Differences in osteocyte and lacunar density between Black and White American women.

We examined the differences in osteocyte and lacunar density between Black and White women, using previously obtained iliac bone biopsies from 34 healthy Black women, aged 21-70 years, and 94 White women, aged 20-73 years. For each subject, the density of osteocytes (Ot.N/B.Ar), empty lacunae (EL.N/B.Ar), and total lacunae (Tt.L.N/B.Ar) and the proportion of osteocyte-occupied lacunae (Ot.N/Tt.L.N) were separately measured in whole trabeculae, superficial bone (<25 microm from the bone surface), and deep bone (>45 microm from the bone surface). Compared with White women, Black women had higher values for osteocytes, empty lacunae, and total lacunae and lower values for percent occupied lacunae in superficial bone and whole trabeculae (P < 0.01 to <0.001). In deep bone there were more osteocytes and total lacunae in Black women, but the other measurements did not differ significantly between the two groups. As in White women, there were fewer osteocytes and total lacunae and more empty lacunae in deep than in superficial bone. The regressions of osteocyte and total lacunar density on age were not significant in Black women, but postmenopausal Black women had fewer osteocytes than premenopausal Black women, and percent occupied lacunae declined significantly with age in whole trabeculae and deep bone, which could only have resulted from osteocyte death. In contrast to White women, there was no inverse relationship between bone formation rate and osteocyte density in superficial bone and the observed bone formation rate was lower than predicted by osteocyte density. We conclude the following: (1) Cancellous bone is made with more osteocytes in Black than in White women, most likely because of diminished apoptosis of osteoblasts; this could contribute to increased bone strength in Black women. (2) In Black women, as in White women, there are fewer osteocytes and total lacunae and more empty lacunae in deep than in superficial bone. (3) There was moderate age-related loss of osteocytes in deep bone in Black women, indicating that osteocyte density depends more on the age of the bone than on the age of the subject. (4) The higher osteocyte density in Black women was not responsible for their lower bone formation rate.