A New Model to Study Healing of a Complex Femur Fracture with Concurrent Soft Tissue Injury in Sheep

High energy bone fractures resulting from impact trauma are often accompanied by subcutaneous soft tissue injuries, even if the skin remains intact. There is evidence that such closed soft tissue injuries affect the healing of bone fractures, and vice versa. Despite this knowledge, most impact trauma studies in animals have focussed on bone fractures or soft tissue trauma in isolation. However, given the simultaneous impact on both tissues a better understanding of the interaction between these two injuries is necessary to optimise clinical treatment. The aim of this study was therefore to develop a new experimental model and characterise, for the first time, the healing of a complex fracture with concurrent closed soft tissue trauma in sheep. A pendulum impact device was designed to deliver a defined and standardised impact to the distal thigh of sheep, causing a reproducible contusion injury to the subcutaneous soft tissues. In a subsequent procedure, a reproducible femoral butterfly fracture (AO C3-type) was created at the sheep’s femur, which was initially stabilised for 5 days by an external fixator construct to allow for soft tissue swelling to recede, and ultimately in a bridging construct using locking plates. The combined injuries were applied to twelve sheep and the healing observed for four or eight weeks (six animals per group) until sacrifice. The pendulum impact led to a moderate to severe circumferential soft tissue injury with significant bruising, haematomas and partial muscle disruptions. Posttraumatic measurements showed elevated intra-compartmental pressure and circulatory tissue breakdown markers, with recovery to normal, pre-injury values within four days. Clinically, no neurovascular deficiencies were observed. Bi-weekly radiological analysis of the healing fractures showed progressive callus healing over time, with the average number of callus bridges increasing from 0.4 at two weeks to 4.2 at eight weeks. Biomechanical testing after sacrifice showed in- creasing torsional stiffness between four and eight weeks healing time from 10% to 100%, and increasing ultimate torsional strength from 10% to 64% (relative to the contralateral control limb). Our results demonstrate the robust healing of a complex femur fracture in the presence of a severe soft tissue contusion injury in sheep and demonstrate the establishment of a clinically relevant experimental model, for research aimed at improving the treatment of bone fractures accompanied by closed soft tissue injuries.

ATP binding cassette proteins ABCG37 and ABCG33 function as potassium-independent cesium uptake carriers in Arabidopsis roots

Radiocesium accumulated in the soil by nuclear accidents is a major environmental concern.The transport process of cesium(Cs^(+))is tightly linked to the indispensable plant nutrient potassium(K^(+))as they both belong to the group I alkali metals with similar chemical properties.Most of the transporters that had been characterized to date as Cs*transporters are directly or indirectly linked to K^(+).Using a combinatorial approach of physiology,genetics,cell biology,and root uptake assay,here we identified two ATP-binding cassette(ABC)proteins,ABCG37 and ABCG33,as facilitators of Cs^(+)influx.A gain-of-function mutant of ABCG37(abcg37-1)showed increased sensitivity to Cs^(+)-induced root growth inhibition,while the double knockout mutant of ABCG33 and ABCG37(abcg33-1abcg37-2)showed resistance,whereas the single loss-of-function mutants of ABCG33 and ABCG37 did not show any alteration in Cs^(+)response.In planta short-term radioactive Cs^(+)-uptake assay along with growth and uptake assays in a heterologous system confirmed ABCG33 and ABCG37 as Cs^(+)-uptake carriers.Potassium response and content were unaffected in the double-mutant background and yeast cells lacking potassium-uptake carriers transformed with ABCG33 and ABCG37 failed to grow in the absence of K^(+),confirming that Cs^(+)uptake by ABCG33 and ABCG37 is independent of K^(+).Collectively,this work identified two ABC proteins as new Cs^(+)-influx carriers that act redundantly and independent of the K^(+)-uptake pathway.