title: The effect of step-wise increased stretching on rat calvarial osteoblast collagen production.
abstract: Mechanical forces regulate the function of bone cells. In this paper, the effects of cyclic stretching on osteoblasts derived from rat calvaria were studied at a magnitude occurring in physiological loaded bone tissue. A four-point bending apparatus was used to apply cyclic stretching on osteoblasts. Stretching at 500 microepsilon for 2-24 h resulted in an increase in matrix synthesis(P<0.01). In contrast, the cyclic stretching at 1000 and 1500 microepsilon for 2-24 h inhibited osteoblast collagen production (P<0.01). We also described our new loading method to increase strain magnitude step-by-step. The strain magnitude increased by 500 microepsilon increments from 500 to 1500 microepsilon every 2 or 12 h, respectively. Results showed that osteoblasts could absorb large amount of proline for collagen synthesis when stretched at 500 microepsilon. However, not all the absorbed proline was used to synthesize collagen. Some of it was stored in cells. When the suitable signal (500 microepsilon) was changed to an inhibiting signal (1000 microepsilon), cells responded to it accordingly and released proline to medium. These results demonstrate that the response of osteoblasts is dependent on the magnitude of the strain applied and cells can adjust their bio-chemical response to adapt to the changing environmental stimulation.
authors.affiliation: Key Lab for Biomechanics and Tissue Engineering under the State Ministry of Education, Bio-engineering college, Chongqing University, Chongqing 400044, People's Republic of China. huayue@cta.cq.cn
authors.forename: Li-Ling
authors.initials: LL
authors.lastname: Tang
authors.forename: Yuan-Liang
authors.initials: YL
authors.lastname: Wang
authors.forename: Jun
authors.initials: J
authors.lastname: Pan
authors.forename: Shao-Xi
authors.initials: SX
authors.lastname: Cai
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D018929:Cell Culture Techniques / Q000295:instrumentation / Q000379:methods*; D002478:Cells, Cultured; D003094:Collagen / Q000378:metabolism*; D004548:Elasticity; D040542:Mechanotransduction, Cellular / Q000502:physiology*; D010006:Osteoblasts / Q000502:physiology*; D010812:Physical Stimulation / Q000295:instrumentation / Q000379:methods*; D011392:Proline / Q000493:pharmacokinetics*; D051381:Rats; D017208:Rats, Wistar; D012886:Skull / Q000502:physiology*; D013314:Stress, Mechanical; D016474:Weight-Bearing / Q000502:physiology*
chemical_list: D003094:Collagen; D011392:Proline