Osteoblasts in HIV-infected patients: HIV-1 infection and cell function

HIV-infected patients have been shown to have a severe alteration in osteoblast function that appears to be related to the infection.

To determine whether normal human osteoblasts express CD4, whether osteoblasts from patients with HIV infection are infected by HIV-1 and whether osteoblast dysfunction observed in vivo also occurs in vitro.

Osteoblast cultures from bone marrow biopsies of HIV-infected patients (n = 14) and control patients (n = 10) were used in a cross-sectional study and a case-control prospective study. Expression of CD4 was analysed using flow cytometry and reverse transcriptase polymerase chain reaction; the presence of HIV-1 particles was determined by measuring p24 antigen in the supernatants of osteoblast cultures and viral DNA or RNA in the osteoblasts using the polymerase chain reaction. Osteoblast function was assessed by measuring cell proliferation, type I collagen and osteocalcin synthesis.

In human osteoblasts, CD4 expression could not be determined using flow cytometry, although low levels of mRNA coding for CD4 were detected. HIV infection was not observed in osteoblast cultures from HIV-infected patients nor was there any alteration in replication and synthesis of type I collagen, although osteocalcin synthesis was increased.

It is unlikely that HIV-1 infects human osteoblasts in vivo; therefore, the hypothesis that these cells could act as local HIV-1 reservoirs should be reconsidered.