Establishment of an in vivo Streptozotocin-Induced Type 1 Diabetes Model Recapitulating Early Brain and Retinal Fibrosis

INTRODUCTION: Diabetes has risen to one of the top American public health concerns. The hyperglycemic state of chronic diabetes leads to microvascular and macrovascular changes that predispose patients to delayed wound healing and organ fibrosis. The validation of models to specifically detect early, quantifiable fibrotic changes seen in the diabetic state is of fundamental importance for understanding the diabetic pathophysiology and exploring earlier management options. Here, we investigated if we could detect early signs of internal fibrosis in a streptozotocin (STZ) diabetic mouse model by quantifying
α-SMA expression in various organs using flow cytometry.
METHODS: We used a low-dose STZ-induced T1DM model. T1DM was confirmed via sustained hyperglycemia (>250mg/dl) over 8-10 weeks. Delayed healing of full thickness wounds was confirmed by tracking wound healing progression over two weeks. Wounded and unwounded skin samples were analyzed histologically to quantify collagen deposition as a sign of fibrosis. Organ fibrosis was assessed in a semi-high-throughput manner using flow cytometry to quantify the percentage of alpha-Smooth Muscle Actin (α-SMA) positive cells in diabetic versus normoglycemic controls.
RESULTS: Combining STZ with post-injection glucose treatment yielded highly efficient 100% pathogenesis with 100% survival. Diabetic mice showed signs of hyperglycemia, polyuria, and delayed wound healing. Histological analysis indicated a greater increase in epidermal height and lower levels of collagen deposition in diabetic wounds. After 10-12 weeks of hyperglycemia, we observed elevated
α-SMA in brain and retinal tissues.
 
DISCUSSION: The STZ model has previously presented cumbersome, costly, and time-intensive limitations for the study of diabetic complications. Here we tested a quantitative method for detecting early signs of fibrosis using flow cytometry. The higher percentage of α-SMA positive cells in retinal and brain tissue of diabetic mice suggests fibrosis of these tissues. We argue that this is a suitable method to study early diabetic complications.
Keywords: diabetes, hyperglycemia, fibrosis, murine