Long-term cyclical in vivo loading increases cartilage proteoglycan content in a spatially specific manner: an infrared microspectroscopic imaging and polarized light microscopy study

Table 5 Zonal distribution of proteoglycan

	Normalized PG in superficial zone^a			Normalized PG in mid zone^b			Normalized PG in deep zone^c
Rabbit no.	Control	Loaded	Difference	Control	Loaded	Difference	Control	Loaded	Difference
1	0.14	0.20	0.06	0.06	0.29	0.23	0.03	0.11	0.08
2	0.05	0.01	-0.04	0.09	0.06	-0.02	0.06	0.09	0.03
3	0.27	0.33	0.06	0.22	0.31	0.09	0.19	0.28	0.09
4	0.27	0.18	-0.08	0.13	0.19	0.05	0.07	0.14	0.07
5	0.18	0.17	-0.01	0.17	0.16	-0.01	0.14	0.18	0.04
6	0.06	0.17	0.11	0.15	0.15	0.00	0.18	0.22	0.04
Mean	0.16	0.18	0.02	0.14	0.20	0.06	0.11	0.17	0.06
SD	0.09	0.10	0.07	0.06	0.09	0.10	0.07	0.07	0.03
Significance^d			>0.05			>0.05			0.003

^aSuperficial zone of cartilage is from 0 to 8 μm; ^bmid zone is from 8 to 53 μm; ^cdeep zone is from 53 to 100 μm; the zone thicknesses were determined by polarized light microscopy; ^dsignificance was calculated using the two-tailed, paired Student t test (α = 0.05). PG, proteoglycan; SD, standard deviation.