Tubular cells urinary biomarkers

Cystatin C is nearly completely metabolized by proximal renal tubular cells. As a consequence, under ordinary circumstances there is little to no detectable cystatin C present in the urine. Thus, a true clearance of cystatin C cannot be determined. However, in the presence of tubular damage, cystatin C may be detected in the urine [147,148] and may be more sensitive to early and mild changes of kidney function compared with creatinine [149,150]. In this regard, elevation in serum cystatin C consistent with AKI, defined by at least a 50% increase from baseline, was evident 1-2 days prior to changes in SCr [151]. Finally, in patients with AKI, elevated urinary cystatin C was highly predictive of subsequent need for acute renal replacement therapy and outperformed several other urinary biomarkers in some studies [152]., but not in others [152a]... 

Wilson PD (2009) In vitro methods in renal research. In Avner ED, Harmon WE, Niaudet P, Yoshikawa N (eds) Pediatric nephrology, 6th edn. Springer, Berlin, pp 379-396 Yu Y, Jin H, Holder D, Ozer JS, Villarreal S (2010) Urinary biomarkers trefoil factor 3 and albumin enable early detection of kidney tubular injury. Nat Biotechnol 28 470-477 Zhu HY, Liu MY, Hong Q, Zhang D, Geng WJ, Xie YS, Chen XM (2012) Role of microRNA-181a in the apoptosis of tubular epithelial cell induced by cisplatin. Chin Med J (Engl) 125(3) 523-526... 

After chronic exposure, cadmium accumulates in the human body and causes kidney diseases, especially lesions of proximal tubular cells. A tubular proteinuria causes an increase in urinary excretion of microproteins. Excretions of retinol binding protein (RBP), (32-microglobulin ((32-M), and a 1-microglobulin are validated biomarkers for analyzing cadmium effects. For this purpose, immunological procedures such as ELISA, and radio- and latex-immunoassays are used. 

The unique distribution of various enzymes along the length of the nephron provides the potential for identifying the specific injury site. Enzymes may not be uniformly distributed along or between nephrons thus the site selechvity of single enzymes is questionable, however it should be possible to localize the area of kidney damage on the basis of the pattern of enzymuria. While many urinary enzymes have been evaluated [169] as markers of damage or dysfunction of tubular epithelial cells [162,170], only a small number are considered to be valuable as biomarkers[152]. 

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