Automated Cell Detection and Morphometry on Growth Plate Images of Mouse Bone.

“The resting zone contains relatively quiescent small, round, densely packed cells. Upon entry in the proliferating zone, cells elongate medial-laterally and undergo division by mitosis. At each division, the newly produced daughter cell remains closely situated with respect to the mother cell but may be far apart from other cells. The cells begin to form stacks. In pre-hypertrophic and hypertrophic zones, chondrocytes become arranged in columns. Such cells begin to enlarge and express Indian Hedgehog while the expression of Sox9 is reduced. In the hypertrophic zone, the terminal enlarged chondrocytes are larger than in the rest of the growth plate, either round or elongated in the longitudinal direction, and packed closely to one another. The bottom of this region is marked by ossification. Correlations exist among height of hypertrophic chondrocytes, growth plate length, and limb length[remember that correlation does not equal causation]”

“the mean cell area is significantly smaller in the resting zone than in the proliferative zone”

“the mean cell area is significantly smaller in the proliferative zone than in the hypertrophic zone; and that the mean orientation differs significantly between resting and proliferative, but not between proliferative and hypertrophic zones. Further, the mean isoperimetric ratio IR is significantly different between resting and proliferative zones, and between proliferative and hypertrophic zones, indicating that the cells become less circular as they progress from the resting to proliferative, and from proliferative to hypertrophic zone. ”

“the chondrocytes of the Smad1/5CKO mutant [havea] rounder shape, and the orientation off the horizontal (medial-lateral) direction,  in comparison with the control WT mouse”