Fracture Healing in Aging: Improving Angiogenesis
Medicine and Health Sciences
BACKGROUND: With an aging world population, there is an increased risk of fracture and impaired fracture healing. Enhancement of angiogenesis is one potential mechanism for improved fracture healing. The question then becomes: How do therapeutic targets improve these angiogenic and vasculitic conditions to facilitate successful fracture union? The current therapy, bone morphogenetic protein 2 (BMP-2), while successful in promoting fracture union, presents with several potential side effects, including excess bone growth and an increased risk of developing cancer. We hypothesize that thrombopoietin (TPO) may serve as a novel therapeutic modality for improved angiogenesis and fracture union. Here we characterize and stimulate endothelial cells (ECs) with TPO in vitro. OBJECTIVE: We hypothesize that thrombopoietin (TPO) may serve as a novel therapeutic modality for improved angiogenesis and fracture union. METHODS: Five young (3 month-old) and 5 old (22-24 month-old) C57BL/6 mice were euthanized and bone marrow was collected from the tibia and humeri for EC isolation. Additionally, five young mice underwent a 2 mm femoral diaphyseal defect surgery. Three weeks post-surgery mice were euthanized and bone marrow from the ipsilateral and contralateral tibia as well as the humeri were collected and ECs isolated. All ECs were assessed for vessel-like formation and proliferation. All in vitro studies were completed at least 3 times with triplicate samples. Statistical analyses were performed using a two-way ANOVA with Tukey’s post-hoc testing. All procedures were approved by the Indiana University IACUC. RESULTS: In vitro characterization of ECs showed impaired vessel-like formation, branch length, number of nodes, mesh area, and proliferation in old ECs compared to young ECs. ECs isolated from the ipsilateral tibia of mice undergoing a SBD surgery had impaired ECs vessel-like parameters and proliferation compared to ECs from the contralateral tibia. Finally, treatment of old ECs with TPO improved vessel-like parameters and proliferation compared to untreated cells. CONCLUSIONS: Although preliminary, our results confirm that EC proliferation and vessel formation are impaired in aging and in the ipsilateral tibia of mice, which underwent a femoral SBD surgery. Although BMP-2 is used by orthopaedic surgeons for bone healing, its use is not without side effects, leaving researchers to investigate alternative treatments. We have previously shown that TPO is effective for bone healing. Here we show that TPO improves vessel formation in aged ECs, and therefore, TPO may improve angiogenesis and fracture healing in old mice, which is currently under investigation.
Copyright 2019 all authors
Perugini, Anthony J. OMS-2; Dadwal, Ushashi C.; Bhatti, Fazal Ur Rehman; Babu, Deepa Sheik Pran; Blosser, Rachel J.; Sun, Seungyup; Awosanya, Olatundun D.; Li, Jiliang; and Kacena, Melissa A., "Fracture Healing in Aging: Improving Angiogenesis" (2019). MU-COM Research Day. 116.