Dr. Lior Ofer (DVM,PhD)
Lior is especially interested in the macro and micro mechanics of fish bones and in understanding the remodeling process of acellular bone.
As fish are the only representatives of bones without osteocytes (which are considered to be the bone load-sensors cells), Lior intents to investigate the ability of their acellular bones to efficiently reshape and change its architecture, in order to adapt to increasing physiological loads.
Lior hopes to determine whether acellular bone can efficiently achieve optimal load-bearing capacity compared with cellular bone. We assume acellular bones have evolutionary advantages over cellular bones due to the fact that there is a clear trend toward acellular bones development in fish evolution (most of the extant and derived fishes have acellular bones). Considering the importance of bone’s ability to resist loads in order to fulfill their role in body support and movement, it is very reasonable that this presumed advantage will be expressed in the mechanical properties of the bone affecting related processes such as modeling and remodeling. On the other hand, acellular bones supposedly lack load-sensors cells which are crucial for initiating, directing and orchestrating the bone sculptors (osteoblasts and osteoclasts) in order to achieve the right architecture for optimal load-bearing capacity in specific repetitive loads. Thus, another possibility is that the modeling process of acellular bones is less efficient than in cellular bones – this would support the claim that osteocytes are essential in the modeling process. However, similar or better remodeling performance of acellular over cellular bones will indicate the possible presence of a yet-undiscovered load-sensing mechanism in the unosteocytic acellular bones.
In order to analyze the bone’s response to physiological increasing loads, zebrafish (cellular) and medaka (acellular) bones will be exposed to high muscle forces produced by strenuous swimming against high water current and against increased gravitational force (by hampering swim bladder function). The effect on the bones will be assessed by various imaging techniques. Bone modeling efficiency and strain distributions will be assessed using finite element models of the vertebrae. Bone mineralization and morphology will be analyzed from Micro-CT scans, and the micro-mechanical properties of the bone material will be acquired by micro-indentation mechanical testing.
Lior will also use transgenic osteoblasts-labeled zebrafish and medakas to characterize the cell’s reaction to mechanical stimuli in-vivo and compare osteoblast differentiation and migration patterns in acellular and cellular bones.
Lior will examine the duration and magnitude of the loads needed to be applied on both bone types in order to achieve osteoblasts reaction –this will hopefully further help us to assess and compare the sensitivity of the bones to mechanical stimuli and maybe reveal the load sensing mechanism resemblance or divergences between acellular and cellular bones.
In summery, Lior wishes to focus on the enigma of acellular bone response to loads and to thoroughly investigate the modeling process mechanics and the osteoblastic reaction patterns of fish bones.