טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentRozen Nimrod
SubjectEnhancement of Fracture Healing by Factors that Accelerate
Bone Turnover
DepartmentDepartment of Medicine
Supervisors Assistant Professor Dina Lewinson
Professor Abraham Reznick


Abstract

Fracture healing after injury in a long bone presents a sequence of three stages: Inflammation and granulation tissue formation, callus formation and remodeling. Under unstable conditions, callus formation proceeds through two maturation pathways, namely intramembranous ossification and endochondral ossification. The regulation of the various complicated stages in the differentiation of the callus is maintained by systemic hormones and locally secreted cytokines and growth factors. As cartilage development is an integral part of the healing process, especially under unstable conditions, we proceeded to examine the effect of the mid fragment of PTH (PTH 28-48), and the amino terminal fragment of PTH (PTH 1-34), on closed fracture repair in a long bone. In the present study, we took advantage of a novel device developed by us for creating standardized closed fractures in rat limbs to investigate the effect of locally injected PTH (28-48), PTH (1-34), alone and in combination with IL-6 and its soluble receptor on fracture repair. The unique properties of our fracture-inducing device enable to produce a uniform closed fracture environment without any surgical intervention. 54 adult female wistar rats (200-250g) were devided into 6 groups: Vehicle treated, PTH 28-48, PTH 1-34, PTH 28-48+ Il-6 + sIL-6R, PTH 1-34+ Il-6 + sIL-6R. All animals were fractured on the same day and sacrificed 14 days later.  Callus volume and mechanical strength were measured and compared. Our results demonstrated that although rhPTH (28-48) and rhPTH (1-34), when applied during the early stages of the healing process, had a stimulatory effect on proliferation and differentiation of skeletal progenitors and chondrocytes, thereby enhancing significantly the size of the cartilaginous component of the callus, they did not confer more resistance to the healing bone. On the other hand, a combination of the PTH fragments with IL-6 and its soluble receptor increased not only the callus volume but also changed dramatically the quality of bone as presented by a 300% increase in mechanical strength when PTH (1-34) was combined and 200% when PTH (28-48) was combined when compared with vehicle treated fractured bones. We conclude that the sequential combination of IL-6 and its soluble receptor with PTH fragments has the potential of enhancing fracture healing in long bones and should be further explored in preclinical and in clinical studies. Furthermore, we suggest to add VEGF to future studies and explore its potential when combined with the already tested PTH fragments and cytokine.