Dr Limy Wong1,2, Ms Rachel Kenny2, Professor Lawrence McMahon1,2
1Department of Renal Medicine, Eastern Health, Box Hill, Australia, 2Department of Renal Medicine, Monash University Eastern Health Clinical School, Box Hill, Australia
Aim: To investigate the effect of fibroblast growth factor 23 (FGF23) on myoblast proliferation and differentiation.
Background: FGF23 is a bone-derived hormone whose signalling depends upon several factors, including FGF receptors (FGFRs), α-klotho coreceptor, and cell types. FGF23 levels are elevated in chronic kidney disease patients, and are linked to left ventricular hypertrophy and mortality risk. However, effects on skeletal muscle remain unclear.
Methods: Human skeletal muscle myoblasts were cultured in growth medium (SkGM™-2 Medium, Lonza) at 37° in a controlled humidified 5% CO2 atmosphere. To induce differentiation into myotubes, upon 70-80% confluency growth medium was switched to differentiation medium (DMEM) supplemented with 2% horse serum and 1% penicillin-streptomycin. The expression of FGFRs and key regulatory myogenic genes (MyoD, MyoG and MTSN) were measured using quantitative RT-PCR. For proliferation assays, undifferentiated human myoblasts were treated with vehicle, FGF23 (100ng/ml), FGF2 (100ng/ml) as positive control, uraemic toxin (indoxyl sulfate 1mM and p-cresyl sulfate 0.2mM) as negative control for 48 and 72 hr. Proliferation was measured in 96-well plates using the CellTiter-Glo® (Promega) and BrdU (Roche) assays.
Results: FGFR1, FGFR4 and α-klotho (in decreasing order) were expressed in human myoblasts and myotubes. FGF23 stimulated myoblast proliferation after 48 and 72 hr treatment, similar to FGF2, while uraemic toxins had opposite effects. At 48 hr of differentiation, compared to control, the expression of MyoD decreased significantly in cells treated with FGF23, FGF2 and with similar trend in the uraemic toxin group. MyoG was significantly downregulated in the FGF2-treated group, with similar trends in FGF23 and uraemic toxin-treated groups. MSTN was significantly downregulated in all three groups.
Conclusions: FGF23 promotes myoblast proliferation but appears to inhibit myogenic differentiation.
Biography:
Limy Wong is a Nephrologist and Postdoctoral Fellow at Eastern Health. She graduated with First Class Honours in Medicine from the Royal College of Surgeons in Ireland and completed Nephrology specialist training in Ireland and the UK, gaining the Specialty Certificate in Nephrology from the Royal College of Physicians. She completed a Wellcome Trust Clinical PhD Fellowship at the University of Cambridge, studying the genetics of ANCA-associated vasculitis. She was recently awarded the 2021 and 2022 RACP Jacquot Research Establishment Fellowship, to conduct basic science and translational research to answer the questions surrounding the pathogenesis of sarcopenia in CKD patients.