Bisphosphonates induce apoptosis of circulating endothelial cells in multiple myeloma patients and in subjects with bisphosphonate-induced osteonecrosis of the jaws.

Bisphosphonates (BPs) are the current standard of care for bone lesions in patients with multiple myeloma (MM) but they are associated with a number of side effects such as osteonecrosis of the jaw. The exact mechanisms of osteonecrosis are not elucidated, and its physiopathology is based on several hypotheses such as a decrease in bone remodeling or an inhibitory effect on angiogenesis. The aim of our study was to investigate the mechanism involved in the pathogenesis of osteonecrosis. We examined the apoptosis of circulating endothelial progenitor cells in MM subjects before and after BP treatment and in osteonecrosis patients using a flow-cytometric analysis. Our data showed an increase in endothelial cell apoptosis in MM patients after BP administration and in osteonecrosis subjects. Our study seems in agreement with the hypothesis that BPs can inhibit angiogenesis interfering with endothelial cell proliferation and survival, leading to loss of blood vessels and avascular necrosis.

Association of osteonecrosis of the jaws and POEMS syndrome in a patient assuming rituximab.

POEMS syndrome, is a rare condition characterized by polyneuropathy, organomegaly, endocrinopathy, monoclonal proteinaemia, and skin lesions. We report a rare case of a patient affected by Waldenström macroglobulinemia, who developed POEMS syndrome and who presented at the time of diagnosis with oral manifestations of the lymphoma and an osteonecrosis of the jaw (ONJ) after rituximab treatment. Although the etiology of ONJ is not known, it is likely that several factors are at play, including endothelial cell damage, decreased angiogenesis, and microvascular compromise. Our patient was treated with rituximab for a long period, and recent studies have demonstrated the possibility that rituximab, a monoclonal antibody directed against the CD20 can exert part of its anti-tumor action, through its action on angiogenesis. Although our report does not allow identification of rituximab as a new risk factor for the onset of the ONJ, further studies seem necessary to exclude a role of the antibody in the alterations of angiogenesis that could lead to the development of the syndrome after rituximab treatment.

Immunohistochemial evaluation of sarcoglycans and integrins in gingival epithelium of multiple myeloma patients with bisphosphonate-induced osteonecrosis of the jaw.

Osteonecrosis of the jaw (ONJ) is an adverse outcome associated to bisphosphonate treatment. However, it is not known whether the ONJ lesion originates in the bone, or whether it may initiate in the oral mucosa. The aim of our study was to evaluate the pattern of basal lamina of oral mucosa after bisphosphonate administration and to analyze the structural damage of the mucosa in ONJ patients, and in subjects treated with bisphosphonates without osteonecrosis. By immunohistochemistry, we evaluated changes in basement membrane by expression of signalling proteins, laminin, and type IV collagen. All tested proteins were almost absent in basal lamina and mucosa of subjects treated with bisphosphonates without osteonecrosis, whereas in mucosa of patients with ONJ, they showed a clearly detectable pattern of the same proteins, specifically in basal lamina, but less in comparison to control samples. Moreover, in pathological mucosa, the clearly detectable staining pattern for VEGF indicated a massive neoangiogenesis. Bisphosphonates induce changes in expression of proteins also in oral mucosa. The increase of these proteins in basal lamina, and the neo-angiogenesis, concomitant with formation of the lesion, could indicate a compensative behaviour in the remodelling of the gingival mucosa in order to restore the epithelial architecture.