The effect of diabetes on fracture repair : alterations in angiogenesis and apoptosis

Abstract

Thesis (MSD)--Boston University, Goldman School of Dental Medicine, 2007 (Endodontics).Includes bibliographical references: leaves 56-65.An abundance of evidence has emerged demonstrating a close link between diabetes and significantly impaired fracture healing. Previous studies have determined that repair of fractures in diabetic animals is characterized by calluses with decreased size and bone formation. To further investigate the possible reasons for the decreased callus size we undertook a detailed histologic and immunohistochemical analysis focusing on the apoptosis of bone cells and angiogenesis that occurs during fracture healing. Angiogenesis was determined in the fractures by quantitative immunohistochemical analysis using the antibody to CD34. Cells expressing CD34 are found in the endothelial lining of blood vessels. Apoptotic cells were stained using the Apoptag Peroxidase In Situ Apoptosis Detection Kit. The decision to target these two parameters was based on the concept that enhanced cell death and decreased angiogenesis may limit the repair process. We used a well characterized type 1 diabetic animal model; the streptozotocin induced diabetic mouse (n=8), and a nondiabetic control group (n=7). Three weeks after establishing diabetes, tibia fractures were induced. The mice were euthanized 12, 16 and 22 days after fracture. The 16 day samples were processed, embedded, sectioned and stained for analysis. The size of the fracture callus, and the amount of new bone and cartilage were determined using slides stained with H&E, masson trichrome and safranin-O/fast green, respectively. The results showed that the diabetic groups have statistically two fold more apoptotic cells per callus (p<0.05). We also found that the number of vessels located in the areas of immature new bone were twice as high in the normal group [TRUNCATED