Observation of Calcification Process in Immature Chick Bone under Mechanical Load: Toward the Establishment of Artificial Morphogenesis Utilizing Controlled Mechanical Adaption

Bone calcification occurs in response to mechanical loading, and is an essential factor in bone maturation. However, how mechanical loading applied to the bone tissue stimulates calcification is largely unknown. In this study, we observed calcification process of immature bone tissue cultured under static stretch to examine its relationship to collagen fiber alignment and amount. Bone thin specimens were obtained from the tibia of 0~2-day-old chicks by cutting the tibia perpendicularly to the bone axis, and calcification process was observed up to 24 h while they were stretched in the direction parallel to the slice. It was found that there are two different modes in calcification process: In ‘mode 1’, calcification proceeds from the specimen circumference to center region, while in ‘mode 2’, calcification radially spreads from the center region to the specimen circumference. There was no significant increase in mode 1 calcification in response to tissue stretch, while mode 2 calcification was observed only in the stretched specimens. Mode 2 calcification might be dominant in bone tissue response to mechanical loading. These differences in calcification might have something to do with collagen fiber alignment and amount in uncalcified area of bone tissue.