Abstract:

Abstract:Objective Through inspecting in vitro fibrillogenesis of the young and the old rat tail tendon collagen,as well as comparing the morphological changes  of the lumbar cancellous bone collagen,to study the influence of  age  in fibrillogenesis.Methods The tail tendon(5 g)  of  2-week and  20-month rats,was obtained,and the tail collagen  was  extracted by the dilute acetic acid.The  extracted collagen was freezed-dried in low temperature.15 mg tail collagen were take from 2-month-old and 20-month-old rats.Each wss divided into three groups,5 mg in each group,and the collagen was melted in 10 mmol/Lacetic acid solution  at 4℃,the titanium metal screws were infiltrated into the solution.After adding buffer the  fibrillogenesis was taken in 37℃.The screws were picked up separately at 2,4  and 8 h,and the  morphological changes of  collagen of the surface of the screws were observed under  scanning electron microscope(SEM).10 2-week rats and 10 20-month rats were sacrificed to remove the L3 vertebral body,the regular specimen were made.The specimens were repeatedly washed by using physiological saline,dehydrated,and  sprayed gold,and then observed under SEM.Results The tail  collagen of rats in two groups did  not take fibrillogenesis in the screw surface at 2 h.At  4 h,the tail collagen   of   20-month-old rats   was gathered into the irregular and massive collagen polymer,no collagen fibers wre formatted  in surface of the screw.The tail collagen of 2-week-old rats turned into 0.07-0.20  μm  collagenousfibres.At 8 h,the tail collagen of  20-month-old rats  in the surface of the screw polymerized into the  different size collagen polymers,no formation of collagen fibers.The  tail collagen of 2-week-old rats  formated 0.65-1.35 μm collagen fibers.The SEM results showed that the  collagen of 2-week rat trabecular bone cross-linked into uniform collagen fibers.The fibers were closely arranged,and the orientation was consistent. The widths of the collagen fibrils of 20-month-old rat trabecular bone were not consistent. The arrangement of the fibrils was loose,sparse and disordered,and the orientations of the oblique collagen fibers between them were unorganized.Conclusion With the increaes of age,the fibrillogenesis capacity of type Ⅰ collagen gradually reduce,and lead to the morphological changes of bone collagen fibers,which may be very important reasons of  senile osteoporosis and increased fracture risk.

Key words: yong rats, old rats, in vitro fibrillogenesis