Dear everyone, I am very interested in the histopathology of bone marrow in obese state. It has been reviewed that obesity might decrease the HSC proliferation. However, it seemed that obesity might promote myelopoiesis and monocytosis. Then, I have a question. Are myeloid / lymphoid lineage populations in bone marrow decreased in absolute quantity in obese state? If so, does it mean monocytes, neutrophils, osteoclasts and lymphocytes would be all decreased in absolute quantity? But how obesity increases myelopoiesis? Does obesity increase the percentage of myeloid populations but decrease their absolute quantity at the expense of lymphoid populations? I am confused about the condition. It would be very appreciated if anyone could give me some explanation.
Dear Ting Yu,
As you know, obesity is associated with an increased expression of TNF alpha (http://www.ncbi.nlm.nih.gov/pubmed/20173393). High level of TNFa means proinflammatory state. Inflammation promotes myelopoiesis and in the same time its suppresses B lymphopoiesis (one of the examples http://www.ncbi.nlm.nih.gov/pubmed/25451836). The are, probably, much more factors that affect bone marrow hematopoietic niche and hematopoiesis in case of obesity, but TNFa seems to be one of the most important factors. I hope that this answer will help (a little).
Dear Marina A Aleksinskaya, thank you for your kind suggestions! I like the concept in the article (http://www.ncbi.nlm.nih.gov/pubmed/25451836) recommended by you, i.e., "LPS-activated stromal cells induce positive-dominant regulation of myelopoiesis and negative-dominant regulation of B lymphopoiesis, which facilitates emergency myelopoiesis during inflammation by suppressing B lymphopoiesis, thereby contributing to the host defense against infection". However, I also wonder if both of the myeloid and lymphoid lineage populations would be decreased in bone marrow with extremely expanded adipogenesis. Although flowcytometry would be necessary to explore the change of myeloid / ymphoid lineage percentage, actually, I have done some test using qPCR in DIO mice on diet for 30 weeks. I did not find any significant changes in Il1b or Il6. Neither osteoclastogenesis or myelopoiesis (maybe it was not appropriate to test the surface markers at gene level). But I did find decreased lymphopoiesis. As you have recommended in the article, G-CSF / GM-CSF and SDF-1 / SCF would be more helpful to expect myelopoiesis and lymphopoiesis respectively at gene level.
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