covid 19: health in Kazakhstan, megakaryocytes, the endothelial hypothesis
two megakaryocytes in the bone marrow, arrowed
Jacinta: So just to point out, from our last post, that Dr Seheult described long-term inhaled corticosteroid as sometimes having serious side-effects, such as cataracts, osteoporosis and pneumonia. He also presented contradictory rat studies on using NAC as a supplement, highlighting the need for more systematic RCTs in humans.
Canto: And what do we make of the Chinese embassy in Kazakhstan warning of a pneumonia outbreak there, which they claim is deadlier than covid19? Can we trust this?
Jacinta: Well, the Kazakhstan government has denied that the pneumonia problem was new and unknown, but it is clearly a problem, and sadly I can’t find any news about it that’s less than a month old, at about the time the news broke internationally. Some Chinese health officials are claiming that the pneumonia outbreak is related to covid19, but there’s no clear evidence about that, and this pneumonia problem in Kazakhstan is well over a year old, though it has become more of a problem with the advent of covid19. More research and information required.
Canto: Update 95 is dated July 14, and starts with conditions in Dr Seheult’s own county in California, where as we know the cases numbers have risen almost catastrophically. Some parts of the county’s hospitals have been newly transformed into ICUs. He presents a graph showing the recent increase in covid19 patients, but also a diminution in the number of suspected cases, indicating an improvement in diagnosis. And then he looks at a paper about ‘megakaryocytes and platelet fibrin thrombi [which] characterise multi-organ thrombosis at autopsy in covid19’..
Jacinta: Yes it looks at some autopsies and finds these megakaryocytes, which are precursors to platelets – they’re large as the name suggests, and they’re produced in the bone marrow, and are normally relatively rare, constituting 1 in 10,000 bone marrow cells, but can rapidly increase in response to some infections – they found these cells throughout the body. So how did they get to these multiple organs? Thrombosis was a feature of multiple organs regardless of anticoagulation treatment, suggesting that this thrombosis process started early in the infection cycle. The paper presents some fairly graphic images of large-scale thrombosis in the pulmonary artery and thickening of alveolar walls, with diffuse alveolar damage (DAD) preventing effective oxygenation, and also megakaryocytes in the kidneys. Other sites, such as the heart epicardium, feature large numbers of white blood cells and megakaryocytes. We also see ECGs apparently during myocardial infarction (heart attack) but I don’t know how to read those. The conclusion of the paper finds that the many thrombi found throughout the microvasculature of principal organs occurred in situ and before death. This was confirmed by ‘lines of Zahn’, visible layering which reveals clot formation while the blood is flowing, pumped by a beating heart. Now, this is very complex but important stuff, so I’m going to quote from the paper and try to make sense of it:
The extensive nature of platelet-fibrin thrombi in the alveolar capillaries in our patients may explain the observation that oxygenation is disrupted in an exaggerated fashion early in the disease course of patients with covid19, as this suggests evidence of ventilation-perfusion mismatch unrelated to hyaline membrane formation. Our patients’ lungs all had histopathologic findings of DAD, which has been the most frequently reported finding in covid19 autopsies thus far.
So firstly, what are hyaline membranes? They’re a composite of fibrin (an insoluble protein used in blood clotting), cellular debris, including various blood cells or parts thereof, and other eosinophilic stuff – stuff that boosts inflammation and curbs infection, or tries to. So what’s being said here is that the ‘ventilation-perfusion mismatch’, the problems with oxygenation, may be more related to the platelet-fibrin thrombi than the hyaline membrane formation, found mostly in the lungs. So now I’m going to quote something even more technical – it’s all a learning process:
Thrombi were located in veins and in the pulmonary arteries and arterioles and in microvessels, but not in systemic arteries. Despite elevated fibrin degradation products, in only one case of a patient with cirrhosis did we observe glomerular thrombotic microangiopathy, arguing against disseminated intravascular coagulation, haemolytic-uremic syndrome, or thrombotic thrombocytopenic purpura as a predominant pathophysiological pathway. Schistocytes may suggest endothelial damage, but we found them only rarely. We found no endothelial abnormalities on microscopic review, in alignment with previous studies, but we cannot rule out increased exposure of tissue factor, erosion of the endothelial glycocalyx, or other mechanisms of endothelial dysfunction that could be pro-coagulant without showing histopathological evidence of activation or erosion.
Canto: Scheisse! I can’t unpack too much of that, but I do note they ‘found no endothelial abnormalities… in alignment with previous studies’. I thought we were establishing that this is an endothelial disease, über alles? Are we being led up zie garden path?
Jacinta: Well let’s look more closely. The systemic arteries are those that carry oxygenated blood away from the heart to the other organs, and return deoxygenated blood to the heart. The pulmonary arteries, on the other hand, carry deoxygenated blood to the lungs. What this means in terms of thrombi I’m not sure. Fibrin degradation products (FDPs) (one sub-type of which are D-dimers, types of protein fragments) are produced by clot degeneration. Clotting creates a net of fibrin as part of the healing process, and after this process the net is broken down by an enzyme called plasmin, releasing protein fragments – FDPs. Now, they say that they observed ‘globular thrombotic microangiopathy’ in only one case of a patient with cirrhosis. Cirrhosis is essentially scar tissue of the liver, and it’s generally permanent – you can’t really unscar it, though you can of course prevent more damage being done. The scarring is a kind of self-repair of damage from a variety of sources – hepatitis, alcohol abuse and other liver diseases. As to glomerular thrombotic angiopathy, a glomerulus is a network of capillaries at the end of each nephron in the kidneys. Thrombotic microangiopathy is a rare but serious disease of those capillaries or microvessels, mostly in the kidney and the brain, obviously involving thrombosis.So the general lack of globular thrombotic microangiopathy – and remember they were only looking at at a handful of autopsy subjects – argued against these other pathologies as a pathway in the aetiology of covid19. But let’s look at them – disseminated intravascular coagulation (DIC) is as it sounds, blood clots forming throughout the body, often blocking small blood vessels…
Canto: But I thought that was just what was happening with covid19? That it was proving to be a a vascular, endothelial disease.
Jacinta: Yes I’m a bit confused too. I just tell myself I’m only the messenger.. So haemolytic-uremic syndrome (HUS) is a group of blood disorders in which the red blood count goes down, platelets are also very low and the kidneys are failing. Very nasty symptoms.
Canto: Right – that hasn’t been associated with covid19 before.
Jacinta: Not that I know of, FWIW. Finally, thrombotic thrombocytopenic purpura (TTP) is another blood disorder with clots forming in small blood vessels throughout the body, and a drop in red blood cells and platelets. Its weird, but perhaps what is written next about schistocytes is key here. They didn’t find many schistocytes in these bodies. These are fragments of red blood cells, broken down, jagged pieces of cells that are characteristic by-products, I think, of the the above-mentioned diseases. So that’s something that marks off covid19. So they found no evidence of endothelial dysfunction, though they couldn’t rule out such things as ‘erosion of the endothelial glycocalyx’. This glycocalyx is a mesh of bound glycoproteins and such covering the lumen side of the endothelium. Anyway, all in all this seems a blow, though maybe only a minor one, to the endothelial hypothesis.
Canto : Well, that was all very technical. Time for a rest….
References
Coronavirus Pandemic Update 94: Inhaled Steroids COVID-19 Treatment; New Pneumonia in Kazakhstan?
Coronavirus Pandemic Update 95: Widespread Clotting on Autopsy; New COVID-19 Prognostic Data
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1915585/
https://en.wikipedia.org/wiki/Schistocyte
https://en.wikipedia.org/wiki/Thrombotic_thrombocytopenic_purpura
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