Localized deferoxamine injection augments vascularity and improves bony union in pathologic fracture healing after radiotherapy

Abstract

Background Medically based efforts and alternative treatment strategies to prevent or remediate the corrosive effects of radiotherapy on pathologic fracture healing have failed to produce clear and convincing evidence of success. Establishing an effective pharmacologic option to prevent or treat the development of non-unions in this setting could have immense therapeutic potential. Experimental studies have shown that Deferoxamine (DFO), an iron- chelating agent, bolsters vascularity and subsequently enhances normal fracture healing when injected locally into a fracture callus in long bone animal models. Since radiotherapy is known to impede angiogenesis, we hypothesized that the pharmacologic addition of DFO would serve to mitigate the effects of radiotherapy on new vessel formation in vitro and in vivo. Materials and Methods In vitro investigation of angiogenesis was conducted utilizing HUVEC cells in Matrigel. Endothelial tubule formation assays were divided into four groups: Control, Radiated, Radiated + Low Dose DFO and Radiated + High Dose DFO. Tubule formation was quantified microscopically and video recorded for the four groups simultaneously during the experiment. In vivo, three groups of Sprague–Dawley rats underwent external fixator placement and fracture osteotomy of the left mandible. Two groups received pre-operative fractionated radiotherapy, and one of these groups was treated with DFO after fracture repair. After 40 days, the animals were perfused and imaged with micro-CT to calculate vascular radiomorphometrics. Results In vitro, endothelial tubule formation assays demonstrated that DFO mitigated the deleterious effects of radiation on angiogenesis. Further, high-dose DFO cultures appeared to organize within 2 hours of incubation and achieved a robust network that was visibly superior to all other experimental groups in an accelerated fashion. In vivo, animals subjected to a human equivalent dose of radiotherapy (HEDR) and left mandibular fracture demonstrated quantifiably diminished μCT metrics of vascular density, as well as a 75% incidence of associated non-unions. The addition of DFO in this setting markedly improved vascularity as demonstrated with 3D angiographic modeling. In addition, we observed an increased incidence of bony unions in the DFO treated group when compared to radiated fractures without treatment (67% vs. 25% respectively). Conclusion Our data suggest that selectively targeting angiogenesis with localized DFO injections is sufficient to remediate the associated severe vascular diminution resulting from a HEDR. Perhaps the most consequential and clinically relevant finding was the ability to reduce the incidence of non-unions in a model where fracture healing was not routinely observed.

Fabrication of open-cellular (porous) titanium alloy implants: osseointegration, vascularization and preliminary human trials

“…Fig. 7 illustrates that angiogenesis is induced in endothelial cells through exposure to DFM which promotes capillarity in a 3D collagen based hydrogel (Matrigel) in a Ti-6Al-4V foam slice similar to previous observations of endothelial capillarity [20]. Fluorescent microscope images near the metal foam ligaments in the prepared slices, similar to Fig.…”

“…Deferoxamine mesylate (DFM) (or deferoxamine (DFO)) promotes angiogenesis by inducing hypoxia [18,19], and it has been reported that endothelial cells are able to form capillaries in gel when exposed to DFM. A hypoxia mimetic environment has been reported to enhance bone repair and endothelial integrity restoration [20].…”

Chronic Gamma-Irradiation Induces a Dose-Rate-Dependent Pro-inflammatory Response and Associated Loss of Function in Human Umbilical Vein Endothelial Cells

“…Donneys et al (49) have recently shown that acute irradiation with low doses increases cellular movement and organization, whereas with high doses endothelial cells form fewer tubules in culture. In their study, time-lapse recording demonstrated a considerable increase in cellular organization, activity and locomotion in response to this low-dose therapy.…”

Deferoxamine expedites consolidation during mandibular distraction osteogenesis

“…This dose was derived from an extensive literature search regarding the use of deferoxamine in long bone animal models, as well as our experimentation with this drug in recent years [18-21,26,27]. We implemented the injection of deferoxamine therapy during the active distraction period to coincide with the known augmentation of angiogenesis naturally occurring in response to the mechanical stretching of the callus [7,8,10].…”