Re: Regulation of Erythropoiesis [Outline]

[E.S.Prakash]

Jaspreet, 

I am suggesting an outline here but varied responses are possible;

In describing regulation of erythropoiesis, I would first bring into discussion the principal stimulus for it: tissue hypoxia. 

Tissue hypoxia (a decrease in oxygen availability for metabolic processes at the level of cells) is sensed by hypoxia-inducible factors (HIF), transcription factors that induce the transcription of genes that facilitate adaptive cellular responses to hypoxia. 

One such adaptive response which occurs principally in the kidneys (interstitial cells surrounding peritubular capillaries in renal cortex) is the release of erythropoietin (EPO), a glycoprotein hormone, that stimulates the development of pluripotent hematopoietic stem cells into erythroid progenitor cells. 

Mention one or two physiologic or pathophysiologic states in which erythropoiesis would be accelerated - example, exposure to high altitude; acute or chronic blood loss. 

Erythropoietin is thus a key mediator and key driver of the adaptive response - erythropoiesis. 

You may make your understanding evident by stating that one of the mechanisms of anemia in individuals with chronic renal failure is erythropoietin insufficiency, and this is why recombinant EPO is administered to individuals with chronic renal failure. 

You may wish to acknowledge that it is evident that erythropoiesis is driven by a "negative feedback" mechanism

There are numerous other "factors" that are required for normal (successful) erythropoiesis - these include iron, vitamin B12, folate, pyridoxine, presence of an adequate population of stem cells, and an appropriate hormonal milieu in the bone marrow (some cytokines typical of a chronic inflammatory state might suppress erythropoiesis) . 

You may wish to briefly allude to other hormones that affect erythropoiesis - example, estrogens are said to have some inhibitory effect; androgens are said to have a stimulatory effect. This may in part account for gender differences in RBC count. 

You may wish to speak of a condition in which erythropoiesis is autonomous and independent of the stimulatory effects of erythropoietin. Primary proliferative polycythemia is a malignancy of hematopoietic stem cells that results in uncontrolled proliferation of aberrant erythroid progenitor cells.

Best, 

Prakash

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On Sat, Oct 9, 2010 at 11:29 AM, MBBS Batch 16 <mbbs.b...@gmail.com> wrote:

I would like to ask regarding the learning outcome of Lecture 10 which requires a general theoretical description of the process of haematopoiesis and its regulation. I am not sure how much explanation is needed for the process. As for regulation is it enough to mention about the growth factors and transcription factors or do i need to explain more? I hope you could help by giving an outline to explain it.

 

Jaspreet