Abstract
Purpose:
Prior studies have demonstrated a protective effect of intrivitreally injected adipose-derived stem cells (ASCs) in the Akimba model of diabetic retinopathy (DR). A paracrine mechanism is suggested by the increased density of retinal vasculature observed even without ASC integration. The purpose of this study was to determine the efficacy of injected ASC-conditioned media (CCM) against DR onset. Additionally we aim to determine effects on ASC secretome of high (HG) vs physiologic (LG) glucose culture conditions.
Methods:
ASCs from both healthy and diabetic Ins2(Akita) mouse inguinal adipose were isolated through serial passage from the stromal vascular fraction. Cells were passaged to P4 in either HG or LG media. ASCs were then cultured for 24 hrs in serum-free media, and the CCM was collected then concentrated. CCM from both culture conditions was analyzed using an Angiogenesis Proteome Profiler. Then, five-week-old Akimba mice received intraocular injections of either (1) healthy or diabetic ASCs with PBS contralateral eye control or (2) healthy CCM with diabetic CCM contralateral eye comparison. Four weeks post-injection, retinae were harvested, fixed, and stained with lectin for analysis.
Results:
When injected intravitreally, 6 of 6 retinae that received healthy ASCs had significantly decreased avascular area compared to PBS control; only 2 of 6 retinae with diabetic ASCs did. Conversely, CCM-injected mice showed no difference in vascular density between diabetic-ASC vs healthy-ASC CCM (vessel length/area 5.0 vs 4.6 mm/mm^2, p=0.59; capillary segments/retina 544 vs 474, p=0.1). Vascular density was worse for CCM treated eyes than healthy-ASC or diabetic-ASC treated eyes for all conditions. We hypothesized that the lack of response was due to standard, HG culture conditions. Indeed, HG CCM had deceased MCP1 (11%), Proliferin (14%), TIMP1 (39%), THBS2 (100%), and SDF1 (48%) compared to LG.
Conclusions:
Our data suggest that 1) intravitreal injection of mASCs in a mouse model of DR exert a greater protective effect than intravitreal injection of media that has been conditioned by mASCs, 2) healthy-ASCs appear to exert a greater protective effect on the retinal vasculature than diabetic-ASCs, 3) Glucose level can cause change in the ASC secretome, though further study is required to determine whether this might enhance healthy-ASC ability to stabilize retinal vasculature.