Myeloid Bias in the Bone Marrow of Septic Patients and Its Correlation With Disease Severity and Prognosis: A Single-Center, Prospective Cohort Study

Official title

Myeloid Bias in the Bone Marrow of Septic Patients

Overview

Sepsis remains a leading cause of critical illness worldwide, yet the underlying mechanisms driving its profound and persistent immune dysfunction are incompletely understood. The bone marrow, as the birthplace of all immune cells, plays a central role in orchestrating systemic immune responses. Emerging evidence from animal models suggests that sepsis triggers emergency myeloid-biased hematopoiesis in the bone marrow, characterized by expansion of myeloid progenitors and myeloid-derived suppressor cells (MDSCs) at the expense of lymphoid and erythroid lineages. This bone marrow remodeling precedes peripheral immune alterations and may represent the initiating event of sepsis-induced immunosuppression. However, direct clinical evidence in humans is scarce. This prospective, single-center cohort study aims to systematically characterize bone marrow hematopoietic remodeling in patients with septic shock, compared to critically ill non-septic patients and healthy volunteers, and to determine whether the degree of myeloid lineage bias correlates with disease severity, immunosuppression, and adverse clinical outcomes. This study will enroll three cohorts. Bone marrow aspirates and peripheral blood samples will be collected at 48-72 hours post-enrollment for flow cytometric immunophenotyping of hematopoietic stem/progenitor cells, MDSC subsets, and PD-L1 expression, as well as cytokine profiling and exploratory single-cell transcriptomics. Rectal swabs will be collected synchronously for 16S rRNA sequencing and untargeted metabolomics to investigate the association between gut microbiota, microbial metabolites, and bone marrow myeloid skewing, testing the gut-bone marrow-immune axis hypothesis. Clinical severity (SOFA/APACHE II), secondary infections, and 90-day mortality will be assessed to evaluate prognostic value. By integrating bone marrow hematopoiesis, gut microbiome, and clinical outcomes, this study seeks to provide novel mechanistic insights into sepsis-induced immunoparalysis and identify potential biomarkers or therapeutic targets for immune restoration.

Interventions

• Procedure Bone marrow aspirate collection
  Bone marrow aspiration was performed at the posterior superior iliac spine under local anesthesia 24-48 hours after enrollment. Using a standard aspirate needle and strict aseptic technique, approximately 2-3 mL of bone marrow aspirate was collected.

Primary outcome measures

• Percentage and Absolute Count of Hematopoietic Stem Cells (HSCs) in Bone Marrow [Time frame: Between 48 and 72 hours after enrollment (preferably day 3)]
• Percentage and Absolute Count of Common Myeloid Progenitors (CMPs) in Bone Marrow [Time frame: Between 48 and 72 hours after enrollment (preferably day 3)]
• Percentage and Absolute Count of Granulocyte-Monocyte Progenitors (GMPs) in Bone Marrow [Time frame: Between 48 and 72 hours after enrollment (preferably day 3)]
• Percentage and Absolute Count of Megakaryocyte-Erythroid Progenitors (MEPs) in Bone Marrow [Time frame: Between 48 and 72 hours after enrollment (preferably day 3)]
• Percentage and Absolute Count of Common Lymphoid Progenitors (CLPs) in Bone Marrow [Time frame: Between 48 and 72 hours after enrollment (preferably day 3)]
• GMP-to-CLP Ratio and Absolute Differential Count Index in Bone Marrow (Primary Composite Index) [Time frame: Between 48 and 72 hours after enrollment (preferably day 3)]
• Percentage and Absolute Count of PMN-MDSCs in Bone Marrow [Time frame: Between 48 and 72 hours after enrollment (preferably day 3)]
• Percentage and Absolute Count of M-MDSCs in Bone Marrow [Time frame: Between 48 and 72 hours after enrollment (preferably day 3)]
• PD-L1 Expression Level and PD-L1⁺ Absolute Count on Bone Marrow MDSCs [Time frame: Between 48 and 72 hours after enrollment (preferably day 3)]
• Percentage and Absolute Count of T Cells in Bone Marrow [Time frame: Between 48 and 72 hours after enrollment (preferably day 3)]

Secondary outcome measures (12)

• Correlation Between Bone Marrow GMP-to-CLP Ratio (Percentage and Absolute) and SOFA score [Time frame: Baseline (bone marrow at 48-72 hours) and days 1, 3, 5, 7 (severity scores)]
• Correlation Between Bone Marrow GMP-to-CLP Ratio (Percentage and Absolute) and APACHE II score [Time frame: Baseline (bone marrow at 48-72 hours) and days 1, 3, 5, 7 (severity scores)]
• Association Between Bone Marrow Myeloid Lineage Bias (Percentages and Absolute Counts) and 90-Day Secondary Infection Rate [Time frame: From enrollment through 90-day follow-up]
• Bone Marrow Myeloid Lineage Bias (Percentages and Absolute Counts) as Predictors of 90-Day All-Cause Mortality [Time frame: From enrollment through 90-day follow-up]
• Association Between Bone Marrow Myeloid Lineage Bias (Percentages and Absolute Counts) and ICU / In-Hospital Mortality [Time frame: From enrollment through hospital discharge (up to 90 days)]
• Correlation Between Bone Marrow MDSC Absolute Counts and Peripheral Blood Lymphocyte Absolute Counts [Time frame: Baseline (bone marrow and peripheral blood at 48-72 hours; peripheral blood also on days 1, 5, 7 for longitudinal correlation)]
• Association Between Bone Marrow Myeloid Progenitor Absolute Counts and Peripheral Blood Cytokine Profile [Time frame: Baseline (bone marrow and peripheral blood at 48-72 hours); CRP/PCT on days 1, 3, 5, 7]
• Longitudinal Dynamics of Peripheral Blood Lymphocyte and MDSC Percentages and Absolute Counts During the First Week [Time frame: Days 1, 3, 5, 7 post-enrollment (peripheral blood)]
• Bone Marrow Microenvironment Cytokine and Chemokine Profile (Concentration) [Time frame: Baseline (bone marrow supernatant at 48-72 hours)]
• Exploratory Single-Cell Transcriptomic Profiling of Bone Marrow Hematopoietic Cells [Time frame: Baseline (bone marrow aspirate at 48-72 hours)]
• Correlation Between Gut Microbiota Alpha Diversity and Bone Marrow Myeloid Lineage Bias [Time frame: At 48-72 hours post-enrollment (rectal swab and bone marrow synchronized)]
• Correlation Between Key Dysbiotic Gut Bacterial Taxa and Bone Marrow Myeloid Lineage Bias [Time frame: At 48-72 hours post-enrollment (rectal swab and bone marrow synchronized)]

Eligibility criteria

1\. Inclusion Criteria

(1) Sepsis-Associated Critical Illness Cohort

• Age 18-80 years, both genders;
• Meets the Sepsis-3.0 criteria: confirmed or suspected infection with an acute increase in SOFA score of ≥2 points;
• Admitted to the intensive care unit (ICU) for 48-72 hours at the time of enrolment;
• Expected ICU length of stay ≥7 days;
• Written informed consent provided by the patient or their legally authorized representative.

(2) Non-Septic Critical Illness Cohort

• Age 18-80 years, both genders;
• Admitted to the ICU for 48-72 hours with a diagnosis of non-infectious critical illness, including but not limited to: (a) severe acute pancreatitis; (b) major trauma (Injury Severity Score ≥16); (c) post-major surgery (e.g., cardiovascular surgery, hepatectomy); (d) acute cerebrovascular disease (ischaemic stroke, intracerebral haemorrhage); (e) other critical conditions requiring ICU support;
• Expected ICU length of stay ≥7 days;
• Written informed consent provided by the patient or their legally authorized representative.

(3) Healthy Volunteer Control Cohort

• Age 18-80 years, both genders.
• No acute or chronic medical history; recent health check-up results are normal.
• Normal complete blood count: white blood cell count, haemoglobin, and platelet count within the normal reference ranges;
• Willing and able to provide written informed consent.

2\. Exclusion Criteria

(1) Sepsis-Associated Critical Illness Cohort

• Haematological disorders: previous or current primary haematological diseases affecting bone marrow haematopoiesis, including leukaemia, myelodysplastic syndromes, aplastic anaemia, multiple myeloma, lymphoma, etc;
• Active malignancy or receipt of chemotherapy/radiotherapy within the past 3 years;
• Immunosuppressed state: (a) use of immunosuppressive agents within the past 3 months (including glucocorticoids ≥0.5 mg/kg/day for ≥2 weeks); (b) history of solid organ or haematopoietic stem cell transplantation; (c) HIV infection or AIDS; (d) congenital immunodeficiency;
• Blood transfusion or bone marrow transplantation within the past 3 months;
• Severe chronic organ dysfunction: (a) Child-Pugh Class C liver disease; (b) end-stage renal disease (eGFR <30 mL/min) without regular dialysis;
• Abnormalities at the puncture site: infection, rash, trauma, or anatomical deformity at the posterior superior iliac spine;
• Pregnancy or breastfeeding;
• Moribund state with expected survival <24 hours;
• Participation in another interventional clinical trial within 3 months before or at enrolment;
• Refusal to sign informed consent by the patient or legal representative.

(2) Non-Septic Critical Illness Cohort

• Evidence of infection: confirmed or suspected active infection (including pneumonia, intra-abdominal infection, urinary tract infection, bloodstream infection, etc.) within 48 hours of ICU admission;
• All other exclusion criteria listed for the Sepsis-Associated Critical Illness Cohort (items 1-10) apply.

(3) Healthy Volunteer Control Cohort

• History of infection within the past 1 month;
• Abnormalities at the puncture site: infection, rash, trauma, or anatomical deformity at the posterior superior iliac spine;
• Pregnancy or breastfeeding.

Criteria are shown verbatim from the registry (in English). Final eligibility is always assessed by the study center.

Healthy volunteers: Yes

Study design

Observational model

Cohort

Study locations

Center list to be confirmed — check the primary protocol.

Identifiers

NCT: NCT07667153 · ZJC202603

Primary sources (government registries)

• ClinicalTrials.gov (US NIH)

View this study on ClinicalTrials.gov ↗