperature (RT) or at 2 to 8°C. The BRMs CCL5/RANTES, TGFß1, TSP1, and DKK1 were measured in PCs' supernatant, lysate, and corresponding plasma. PLT function was assessed by light transmission aggregometry. RESULTS: Concerning the preparation method, higher concentrations of DKK1 were found in pooled PCs compared to APCs. In supernatants, the concentrations of CCL5, TGFß1, TSP1, and DKK1 significantly increased, both over standard (≤4 days) and over extended storage times (7 days). Each of the four BRMs showed an up to twofold increase in concentration after storage at RT compared to cold storage (CS). There was no difference in the aggregation capacity. CONCLUSION: This analysis shows that the release of adult-specific BRMs during storage is lowest in short- and CS APCs. Our study points to strategies for reducing the exposure of sick neonates to BRMs that can be specifically associated to PLT transfusion-related morbidity.

Changes in megakaryopoiesis over ontogeny and their implications in health and disease.

A growing body of research has made it increasingly clear that there are substantial biological differences between fetal/neonatal and adult megakaryopoiesis. Over the last decade, studies revealed a developmentally unique uncoupling of proliferation, polyploidization, and cytoplasmic maturation in neonatal MKs that results in the production of large numbers of small, low ploidy, but mature MKs during this period of development, and identified substantial molecular differences between fetal/neonatal and adult MKs. This review will summarize our current knowledge on the developmental differences between fetal/neonatal and adult MKs, and recent advances in our understanding of the underlying molecular mechanisms, including newly described developmentally regulated pathways and miRNAs. We will also discuss the implications of these findings on the ways MKs interact with the environment, the response of neonates to thrombocytopenia, the pathogenesis of Down syndrome-transient myeloproliferative disorder (TMD), and the developmental stage specific-manifestations of congenital amegakaryocytic thrombocytopenia.

Selinexor-induced thrombocytopenia results from inhibition of thrombopoietin signaling in early megakaryopoiesis.

Selinexor is the first oral selective inhibitor of nuclear export compound tested for cancer treatment. Selinexor has demonstrated a safety therapy profile with broad antitumor activity against solid and hematological malignancies in phases 2 and 3 clinical trials (#NCT03071276, #NCT02343042, #NCT02227251, #NCT03110562, and #NCT02606461). Although selinexor shows promising efficacy, its primary adverse effect is high-grade thrombocytopenia. Therefore, we aimed to identify the mechanism of selinexor-induced thrombocytopenia to relieve it and improve its clinical management. We determined that selinexor causes thrombocytopenia by blocking thrombopoietin (TPO) signaling and therefore differentiation of stem cells into megakaryocytes. We then used both in vitro and in vivo models and patient samples to show that selinexor-induced thrombocytopenia is indeed reversible when TPO agonists are administered in the absence of selinexor (drug holiday). In sum, these data reveal (1) the mechanism of selinexor-induced thrombocytopenia, (2) an effective way to reverse the dose-limiting thrombocytopenia, and (3) a novel role for XPO1 in megakaryopoiesis. The improved selinexor dosing regimen described herein is crucial to help reduce thrombocytopenia in selinexor patients, allowing them to continue their course of chemotherapy and have the best chance of survival. This trial was registered at www.clinicaltrials.gov as #NCT01607905.

Developmental differences between newborn and adult mice in response to romiplostim.

Thrombocytopenia is frequent among sick neonates. While most cases are transient, some neonates experience prolonged and severe thrombocytopenia. These infants often pose diagnostic and therapeutic challenges, and may receive large numbers of platelet transfusions. Romiplostim (ROM) is a thrombopoietin (TPO)-receptor-agonist approved for treatment of adults with chronic immune thrombocytopenia (ITP). The immature platelet fraction (IPF) is a novel measure of newly produced platelets, which could aid with the diagnostic evaluation of thrombocytopenic neonates. This study had the following two objectives: (1) compare the response of newborn and adult mice to escalating doses of ROM in vivo and (2) assess the correlation between IPF and megakaryocyte (MK) mass in newborn and adult treated and untreated mice. In the first set of studies, newborn (day 1) and adult mice received a single subcutaneous (SC) dose of ROM ranging from 0 to 300 ng/g, and platelet counts were followed every other day for 14 days. Both sets of mice responded with dose-dependent platelet and IPF increases, peaking on days 5-7 post-treatment, but neonates had a blunted response (2.1-fold compared to 4.2-fold maximal increase in platelet counts, respectively). On day 5 post-treatment with 300 ng/g ROM, MKs in the bone marrow (BM) and spleen of adult mice were significantly increased in numbers and size (p < 0.0001 for both) compared to controls. MKs in the spleen and BM (but not liver) of treated neonates also increased in number, but not in size. The immature platelet count (IPC, calculated as IPF x platelet count) was highly correlated with the MK number and size in neonatal and adult BM and spleen, but not neonatal liver. The lack of response of neonatal liver MKs was not due to a cell-intrinsic reduced responsiveness to TPO, since neonatal liver progenitors were more sensitive to murine TPO (mTPO) in vitro than adult BM progenitor. In vivo treatment of newborn mice with high mTPO doses or with higher doses of ROM (900 ng/g) resulted in peak platelet counts approaching 3-fold of controls. Taken together, our data indicate that newborn mice are less responsive to ROM than adult mice in vivo, due to a combination of likely pharmacokinetic differences and developmental differences in the response of MKs to thrombopoietic stimulation, evidenced by neonatal MKs increasing in numbers but not in size. PK/PD studies in human infants treated with ROM are warranted.

Effects of Short-term High Dose Atorvastatin on Left Ventricular Remodeling in Patients with First Time Attack of Anterior Acute Myocardial Infarction.

Objects The aim of this trial was to evaluate the effect of short-term high-dose atorvastatin therapy on levels of high-sensitivity C-reactive protein (hs-CRP), malonaldehyde (MDA), endothelin-1(ET-1), matrix metalloproteinases (MMPs), and left ventricular (LV) remodeling in patients with first time attack of acute anterior myocardial infarction (AAMI) .Methods A hundred and three patients with first time attack of AAMI who underwent successful primary percutaneous coronary intervention were randomized to receive atorvastatin 40 mg once daily for 1 week followed by 20 mg once daily (intensive treatment group, IT group, n=49), or atorvastatin 20 mg once daily (standard treatment group, ST group, n=54). Plasma levels of hs-CRP, MDA, ET-1, MMP-2 and MMP-9 were measured on admission, at 1 week, 2 weeks and 6 months follow up and compared between the IT group and ST group. Echocardiography was performed on admission, at 2 week, and 1 year follow up. The left ventricular end-diastolic volume (LVEDV), left ventricular end-systolic volume (LVESV) and left ventricular ejection fraction (LVEF) were measured at each echocardiographic examination and compared between the IT group and ST group.Results Plasma levels of hs-CRP (F=7.718, P=0.009), ET-1 (F=7.882, P=0.006), MMP-9 (F=4.834, P=0.028) and pro-BNP (F=4.603, P=0.032) were significantly lower at 1 week after initial onset of AAMI in the IT group compared with the ST group. The changes of LVEDV, LVESV, and LVEF at the 1 year follow-up from the admission did not differ between the IT group and the ST group (t=0.722, P=0.444; t=1.228, P=0.221; t=1.354, P=0.187, repectively).Conclusions Short-term high-dose atorvastatin treatment for AAMI was associated with lower hs-CRP, ET-1 and MMP-9 levels compared to the standard dose treatment. However, this beneficial effect is not likely to related to the left ventricular remodeling.

Suppression of in vitro megakaryopoiesis by maternal sera containing anti-HPA-1a antibodies.

Incompatibility of the human platelet antigen-1 (HPA-1) system is the most common cause of fetal/neonatal alloimmune thrombocytopenia (F/NAIT) and is thought to be mediated by accelerated clearance of antibody-opsonized fetal platelets. We evaluated the effect of maternal sera containing anti-HPA-1a antibodies (F/NAIT sera) on in vitro megakaryopoiesis. Compared with control maternal sera, 14 out of 17 F/NAIT sera significantly reduced megakaryocyte (MK) number. This finding was associated with increased apoptosis and cell death of early MKs/MK progenitors, but normal maturation and differentiation of surviving MKs. An analysis of platelet counts in infants born to mothers following antenatal intravenous immunoglobulin (IVIG) ± prednisone therapy demonstrated a significant and moderately strong correlation between the MK growth in cultures and the infants' platelet counts at birth. These findings suggest that maternal anti-HPA-1a antibodies can suppress fetal megakaryopoiesis by inducing early cell death and that this influences the neonatal platelet count. Thus, the ability of maternal antibodies to suppress MK growth is a potential predictive factor for the fetal response to maternal IVIG therapy.

The outcomes of initial endoscopic transluminal drainage are superior to percutaneous drainage for patients with infected pancreatic necrosis: a prospective cohort study.

BACKGROUND AND STUDY AIM: The commonly used minimally invasive methods for patients with infected pancreatic necrosis (IPN) are initial endoscopic transluminal drainage (ETD) and percutaneous catheter drainage (PCD), which are followed, if necessary, by endoscopic or surgical necrosectomy. This study intends to explore which of the two minimally invasive treatments leads to a better prognosis. PATIENTS AND METHODS: Patients with IPN and an indication for intervention were prospectively enrolled and underwent either initial ETD or PCD followed, if necessary, by endoscopic or surgical necrosectomy. RESULTS: Initial treatment success occurred in 8 of 11 patients after ETD (72.7%) and in 3 of 13 patients after PCD (30.8%) (risk ratio [RR] with ETD, 2.36; 95% CI 0.97-5.77; P = 0.04). After 1 year of follow-up, 72.7% of patients survived with ETD, and 69.2% survived with PCD (RR 1.05; 95% CI 0.63-1.75; P = 0.85). Intestinal fistula seems to have occurred less in the patients who received initial ETD rather than PCD therapy (9.1 vs. 38.5%; RR 0.24; 95% CI 0.03-1.73; P = 0.098). Fewer patients who underwent an initial ETD were transferred to surgery (9.1 vs. 46.2%; RR 0.20; 95% CI 0.03-1.40; P = 0.047). A higher rate of new-onset diabetes (3 cases) or impaired glucose tolerance (1 case) occurred in initial PCD compared to ETD (40 vs. 0%, P = 0.042). CONCLUSION: The outcomes of initial endoscopic transluminal drainage are superior to percutaneous drainage for patients with infected pancreatic necrosis (ChiCTR-ONRC-13003653).

Expansion of the neonatal platelet mass is achieved via an extension of platelet lifespan.

The fetal/neonatal hematopoietic system must generate enough blood cells to meet the demands of rapid growth. This unique challenge might underlie the high incidence of thrombocytopenia among preterm neonates. In this study, neonatal platelet production and turnover were investigated in newborn mice. Based on a combination of blood volume expansion and increasing platelet counts, the platelet mass increased sevenfold during the first 2 weeks of murine life, a time during which thrombopoiesis shifted from liver to bone marrow. Studies applying in vivo biotinylation and mathematical modeling showed that newborn and adult mice had similar platelet production rates, but neonatal platelets survived 1 day longer in circulation. This prolonged lifespan fully accounted for the rise in platelet counts observed during the second week of murine postnatal life. A study of pro-apoptotic and anti-apoptotic Bcl-2 family proteins showed that neonatal platelets had higher levels of the anti-apoptotic protein Bcl-2 and were more resistant to apoptosis induced by the Bcl-2/Bcl-xL inhibitor ABT-737 than adult platelets. However, genetic ablation or pharmacologic inhibition of Bcl-2 alone did not shorten neonatal platelet survival or reduce platelet counts in newborn mice, indicating the existence of redundant or alternative mechanisms mediating the prolonged lifespan of neonatal platelets.

MELD-Na: effective in predicting rebleeding in cirrhosis after cessation of esophageal variceal hemorrhage by endoscopic therapy.

BACKGROUND AND AIMS: There is no study verifying the predictive value of model for end-stage liver disease and sodium (MELD-Na) for rebleeding and its associated mortality in cirrhotic patients after cessation of acute esophageal variceal hemorrhage (AVH) by endoscopic therapy. This study aimed to determine the predictive value of MELD-Na by comparing with MELD or Child-Turcotte-Pugh (CTP) scores. PATIENTS AND METHODS: Consecutive adult cirrhotic patients after cessation of AVH by endoscopic therapy (endoscopic variceal ligation or sclerotherapy injections) within 48 hours of admission admitted from 2003 to 2012 were analyzed. The clinical characteristics and laboratory data at admission were documented, based on which MELD-Na, MELD, and CTP scores were calculated. RESULTS: Among 429 patients who had complete control of AVH, 97 patients (22.6%) suffered esophageal variceal rebleeding within 3 months and 206 patients (48.0%) within 1 year. Fifty-three patients (12.4%) died within 3 months and 98 patients (22.8%) within 1 year from rebleeding. The area under receiver operator characteristics curve of the MELD-Na score for predicting rebleeding and its associated mortality was significantly higher than that of the MELD and the CTP score (rebleeding: 0.83 vs. 0.77 vs. 0.69 for 3 months and 0.85 vs. 0.80 vs. 0.65 for 1 year, P<0.05; mortality: 0.81 vs. 0.75 vs. 0.66 for 3 months and 0.82 vs. 0.78 vs. 0.68 for 1 year, P<0.05). CONCLUSIONS: The MELD-Na score is clinically useful in predicting 3-month and 1-year rebleeding and its associated mortality in cirrhotic patients after cessation of AVH by endoscopic therapy.

The Correlation between Epicardial Adipose Tissue Thickness Measured by Echocardiography and P-Wave Dispersion and Atrial Fibrillation.

Background: Recent studies have indicated a close relationship between the thickness of epicardial adipose tissue (EAT) and the occurrence as well as persistence of atrial fibrillation (AF). However, the pathogenesis of this association is still in the exploratory stage. The aim of this study is to explore the correlation EAT, as measured by echocardiography, and P-wave dispersion (Pd) in the context of atrial fibrillation. Additionally, the study seeks to analyze the utility of EAT at different anatomical sites in identifying individuals who are predisposed to atrial fibrillation. Methods: A total of 136 subjects were enrolled and categorized into groups based on the guidelines: paroxysmal atrial fibrillation group (PAF group), persistent atrial fibrillation group (AF group), and non-atrial fibrillation group. Comprehensive clinical data, including general information and medications that could impact the occurrence of atrial fibrillation, were gathered for all patients. Echocardiography was employed to measure the maximum EAT thickness near the apex of the heart on the anterior right ventricular wall and near the base of the right ventricle for each participant. Pd values were computed for each patient based on standard 12-lead synchronous electrocardiogram (ECG). The study involved comparing the disparity in EAT thickness between the two specified sites across the three groups. Additionally, correlation analyses were performed to assess the relationship between EAT thickness at the two sites and Pd. Regression analysis was applied to explore potential risk factors for atrial fibrillation. The diagnostic value of EAT at each site in predicting atrial fibrillation was evaluated using Receiver Operating Characteristic curve (ROC) analysis. Results: EAT thickness of the anterior wall near the apex of the heart and near the base of the right ventricle were significantly positively correlated with Pd (p < 0.05), EAT thickness near the base and left atrial diameter were independent risk factors for atrial fibrillation (OR = 13.673, 95% CI 2.819~66.316, p = 0.001; OR = 2.294, 95% CI 1.020~5.156, p = 0.045). ROC analysis showed that the area under the curve of EAT thickness near the heart base was 0.723, and the best threshold for predicting the occurrence of AF was 1.05 cm. Conclusions: The echocardiography-measured epicardial adipose tissue thickness, particularly in proximity to the heart base, exhibits a significant correlation with Pd. Notably, EAT thickness near the heart base demonstrates superior predictive capability for atrial fibrillation compared to thickness near the apex.

Serum sex hormones correlate with pathological features of papillary thyroid cancer.

PURPOSE: Sex hormones are thought to be responsible for the unique gender differences in papillary thyroid cancer(PTC). Most previous studies on these have focused on the expression of estrogen receptors, or have been limited to animal studies. The aim of our study was to explore the relationship between serum sex hormones and the pathological features of PTC in the clinical setting, as further evidence of the role of sex hormones in PTC. METHODS: Retrospective data analysis of patients who underwent thyroid surgery at the Department of Thyroid Surgery, Nanjing Drum Tower Hospital from January 2022 to September 2022 Correlation between serum sex hormone and pathological features was analyzed in male patients and in menopausal female patients. Serum sex hormones include luteinizing hormone(LH), follicle stimulating hormone(FSH), estradiol(E2), total testosterone(TT), progesterone(P), and prolactin(PRL). Tumor pathological characteristics include the number and size of tumor, presence of extrathyroidal extension(ETE), presence of lymph node metastasis(LNM). RESULTS: Preoperative serum E2 in male patients was positively correlated with tumor size in PTC, LH was negatively correlated with LNM, while TT and P were negatively correlated with ETE. Similar findings were not observed in menopausal female patients. CONCLUSION: We observed that serum sex hormones correlate with the pathological features of PTC in male patients, for the first time in a clinical study. High serum estrogens may be a risk factor for PTC, while androgens are the opposite. This somewhat corroborates previous research and provides new variables for future PTC prediction models.

Quantitative label-free mass spectrometry reveals content and signaling differences between neonatal and adult platelets.

BACKGROUND: Recent clinical studies have shown that transfusions of adult platelets increase morbidity and mortality in preterm infants. Neonatal platelets are hyporesponsive to agonist stimulation, and emerging evidence suggests developmental differences in platelet immune functions. OBJECTIVES: This study was designed to compare the proteome and phosphoproteome of resting adult and neonatal platelets. METHODS: We isolated resting umbilical cord blood-derived platelets from healthy full-term neonates (n = 8) and resting blood platelets from healthy adults (n = 6) and compared protein and phosphoprotein contents using data-independent acquisition mass spectrometry. RESULTS: We identified 4770 platelet proteins with high confidence across all samples. Adult and neonatal platelets were clustered separately by principal component analysis. Adult platelets were significantly enriched in immunomodulatory proteins, including ß2 microglobulin and CXCL12, whereas neonatal platelets were enriched in ribosomal components and proteins involved in metabolic activities. Adult platelets were enriched in phosphorylated GTPase regulatory enzymes and proteins participating in trafficking, which may help prime them for activation and degranulation. Neonatal platelets were enriched in phosphorylated proteins involved in insulin growth factor signaling. CONCLUSION: Using label-free data-independent acquisition mass spectrometry, our findings expanded the known neonatal platelet proteome and identified important differences in protein content and phosphorylation between neonatal and adult platelets. These developmental differences suggested enhanced immune functions for adult platelets and presence of molecular machinery related to platelet activation. These findings are important to understanding mechanisms underlying key platelet functions as well as the harmful effects of adult platelet transfusions given to preterm infants.

Developmental differences in megakaryocytopoiesis are associated with up-regulated TPO signaling through mTOR and elevated GATA-1 levels in neonatal megakaryocytes.

Multiple observations support the existence of developmental differences in megakaryocytopoiesis. We have previously shown that neonatal megakaryocyte (MK) progenitors are hyperproliferative and give rise to MKs smaller and of lower ploidy than adult MKs. Based on these characteristics, neonatal MKs have been considered immature. The molecular mechanisms underlying these differences are unclear, but contribute to the pathogenesis of disorders of neonatal megakaryocytopoiesis. In the present study, we demonstrate that low-ploidy neonatal MKs, contrary to traditional belief, are more mature than adult low-ploidy MKs. These mature MKs are generated at a 10-fold higher rate than adult MKs, and result from a developmental uncoupling of proliferation, polyploidization, and terminal differentiation. This pattern is associated with up-regulated thrombopoietin (TPO) signaling through mammalian target of rapamycin (mTOR) and elevated levels of full-length GATA-1 and its targets. Blocking of mTOR with rapamycin suppressed the maturation of neonatal MKs without affecting ploidy, in contrast to the synchronous inhibition of polyploidization and cytoplasmic maturation in adult MKs. We propose that these mechanisms allow fetuses/neonates to populate their rapidly expanding bone marrow and intravascular spaces while maintaining normal platelet counts, but also set the stage for disorders restricted to fetal/neonatal MK progenitors, including the Down syndrome-transient myeloproliferative disorder and the thrombocytopenia absent radius syndrome.

Unique Features of Nanomaterials and their Combination Support Applications in Orthodontics.

Nanotechnology is a rapidly evolving field with numerous biological applications and is becoming increasingly significant due to its immense potential to enhance the properties of orthodontic and biomaterials. It is employed in various emerging areas of orthodontics, focusing on improving the performance of diverse orthodontic appliances and accessories, as well as nanoelectromechanical systems (NEMS) and nanorobots. Nevertheless, the biocompatibility and cytotoxicity of nanomaterials in orthodontic applications require further investigation. This paper reviews the latest applications of nanomaterials in orthodontics, elucidates their unique features and synergistic applications in orthodontics, and outlines prospective developments in the field.

Phosphoproteomics reveals content and signaling differences between neonatal and adult platelets.

Background and Objective: Recent clinical studies have shown that transfusions of adult platelets increase morbidity and mortality in preterm infants. Neonatal platelets are hyporesponsive to agonist stimulation, and emerging evidence suggests developmental differences in platelet immune functions. This study was designed to compare the proteome and phosphoproteome of resting adult and neonatal platelets. Methods: We isolated resting umbilical cord blood-derived platelets from healthy full term neonates (n=9) and resting blood platelets from healthy adults (n=7), and compared protein and phosphoprotein contents using data independent acquisition mass spectrometry. Results: We identified 4745 platelet proteins with high confidence across all samples. Adult and neonatal platelets clustered separately by principal component analysis. Adult platelets were significantly enriched for immunomodulatory proteins, including ß2 microglobulin and CXCL12, whereas neonatal platelets were enriched for ribosomal components and proteins involved in metabolic activities. Adult platelets were enriched for phosphorylated GTPase regulatory enzymes and proteins participating in trafficking, which may help prime them for activation and degranulation. Neonatal platelets were enriched for phosphorylated proteins involved in insulin growth factor signaling. Conclusions: Using state-of-the-art mass spectrometry, our findings expanded the known neonatal platelet proteome and identified important differences in protein content and phosphorylation compared with adult platelets. These developmental differences suggested enhanced immune functions for adult platelets and presence of a molecular machinery related to platelet activation. These findings are important to understanding mechanisms underlying key platelet functions as well as the harmful effects of adult platelet transfusions given to preterm infants.

The hibernating 13-lined ground squirrel as a model organism for potential cold storage of platelets.

Hibernating mammals have developed many physiological adaptations to extreme environments. During hibernation, 13-lined ground squirrels (Ictidomys tridecemlineatus) must suppress hemostasis to survive prolonged body temperatures of 4-8°C and 3-5 heartbeats per minute without forming lethal clots. Upon arousal in the spring, these ground squirrels must be able to quickly restore normal clotting activity to avoid bleeding. Here we show that ground squirrel platelets stored in vivo at 4-8°C were released back into the blood within 2 h of arousal in the spring with a body temperature of 37°C but were not rapidly cleared from circulation. These released platelets were capable of forming stable clots and remained in circulation for at least 2 days before newly synthesized platelets were detected. Transfusion of autologous platelets stored at 4°C or 37°C showed the same clearance rates in ground squirrels, whereas rat platelets stored in the cold had a 140-fold increase in clearance rate. Our results demonstrate that ground squirrel platelets appear to be resistant to the platelet cold storage lesions observed in other mammals, allowing prolonged storage in cold stasis and preventing rapid clearance upon spring arousal. Elucidating these adaptations could lead to the development of methods to store human platelets in the cold, extending their shelf life.

Neonatal and adult megakaryopoiesis.

PURPOSE OF REVIEW: It has become increasingly clear that there are substantial biological differences between fetal/neonatal and adult megakaryopoiesis. Over the last 18 months, studies challenged the paradigm that neonatal megakaryocytes are immature and revealed a developmentally unique uncoupling of proliferation, polyploidization, and cytoplasmic maturation. Several studies also described substantial molecular differences between fetal/neonatal and adult megakaryocytes involving transcription factors, signaling pathways, cytokine receptors, and microRNAs. RECENT FINDINGS: This review will summarize our current knowledge on the developmental differences between fetal/neonatal and adult megakaryocytes, and recent advances in the underlying molecular mechanisms, including differences in transcription factors, in the response to thrombopoietin (Tpo), and newly described developmentally regulated signaling pathways. We will also discuss the implications of these findings on the way megakaryocytes interact with the environment, the response of neonates to thrombocytopenia, and the pathogenesis of Down syndrome-transient myeloproliferative disorder (TMD) and Down syndrome-acute megakaryoblastic leukemia (DS-AMKL). SUMMARY: A better characterization of the molecular differences between fetal/neonatal and adult megakaryocytes is critical to elucidating the pathogenesis of a group of disorders that selectively affect fetal/neonatal megakaryocyte progenitors, including the thrombocytopenia-absent radius (TAR) syndrome, Down syndrome-TMD or Down syndrome-AMKL, and the delayed platelet engraftment following cord blood transplantation.

Erratum: MicroRNA-101-3p suppresses cell proliferation, invasion and enhances chemotherapeutic sensitivity in salivary gland adenoid cystic carcinoma by targeting Pim-1.

[This corrects the article on p. 3015 in vol. 5, PMID: 26693056.].