Modulation of megakaryopoiesis and platelet production during inflammation

Research progress of megakaryocytes and platelets in lung injury

The lung is an important site of extramedullary platelet formation, and megakaryocytes in the lung participate in immune responses in addition to platelet production. In acute lung injury and chronic lung injury, megakaryocytes and platelets play a promoting or protective role through different mechanisms. The authors reviewed the role of megakaryocytes and platelets in common clinical lung injuries with different course of disease and different pathogenic factors in order to provide new thinking for the diagnosis and treatment of lung injuries.

Role of Systemic Immune Inflammation Index, Systemic Immune Response Index, Neutrophil Lymphocyte Ratio and Platelet Lymphocyte Ratio in Predicting Peritoneal Culture Positivity and Prognosis in Cases of Spontaneous Bacterial Peritonitis Admitted to the Emergency Department

Background and Objectives: Spontaneous bacterial peritonitis (SBP) is a life-threatening disease that requires early diagnosis and treatment. It is known that a positive culture result for SBP, which is a common reason for admission to the emergency department, is related to the severity and prognosis of the disease. However, as it is not possible to determine the culture result in the early stage of the disease, different methods are required to predict prognosis in the emergency department. This study was conducted to evaluate the success of the SII, SIRI, NLR and PLR in predicting culture results, intensive care needs and mortality in patients with SBP admitted to the emergency department. Materials and Methods: This study was a retrospective, observational study. Patients with SBP who applied to the emergency department were included in this study. Pregnant women, patients with a malignancy, patients with another infection and patients with liver failure were excluded from this study. Data were analyzed in terms of culture results, the need for intensive care and mortality development. Analyses were performed using SPSS version 26. Results are presented with a 95% confidence interval. A p value less than 0.05 was considered statistically significant. Participant data were analyzed using the independent samples t-test or the Mann-Whitney U test based on normality, and ROC analyses were conducted to assess test accuracies and determine cut-off values. Results: A total of 275 patients were included in this study. Although the culture results of 183 patients were positive, 92 were negative. The SII, NLR and PLR were found to be significantly higher in culture-positive patients (p < 0.001, p = 0.013 and p = 0.002, respectively). The SII and NLR were found to be significantly higher in patients with high mortality (p < 0.001 and p = 0.017, respectively). Conclusions: This study showed that the SII, NLR and PLR may be useful in predicting culture positivity and prognosis in SBP patients in the emergency department.

The association of platelet to white blood cell ratio with diabetes: a nationwide survey in China

Background

Inflammation is integral to diabetes pathogenesis. The novel hematological inflammatory biomarker, platelet to white blood cell ratio (PWR), is linked with various conditions such as chronic kidney disease and stroke. However, the association of this novel clinical indicator with diabetes still remains unclear, which is investigated in this study.

Materials and Methods

A total of 10,973 Chinese participants were included and grouped according to the tertiles of PWR (T1, T2, and T3 groups). Diagnosis of prediabetes and diabetes adhered to American Diabetes Association criteria. Binary logistic regression was adopted to assess the relationship between PWR and both diabetes and prediabetes. The dose-response relationship of PWR and diabetes was examined using restricted cubic spline regression. Subgroup and interaction analyses were conducted to investigate potential covariate interactions.

Results

Individuals with higher PWR had better lifestyles and lipid profiles (all P < 0.05). After adjusting for all the covariates, the T2 group had a 0.83-fold (95% CI: 0.73-0.93, P < 0.01) risk of diabetes and that for the T3 group was 0.68-fold (95% CI: 0.60-0.78. P < 0.001). Dose-response analysis identified non-linear PWR-diabetes associations in the general population and females (both P < 0.05), but absent in males. Participants with prediabetes in the T2 and T3 groups had lower risks of diabetes (OR = 0.80 for the T2 group, P < 0.001 and 0.68 for the T3 group, P < 0.001) in the full models. All the sensitivity analysis support consistent conclusions.

Conclusions

An increase in PWR significantly correlates with reduced diabetes risks. A non-linear PWR-diabetes relationship exists in the general population and females, but not in males. The correlation between PWR and diabetes indicates that PWR holds potentials in early identification and prevention of diabetes.

Immunity to pathogenic mucosal C. albicans infections mediated by oral megakaryocytes activated by IL-17 and candidalysin

The fungus Candida albicans can cause mucosal infections including oropharyngeal candidiasis (OPC) in immunocompromised patients. In humans, an increased risk of fungal infections correlates with thrombocytopenia. However, our understanding of platelets and megakaryocytes (Mks) in mucosal fungal infections is almost entirely unknown. When megakaryocyte- and platelet-depleted mice were infected with OPC, the tongue showed higher fungal burden, due to decreased neutrophil accumulation. Protection depended on a distinct population of oral-resident Mks. Interleukin-17, important in antifungal immunity, was required since mice lacking the IL-17 receptor had decreased circulating platelets and their oral Mks did not expand during OPC. The secretion of the peptide toxin candidalysin activated human Mks to release platelets with antifungal capacity. Infection with a candidalysin-deficient strain resulted in decreased expansion of tongue Mks during OPC. This is the first time that a distinct megakaryocyte population was identified in the oral mucosa which is critical for immunity against fungal infection.

Harmful Free Radicals in Aging: A Narrative Review of Their Detrimental Effects on Health

The production of harmful free radicals (H-FRs), especially those with oxygen or nitrogen atoms, depends on both internal and environmental causes. The negative effects of H-FRs are greatly alleviated by antioxidant protection. The harmful impact of oxidative stress, or OS, is brought on by a disparity between the defense mechanisms of the body and the creation of H-FRs. Aging is characterized by a slow decline in tissue and organ competence. Age-mediated pathologies start as an aberrant accumulation of H-FRs, which inhibit cells' capacity to divide, repair, and operate, based on the OS theorem of aging. The natural outcome of this situation is apoptosis. These conditions may include skeletal muscle dysfunction, cancer, cardiovascular, chronic hepatitis, chronic renal, and chronic pulmonary disorders. Given the substantial role that OS plays in the progression of many of these illnesses, antioxidant-based therapy may have a favorable impact on how these diseases progress. To ascertain the true efficacy of this therapy strategy, more research is necessary. The aim of this study is to provide an overview of the literature on this challenging issue that is attracting interest.

The localization, origin, and impact of platelets in the tumor microenvironment are tumor type-dependent

BACKGROUND

How platelets interact with and influence the tumor microenvironment (TME) remains poorly characterized.

METHODS

We compared the presence and participation of platelets in the TME of two tumors characterized by highly different TME, PyMT AT-3 mammary tumors and B16F1 melanoma.

RESULTS

We show that whereas firmly adherent platelets continuously line tumor vessels of both AT-3 and B16F1 tumors, abundant extravascular stromal clusters of platelets from thrombopoietin-independent origin were present only in AT-3 mammary tumors. We further show that platelets influence the angiogenic and inflammatory profiles of AT-3 and B16F1 tumors, though with very different outcomes according to tumor type. Whereas thrombocytopenia increased bleeding in both tumor types, it further caused severe endothelial degeneration associated with massive vascular leakage, tumor swelling, and increased infiltration of cytotoxic cells, only in AT-3 tumors.

CONCLUSIONS

These results indicate that while platelets are integral components of solid tumors, their localization and origin in the TME, as well as their impact on its shaping, are tumor type-dependent.

Interleukins in Platelet Biology: Unraveling the Complex Regulatory Network

Interleukins, a diverse family of cytokines produced by various cells, play crucial roles in immune responses, immunoregulation, and a wide range of physiological and pathological processes. In the context of megakaryopoiesis, thrombopoiesis, and platelet function, interleukins have emerged as key regulators, exerting significant influence on the development, maturation, and activity of megakaryocytes (MKs) and platelets. While the therapeutic potential of interleukins in platelet-related diseases has been recognized for decades, their clinical application has been hindered by limitations in basic research and challenges in drug development. Recent advancements in understanding the molecular mechanisms of interleukins and their interactions with MKs and platelets, coupled with breakthroughs in cytokine engineering, have revitalized the field of interleukin-based therapeutics. These breakthroughs have paved the way for the development of more effective and specific interleukin-based therapies for the treatment of platelet disorders. This review provides a comprehensive overview of the effects of interleukins on megakaryopoiesis, thrombopoiesis, and platelet function. It highlights the potential clinical applications of interleukins in regulating megakaryopoiesis and platelet function and discusses the latest bioengineering technologies that could improve the pharmacokinetic properties of interleukins. By synthesizing the current knowledge in this field, this review aims to provide valuable insights for future research into the clinical application of interleukins in platelet-related diseases.

Platelet lifespan and mechanisms for clearance

PURPOSE OF REVIEW

Activated or aged platelets are removed from circulation under (patho)physiologic conditions, the exact mechanism of platelet clearance under such conditions remains unclear and are currently being investigated. This review focuses on recent findings and controversies regarding platelet clearance and the disruption of platelet life cycle.

RECENT FINDINGS

The platelet life span is determined by glycosylation of platelet surface receptors with sialic acid. Recently, it was shown that platelet activation and granule release leads to desialylation of glycans and accelerated clearance of platelets under pathological conditions. This phenomenon was demonstrated to be a main reason for thrombocytopenia being a complication in several infections and immune disorders.

SUMMARY

Although we have recently gained some insight into how aged platelets are cleared from circulation, we are still not seeing the full picture. Further investigations of the platelet clearance pathways under pathophysiologic conditions are needed as well as studies to unravel the connection between platelet clearance and platelet production.

The Albumin to Globulin Ratio Performs Well for Diagnosing Periprosthetic Joint Infection: A Single-Center Retrospective Study

BACKGROUND

Accurate diagnosis of the periprosthetic joint infection (PJI) remains a challenge for surgeons. The purpose of this study was to assess the value of albumin to globulin ratio (AGR) and globulin (GLB) for diagnosing PJI.

METHODS

A total of 182 patients undergoing revision after arthroplasty were included and divided into 2 groups, 61 in knee group (PJI: 38; non-PJI: 23) and 121 in hip group (PJI: 26; non-PJI: 95). We used receiver operating characteristic curves to determine the diagnostic value of AGR, GLB, inflammatory markers (erythrocyte sedimentation rate [ESR] and C-reactive protein [CRP]).

RESULTS

The receiver operating characteristic curves showed the areas under the curve of AGR, GLB, ESR, and CRP in the knee group were 0.940, 0.928, 0.867, and 0.848, respectively, and they were 0.855, 0.831, 0.886, and 0.912 in the hip group. The optimal predictive cut-off values for AGR in knee and hip groups were 1.375 and 1.295, respectively. The sensitivity and specificity of AGR, respectively, were 94.7% and 87.0% (knee group) and 84.6% and 75.8% (hip group) for diagnosing PJI. The sensitivity of "AGR or ESR" and specificity of "AGR and GLB" in the knee group were 99.6% and 98.9%, respectively.

CONCLUSION

For knee or hip groups, the AGR exhibits good value for the diagnosis of PJI comparable with ESR and CRP. The AGR and GLB, together with CRP and ESR, should be used as the preferred indicators for diagnosing PJI. The "AGR or ESR" and "AGR and GLB" in the knee group have an excellent diagnostic value in sensitivity and specificity, respectively.

Mean platelet volume as a potential biomarker for survival outcomes in ovarian clear cell carcinoma

OBJECTIVE

This study aimed to explore the prognostic value of mean platelet volume (MPV) in patients with ovarian clear cell carcinoma (OCCC) and evaluate the predictive performance of a random forest model incorporating MPV and other key clinicopathological factors.

METHODS

A total of 204 patients with OCCC treated between January 2004 and December 2019 were retrospectively analyzed. Clinicopathological characteristics and preoperative laboratory data were collected, and survival outcomes were evaluated using the Kaplan-Meier method and Cox proportional hazards models. An optimal MPV cutoff was determined by receiver operating characteristic (ROC) curve analysis. A random forest model was then constructed using the identified independent prognostic factors, and its predictive performance was evaluated.

RESULTS

The ROC analysis identified 9.3 fL as the MPV cutoff value for predicting 2-year survival. The MPV-low group had lower 5-year overall survival and progression-free survival rates than the MPV-high group (p = 0.003 and p = 0.034, respectively). High MPV emerged as an independent prognostic factor (p = 0.006). The random forest model, incorporating the FIGO stage, residual tumors, peritoneal cytology, and MPV, demonstrated robust predictive performance (area under the curve: 0.905).

CONCLUSION

MPV is a promising prognostic indicator in OCCC. Lower MPV correlated with worse survival rates, advocating its potential utility in refining patient management strategies. The commendable predictive performance of the random forest model, integrating MPV and other significant prognostic factors, suggests a pathway toward enhanced survival prediction, thereby warranting further research.

Evaluation of Mean Platelet Volume in Children with Hypertension

Background

Childhood hypertension, a disease with increasing prevalence, can lead to severe health problems. With the increased pressure on the vascular endothelium in hypertension, lesions in the endothelium result in endothelial activation and a process of inflammation, which causes platelet activation and in the bone marrow the release of platelet precursor cells into the peripheral blood stream. During inflammation, changes in the number and size of platelets are observed. With the release of platelet precursors into the peripheral blood stream due to platelet activation, an increase in mean platelet volume (MPV) is also seen.

Aim

Our aim in this study is the evaluation of MPV changes in the hemogram of children suffering from hypertension, a condition causing severe cardiovascular problems. Material and Methods. This research is a descriptive retrospective cross-sectional study. It consists of a patient group diagnosed with hypertension and a control group of children presenting for routine check-ups with no diagnosed hypertension. Demographic characteristics, arterial pressure values, and hemogram parameters have been evaluated.

Results

A total of 90 cases were enrolled in the study, including a patient group of 45 cases with hypertension (19 females, 26 males) and a control group of 45 cases (27 females, 18 males). The median age was 15 years in the hypertension group and 13 years in the control group. In the hypertension cases, the thickness of the carotis intima media was statistically significantly greater than in the control group (p < 0.001). Echocardiographic findings (IVSd, LVDd, LVPWd, IVSs, LVDs, LVPWs, and LV mass) were significantly higher in the hypertension group compared to the control group (p < 0.001). A statistically significant difference in platelet count and MPV values between the groups was not found (p = 0.151, p = 0.405, respectively).

Conclusion

While MPV is hypothesized to be higher in hypertensive individuals, there was no statistically significant difference between the hypertensive and non-hypertensive groups in this study.

Efficient megakaryopoiesis and platelet production require phospholipid remodeling and PUFA uptake through CD36

Lipids contribute to hematopoiesis and membrane properties and dynamics; however, little is known about the role of lipids in megakaryopoiesis. Here we show that megakaryocyte progenitors, megakaryocytes and platelets present a unique lipidome progressively enriched in polyunsaturated fatty acid (PUFA)-containing phospholipids. In vitro, inhibition of both exogenous fatty acid functionalization and uptake as well as de novo lipogenesis impaired megakaryocyte differentiation and proplatelet production. In vivo, mice on a high saturated fatty acid diet had significantly lower platelet counts, which was prevented by eating a PUFA-enriched diet. Fatty acid uptake was largely dependent on CD36, and its deletion in mice resulted in low platelets. Moreover, patients with a CD36 loss-of-function mutation exhibited thrombocytopenia and increased bleeding. Our results suggest that fatty acid uptake and regulation is essential for megakaryocyte maturation and platelet production and that changes in dietary fatty acids may be a viable target to modulate platelet counts.

Mutations, inflammation and phenotype of myeloproliferative neoplasms

Knowledge on the myeloproliferative neoplasms (MPNs) - polycythemia vera (PV), essential thrombocythemia (ET), primary myelofibrosis (PMF) - has accumulated since the discovery of the JAK/STAT-activating mutations associated with MPNs: JAK2V617F, observed in PV, ET and PMF; and the MPL and CALR mutations, found in ET and PMF. The intriguing lack of disease specificity of these mutations, and of the chronic inflammation associated with MPNs, triggered a quest for finding what precisely determines that MPN patients develop a PV, ET or PMF phenoptype. The mechanisms of action of MPN-driving mutations, and concomitant mutations (ASXL1, DNMT3A, TET2, others), have been extensively studied, as well as the role played by these mutations in inflammation, and several pathogenic models have been proposed. In parallel, different types of drugs have been tested in MPNs (JAK inhibitors, interferons, hydroxyurea, anagrelide, azacytidine, combinations of those), some acting on both JAK2 and inflammation. Yet MPNs remain incurable diseases. This review aims to present current, detailed knowledge on the pathogenic mechanisms specifically associated with PV, ET or PMF that may pave the way for the development of novel, curative therapies.

A double-edged sword of platelet-derived extracellular vesicles in tissues, injury or repair: The current research overview

Extracellular vesicles (EVs) are vesicular bodies with a double-layered membrane structure that are detached from the cell membrane or secreted by the cells. EVs secreted by platelets account for the main part in the blood circulation, which account for about 30% or even more. Many types of cells are regulated by PEVs, including endothelial cells, leukocytes, smooth muscle cells, etc. Nevertheless, despite the growing interest in the study of extracellular vesicles, there are still only a few studies on the role of PEVs. Therefore, this overview mainly focuses on one method of isolation and the functions of PEVs in tissues found so far, including promoting tissue repair and mediating tissue damage, which can be used for researchers to continue to explore the role of PEVs in other fields.

Efficient megakaryopoiesis and platelet production require phospholipid remodeling and PUFA uptake through CD36

Lipids contribute to hematopoiesis and membrane properties and dynamics, however, little is known about the role of lipids in megakaryopoiesis. Here, a lipidomic analysis of megakaryocyte progenitors, megakaryocytes, and platelets revealed a unique lipidome progressively enriched in polyunsaturated fatty acid (PUFA)-containing phospholipids. In vitro, inhibition of both exogenous fatty acid functionalization and uptake and de novo lipogenesis impaired megakaryocyte differentiation and proplatelet production. In vivo, mice on a high saturated fatty acid diet had significantly lower platelet counts, which was prevented by eating a PUFA-enriched diet. Fatty acid uptake was largely dependent on CD36, and its deletion in mice resulted in thrombocytopenia. Moreover, patients with a CD36 loss-of-function mutation exhibited thrombocytopenia and increased bleeding. Our results suggest that fatty acid uptake and regulation is essential for megakaryocyte maturation and platelet production, and that changes in dietary fatty acids may be a novel and viable target to modulate platelet counts.

Moderate level platelet count might be a good prognostic indicator for intra-abdominal infection in acute pancreatitis: A retrospective cohort study of 1,363 patients

Background

Early recognition of the risk factors is important for acute pancreatitis management. The aim of this study is to investigate the relationship between platelet count and clinical outcomes in patients with acute pancreatitis.

Methods

The data are collected from a university-affiliated hospital between January 2013 and December 2020. A generalized additive model and a two-piecewise linear regression model are used to estimate the association between platelet count and the risks of intra-abdominal infection, surgical intervention, in-hospital mortality, and length of hospital stay.

Results

Among the 1,363 patients, 99 (7.3%) patients suffered intra-abdominal infection, 190 (13.9%) patients underwent surgical intervention, and 38 (2.8%) patients died in the hospital. The median length of hospital stay is 21 days. Generalized additive model and two-piecewise linear regression analysis show that the risk of intra-abdominal infection decreases as the platelet count increases to 160 × 10⁹/L (OR: 0.991, 95% CI: 0.984-0.998, p = 0.015) and then increases as the platelet count levels up (OR: 1.007, 95% CI: 1.004-1.010, p < 0.001). The trend is similar to the risk of surgical intervention and length of hospital stay. Even though there seems a declining trend in mortality, no significant association is found after adjustment for potential confounders. Further analysis shows that changes in platelet count within the first 3 days after admission have no obvious association with clinical outcomes.

Conclusion

A platelet count of approximately 160 × 10⁹/L on admission is associated with the lowest risk of intra-abdominal infection, surgical intervention, and shortest hospital stay in patients with acute pancreatitis.

Characterization of the impact of immune checkpoint inhibitors on platelet activation and aggregation

Immune checkpoint inhibitors (ICIs) are effective oncological drugs which block cellular check-point receptors typically targeted by tumor immune evasion strategies. Despite their benefits, clinicians have reported treatment-associated thromboembolism during ICI therapy in recent years. Though several theories on this ICI-associated pathogenesis exist, the direct effects of ICIs on platelets remains unknown. We therefore investigated the potential direct and indirect effect of PD-1, PD-L1 and CTLA-4-targeting ICIs on platelet functionality in multifaceted in vitro experiments. Interestingly, we could not observe a clear effect of ICI on platelet aggregation and primary hemostasis in whole blood and platelet concentrate-based assays. Furthermore, the presence of ICIs in toll-like receptor stimulation had no significant impact on platelet surface marker expression. In a second approach, we investigated the indirect immunological impact of ICIs on platelet activation by exposing platelets to supernatants from ICI- and Staphylococcal enterotoxin B-exposed PBMCs. Whereas ICIs affected IL-2 levels in supernatants, we could not detect clear differences in the secretion of pro-thrombogenic factors and platelet responses. The obtained data suggest that the direct influence of ICIs on platelet activation or the influence of altered T cell function on platelet activation cannot be considered a major factor in the development of thrombotic events.

Unique crosstalk between platelet and leukocyte counts during treatment for acute coronary syndrome: A retrospective observational study

In the pathophysiology of acute coronary syndrome (ACS), platelet (PLT) and neutrophil (Neu) crosstalk may be important for activating coagulation and inflammation. It has been speculated that PLTs and Neu may affect each other's cell counts; however, few studies have investigated this hypothesis. In this study, we measured changes in blood cell counts in 245 patients with ACS during treatment and investigated the mutual effects of each blood cell type. Path diagrams were drawn using structural equation modeling, and temporal changes in the count of each blood cell type and the relevance of these changes were analyzed. Throughout the treatment period, the numbers of all blood cell types (red blood cells [RBCs], leukocytes, and PLTs) were associated with each other before and after treatment. A detailed examination of the different cell types revealed that the PLT count at admission had a significant positive effect on the leukocyte (especially Neu) count after treatment. Conversely, the leukocyte (especially Neu) count at admission had a significant positive effect on the PLT count after treatment. During ACS, PLTs and leukocytes, especially Neu, stimulate each other to increase their numbers. The formation of a PLT-leukocyte complex may increase coagulation activity and inflammation, which can lead to a further increase in the counts of both blood cell types.

Bifunctional effect of the inflammatory cytokine tumor necrosis factor α on megakaryopoiesis and platelet production

BACKGROUND AND OBJECTIVES

Platelets are affected by many factors, such as infectious or aseptic inflammation, and different inflammatory states may induce either thrombocytopenia or thrombocytosis. Tumor necrosis factor α (TNFα) is an important inflammatory cytokine that has been shown to affect the activity of hematopoietic stem cells. However, its role in megakaryocyte (MK) development and platelet production remains largely unknown. This study aimed to investigate the effects of TNFα on MK and platelet generation.

METHODS AND RESULTS

The ex vivo study with human CD34+ cells demonstrated that TNFα differentially modulated commitment toward the MK lineage. Specifically, a low concentration of 0.5 ng/ml TNFα promoted MK maturation, proplatelet formation, and platelet production, whereas a high concentration of 10 ng/ml or more TNFα exhibited a substantial inhibitory effect on MK and platelet production. The distinct effect of TNFα on MKs was mainly dependent on TNFα receptor 1. TNFα differentially regulated the MAPK-ERK1/2 signaling pathway and the cytoskeletal proteins cofilin and MLC2. The in vivo study with Balb/c mice indicated that low-dose or high-dose TNFα administration differentially affected short-term platelet recovery after bone marrow transplantation.

CONCLUSIONS

Our study revealed distinct roles for TNFα in megakaryopoiesis and thrombopoiesis and may provide new insights regarding the treatment for platelet disorders.

CXCR4high megakaryocytes regulate host-defense immunity against bacterial pathogens

Megakaryocytes (MKs) continuously produce platelets to support hemostasis and form a niche for hematopoietic stem cell maintenance in the bone marrow. MKs are also involved in inflammatory responses; however, the mechanism remains poorly understood. Using single-cell sequencing, we identified a CXCR4 highly expressed MK subpopulation, which exhibited both MK-specific and immune characteristics. CXCR4high MKs interacted with myeloid cells to promote their migration and stimulate the bacterial phagocytosis of macrophages and neutrophils by producing TNFα and IL-6. CXCR4high MKs were also capable of phagocytosis, processing, and presenting antigens to activate T cells. Furthermore, CXCR4high MKs also egressed circulation and infiltrated into the spleen, liver, and lung upon bacterial infection. Ablation of MKs suppressed the innate immune response and T cell activation to impair the anti-bacterial effects in mice under the Listeria monocytogenes challenge. Using hematopoietic stem/progenitor cell lineage-tracing mouse lines, we show that CXCR4high MKs were generated from infection-induced emergency megakaryopoiesis in response to bacterial infection. Overall, we identify the CXCR4high MKs, which regulate host-defense immune response against bacterial infection.

Infection of lung megakaryocytes and platelets by SARS-CoV-2 anticipate fatal COVID-19

SARS-CoV-2, although not being a circulatory virus, spread from the respiratory tract resulting in multiorgan failures and thrombotic complications, the hallmarks of fatal COVID-19. A convergent contributor could be platelets that beyond hemostatic functions can carry infectious viruses. Here, we profiled 52 patients with severe COVID-19 and demonstrated that circulating platelets of 19 out 20 non-survivor patients contain SARS-CoV-2 in robust correlation with fatal outcome. Platelets containing SARS-CoV-2 might originate from bone marrow and lung megakaryocytes (MKs), the platelet precursors, which were found infected by SARS-CoV-2 in COVID-19 autopsies. Accordingly, MKs undergoing shortened differentiation and expressing anti-viral IFITM1 and IFITM3 RNA as a sign of viral sensing were enriched in the circulation of deadly COVID-19. Infected MKs reach the lung concomitant with a specific MK-related cytokine storm rich in VEGF, PDGF and inflammatory molecules, anticipating fatal outcome. Lung macrophages capture SARS-CoV-2-containing platelets in vivo. The virus contained by platelets is infectious as capture of platelets carrying SARS-CoV-2 propagates infection to macrophages in vitro, in a process blocked by an anti-GPIIbIIIa drug. Altogether, platelets containing infectious SARS-CoV-2  alter COVID-19 pathogenesis and provide a powerful fatality marker. Clinical targeting of platelets might prevent viral spread, thrombus formation and exacerbated inflammation at once and increase survival in COVID-19.

Platelet and immune signature associated with a rapid response to the BNT162b2 mRNA COVID-19 vaccine

BACKGROUND

A rapid immune response is critical to ensure effective protection against COVID-19. Platelets are first-line sentinels of the vascular system able to rapidly alert and stimulate the immune system. However, their role in the immune response to vaccines is not known.

OBJECTIVE

To identify features of the platelet-immune crosstalk that would provide an early readout of vaccine efficacy in adults who received the mRNA-based COVID-19 vaccine (BNT162b2).

METHODS

We prospectively enrolled 11 young healthy volunteers (54% females, median age: 28 years) who received two doses of BNT162b2, 21 days apart, and we studied their platelet and immune response before and after each dose of the vaccine (3 and 10 ± 2 days post-injection), in relation to the kinetics of the humoral response.

RESULTS

Participants achieving an effective level of neutralizing antibodies before the second dose of the vaccine (fast responders) had a higher leukocyte count, mounted a rapid cytokine response that incremented further after the second dose, and an elevated platelet turnover that ensured platelet count stability. Their circulating platelets were not more reactive but expressed lower surface levels of the immunoreceptor tyrosine-based inhibitory motif (ITIM)-coupled receptor CD31 (PECAM-1) compared to slow responders, and formed specific platelet-leukocyte aggregates, with B cells, just 3 days after the first dose, and with non-classical monocytes and eosinophils.

CONCLUSION

We identified features of the platelet-immune crosstalk that are associated with the development of a rapid humoral response to an mRNA-based vaccine (BNT162b2) and that could be exploited as early biomarkers of vaccine efficacy.

Angiopoietin-2/-1 ratios and MMP-3 levels as an early warning sign for the presence of giant cell arteritis in patients with polymyalgia rheumatica

Background

Diagnosing patients with giant cell arteritis (GCA) remains difficult. Due to its non-specific symptoms, it is challenging to identify GCA in patients presenting with symptoms of polymyalgia rheumatica (PMR), which is a more common disease. Also, commonly used acute-phase markers CRP and ESR fail to discriminate GCA patients from PMR and (infectious) mimicry patients. Therefore, we investigated biomarkers reflecting vessel wall inflammation for their utility in the accurate diagnosis of GCA in two international cohorts.

Methods

Treatment-naïve GCA patients participated in the Aarhus AGP cohort (N = 52) and the Groningen GPS cohort (N = 48). The AGP and GPS biomarker levels and symptoms were compared to patients presenting phenotypically as isolated PMR, infectious mimicry controls and healthy controls (HCs). Serum/plasma levels of 12 biomarkers were measured by ELISA or Luminex.

Results

In both the AGP and the GPS cohort, we found that weight loss, elevated erythrocyte sedimentation rate (ESR) and higher angiopoietin-2/-1 ratios but lower matrix metalloproteinase (MMP)-3 levels identify concomitant GCA in PMR patients. In addition, we confirmed that elevated platelet counts are characteristic of GCA but not of GCA mimicry controls and that low MMP-3 and proteinase 3 (PR3) levels may help to discriminate GCA from infections.

Conclusion

This study, performed in two independent international cohorts, consistently shows the potential of angiopoietin-2/-1 ratios and MMP-3 levels to identify GCA in patients presenting with PMR. These biomarkers may be used to select which PMR patients require further diagnostic workup. Platelet counts may be used to discriminate GCA from GCA look-alike patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-022-02754-5.

C-type lectin-like receptor 2 specifies a functionally distinct subpopulation within phenotypically defined hematopoietic stem cell population that contribute to emergent megakaryopoiesis

C-type lectin-like receptor 2 (CLEC-2) expressed on megakaryocytes plays important roles in megakaryopoiesis. We found that CLEC-2 was expressed in about 20% of phenotypical long-term hematopoietic stem cells (LT-HSCs), which expressed lower levels of HSC-specific genes and produced larger amounts of megakaryocyte-related molecules than CLEC-2low LT-HSCs. Although CLEC-2high LT-HSCs had immature clonogenic activity, cultured CLEC-2high LT-HSCs preferentially differentiated into megakaryocytes. CLEC-2high HSCs yielded 6.8 times more megakaryocyte progenitors (MkPs) and 6.0 times more platelets 2 weeks and 1 week after transplantation compared with CLEC-2low LT-HSCs. However, platelet yield from CLEC-2high HSCs gradually declined with the loss of MkPs, while CLEC-2low HSCs self-renewed long-term, indicating that CLEC-2high LT-HSCs mainly contribute to early megakaryopoiesis. Treatment with pI:C and LPS increased the proportion of CLEC-2high LT-HSCs within LT-HSCs. Almost all CLEC-2low LT-HSCs were in the G0 phase and barely responded to pI:C. In contrast, 54% of CLEC-2high LT-HSCs were in G0, and pI:C treatment obliged CLEC-2high LT-HSCs to enter the cell cycle and differentiate into megakaryocytes, indicating that CLEC-2high LT-HSCs are primed for cell cycle entry and rapidly yield platelets in response to inflammatory stress. In conclusion, CLEC-2high LT-HSCs appear to act as a reserve for emergent platelet production under stress conditions.

The bone marrow niche from the inside out: how megakaryocytes are shaped by and shape hematopoiesis

Megakaryocytes (MKs), the largest of the hematopoietic cells, are responsible for producing platelets by extending and depositing long proplatelet extensions into the bloodstream. The traditional view of megakaryopoiesis describes the cellular journey from hematopoietic stem cells (HSCs) along the myeloid branch of hematopoiesis. However, recent studies suggest that MKs can be generated from multiple pathways, some of which do not require transit through multipotent or bipotent MK-erythroid progenitor stages in steady-state and emergency conditions. Growing evidence suggests that these emergency conditions are due to stress-induced molecular changes in the bone marrow (BM) microenvironment, also called the BM niche. These changes can result from insults that affect the BM cellular composition, microenvironment, architecture, or a combination of these factors. In this review, we explore MK development, focusing on recent studies showing that MKs can be generated from multiple divergent pathways. We highlight how the BM niche may encourage and alter these processes using different mechanisms of communication, such as direct cell-to-cell contact, secreted molecules (autocrine and paracrine signaling), and the release of cellular components (eg, extracellular vesicles). We also explore how MKs can actively build and shape the surrounding BM niche.

Vitamin D and Platelets: A Menacing Duo in COVID-19 and Potential Relation to Bone Remodeling

Global data correlate severe vitamin D deficiency with COVID-19-associated coagulopathy, further suggesting the presence of a hypercoagulable state in severe COVID-19 patients, which could promote thrombosis in the lungs and in other organs. The feedback loop between COVID-19-associated coagulopathy and vitamin D also involves platelets (PLTs), since vitamin D deficiency stimulates PLT activation and aggregation and increases fibrinolysis and thrombosis. Vitamin D and PLTs share and play specific roles not only in coagulation and thrombosis but also during inflammation, endothelial dysfunction, and immune response. Additionally, another ‘fil rouge’ between vitamin D and PLTs is represented by their role in mineral metabolism and bone health, since vitamin D deficiency, low PLT count, and altered PLT-related parameters are linked to abnormal bone remodeling in certain pathological conditions, such as osteoporosis (OP). Hence, it is possible to speculate that severe COVID-19 patients are characterized by the presence of several predisposing factors to bone fragility and OP that may be monitored to avoid potential complications. Here, we hypothesize different pervasive actions of vitamin D and PLT association in COVID-19, also allowing for potential preliminary information on bone health status during COVID-19 infection.

Granuloma Formation in a Cyba-Deficient Model of Chronic Granulomatous Disease Is Associated with Myeloid Hyperplasia and the Exhaustion of B-Cell Lineage

Haematopoiesis is a paradigm of cell differentiation because of the wide variety and overwhelming number of mature blood cells produced daily. Under stress conditions, the organism must adapt to a boosted demand for blood cells. Chronic granulomatous disease (CGD) is a genetic disease caused by inactivating mutations that affect the phagocyte oxidase. Besides a defective innate immune system, CGD patients suffer from recurrent hyper-inflammation episodes, circumstances upon which they must face emergency haematopoiesis. The targeting of Cybb and Ncf1 genes have produced CGD animal models that are a useful surrogate when studying the pathophysiology and treatment of this disease. Here, we show that Cyba^−/− mice spontaneously develop granuloma and, therefore, constitute a CGD animal model to complement the existing Cybb^−/− and Ncf1^−/− models. More importantly, we have analysed haematopoiesis in granuloma-bearing Cyba^−/− mice. These animals showed a significant loss of weight, developed remarkable splenomegaly, bone marrow myeloid hyperplasia, and signs of anaemia. Haematological analyses showed a sharped decrease of B-cells and a striking development of myeloid cells in all compartments. Collectively, our results show that granuloma inflammatory lesions dramatically change haematopoiesis homeostasis. Consequently, we suggest that besides their defective innate immunity, the alteration of haematopoiesis homeostasis upon granuloma may contribute to the dismal outcome of CGD.

Three new inflammatory markers C reactive protein to albumin ratio, neutrophil to lymphocyte ratio, and platelet to lymphocyte ratio correlated with relapsing polychondritis disease activity index

OBJECTIVE

The novel inflammatory markers C-reactive protein to albumin ratio (CAR), neutrophil to lymphocyte ratio (NLR), and platelet to lymphocyte ratio (PLR) were associated with the disease activity of many autoimmune diseases. The aim of this study was to evaluate the association of these new inflammatory indexes with relapsing polychondritis disease activity index (RPDAI).

METHODS

The data of relapsing polychondritis (RP) patients hospitalized between 2004 and 2020 at Peking Union Medical College Hospital were collected. One of the exclusive criteria was that RP patients overlapped with other diseases. Another was the RP patients with incomplete data. A total of 170 RP patients and 170 healthy controls (HCs) were included. The association of new inflammatory makers with RPDAI was assessed by Spearman's correlation analysis.

RESULTS

Compared to HCs, the CAR, NLR, and PLR were significantly higher in RP patients (both p < 0.001). The CAR, NLR, PLR, erythrocyte sedimentation rate and neutrophil counts in peripheral blood positively correlated with RPDAI. Blood albumin, lymphocyte count, hemoglobin (Hb) negatively correlated with RPDAI. The association of CAR, NLR, and PLR with RPDAI was demonstrated by Spearman's correlation analysis.

CONCLUSION

The novel inflammatory markers CAR, NLR and PLR were associated with RPDAI. Key Points • This is the first research to explore the association of CAR, NLR, and PLR with disease activity in patients with RP • CAR, NLR, and PLR are positively correlated with RPDAI • CAR, NLR, and PLR might be the potential predictors of disease activity in RP.

Airborne particulate matters induce thrombopoiesis from megakaryocytes through regulating mitochondrial oxidative phosphorylation

BACKGROUND

Although airborne fine particulate matter (PM) pollution has been demonstrated as an independent risk factor for pulmonary and cardiovascular diseases, their currently-available toxicological data is still far from sufficient to explain the cause-and-effect. Platelets can regulate a variety of physiological and pathological processes, and the epidemiological study has indicated a positive association between PM exposure and the increased number of circulative platelets. As one of the target organs for PM pollution, the lung has been found to be involved in the storage of platelet progenitor cells (i.e. megakaryocytes) and thrombopoiesis. Whether PM exposure influences thrombopoiesis or not is thus explored in the present study by investigating the differentiation of megakaryocytes upon PM treatment.

RESULTS

The results showed that PM exposure promoted the thrombopoiesis in an exposure concentration-dependent manner. PM exposure induced the megakaryocytic maturation and development by causing cell morphological changes, occurrence of DNA ploidy, and alteration in the expressions of biomarkers for platelet formation. The proteomics assay demonstrated that the main metabolic pathway regulating PM-incurred alteration of megakaryocytic maturation and thrombopoiesis was the mitochondrial oxidative phosphorylation (OXPHOS) process. Furthermore, airborne PM sample promoted-thrombopoiesis from megakaryocytes was related to particle size, but independent of sampling filters.

CONCLUSION

The findings for the first time unveil the potential perturbation of haze exposure in thrombopoiesis from megakaryocytes by regulating mitochondrial OXPHOS. The substantial evidence on haze particle-incurred hematotoxicity obtained herein provided new insights for assessing the hazardous health risks from PM pollution.

Platelet-derived extracellular vesicles infiltrate and modify the bone marrow during inflammation

During inflammation, steady-state hematopoiesis switches to emergency hematopoiesis to repopulate myeloid cells, with a bias toward the megakaryocytic lineage. Soluble inflammatory cues are thought to be largely responsible for these alterations. However, how these plasma factors rapidly alter the bone marrow (BM) is not understood. Inflammation also drives platelet activation, causing the release of platelet-derived extracellular vesicles (PEVs), which package diverse cargo and reprogram target cells. We hypothesized that PEVs infiltrate the BM, providing a direct mode of communication between the plasma and BM environments. We transfused fluorescent, wild-type (MPL+) platelets into recipient cMpl-/-mice before triggering systemic inflammation. Twenty hours postinfusion, we observed significant infiltration of donor platelet-derived particles in the BM, which we tracked immunophenotypically (MPL+ immunohistochemistry staining) and quantified by flow cytometry. To determine if this phenomenon relates to humans, we extensively characterized both megakaryocyte-derived and PEVs generated in vitro and in vivo, and found enrichment of extracellular vesicles in bone marrow compared with autologous peripheral blood. Last, BM from cMpl-/- mice was cultured in the presence or absence of wild-type (MPL+) PEVs. After 72 hours, flow cytometry revealed increased megakaryocytes only in cultures with added PEVs. The majority of CD41+ cells were bound to PEVs, suggesting a PEV-mediated rescue of megakaryopoiesis. In conclusion, we report for the first time that plasma-residing PEVs infiltrate the BM. Further, PEVs interact with BM cells in vivo and in vitro, causing functional reprogramming that may represent a novel model of inflammation-induced hematopoiesis.

Platelet Proteomes, Pathways, and Phenotypes as Informants of Vascular Wellness and Disease

Platelets rapidly undergo responsive transitions in form and function to repair vascular endothelium and mediate hemostasis. In contrast, heterogeneous platelet subpopulations with a range of primed or refractory phenotypes gradually arise in chronic inflammatory and other conditions in a manner that may indicate or support disease. Qualitatively distinguishable platelet phenotypes are increasingly associated with a variety of physiological and pathological circumstances; however, the origins and significance of platelet phenotypic variation remain unclear and conceptually vague. As changes in platelet function in disease exhibit many similarities to platelets following the activation of platelet agonist receptors, the intracellular responses of platelets common to hemostasis and inflammation may provide insights to the molecular basis of platelet phenotype. Here, we review concepts around how protein-level relations-from platelet receptors through intracellular signaling events-may help to define platelet phenotypes in inflammation, immune responses, aging, and other conditions. We further discuss how representing systems-wide platelet proteomics data profiles as circuit-like networks of causally related intracellular events, or, pathway maps, may inform molecular definitions of platelet phenotype. In addition to offering insights into platelets as druggable targets, maps of causally arranged intracellular relations underlying platelet function can also advance precision and interceptive medicine efforts by leveraging platelets as accessible, dynamic, endogenous, circulating biomarkers of vascular wellness and disease. Graphic Abstract: A graphic abstract is available for this article.

Obesity-induced inflammation: The impact of the hematopoietic stem cell niche

Obesity and obesity-related diseases like type 2 diabetes (T2D) are prominent global health issues; therefore, there is a need to better understand the mechanisms underlying these conditions. The onset of obesity is characterized by accumulation of proinflammatory cells, including Ly6c^hi monocytes (which differentiate into proinflammatory macrophages) and neutrophils, in metabolic tissues. This shift toward chronic, low-grade inflammation is an obese-state hallmark and highly linked to metabolic disorders and other obesity comorbidities. The mechanisms that induce and maintain increased inflammatory myelopoiesis are of great interest, with a recent focus on how obesity affects more primitive hematopoietic cells. The hematopoietic system is constantly replenished by proper regulation of hematopoietic stem and progenitor (HSPC) pools in the BM. While early research suggests that chronic obesity promotes expansion of myeloid-skewed HSPCs, the involvement of the hematopoietic stem cell (HSC) niche in regulating obesity-induced myelopoiesis remains undefined. In this review, we explore the role of the multicellular HSC niche in hematopoiesis and inflammation, and the potential contribution of this niche to the hematopoietic response to obesity. This review further aims to summarize the potential HSC niche involvement as a target of obesity-induced inflammation and a driver of obesity-induced myelopoiesis.

On the Quest for In Vitro Platelet Production by Re-Tailoring the Concepts of Megakaryocyte Differentiation

The demand of platelet transfusions is steadily growing worldwide, inter-donor variation, donor dependency, or storability/viability being the main contributing factors to the current global, donor-dependent platelet concentrate shortage concern. In vitro platelet production has been proposed as a plausible alternative to cover, at least partially, the increasing demand. However, in practice, such a logical production strategy does not lack complexity, and hence, efforts are focused internationally on developing large scale industrial methods and technologies to provide efficient, viable, and functional platelet production. This would allow obtaining not only sufficient numbers of platelets but also functional ones fit for all clinical purposes and civil scenarios. In this review, we cover the evolution around the in vitro culture and differentiation of megakaryocytes into platelets, the progress made thus far to bring the culture concept from basic research towards good manufacturing practices certified production, and subsequent clinical trial studies. However, little is known about how these in vitro products should be stored or whether any safety measure should be implemented (e.g., pathogen reduction technology), as well as their quality assessment (how to isolate platelets from the rest of the culture cells, debris, microvesicles, or what their molecular and functional profile is). Importantly, we highlight how the scientific community has overcome the old dogmas and how the new perspectives influence the future of platelet-based therapy for transfusion purposes.

Role of thrombopoiesis in leishmaniasis

The blood vascular system of mammals is unique in nature; inhabited with a pool of tiny small cell fragments called platelets; attributed with the most important patrolling tasks to check integrity of the entire endothelial landscape. Their production is tightly coupled with hematopoietic system where everything starts from self renewable multipotent hematopoietic stem cells (HSCs) which eventually undergo dual step (megakaryopoiesis-thrombopoiesis) thrombocytes production. Several cytokines tune the fate of every progenitor cells during hematopoiesis through temporal activation of specific transcription factors. Though platelets generated through steady state hematopoiesis are involved in the regulation of vascular homeostasis, these cells can sense pathogens through its innate immune sensors and can mount crucial responses against the invading pathogen. For this, the primary aim of many infections including Leishmania is to induce thrombocytopenia within infected host. But the underlying mechanism of this induced thrombocytopenia in Leishmania infection has not been evaluated. Elucidation of these mechanisms will be fruitful to design new chemotherapeutic strategies.

Abnormal liver-related biomarkers in COVID-19 patients and the role of prealbumin

BACKGROUND/AIMS

We aimed to evaluate the distribution of abnormal liver-related biomarkers in patients with coronavirus disease (COVID-19) and explore the prognostic value of elevated liver enzymes and abnormal liver synthetic capacity with regards to patient mortality.

PATIENTS AND METHODS

This retrospective observational study included 80 laboratory-confirmed COVID-19 cases. Data were collected from the electronic medical record system by a trained team of physicians. Alanine aminotransferase (ALT), aspartate aminotransferase (AST), total bilirubin (TB), albumin, and prealbumin levels at admission and on day 7 after admission were collected. The primary outcome of the current study was patient mortality.

RESULTS

Abnormal ALT, AST, TB, albumin, and prealbumin levels were observed in 11 (13.8%), 15 (18.8%), 5 (6.3%), 22 (27.5%), and 31 (38.8%) patients, respectively. Male gender correlated with elevated ALT and AST levels (p = 0.027 and 0.036, respectively). Higher levels of AST and lower levels of albumin and prealbumin were associated with patient mortality (p = 0.009, 0.002, and 0.003, respectively). Multivariate Cox regression analysis identified patient age (p = 0.013, HR 1.108) and prealbumin levels (p = 0.015, HR 0.986) as independent predictors for patient mortality. However, changes in liver-related biomarkers were not associated with poor outcome in multivariate analysis (p > 0.05).

CONCLUSIONS

Abnormalities in albumin and prealbumin levels are common among COVID-19 patients and hypoprealbuminemia independently predicts adverse outcome and should be carefully considered in clinical practice. Moreover, changes in liver-related biomarkers is not a salient feature of COVID-19.

J-shaped association of platelet-to-lymphocyte ratio with 5-year mortality among patients with chronic kidney disease in a prospective cohort study

PURPOSE

To examine whether platelet-to-lymphocyte ratio (PLR) is associated with 5-year mortality in patients with chronic kidney disease (CKD), we performed this study using data from the National Health and Nutrition Examination Survey (NHANES) through 1999 to 2006.

METHODS

3285 patients with CKD stage 1-5 were included. Patients' baseline characteristics were collected. Cox proportional hazards models were used to investigate the association of PLR with 5-year mortality including all-cause and cardiovascular mortality. Subgroup analysis was performed.

RESULTS

Within 5 years following the date of the NHANES 1999 to 2006 survey participation, 655 (19.94%) deaths were recorded and 207 patients died from cardiovascular disease. A J-shaped association between PLR and 5-year mortality was observed. In adjusted model 2, the elevated PLR Z-score was not significantly associated with a decreased 5-year all-cause mortality risk (HR: 0.44, 95% CI: 0.16-1.22) when PLR Z-score < - 0.91 whereas the elevated PLR Z-score was significantly associated with an increased 5-year all-cause mortality risk (HR: 1.09, 95% CI: 1.01-1.17) when PLR Z-score ≥ - 0.91. In adjusted model 2, neither the elevated PLR Z-score was significantly associated with a decreased 5-year cardiovascular mortality risk (HR: 0.85, 95% CI: 0.36-2.04) when PLR Z-score < - 0.47 nor the elevated PLR Z-score was significantly associated with an increased 5-year cardiovascular mortality risk (HR: 1.12, 95% CI: 0.93-1.34) when PLR Z-score ≥ - 0.47.

CONCLUSION

The elevated PLR is independently associated with an increased 5-year all-cause mortality risk among patients with CKD stage 1-5 when PLR ≥ 83.18, indicating that PLR might be a potential biomarker to predict 5-year all-cause mortality in CKD patients.

In vitro platelet production for transfusion purposes: Where are we now?

Over the last decade there has been a worldwide increase in the demand of platelet concentrates (PCs) for transfusion. This is, to a great extent, due to a growing and aging population with the concomitant increase in the incidence of onco-hematological diseases, which require frequent platelet (PLT) transfusions. Currently, PLTs are sourced uniquely from donations, and their storage time is limited only to a few days. The necessity to store PCs at room temperature (to minimize loss of PLT functional integrity), poses a major risk for bacterial contamination. While the implementation of pathogen reduction treatments (PRTs) and new-generation PLT additive solutions have allowed the extension of the shelf life and a safer PLT transfusion product, the concern of PCs shortage still pressures the scientific community to find alternative solutions with the aim of meeting the PLT transfusion increasing demand. In this concise report, we will focus on the efforts made to produce, in in vitro culture, high yields of viable and functional PLTs for transfusion purposes in a cost-effective manner, meeting not only current Good Manufacturing Practices (cGMPs), but also transfusion safety standards.

Plasma Fibrinogen and Platelet Count Are Referable Tools for Diagnosing Periprosthetic Joint Infection: A Single-Center Retrospective Cohort Study

BACKGROUND

Although the MusculoSkeletal Infection Society has suggested a series of markers to diagnose periprosthetic joint infection (PJI), no single marker can accurately identify infection before revision hip or knee arthroplasty, and exploring promising markers to easily and reliably diagnose PJI is ongoing. The aim of this study was to evaluate the diagnostic value of plasma fibrinogen and platelet count for diagnosing PJI.

METHODS

We retrospectively included 439 patients who underwent revision arthroplasty from January 2008 to December 2018; 79 patients with coagulation-related comorbidities were evaluated separately. The remaining 360 patients constituted 153 PJI and 207 non-PJI patients. Receiver operating characteristic curves were used to evaluate the maximum sensitivity and specificity of the tested markers.

RESULTS

The receiver operating characteristic curves showed that the areas under the curve for plasma fibrinogen, platelet count, and serum C-reactive protein and erythrocyte sedimentation rate were 0.834, 0.746, 0.887, and 0.842, respectively. Based on Youden's index, the optimal predictive cutoffs for fibrinogen and platelet count were 3.57 g/L and 221 × 10⁹/L, respectively. The sensitivity and specificity, respectively, were 68.6% and 86.0% (fibrinogen) and 57.5% and 83.1% (platelet count) for diagnosing PJI. The sensitivity and specificity, respectively, were 76.7% and 72.2% (fibrinogen) and 48.8% and 63.9% (platelet count) for diagnosing PJI in patients with coagulation-related comorbidities.

CONCLUSION

Plasma fibrinogen performed well for diagnosing PJI before revision arthroplasty, and its value neared that of traditional inflammatory markers. Although the diagnostic value of the platelet count was inferior to traditional markers, its diagnostic value was fair for diagnosing PJI. Fibrinogen also may be useful for diagnosing PJI in patients with coagulation-related comorbidities.