Could multiple myeloma VEGF modify the systemic microcirculation?

We studied eight patients with active multiple myeloma (aMM, six males and two females; mean age 62 years), nine patients in objective/complete response (rMM, three males and six females; mean age 70 years), and seven patients with monoclonal gammopathy of undetermined significance (MGUS, three males and four females; mean age 57 years). We used a laser Doppler to evaluate capillary blood flow and a transcutaneous oxymeter to measure transcutaneous oxygen partial pressure (TcpO₂). Red blood cell (RBC) aggregation index (AI and t1/2) and elongation index (EI) were assessed using laser-assisted optical rotational cell analysis (LORCA), while the serum vascular endothelial growth factor (VEGF) levels were measured using enzyme-linked immunoabsorbant assay (ELISA). VEGF values were significantly increased (p < 0.001) in aMM vs. rMM and vs. MGUS. Also AI was increased (p < 0.05) in aMM vs. rMM and vs. MGUS and t1/2 was decreased (p < 0.05) in the aMM vs. rMM and MGUS groups; no variations were detected in EI. We found a significant correlation (p < 0.001) between AI/t1/2/EI and VEGF. Periflux tests were performed evaluating the basal values (t0), the physical stress (t1) and the heat stress (t3) followed by their respective relaxing times (t2, t4). A significant increase (p < 0.01) in t1 vs. t0 values was observed in all groups. No significant increase in aMM t3 vs. t0 was seen, while the increase was significant in rMM and MGUS (p < 0.01). We found a significant correlation (p < 0.001) between t0 blood flow and VEGF in aMM, rMM and MGUS. TcpO₂ t0 values were significantly correlated to VEGF (p < 0.001) in all groups. Our data show that VEGF modifies the microcirculation in aMM and also modifies RBC. It is possible that other mechanisms could interfere with the peripheral microcirculation as we saw in t3 blood flow.