Effects of Local Opioid Antagonist on Diabetic Fracture Rat Model

Abstract

Category: Diabetes Introduction/Purpose: Complications associated with the diabetes include increased incidence of fracture healing, delayed fracture healing, delayed osteoblasts cell replication, decreased angiogenesis, migration and/or osteoblast cell differentiation. The cellular events involved in bone healing are adversely affected by diabetes; however, can be modulated by the Opioid Growth Factor (OGF)–OGF receptor (OGFr) is an inhibitory peptide that downregulates DNA synthesis in a tissue nonspecific manner. Diabetes is associated with elevated serum levels of OGF and dysregulation of the OGFr leading to multiple complications related to healing, sensitivity, and regeneration. This study explores the presence and function of the OGF-OGFr axis in bone tissue from type 1 diabetic rats examining intact and fractured femurs during early phases of the repair process Methods: Seven-week-old Sprague Dawley rats were injected with streptozotocin (40mg/kg i.p.) to induce T1D; other rats received buffer only and served as controls. After one month, hyperglycemia rats underwent surgery to produce a fracture at the distal third of the femur. Four diabetic rats received opioid antagoinist (naltrexone) and calcium sulfate and all remaining rats received calcium sulfate with water only. X-rays were taken immediately after surgery and after rats were euthanized on post-surgery; femur and tibia were collected for protein isolation, western blot analysis along with frozen or paraffin-embedded for histological analysis Results: Immunofluorescence indicated approximately 90% increase in opioid growth factor receptor expression in diabetic femurs compared to age-matched normal femurs. Western Blotting also suggested an increase in the receptor protein in diabetic bones relative to normal bone. TRAP staining for osteoclasts was greater in control and opioid antagonist-treated diabetic fractures when compared to the number of osteoclasts in vehicle-treated diabetic fractured femurs. Safranin O stained sections revealed approximately more bone in opioid growth receptor antagonist-treated diabetic bone fractures than in vehicle-treated bone fractures Conclusion: These data support our hypothesis that expression levels of OGFr are dysregulated in the bone of diabetic patients leading to complications in bone healing. Moreover, modulation of the OGF-OGFr pathway with receptor antagonists restored some aspects of bone healing. With further study, these preliminary results support the role of the OGF-OGFr axis in treatment of diabetic bone healing. New therapies to target dysregulation of the OGF-OGFr regulatory pathway in diabetes would provide a safe and effective disease-modifying treatment for delayed bone healing.