RESUMEN
Multiple myeloma (MM) is characterized by the impaired osteogenic differentiation of human mesenchymal stromal cells (hMSCs). Canonical Wnt signaling is critical for the regulation of bone formation, however, recent evidence suggests that the non-canonical Wnt agonist Wnt5a stimulates human osteoblastogenesis through its co-receptor Ror2. The effects of MM cells on non-canonical Wnt signaling and the effect of the activation of this pathway on MM-induced osteoblast exhaustion are not known and were investigated in this study. We found that the osteogenic differentiation of bone marrow hMSCs toward osteoprogenitor cells (PreOB) significantly increased Ror2 expression, and that MM cells inhibit Ror2 expression by PreOB in co-culture by inhibiting the non-canonical Wnt5a signaling. The activation of the non-canonical Wnt pathway in hMSCs by means of Wnt5a treatment and the overexpression of Wnt5 or Ror2 by lentiviral vectors increased the osteogenic differentiation of hMSCs and blunted the inhibitory effect of MM in co-culture. Consistently, Wnt5a inhibition by specific small interfering RNA reduced the hMSC expression of osteogenic markers. Our findings demonstrate that the Wnt5a/Ror2 pathway is involved in the pathophysiology of MM-induced bone disease and that the activation of the non-canonical Wnt5a/Ror2 pathway in hMSCs increases osteogenic differentiation and may counterbalance the inhibitory effect of MM cells.
Asunto(s)
Células de la Médula Ósea/citología , Diferenciación Celular , Mieloma Múltiple/patología , Osteoblastos/citología , Osteogénesis , Proteínas Proto-Oncogénicas/metabolismo , Receptores Huérfanos Similares al Receptor Tirosina Quinasa/metabolismo , Células Madre/citología , Proteínas Wnt/metabolismo , Animales , Biomarcadores de Tumor/genética , Biomarcadores de Tumor/metabolismo , Western Blotting , Células de la Médula Ósea/metabolismo , Estudios de Casos y Controles , Proliferación Celular , Técnicas de Cocultivo , Citometría de Flujo , Perfilación de la Expresión Génica , Humanos , Células Madre Mesenquimatosas/citología , Células Madre Mesenquimatosas/metabolismo , Ratones , Mieloma Múltiple/genética , Mieloma Múltiple/metabolismo , Análisis de Secuencia por Matrices de Oligonucleótidos , Osteoblastos/metabolismo , Proteínas Proto-Oncogénicas/antagonistas & inhibidores , Proteínas Proto-Oncogénicas/genética , ARN Mensajero/genética , ARN Interferente Pequeño/genética , Reacción en Cadena en Tiempo Real de la Polimerasa , Receptores Huérfanos Similares al Receptor Tirosina Quinasa/genética , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Transducción de Señal , Células Madre/metabolismo , Proteínas Wnt/antagonistas & inhibidores , Proteínas Wnt/genética , Proteína Wnt-5aRESUMEN
The involvement of osteocytes in multiple myeloma (MM)-induced osteoclast (OCL) formation and bone lesions is still unknown. Osteocytes regulate bone remodelling at least partially, as a result of their cell death triggering OCL recruitment. In this study, we found that the number of viable osteocytes was significantly smaller in MM patients than in healthy controls, and negatively correlated with the number of OCLs. Moreover, the MM patients with bone lesions had a significantly smaller number of viable osteocytes than those without, partly because of increased apoptosis. These findings were further confirmed by ultrastructural in vitro analyses of human preosteocyte cells cocultured with MM cells, which showed that MM cells increased preosteocyte death and apoptosis. A micro-array analysis showed that MM cells affect the transcriptional profiles of preosteocytes by upregulating the production of osteoclastogenic cytokines such as interleukin (IL)-11, and increasing their pro-osteoclastogenic properties. Finally, the osteocyte expression of IL-11 was higher in the MM patients with than in those without bone lesions. Our data suggest that MM patients are characterized by a reduced number of viable osteocytes related to the presence of bone lesions, and that this is involved in MM-induced OCL formation.
