Cell Kinetics and the Control of Growth In Long Bones

Abstract

The cell kinetics of the cartilage growth plate are outlined and discussed in terms of the probable levels of control on the system. Possible mechanisms of growth control at the cellular level are examined for (i) the rate of cell division in the proliferation zone, (ii) the command to differentiate that limits the size of the proliferation zone and (iii) the ageing process in the cartilage plate. the evidence of cell kinetics does not point unequivocally to any particular mechanism.

Fractionation Effect on Radiation-Induced Growth Retardation of Tibia in Rabbits and Rats

“…This observation can be explained by the contribution of the unirradiated distal epiphysis to longitudinal growth of the tibia, and necessitates grouping of all values less than 60% as a single level for graded-response analysis. In studies on unirradiated bone in humans and rats other researchers have found that the contribution of the distal epiphysis to tibia growth is about 30-40% (26,27). These estimates correspond well with the growth of tibia found in our study after high-dose irradiation.…”

Continuous Activation of Gαq in Osteoblasts Results in Osteopenia through Impaired Osteoblast Differentiation

“…Classical teaching was that there was a linear relationship between the volume of hypertrophic chondrocytes and the rate of longitudinal bone growth and that limb-shortening defects were because of defects in the growth plate (27)(28)(29)(30). Studies from Karsenty and co-workers (31) have challenged this paradigm.…”

Three‐dimensional in situ zonal morphology of viable growth plate chondrocytes: A confocal microscopy study

“…The several-fold chondrocytic hypertrophy is believed to contribute to the major portion of long bone growth, with the remainder due to matrix synthesis in proliferative and hypertrophic zones as well as chondrocyte proliferation. 6,10,11,14,15,17,18 According to Hunziker and Schenk, 6 the normal growth process of long bones is mostly controlled by the morphometric modulation of chondrocyte phenotype. A strong linear relationship was indeed established between hypertrophic chondrocytes volume and longitudinal bone growth rate in both tibial and radial growth plates of three animal species (rats, mice, and pigs).…”

“…5 Chondrocytes located at epiphyseal end of the proliferative zone divide rapidly while chondrocytes located at metaphyseal end of the proliferative columns start to increase in size towards the hypertrophic zone. [6][7][8][9][10][11] In the hypertrophic zone, cell division stops and terminal differentiation associated with a large increase in cell volume begins. 5 The mechanisms by which growth plate chondrocytes modulate longitudinal bone growth are still not well understood.…”