Methotrexate chemotherapy reduces osteogenesis but increases adipogenic potential in the bone marrow

Abstract

Intensive use of cancer chemotherapy is increasingly linked with long-term skeletal side effects such as osteopenia, osteoporosis and fractures. However, cellular mechanisms by which chemotherapy affects bone integrity remain unclear. Methotrexate (MTX), used commonly as an anti-metabolite, is known to cause bone defects. To study the pathophysiology of MTX-induced bone loss, we examined effects on bone and marrow fat volume, population size and differentiation potential of bone marrow stromal cells (BMSC) in adult rats following chemotherapy for a short-term (five once-daily doses at 0.75 mg/kg) or a 6-week term (5 doses at 0.65 mg/kg + 9 days rest + 1.3 mg/kg twice weekly for 4 weeks). Histological analyses revealed that both acute and chronic MTX treatments caused a significant decrease in metaphyseal trabecular bone volume and an increase in marrow adipose mass. In the acute model, proliferation of BMSCs significantly decreased on days 3-9, and consistently the stromal progenitor cell population as assessed by CFU-F formation was significantly reduced on day 9. Ex vivo differentiation assays showed that while the osteogenic potential of isolated BMSCs was significantly reduced, their adipogenic capacity was markedly increased on day 9. Consistently, RT-PCR gene expression analyses showed osteogenic transcription factors Runx2 and Osterix (Osx) to be decreased but adipogenic genes PPARγ and FABP4 up-regulated on days 6 and 9 in the stromal population. These findings indicate that MTX chemotherapy reduces the bone marrow stromal progenitor cell population and induces a switch in differentiation potential towards adipogenesis at the expense of osteogenesis, resulting in osteopenia and marrow adiposity.

Cancer treatment-induced bone loss (CTIBL): Pathogenesis and clinical implications

“…These effects were associated with a reduced osteogenic and increased adipose differentiation potential of BMSCs that demonstrated up-regulated pro-adipogenic transcription factors, including the Peroxisome Proliferator-Activated Receptor (PPAR)-c [50]. The same authors suggested, indeed, that MTX-induced bone damage could be attributed to the inhibition of the canonical wingless (Wnt)/b-catenin pathway, whose role is essential in the regulation of BMSC commitment.…”

Dietary emu oil supplementation suppresses 5-fluorouracil chemotherapy-induced inflammation, osteoclast formation, and bone loss

“…A previous study has reported that the bone marrow stromal cells obtained from the femur and tibia of rats respond the same way to treatment with MTX (another commonly used antimetabolite) (14). Therefore, to obtain a large enough number of cells to perform the cell culture assays needed, more than one marrow cavity was used to obtain the marrow cells.…”

Perinatal Maternal Dietary Supplementation of ω3-Fatty Acids Transiently Affects Bone Marrow Microenvironment, Osteoblast and Osteoclast Formation, and Bone Mass in Male Offspring

“…Effects of n3FA supplementation on the osteoprogenitor cell pool in the bone marrow were examined ex vivo using bone marrow specimens from the offspring in a CFU-f assay plus osteoblast differentiation marker ALP staining as previously described (29,33). ALP ϩ stained colonies (aggregates of Ͼ50 cells) were counted and expressed as ALP ϩ colonies/well.…”

“…The right tibia was used for collecting fresh growth plate cartilage (by scraping off using a fine scalpel blade), which was then snap frozen in liquid nitrogen and stored at Ϫ80 C. In addition, the proximal metaphysis of the right tibia was also collected and stored frozen at Ϫ80 C for subsequent RNA extraction. All the remaining bone and the humeri were used to collect bone marrow samples for cell culture using established methods (29).…”