Abstract
Purpose: :
Diabetic retinopathy (DR) is the most common vascular complication in patients with long-standing diabetes, and is the leading cause of blindness in working-age adults. Early stage DR has been shown to involve inflammation, vascular leakage and apoptosis of vascular cells. In this study, we hypothesized that cells derived from the stromal fraction of adipose tissue (ASC; which have been shown to improve ischemia reperfusion, limit myocardial infarction and possess neuroprotective function) therapeutically might rescue early stage DR features. Furthermore, we hypothesized that ASC withstand hyperglycemic stress and prove beneficial for transplantation studies.
Methods: :
Streptozotocin (STZ) induced diabetic athymic nude rats were intravitreally injected 150,000 human ASC cells into the right eye, and the ipsilateral eye served as control with equal volume of saline. After 7 days, rats were sacrificed, retinal vascular leakage was analyzed by FITC-albumin extravasation assay, apoptosis was measured by TUNEL assay, and inflammatory genes were assessed by real-time RT-PCR method. In vitro, ASC were subjected to varying concentrations of glucose and proliferation assessed by MTT assay, cell death by Caspase-3 assay, and oxidative stress by DCF assay.
Results: :
By two months post induction of diabetes, athymic nude rats had developed blood glucose >250mg/dL and showed impaired glucose tolerance. Diabetic rats that received saline injection after day 7 demonstrated significantly (p<0.01) increased vascular leakage, TUNEL-positive cells in the retinal ganglion cell layer (as well as around vessels), and upregulation of inflammatory genes such as ICAM-1, Edn2, Ccl2, Timp1, TGFβ, TNFα and Stat3 (>2 fold) compared to non-diabetic rats. On the other hand, diabetic rats that received ASC injection were as hyperglycemic as control diabetics, but nevertheless demonstrated significantly less of all the retinal parameters above. In vitro, ASC subjected to elevated glucose concentration displayed sustained proliferation, and decreased apoptosis and oxidative stress.
Conclusions: :
This is the first demonstration of the use of ASC in the treatment of early lesions of DR. Future studies in long-term diabetes models will address if ASC repair and stabilize vasculature in the treatment of DR. By evaluating this approach in the rodent model, we will be in a better position to determine whether such an approach should be tested in humans. The diabetic rat studies will provide valuable insights to guide the design of our future clinical studies in human patients.
Keywords: diabetic retinopathy • inflammation • apoptosis/cell death