Urinary mulberry bodies as a potential biomarker for early diagnosis and efficacy assessment of enzyme replacement therapy in Fabry nephropathy

Abstract

Background The inability of enzyme replacement therapy (ERT) to prevent progression of Fabry nephropathy (FN) in the presence of >1 g/day proteinuria underscores the necessity of identifying effective biomarkers for early diagnosis of FN preceding proteinuria. Here we attempted to identify biomarkers for early detection of FN. Methods Fifty-one Fabry disease (FD) patients were enrolled. Urinary mulberry bodies (uMBs) were immunostained for globotriaosylceramide (Gb3) and renal cell markers to determine their origin. The association between semiquantitative uMB excretion and the histological severity of podocyte vacuolation was investigated in seven patients using the vacuolated podocyte:glomerular average area ratio. The association between the semiquantitative estimate of uMB excretion and duration of ERT was analyzed. A longitudinal study was conducted to assess the effect of ERT on uMB excretion. Results Thirty-two patients (63%) had uMBs, while only 31% showed proteinuria. The uMBs were positive for Gb3, lysosomal-associated membrane protein 1 and podocalyxin, suggesting they were derived from lysosomes with Gb3 accumulation in podocytes. We observed more severe podocyte vacuolation with increased uMB excretion (P = 0.03 for trend); however, the same was not observed with increased proteinuria. The percentage of patients with substantial uMB excretion increased with shorter ERT duration (P = 0.018). Eighteen-month-long ERT reduced uMB excretion (P = 0.03) without affecting proteinuria. Conclusions uMB excretion, implying ongoing podocyte injury, preceded proteinuria in most patients. Semiquantitative uMB estimates can serve as novel biomarkers for early FN diagnosis and for monitoring the efficacy of FD-specific therapies.

Potential Usefulness of a Lifetime Lyso-Gb3 Exposure at Diagnosis and Baseline Modified Disease Severity Score in Early-Diagnosed Patients with Fabry Disease

“…uMBs, which are observed in the urine by light microscopy as laminated bodies with a whorled shape, are a speci c nding in FD. uMBs originate from mainly podocytes that have accumulated GL3 and are detected before proteinuria develops [37][38][39]. In previous report, high renal pathological score was observed in female patients with only uMBs without albuminuria [40].…”

“…This suggests that uMBs are potential early biomarkers of renal injury. Furthermore, a recent study showed that degree of uMBs excretion correlated with podocyte vacuolation and ERT reduces uMBs excretion [39,41]. Podocyturia has also been reported as an early marker of renal injury, but detection requires staining [42].…”

Clinical utility of urinary mulberry bodies/cells testing in the diagnosis of Fabry disease

“…Selvarajah et al reported that the sensitivity and specificity of these tests were 97.1% and 100%, respectively, in 35 patients with FD and 21 controls with other renal diseases [ 12 ]. In contrast, Yonishi et al reported a relatively lower positivity ratio and showed that 32 of the 51 (62.7%) patients with FD were positive for MBs/MCs [ 13 ]. Here, we evaluated the accuracy of MBs/MCs testing in FD patients and found that these tests have high sensitivity and specificity.…”

“…Mulberry bodies (MBs) are the characteristic fatty components of urinary sediments that appear as whorled laminated bodies, while mulberry cells (MCs) are distal tubular epithelial cells loaded with MBs [ 9 ]. Although the detection of urinary MBs or MCs can aid in the early diagnosis of FD [ 10 , 11 ], few studies have evaluated the accuracy of this diagnostic method [ 12 , 13 ]. Moreover, whether MBs/MCs can be detected in the urine of patients at different stages of FD, heterozygous females, and asymptomatic GLA variant carriers remains unknown.…”

Fabry disease: integrative aspects from diagnosis to treatment

“…Recently, the presence of urinary mulberry cells (MCs) and mulberry bodies (MBs) has been researched as an early diagnosis of FD. Urinary MCs and MBs are characteristic features of Fabry disease, being released from epithelial cells or podocytes with Gb-3 accumulation, reflecting the podocyte injury (SHIMOHATA et al, 2017;YONISHI et al, 2022). MBs can be distinguished from fat particles by their inner lamellar appearance (Shimohata et al, 2017).…”