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Regional variations in growth plate chondrocyte deformation as predicted by three-dimensional multi-scale simulations.

Gao J, Roan E, Williams JL - PLoS ONE (2015)

Bottom Line: The microscale model predicted that chondrocytes sustained compressive height strains of 12% and 6% in the proliferative and hypertrophic zones, respectively, in the interior regions of the plate.This work provides a new approach to study growth plate behavior under compression and illustrates the need for combining computational and experimental methods to better understand the chondrocyte mechanics in the growth plate cartilage.While the current model is relevant to fast dynamic events, such as heel strike in walking, we believe this approach provides new insight into the mechanical factors that regulate bone growth at the cell level and provides a basis for developing models to help interpret experimental results at varying time scales.

View Article: PubMed Central - PubMed

Affiliation: Departments of Mechanical Engineering, University of Memphis Memphis, Tennessee, 38152, United States of America.

ABSTRACT
The physis, or growth plate, is a complex disc-shaped cartilage structure that is responsible for longitudinal bone growth. In this study, a multi-scale computational approach was undertaken to better understand how physiological loads are experienced by chondrocytes embedded inside chondrons when subjected to moderate strain under instantaneous compressive loading of the growth plate. Models of representative samples of compressed bone/growth-plate/bone from a 0.67 mm thick 4-month old bovine proximal tibial physis were subjected to a prescribed displacement equal to 20% of the growth plate thickness. At the macroscale level, the applied compressive deformation resulted in an overall compressive strain across the proliferative-hypertrophic zone of 17%. The microscale model predicted that chondrocytes sustained compressive height strains of 12% and 6% in the proliferative and hypertrophic zones, respectively, in the interior regions of the plate. This pattern was reversed within the outer 300 μm region at the free surface where cells were compressed by 10% in the proliferative and 26% in the hypertrophic zones, in agreement with experimental observations. This work provides a new approach to study growth plate behavior under compression and illustrates the need for combining computational and experimental methods to better understand the chondrocyte mechanics in the growth plate cartilage. While the current model is relevant to fast dynamic events, such as heel strike in walking, we believe this approach provides new insight into the mechanical factors that regulate bone growth at the cell level and provides a basis for developing models to help interpret experimental results at varying time scales.

No MeSH data available.


Related in: MedlinePlus

Distribution of minimum principal logarithmic strains within the ‘m’ shape growth plate obtained from the mesoscale model without cellular detail.Peak compressive strains occurred at the base of the proliferative zone where cell mitosis occurs. This contrasts with regions close to the free surface, where compressive strains were at a minimum around the base of the proliferative zone and maximum in the reserve and hypertrophic zones.
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pone.0124862.g007: Distribution of minimum principal logarithmic strains within the ‘m’ shape growth plate obtained from the mesoscale model without cellular detail.Peak compressive strains occurred at the base of the proliferative zone where cell mitosis occurs. This contrasts with regions close to the free surface, where compressive strains were at a minimum around the base of the proliferative zone and maximum in the reserve and hypertrophic zones.

Mentions: Principal strains were oriented along and transverse to the chondron directions throughout the central region but deviated from these directions at the reserve zone/bone interface near the free surfaces where shear strains developed along the bone interface (Fig 6). These results were obtained from the multi-scale model without chondrocytes. Planes 50 and 300 μm away from the free surface were chosen as being potentially relevant range for the plane of observation in microscopic studies of cell deformation under compression. The strain distributions were significantly different at these locations compared to interior regions of the growth plate. Minimum principal (compressive) strains at the tissue level varied throughout the growth plate zones. In the interior regions of the growth plate the minimum principal strains varied from -10% in the reserve zone peaked at -25% at the base of the proliferative zone and decreased to -10% in the hypertrophic zone (Fig 7). The opposite pattern was observed near the growth plate free surfaces. Similar trends were observed for both growth plate shapes (results not shown).


Regional variations in growth plate chondrocyte deformation as predicted by three-dimensional multi-scale simulations.

Gao J, Roan E, Williams JL - PLoS ONE (2015)

Distribution of minimum principal logarithmic strains within the ‘m’ shape growth plate obtained from the mesoscale model without cellular detail.Peak compressive strains occurred at the base of the proliferative zone where cell mitosis occurs. This contrasts with regions close to the free surface, where compressive strains were at a minimum around the base of the proliferative zone and maximum in the reserve and hypertrophic zones.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4401775&req=5

pone.0124862.g007: Distribution of minimum principal logarithmic strains within the ‘m’ shape growth plate obtained from the mesoscale model without cellular detail.Peak compressive strains occurred at the base of the proliferative zone where cell mitosis occurs. This contrasts with regions close to the free surface, where compressive strains were at a minimum around the base of the proliferative zone and maximum in the reserve and hypertrophic zones.
Mentions: Principal strains were oriented along and transverse to the chondron directions throughout the central region but deviated from these directions at the reserve zone/bone interface near the free surfaces where shear strains developed along the bone interface (Fig 6). These results were obtained from the multi-scale model without chondrocytes. Planes 50 and 300 μm away from the free surface were chosen as being potentially relevant range for the plane of observation in microscopic studies of cell deformation under compression. The strain distributions were significantly different at these locations compared to interior regions of the growth plate. Minimum principal (compressive) strains at the tissue level varied throughout the growth plate zones. In the interior regions of the growth plate the minimum principal strains varied from -10% in the reserve zone peaked at -25% at the base of the proliferative zone and decreased to -10% in the hypertrophic zone (Fig 7). The opposite pattern was observed near the growth plate free surfaces. Similar trends were observed for both growth plate shapes (results not shown).

Bottom Line: The microscale model predicted that chondrocytes sustained compressive height strains of 12% and 6% in the proliferative and hypertrophic zones, respectively, in the interior regions of the plate.This work provides a new approach to study growth plate behavior under compression and illustrates the need for combining computational and experimental methods to better understand the chondrocyte mechanics in the growth plate cartilage.While the current model is relevant to fast dynamic events, such as heel strike in walking, we believe this approach provides new insight into the mechanical factors that regulate bone growth at the cell level and provides a basis for developing models to help interpret experimental results at varying time scales.

View Article: PubMed Central - PubMed

Affiliation: Departments of Mechanical Engineering, University of Memphis Memphis, Tennessee, 38152, United States of America.

ABSTRACT
The physis, or growth plate, is a complex disc-shaped cartilage structure that is responsible for longitudinal bone growth. In this study, a multi-scale computational approach was undertaken to better understand how physiological loads are experienced by chondrocytes embedded inside chondrons when subjected to moderate strain under instantaneous compressive loading of the growth plate. Models of representative samples of compressed bone/growth-plate/bone from a 0.67 mm thick 4-month old bovine proximal tibial physis were subjected to a prescribed displacement equal to 20% of the growth plate thickness. At the macroscale level, the applied compressive deformation resulted in an overall compressive strain across the proliferative-hypertrophic zone of 17%. The microscale model predicted that chondrocytes sustained compressive height strains of 12% and 6% in the proliferative and hypertrophic zones, respectively, in the interior regions of the plate. This pattern was reversed within the outer 300 μm region at the free surface where cells were compressed by 10% in the proliferative and 26% in the hypertrophic zones, in agreement with experimental observations. This work provides a new approach to study growth plate behavior under compression and illustrates the need for combining computational and experimental methods to better understand the chondrocyte mechanics in the growth plate cartilage. While the current model is relevant to fast dynamic events, such as heel strike in walking, we believe this approach provides new insight into the mechanical factors that regulate bone growth at the cell level and provides a basis for developing models to help interpret experimental results at varying time scales.

No MeSH data available.


Related in: MedlinePlus