Erythropoietin is a glycoprotein hormone and was identified as humoral factor which functions in stimulation of red blood cells production. Earlier the only sites known for erythropoietin production were thought to be kidney and liver. The kidney’s peritubular capillaries play a major role in erythropoietin production.

 

Various other sites of erythropoietin were discovered which includes the retina and brain. Research carried out by Luo et al, at Department of Ophthalmology, Shanghai, China, shows the role of erythropoietin in retina. The high concentrations of erythropoietin in the vitreous fluid of patients with proliferative diabetic retinopathy and diabetic macular edema prove that erythropoietin is expressed in the retinal tissues.

 

Erythropoietin has protective functions in the brain by decreasing the inflammatory response. Similar kind of response is observed in the retinal. A study by Chang et al, shows that erythropoietin benefits the retinal ganglion cells through causing resistance to injuries which are induced by tumor necrosis factor-alpha. It also activates tumour necrosis factor- beta which acts as an antagonist towards tumour necrosis factor-alpha.

 

Erythropoietin was also observed to play a role in facilitating cell survival during hypoxia and hyperoxia. Both hyperoxia and hypoxia lead to oxidative injury and lead to cell dysfunction or death of the retinal cells. Erythropoietin downregulates inflammation and protects the cells. It is also known to protect retina from degeneration. Thus, from these studies it was clear that erythropoietin has various protective functions in the retina too.