Study On The Mechanism Of GDF15 Secreted By Acute Myeloid Leukemia Cells Remodeling Bone Marrow Adipocytes

Objective:As an important component of the bone marrow microenvironment,adipocytes promote the growth of leukemia cells by energy supply.We have previously found that the morphological remodeling of bone marrow adipocytes in patients with acute myeloid leukemia（AML）is closely related to its poor prognosis.And growth differentiation factor15（GDF15）may be a key factor leading to this abnormal phenomenon.However,it is unclear how GDF15 secreted by leukemia cells remodels bone marrow adipocytes.The study found that Ca²⁺channels play an important role in regulating the process of adipocyte remodeling.Morever,transient receptor potential vanilloid（TRPV）is an important molecule regulating the energy balance of adipocytes.Therefore,we hypothesized that GDF15 may regulate bone marrow adipocyte remodeling by regulating TRPV channels in AML.In this study,we intend to use TRPV channel as the entry point to further explore the mechanism of GDF15 regulating AML bone marrow adipocyte remodeling,which provides a possibility for exploring new therapeutic targets for AML patients.Methods:1.Western blot and RT-q PCR were used to detect the expression of TRPV channel in bone marrow adipocytes.And the effects of TRPV on bone marrow adipocyte remodeling were observed by adding specific inhibitors or knocking down TRPV expression.2.In vitro,Transwell assay and neutralizing antibodies further demonstrated that GDF15-mediated TRPV signaling pathway regulates bone marrow adipocyte remodeling.3.GDF15 receptors in bone marrow adipocytes were detected by RT-q PCR,specific inhibitors or lentivirus infection test,and their downstream signaling pathways were screened.4.RNA-Seq sequencing was performed on bone marrow adipocytes treated or untreated with GDF15 to identify the expression of key factors between GDF15 and TRPV,which is the mainly factors causes the remodeling of bone marrow adipocytes.5.The number and size of bone marrow adipocytes were quantified by computer grid counting.It was also validated in obese C57BL/6 mice to further verify the role of TRPV in bone marrow adipocyte remodeling in vivo.Results:1.We found that TRPV4 had the highest expression among six TRPV family members at the gene and protein levels in bone marrow adipocytes.Along with TRPV4 channel inhibition,bone marrow adipocytes subsequently exhibited lipolysis and more free fatty acids.2.GDF15 secreted by leukemia cells inhibited the expression of TRPV4,which promoted the lipolysis of bone marrow adipocytes.However,GDF15 neutralizing antibody partly reversed this effect.3.GDF15 secreted by leukemia cells could bind to TGFβRII on bone marrow adipocytes and subsequently activate downstream PI3K/AKT pathway,which further down-regulate FOXC1 expression and finally inhibit the expression of TRPV4 in bone marrow adipocytes.4.In vivo experiments confirmed that activation of TRPV4 delayed the reduction of bone marrow adipocytes and the progress of leukemia.Conclusions:1.GDF15 secreted by leukemia cells regulates TRPV4 expression in bone marrow adipocytes through PI3K/AKT/FOXC1 pathway,which promotes lipolysis and remodeling of bone marrow adipocytes.2.Activation of TRPV4 in bone marrow adipocytes can delay the progression of AML and prolong the total survival time of obese mice.