(A) CD271-isolated primary MSCs were cultivated for 10 days (3 passages) and were analyzed by flow cytometry for the expression of CD271 and ALP. (B) The percentages of CD271+ALP- MSC and CD271-ALP+ OB were compared between healthy controls (HC, n = 10) and MM patients (n=48). The percentage of CD271-ALP+OB population (of the total population) was significantly lower in patients with osteolytic lesions (MM-B, n=18) than those who exhibited no evidence of bone lesions (MM-NB, n=30). The percentage of CD271-ALP+OB was significantly lower in MM-NB patients than healthy controls (HC) (**p<0.01). In contrast, the percentage of CD271+ALP-MSC was significantly higher in MM-B patients than MM-NB patients (**p<0.01). (C) CD271+ALP-MSC (left) and CD271-ALP+ OB (right) proportion in MM patients based on PC burden in bone marrow (%CD138+), age, and cytogenetics aberrancies. The MM PC infiltration was evaluated by comparing bone marrow from patients with low (≤30% CD138+ cells, n=21) versus high (> 30%, n=27) disease burden. The percentage of CD271-ALP+OB was significantly lower in patients with high disease burden (>30%, n=27) than those who had lower disease burden(≤30% CD138+ cells, n = 21) (**p<0.01). BMMNC from younger (≤60 years, n=28) subjects contained significantly higher CD271-ALP+ OB and lower CD271+ALP- MSC than that from elder subjects (>60 years, n=20) (**p<0.01). The impact of cytogenetic aberrancies was analyzed by comparing samples from patients with del (17p) (n=19) versus with no del (17p) (n=29). The percentage of CD271-ALP+OB was lower in MM patients with del (17p) than those who with no del (17p) (**p<0.01). All values are expressed as mean±SD.