Vascular Pathology, RBC Dysfunction, and Endothelial Senescence (2022–2026)

Added 2026-04-10. This section covers the 2022–2026 vascular literature integrated into Chapters 6, 7, 10, 14, and 18.

1 Nunes et al. 2026 — Virus-Induced Endothelial Senescence as Cause of ME/CFS

Full Citation:: Nunes M, Kell L, Slaghekke A, Wüst RC, Fielding BC, Kell DB, Pretorius E. Virus-induced endothelial senescence as a cause and driving factor for ME/CFS and long COVID: mediated by a dysfunctional immune system. Cell Death & Disease. 2026;17(1):16. DOI:: 10.1038/s41419-025-08162-2 Key Argument:: Viral infection induces endothelial senescence at BBB, cerebral arteries, gut, and skeletal muscle microvasculature. Senescent cells produce SASP (pro-inflammatory, pro-oxidative, procoagulant, vasoconstrictive). NK cell dysfunction and T cell exhaustion in ME/CFS prevent senescent cell clearance, establishing a self-perpetuating loop. IgG from ME/CFS/Long COVID patients causes mitochondrial fragmentation in endothelial cells, not the reverse. Certainty:: 0.40 — mechanistic logic compelling; endothelial senescence not yet directly measured in ME/CFS tissue Integrated into:: Chapter 7 (Virus-Induced Endothelial Senescence), Chapter 10 (Immune Complex–Endothelial Injury as a Central Vascular Mechanism) Key Implication:: Senolytics (dasatinib + quercetin) as rational therapeutic target; explains why cytokine/B-cell therapies have had limited benefit

2 McAlpine et al. 2026 — Vascular Biomarkers Correlate with Cognition in Neuropsychiatric Long COVID

Full Citation:: McAlpine LS, Shorer EF, Chiarella J, Nelson A, Veenhuis R, Azola A, Lee A, Pierce R, Farhadian S, Rubin LH, Spudich SS, for the Yale COVID Mind 2 and IMPACT Study Groups. Vascular inflammation in neuropsychiatric long COVID and its association with cognitive and psychiatric symptoms. Brain, Behavior, and Immunity. 2026;117:101247. DOI:: 10.1016/j.bbih.2026.101247 PMID:: 42056279 Article Type:: Cross-sectional case-control study Sample Size:: n=50 (neuropsychiatric Long COVID), n=28 (acute COVID-19), n=29 (recovered controls); plus validation cohort: n=114 (late Long COVID), n=31 (recovered) Key Findings:

- Long COVID showed elevated endothelial adhesion markers (sL-selectin, ADAMTS13, sP-selectin, sICAM-1) compared to recovered controls
- Coagulation markers (D-dimer, fibrinogen) did NOT differ from controls — critical distinction: endothelial dysfunction without coagulopathy
- Vascular biomarkers correlated with cognitive performance: higher sP-selectin associated with lower fluency and verbal learning; lower α1-acid glycoprotein associated with poorer verbal memory, verbal learning, fluency, depression, and anxiety
- Some biomarkers (fetuin, sL-selectin, α-2 macroglobulin) were higher in Long COVID than acute COVID-19 — persistent dysregulation pattern
- Late Long COVID cohort (>3 years) showed no biomarker differences from controls — normalization over time

Conclusion:: Persistent dysregulation at intersection of inflammation, platelet adhesion, and endothelial dysfunction is strongly linked to neuropsychiatric Long COVID symptoms. Elevated endothelial adhesion markers suggest distinct pathophysiology from acute COVID-19 and correlate with impaired brain function. Limitations:: Cross-sectional design (cannot establish causality); cognitive testing limited to 4 subtests; psychiatric measures self-reported; normalization in late cohort suggests temporal evolution not captured in primary analysis. ME/CFS Relevance:: HIGH — demonstrates vascular biomarker pattern (endothelial dysfunction WITHOUT coagulopathy) that aligns with Heng 2025 ME/CFS findings. Shows direct correlation between vascular biomarkers and cognitive performance, providing testable prediction for ME/CFS. Supports Nunes 2026 endothelial senescence hypothesis. Temporal normalization in late Long COVID suggests vascular mechanisms may be stage-dependent in chronic post-infectious syndromes. Certainty Assessment::

- *Quality:* Medium-High (multicenter validation cohort, rigorous statistical adjustment for age/BMI/diabetes, standardized neuropsychological testing)
- *Sample:* Adequate (n=50 primary LC group, n=114 validation cohort)
- *Replication:* Not yet independently replicated for Long COVID cognitive correlations
- *Score:* 0.75

3 Flaskamp et al. 2022 — Failed Angiogenic Compensation in ME/CFS

Full Citation:: Flaskamp L, Roubal C, Uddin S, Sotzny F, Kedor C, Bauer S, Scheibenbogen C, Seifert M. Serum of Post-COVID-19 Syndrome Patients with or without ME/CFS Differentially Affects Endothelial Cell Function In Vitro. Cells. 2022;11(15):2376. DOI:: 10.3390/cells11152376 Key Finding:: Post-COVID serum (without ME/CFS) enhances angiogenic tube formation in endothelial cells; ME/CFS serum specifically abolishes this response. ME/CFS serum also reduces VCAM-1, ICAM-1, and E-selectin expression. Suggests failed angiogenic compensation as a transition mechanism to ME/CFS chronicity. Certainty:: 0.30 — single in vitro study; in vivo relevance not established Integrated into:: Chapter 10 (Immune Complex–Endothelial Injury as a Central Vascular Mechanism, Failed Angiogenic Compensation as the Transition Mechanism from Post-COVID to ME/CFS)

4 Nunes et al. 2022 — First Documentation of Microclots in ME/CFS

Full Citation:: Nunes JM, Kruger A, Proal A, Kell DB, Pretorius E. The Occurrence of Hyperactivated Platelets and Fibrinaloid Microclots in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS). Pharmaceuticals (Basel). 2022;15(8):931. DOI:: 10.3390/ph15080931 Key Finding:: First paper to document fibrinaloid microclots in ME/CFS (not just Long COVID). Microclot area >10-fold greater than controls. Platelet spreading score 2.72 ± 1.24 vs 1.00 (PAC-1 and CD62P markers). Hypercoagulable state in ~50% by thromboelastography. Certainty:: 0.55 — replicated within the Pretorius group; independent replication needed Integrated into:: Chapter 10 (Coagulation and Rheological Abnormalities)

5 Nunes et al. 2023 — Cardiovascular and Haematological Pathology Review

Full Citation:: Nunes JM, Kell DB, Pretorius E. Cardiovascular and hematological pathology in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS): A role for viruses. Blood Reviews. 2023;60:101075. DOI:: 10.1016/j.blre.2023.101075 Key Finding:: Review documenting 26% mean CBF reduction, orthostatic intolerance >95% in some cohorts, reduced stroke volume (10.2% in severe ME/CFS), fibrinaloid microclots and platelet hyperactivation below Long COVID levels but above healthy controls. Herpesviruses proposed as maintenance factors. Certainty:: 0.50 (review of mostly replicated findings) Integrated into:: Chapter 10 (Coagulation and Rheological Abnormalities)

6 Nunes et al. 2024 — Plasma Proteomics Reveals Prothrombotic State

Full Citation:: Nunes JM, Vlok M, Proal A, Kell DB, Pretorius E. Data-independent LC-MS/MS analysis of ME/CFS plasma reveals a dysregulated coagulation system, endothelial dysfunction, downregulation of complement machinery. Cardiovascular Diabetology. 2024;23:259. DOI:: 10.1186/s12933-024-02315-x Key Finding:: 24 significantly elevated proteins in ME/CFS plasma (n=15 vs 10 controls). THBS1, PF4, P-selectin elevated; Protein S decreased. Complement components reduced. Ongoing prothrombotic, pro-coagulant state — not a residual acute-phase artifact. Certainty:: 0.50 — small cohort; replicated by Heng et al. 2025 for THBS1 and VWF independently Integrated into:: Chapter 10 (Coagulation and Rheological Abnormalities)

7 Kruger et al. 2022 — Microclot Proteomics in Long COVID

Full Citation:: Kruger A, Vlok M, Turner S, Venter C, Laubscher GJ, Kell DB, Pretorius E. Proteomics of fibrin amyloid microclots in long COVID/post-acute sequelae of COVID-19 (PASC) shows many entrapped pro-inflammatory molecules that may also contribute to a failed fibrinolytic system. Cardiovascular Diabetology. 2022;21:190. DOI:: 10.1186/s12933-022-01623-4 Key Finding:: 27 distinct immunoglobulin variants in Long COVID microclots absent from controls. VWF 2.6×, PF4 3.5× elevated. Plasma kallikrein 4.4× decreased. Entrapped pro-inflammatory molecules impair fibrinolysis. Microclots physically obstruct capillaries. Certainty:: 0.55 (replicated within Pretorius group) Integrated into:: Chapter 10 (Coagulation and Rheological Abnormalities)

8 Guo et al. 2025 — ME/CFS RBC Oxygen-Sensing Failure at Capillary Level

Full Citation:: Guo Y, Zhou S, Ren S, Liu X, Nemat-Gorgani M, Gresser MJ, Davis RW, Wan J. Microfluidic Assessment of PO2-Regulated RBC Capillary Velocity in ME/CFS. Blood: Red Cells & Iron. 2025;1(3):100019. DOI:: 10.1182/bloodrci.2024.100019 Institution:: Stanford University Key Finding:: Using microfluidic channels (5.05 × 5.94 μm) under hypoxia (PO₂ 0–34 mmHg), ME/CFS RBCs show significantly compromised capillary velocity vs healthy controls. Hypoxia-sensing mechanism — normally triggering vasodilation — is impaired: a cell-autonomous defect independent of target tissue mitochondrial state. Certainty:: 0.55 — novel methodology from Stanford Davis lab; independent replication needed Integrated into:: Chapter 10 (Coagulation and Rheological Abnormalities), Chapter 6 (Step 1: Substrate Delivery - Glucose, Fatty Acid, and Oxygen Uptake)

9 Grau et al. 2024 — Persistent RBC Morphological Abnormalities in Long COVID

Full Citation:: Grau M, Presche A, Krüger AL, Bloch W, Haiduk B. Red Blood Cell Morphology Is Associated with Altered Hemorheological Properties and Fatigue in Patients with Long COVID. Biology (Basel). 2024;13(11):948. DOI:: 10.3390/biology13110948 Key Finding:: 20.8 ± 10.7% morphologically abnormal RBCs (echinocytes, acanthocytes) vs 2.9 ± 1.5% in controls, at mean 42 weeks post-infection (beyond RBC lifespan — ongoing production of abnormal RBCs). Fatigue correlation r = −0.51 (p = 0.006). Certainty:: 0.55 — quantified hematological-symptom link; Long COVID cohort, ME/CFS-specific replication needed Integrated into:: Chapter 10 (Coagulation and Rheological Abnormalities)

10 Rogers et al. 2024 — Modelling COVID-19 Oxygen Delivery Deficit

Full Citation:: Rogers SC, Brummet M, Safari Z, Wang Q, Rowden T, Boyer T, Doctor A. COVID-19 impairs oxygen delivery by altering red blood cell hematological, hemorheological, and oxygen transport properties. Frontiers in Physiology. 2024;15:1320697. DOI:: 10.3389/fphys.2023.1320697 Key Finding:: Three concurrent RBC defects in COVID-19. Maintaining equivalent oxygen delivery would require ~135% increase in cardiac output — physiologically impossible. Blood type O shows greater deformability impairment than blood type A. Certainty:: 0.55 — quantitative modeling validates clinical severity; COVID-19 acute phase, not ME/CFS Integrated into:: Chapter 10 (Coagulation and Rheological Abnormalities, Coagulation and Rheological Abnormalities)

11 Scheibenbogen & Wirth 2024 — Temporal Model: Vascular to Mitochondrial

Full Citation:: Scheibenbogen C, Wirth KJ. Key Pathophysiological Role of Skeletal Muscle Disturbance in Post COVID and Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS): Accumulated Evidence. Journal of Cachexia, Sarcopenia and Muscle. 2024;16(1):e13669. DOI:: 10.1002/jcsm.13669 Key Finding:: Early post-COVID: predominantly microvascular disturbance. ME/CFS: mitochondrial structural damage appears later and selectively. Causal chain: capillary hypoperfusion → ischaemia/reperfusion → Na+/H+ exchange → Na+ overload → NCX1 reversal → mitochondrial Ca²⁺ toxicity. Termed Acquired Ischaemic Mitochondrial Myopathy (AIMM). Strong evidence for vascular-primary causation. Certainty:: 0.50 — cross-sectional comparison not longitudinal; AIMM framework compelling Integrated into:: Chapter 6 (Step 1: Substrate Delivery - Glucose, Fatty Acid, and Oxygen Uptake), Chapter 10 (Coagulation and Rheological Abnormalities, Vascular Pathology as the Primary Initiating Event in ME/CFS)

12 Van Campen et al. 2023 — Orthostatic Hypocapnia as CBF Amplifier

Full Citation:: van Campen CMC, Rowe PC, Verheugt FWA, Visser FC. Influence of End-Tidal CO2 on Cerebral Blood Flow during Orthostatic Stress in Controls and Adults with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome. Physiological Reports. 2023;11(17):e15639. DOI:: 10.14814/phy2.15639 Key Finding:: n=535 female ME/CFS patients. End-tilt PETCO₂: 26–30 mmHg vs 36 ± 3 mmHg controls. CO₂ reactivity slopes intact — hypocapnia is the amplifier, not impaired reactivity. CBF reduction 28–31% vs 7% controls. Orthostatic hypocapnia functions as a physiological amplifier of CBF deficits beyond what cardiac output alone predicts. Certainty:: 0.60 — large cohort (n=535); single research group Integrated into:: Chapter 10 (Near-Universal Vasopressin Deficiency in ME/CFS, Near-Universal Vasopressin Deficiency in ME/CFS)

13 El-Medany et al. 2024 — Carotid Body Sensitisation in Long COVID

Full Citation:: El-Medany A, Carberry J, McConnachie A, et al. Carotid body dysregulation contributes to Long COVID symptoms. Communications Medicine. 2024;4:20. DOI:: 10.1038/s43856-024-00447-5 Key Finding:: HVR 145% higher in Long COVID vs controls (p=0.0007). VE/VCO₂ slope significantly elevated. ACE2 receptor abundance in carotid body provides direct viral entry mechanism. P2X3 receptor antagonism (gefapixant) proposed as therapeutic target. Certainty:: 0.40 — small study (n=14); novel finding requiring replication; Long COVID not ME/CFS Integrated into:: Chapter 18 (Additional Integrative Topics)

14 Edgell et al. 2025 — IMT Pilot RCT in ME/CFS

Full Citation:: Edgell H, Pereira TJ, Kerr K, Badhwar S, et al. Inspiratory muscle training improves autonomic function in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome and post-acute sequelae of SARS-CoV-2: A pilot study. Respiratory Physiology & Neurobiology. 2025;331:104360. DOI:: 10.1016/j.resp.2024.104360 NCT:: NCT05196529 Key Finding:: 8-week IMT pilot RCT (n=12 ME/CFS). PEM-avoiding design (frequency, not effort). Improved: inspiratory muscle pressure, 6MWT, resting HR, HRV, sleep. Additional ME/CFS-specific improvements: vascular function, COMPASS-31 autonomic score, pain. No PEM exacerbations. Certainty:: 0.35 — pilot (n=12); no sham comparator; positive signal warrants definitive trial Integrated into:: Chapter 18 (Additional Integrative Topics)