Glycolysis Restoration Attenuates Damaged Bone Marrow Endothelial Cells

Background: Bone marrow(BM) endothelial cells(ECs), a key component of BM microenvironment, is essential for the physiology and regeneration of hematopoietic stem cells (HSCs). The damage of ECs is recognized by us and other researchers as a mainstay in the pathophysiology of a serious of life-threatening complications after chemoradiotherapy and myeloablative hematopoietic cell transplantation(HSCT), including poor graft function (PGF) (2013BBMT, 2015BMT, 2016Blood, 2019Blood Advances). Despite numerous researches focused on the BM ECs contributing to HSC regeneration following myelotoxicity, the mechanisms underlying the injured BM ECs itself remain to be elucidated. Under physiological conditions, energy metabolism plays an instrumental role in maintaining EC function, and markedly perturbed of EC metabolism is linked to many pathologies, like cancer and diabetes. However, little is known about the metabolism state and its role in impaired BM ECs.

Aims: The current study was performed to investigate the metabolism status in BM ECs after chemotherapy-induced injury. Moreover, we evaluated the metabolic state and its role in BM ECs of PGF patients post-allotransplant. Finally, we evaluated the therapeutical potential of anti-metabolic drugs to the dysfunctional BM ECs derived from PGF patients.

Methods: Two EC injury models in vitro were established with the cultivated human BM ECs treated by 5-Fluorouracil (5-FU) and hydrogen peroxide. The findings from the above models were further validated by a prospective case-control study enrolled 15 patients with PGF, 30 matched patients with good graft function (GGF) and 15 healthy donors (HD). To determine the metabolic status of BM ECs, the expression of metabolism regulating genes was analyzed by qRT-PCR (mRNA level) and flow cytometry (protein level). Glucose metabolism levels were measured by glucose consumption and lactate production assays. To evaluate the functions of BM ECs, apoptosis, migration and tube formation assays were performed. To investigate the effect of anti-metabolic drugs to injured BM ECs, the glycolysis inhibitor 3PO and PPARd agonist GW501516 were administrated to the cultivated BM ECs treated by 5-FU , hydrogen peroxide or derived from PGF.

Results: We demonstrated that the glycolysis in BM ECs could be induced by the treatment with either 5-FU or hydrogen peroxide in vitro, consistent with the dysfunction(impaired migration, angiogenesis, and higher level of apoptosis) of BM ECs, which could be attenuated by glycolysis restoration. Mechanistically, we revealed that the aberrant glycolysis and dysfunction of BM ECs could be triggered by PPARd knockdown in vitro, while the PPARd were down-regulated by either 5-FU or hydrogen peroxide treatment in vitro, Furthermore, PPARd agonist GW501516 treatment attenuated the perturbed function and number of injured BM ECs treated by either 5-FU or hydrogen peroxide. Subsequently, the prospective case-control study demonstrated elevated expressions of the glycolytic activator PFKFB3 and decreased PPARd were observed in BM ECs of PGF patients, when compared with those of GGF patients and HD, indicating that BM ECs of PGF patients have a hyper-glycolytic metabolism. Moreover, either glycolysis (PFKFB3) inhibitor 3PO or PPARd agonist GW501516 treatment reduced the aberrant glycolysis and improved the number and function of BM ECs derived from patients with PGF in vitro, revealing the critical role of defective glycolysis in the impaired BM ECs of PGF.

Summary / Conclusions: These findings reveal that hyper-glycolysis mediated by PPARd inhibition is involved in the dysfunction of BM ECs after injury. Defective glycolysis may contribute to the pathobiology of BM ECs of PGF patients, which could be attenuated by glycolysis inhibitor 3PO or PPARd agonist GW501516 in vitro. Our findings might merit further consideration of targeting BM ECs glycolysis or PPARd as a promising therapeutic approach for PGF patients post-allotransplant in the future.