Urinary Epidermal Growth Factor: A Promising “Next Generation” Biomarker in Kidney Disease Ⅲ

Kidney Transplantation 

EGF excretion has been assessed in the urine of living human kidney donors and recipients. After uninspiredtomy, uEGF was approximately 65% of the preoperative value, reflecting a compensatory increase in uEGF excretion rate from the remaining kidney of approximately 30% [65]. This was in contrast to a 50% decrease in uEGF/ Cr in five persons who underwent uninephrectomy due to renal malignancies [66]. GFR was also increased in response to compensatory changes in uEGF excretion rate, suggesting that compensatory changes in uEGF and eGFR are related, with both possibly being symptoms of nephron hypertrophy and hyperperfusion. The increased uEGF excretion of the recipients' kidneys may enhance the transplanted kidney's EGF excretion. However, this impact is likely minimal owing to ESKD. GFR was consistently approximately 15% lower and uEGF excretion rate was consistently 40% lower in transplanted kidneys compared to identical kidneys remaining in donors. This could be due to ischemia and drug-induced damage, as well as the transplanted kidneys' denervated status [65, 67].

NEW HERBAL FORMULATION SUITS HIGH RISK OF TRANSPLANT FAILURE

Acute cellular rejection (ACR) of renal allografts is still a major cause of graft loss in human kidney transplantation. The kidney gene and protein expression, as well as the urine excretion rate of EGF, were examined in renal transplant recipients (16 with ACR and 13 with tubular damage/cyclosporine toxicity [ATD]). ACR patients had significantly lower EGF expression in the ascending limb of Henle's loop and the distal convoluted tubule cells, as well as a prolonged positive IL-6 signal. The changed expression and distribution inside the allograft were closely paralleled in the urine pattern of IL-6 and EGF excretion. In ATD patients, EGF expression was significantly reduced. The IL-6/EGF ratio was considerably greater in ACR patients, but only modestly higher in ATD patients. As a result, kidney transplant patients with ACR or ATD had a specific pattern of IL-6 and EGF intragraft expression that was closely mirrored by their urinary excretion rate. EGF expression may be reduced as a result of tubular injury or as a reaction to an inhibitory signal. In individuals who recovered from ACR, uEGF levels returned to normal. To assess the therapeutic value and prognostic importance of EGF in each transplanted patient, more research is needed [68].

Although short-term graft survival has improved significantly in recent decades, chronic graft failure remains a key barrier to improving long-term outcomes in renal transplant recipients [69]. Chronic rejection, hypertension, oxidative stress, infection, calcineurin inhibitor toxicity, and proteinuria are all factors that contribute to graft failure, which leads to progressive fibrosis and loss of renal function [70]. The majority of biomarkers employed for follow-up are indicators of glomerular damage  (uACR and uPCR) [71], which are indicative of the development of fibrosis and represent an early event in chronic rejection's natural history [72]. Noninvasive biomarkers that can identify pathophysiological changes in renal tissue are being studied as prospective techniques for patient monitoring and early detection of persons at high risk of transplant failure [47].

In a prospective cohort research study [47], uEGF/Cr was measured in 649 stable renal transplant recipients with a working allograft of 1 year, no history of drug or alcohol addiction, or malignancy, and who were followed for 3 years. In individuals with impaired renal function, uEGF excretion was significantly lower. After adjusting for possible confounders, uEGF/Cr was negatively linked with the incidence of graft failure (p < 0.001). EGF/Cr seems to be a better predictor of graft failure than albuminutia and urinary protein excretion. Although it is challenging to capture the complexities of graft failure with a single biomarker, fibrosis is a pivotal stage in the development of graft failure [73], and VEGF suppression is an early indicator of this phenomenon [17]. EGF/Cr may be a marker for a specific pathological aspect of graft failure that begins before the development of glomerular injury [47]. The lack of a drop in uEGF with time following transplantation could be explained by a confusing impact of cyclosporin A (CsA) treatment, which lowers uEGF. It has been discovered that uEGF and the usage of calcineurin inhibitors have an inverse relationship [74, 75]. Besides the calcineurin inhibitors' nephrotoxic impact, the relationship between uEGF/Cr and graft failure is probably mediated by other processes, including renal fibrosis [76]. Patients with stable graft function and proproteinuria>500 mg/24 h had no significant differences in VEGF mRNA when compared to those with chronic al-lograft nephropathy [77]. More research and validation in larger and more diverse clinical trials are needed to establish the potential value of EGF-directed treatment or the use of uEGF/Cr in the clinical care of stable renal transplant patients [47].

Because of a renal Mg2+ leak, hypomagnesemia has been linked to CsA therapy. As a result of CsA therapy, 60% of people develop hypomagnesemia, with occurrences ranging from 1.5 to 100%. Confusion, muscular weakness, dysphagia, tetany, tremor, and general convulsions are some of the clinical symptoms of severe magnesium deficiency after CsA therapy [76, 78]. Animal studies have revealed a function for the Mg2+ channel Transient Receptor Potential Cation Channel Subfamily M Member 6, which is situated in the distal convoluted tubule and is activated by EGF [79, 80]. Transient Receptor Potential Cation Channel Subfamily M Member 6 mRNA was downregulated concurrently with EGF in an in vivo rat model of CsA nephrotoxicity, resulting in increased renal magnesium excretion [81]. Serum Mg2+ was considerably lower in the CsA group compared to the CKD group in a case-control study involving 55 renal transplant patients treated with CsA and 35 CKD patients, with significantly more CsA-treated patients developing hypomagnesemia. Although the fractional Mg2+ excretion (FE Mg2+) did not differ substantially between the two groups, it was much higher in both when compared to normal reference values (FE Mg2+ <2%) [76, 82], as predicted given the degree of renal impairment [83, 84]. CsA-treated patients showed a substantially higher FE Mg2+ than CKD patients in a subanalysis of hypomaniaanemia patients (p = 0.05). The CsA group had a considerably lower uEGF excretion, which was a predictor of FE Mg2+ in both groups.

Renal magnesium reabsorption has been demonstrated to be enhanced in CKD patients in an attempt to maintain blood magnesium levels within normal ranges. However, in CsA-treated patients, the kidney is unable to augment magnesium reabsorption, and magnesium is lost in the urine. The CsA group had a more dramatic drop in EGF, which could be linked to FE Mg2+. Renal EGF production is connected to FE Mg2+, indicating that EGF regplates Mg2+ reabsorption in humans [74].

Primary Glomerulonephritis 

Primary glomerulonephritis (GN) is a group of illnesses that together account for one of the leading causes of ESKD [85]. Regardless of the underlying disease, glomerular injury activates similar profibrotic pathways such as tubular shrinkage and interstitial fibrosis, resulting in progressive nephron loss [86, 87]. Renal function degrades at varying rates in GN and is more strongly related to the degree of tubulointerstitial disease than to glomerular lesions [86–88]. Patients with extensive tubulointerstitial involvement at risk of more rapid development cannot be properly identified using traditional clinical indicators such as proteinuria, hypertension, or a lowered GFR. Currently, only a kidney biopsy can establish the extent of IFTA, which is a major prognostic factor in GN. The severity of IFTA is likely determined by an imbalance to between pro-inflammatory cytokines like MCP-1 and protective cytokines like EGF. A link was discovered between IFTA and uEGF, uMCP-1, and the uEGF/MCP-1 ratio in a cross-sectional study. eGFR, uEGF, and uEGF/MCP-1 ratio were all linked to IFTA in univariate analysis. In multivariate analysis, only the uEGF/MCP-1 ratio was independently associated with IFTA. The EGF/MCP-1 ratio had an IFTA sensitivity of 88% and a specificity of 74%. uEGF/MCP-1 discriminated well against IFTA (AUC = 0.85). However, there was no significant difference between uEGF alone and uEGF/MCP-1. Because of their op-posing fibrotic effects, the balance of uEGF and uMCP-1 may be a better predictor of IFTA severity and renal disease progression than either cytokine alone. In univariate analysis, the eGFR, uEGF, and uEGF/MCP-1 ratios were all shown to be significant. VEGF may be a good candidate biomarker for moderate to severe IFTA, while it may not be as beneficial in detecting persons with early tubulointerstitial damage. More research with larger study populations is needed to thoroughly examine the function of uEGF/MCP-1 as a biomarker in predicting long-term prognosis or response to therapy [48]. 

IgAN is the most common primary GN, and many people develop ESKD within 10–20 years after initial renal biopsy. The presence of impaired renal function, arterial hypertension, and the severity of histologic lesions, as well as the degree of proteinuria at the time of renal biopsy, are all well-known prognostic indicators for the development of ESKD in IgAN patients [89]. Evidence suggests that the degree of tubulointerstitial alterations, such as tubular atrophy, interstitial cell infiltration, and fibrosis, is closely linked to the loss of renal function in the course of renal injury [90]. The relationships between urine levels of IL-6, EGF, MCP-1, and TGF-β1 and clinical, biochemical, and histological aspects were evaluated in 58 individuals with primary IgAN, as well as their ability to predict the degree of glomerular and/or interstitial sclerosis lesions. uIL-6, uTGF-β1, and uMCP-1 were associated with focused glomerulosclerosis and interstitial fibrosis extension, but not with mesangial, extra capillary, or endocapillary proliferation. EGF had a negative connection with interstitial fibrosis. Individuals with T1 and T2 scores exhibited significantly higher levels of uIL-6, uMCP-1, and uTGF-β1, and significantly lower uEGF levels than patients with T0 scores, according to the Oxford classification. uMCP-1, uIL-6, and uEGF concentrations were revealed to be independent predictors of the fibrosis surface in multiple regression and logistic regression studies after age and eGFR were corrected [49].

Cytokines generated by both resident and nonresident renal cells play a significant role in the advancement of renal damage during IgAN. Subjects with uEGF/MCP-1 ratios in the lowest tertile showed a significant worsening in renal survival at 48 and 84 months of follow-up in a cohort of 132 patients with biopsy-proven IgAN, whereas individuals in the highest tertile achieved 100% renal survival. In a multivariate Cox regression analysis, the uEGF/MCP-1 ratio was revealed to be an independent predictive factor and to be indirectly related to the combined outcome. The AUC was also used to compute the predictive value. The AUC of the uEGF/MCP-1 ratio was significantly greater than that of uEGF or uMCP-1 alone, histologic grade, creatinine clearance, or proteinuria. 

As a result, the EGF/MCP-1 ratio could be employed as a predictive diagnostic for ESRD in IgAN patients [50]. In IgAN patients, it is occasionally essential to repeat the kidney biopsy, but because this is an intrusive procedure, a cost-benefit analysis is required. In these circumstances, measuring the EGF/MCP-1 ratio could help us foresee the ongoing loss of renal function, avoiding more intrusive procedures when they are not necessary. These findings could be used to identify high-risk patients who would benefit from more frequent monitoring and vigorous treatment. To back up this idea, more prospective trials with a bigger patient group are needed [50].

Antineutrophil Cytoplasmic Antibody Vasculitis 

Antineutrophil cytoplasmic antibody-associated vasculitis (AAV) is a collection of potentially fatal autoimmune diseases that includes granulomatosis with polyangiitis, microscopic polyangiitis, and eosinophilic granulomatosis with polyangiitis [91]. Approximately 25% of AAV patients are still resistant to induction therapy, and 20–25% of AAV patients develop ESKD [92]. Finding noninvasive biomarkers that can predict renal response to therapy and renal function decline in AAV patients is crucial.

The relationship between uEGF/Cr and renal disease severity and outcomes was studied in a cohort of 173 patients with active AAV and 143 patients in remission [51]. Intrarenal EGF mRNA expression was found to be highly related to log2eGFR at biopsy in AAV patients (β = 0.63, p < 0.001). It's not unexpected that the quantity of uEGF/ Cr was linked to eGFR because uEGF levels are strongly tied to EGF mRNA levels. The quantity of uEGF/Cr in patients in remission was substantially higher than in individuals with ongoing disease, both in patients with sesequential readings and in cross-sectional comparison. The quantity of uEGF/Cr at the time of sampling was favorably related to log2eGFR in both the active and remission periods (p < 0.001, p < 0.001, respectively). Patients with resistive renal illness had significantly lower uEGF/Cr levels than responders. EGF/Cr was also linked with a composite outcome of ESKD or a 30% reduction in eGFR after controlling for other potential predictors [93, 94].

Lower uEGF/Cr ratios in AAV patients are associated with more severe renal impairment, treatment resistance, and a higher chance of progression to the composite outcome. The strong link between a lower uEGF/Cr and a worse long-term outcome in AAV patients could be a re-flection of the degree of tubular damage occurring. This could be due to the severity of an ongoing autoimmune disease or to immunological injury to the tubular compartment in the past. Studies have demonstrated that high uEGF levels diminish renal epithelial sodium channel activity, potentially lowering glomerular and renal tubular damage [93, 94]. However, more research into EGF's protective role in AAV development is needed. In individuals with AAV, the amount of uEGF/Cr may be a valuable noninvasive biomarker for evaluating tubular damage and the possibility of advancing to chronic progressive kidney disease, but it has to be verified in a larger, multi-center cohort research [51].

Polycystic Kidney Disease 

EGF and EGF-reactive peptide species are formed in the apical media of cultured autosomal dominant polycystic kidney disease (ADPKD) epithelia, and cyst fluids from ADPKD patients contain large, possibly mitogenic amounts [95, 96]. EGF and other growth factors play a role in the regulation of numerous epithelial ion channels in the kidney. EGF, for example, increases the number of store-operated Ca2+ channels in human mesangial cells via an intracellular signaling cascade that includes tyrosine kinase and protein kinase C [97]. EGF activates store-operated Ca2+ channels via phospholipase C, but not intostill triphosphate receptors [98]. VEGF levels have been measured in patients with ADPKD with or without CKD, as well as their relatives and 20 healthy subjects. VEGF was significantly lower in ADPKD patients with CKD than in those without CKD (p = 0.004). There was no statistically significant difference between ADPKD patients who did not have CKD, their relatives, or healthy controls, respectively. Only a small rise in VEGF was observed in the ADPKD group without CKD, suggesting that EGF production is linked to kidney mass in the early stages of renal function impairment [99]. Before uEGF may be utilized as a prognostic indicator in ADPKD patients to anticipate the onset of renal function impairment, more research is needed [99].

Alport Syndrome 

Alport syndrome is a rare inherited kidney disease that results in kidney failure. In recent decades, it has become well-known as a kind of glomerular disease with the usual pathological alterations of the glomerular basement membrane. In terms of illness development, Alport syndrome patients have a wide range of symptoms. The necessity for identifying patients at high risk of fast kidney function decline remains unfulfilled [100]. Patients with Alport syndrome have been found to have tubulointerstitial fibrosis, a sign of renal disease development [101, 102]. In a cross-sectional study of 117 pediatric patients with Alport syndrome and 146 healthy children, uEGF/Cr dropped much quicker in pediatric patients with Alport syndrome than in healthy children of the same age group. After adjusting for age, uEGF/Cr was strongly linked with eGFR (r = 0.75, p < 0.001), but not with 24-h proteinuria. In 38 patients with long-term follow-up, there was a substantial correlation between uEGF/Cr and the eGFR slope (r = 0.58, p < 0.001). Patients with a lower uEGF/Cr level had a higher chance of progressing to a later stage of CKD [100]. The regenerative activity of EGF is likely to explain the link between uEGF/Cr and progression [15]. Lower uEGF/Cr indicates that the tubular cells' regenerative capacity is hindered, which is linked to progression. Even while eGFRs were still above 60 mL/min/1.73 m2, uEGF/ Cr had an AUC of 0.88 for distinguishing progressors from nonprogressors, compared to 0.77 for eGFR and 0.81 for 24-h urine protein [100]. Further research into whether and how EGF is involved in tubular damage healing and regeneration in Alport syndrome is needed. To validate the predictive usefulness of uEGF/Cr in children with Alport syndrome, a prospective study with more patients and a longer follow-up is needed [100].

Conclusion and Future Perspectives 

The present review article shows that the majority of studies have looked at uEGF, uEGF/Cr, or uEGF/MCP-1 as a standalone biomarker. As a result, its performance and connection with other tubule function biomarkers are unknown, and more research is needed. Despite this, the significant signals seen with uEGF, which are independent of baseline eGFR, albuminuria, and other risk variables, make it a promising new addition to the list of tubule cell dysfunction markers [103]. As there is currently no uEGR, uEGF/Cr, or uEGF/MCP-1 reference values, it is necessary to use standardized uEGF tests with calculated reference values [47]. The next step would be to establish an age-dependent normal uEGF/Cr and uEGF/MCP-1 range [100].

The widespread clinical standardization of uEGF by creatinine as a biomarker of renal tissue damage would have several advantages: (1) it is tissue-specific, making it resistant to extrarenal events that may damage the accuracy of other nonspecific biomarkers; and (2) it is well proven that the kidney function has a considerable influence on uEGF/Cr, even in the normal creatinine range [104]. EGF/Cr has only a weak relationship with glomacular damage indicators such as urine protein excretion, indicating that this ratio is a representation of a distinct independent pathophysiologic process [105–107] and could be used in conjunction with these other parameters. The precise place of uEGF, uEGF/Cr, and uEGF/MCP- 1 measurement to indicate rapid renal function decrease is still unknown [38]. Because EGF is a possible indicator of intrarenal health, integrating it into a risk assessment system may help predict which patients at high risk of CKD progression will progress. EGR determination may also be useful in assessing kidney function beyond serum creatinine and proteinuria, as well as in selecting subjects for kidney transplantation and before prescribing medications known to cause toxicity to kidney tubular cells, such as certain antibiotics and anti-HIV medications [38, 108, 109]. Changes in uEGF/Cr can only be regarded as significant when they vary by at least 30% when monitoring repeated samples in the same person. In contrast to increasing serum creatinine, which can indicate either acute renal injury or chronic kidney damage, reduced uEGF/Cr levels may indicate an increased disease activity and is related to the severity of chronic kidney impairment. Low uEGF/Cr levels during a flare, as well as declining levels over time, are linked to poor long-term kidney outcomes [19].

Conflict of Interest Statement 

The authors have no conflicts of interest to declare. 

Funding Sources No funding has been received for this study. 

Author Contributions 

C.C. and M.M.S. wrote the first draft and edited the manuscript. R.S. and J.R.D. were responsible for the conceptualization, critical review, and editing of the manuscript. All the authors have read and approved the final manuscript.

References

1 Cohen S. The epidermal growth factor (EGF). Cancer. 1983;51(10):1787–91. 

2 Taylor JM, Cohen S, Mitchell WM. Epidermal growth factor: high and low molecular weight forms. Proc Natl Acad Sci U S A. 1970;67(1): 164–71. 

3 Baer PC, Geiger H. Different effects of growth factors on human renal early distal tubular cells in vitro. Kidney Blood Press Res. 2006; 29(4):225–30. 

4 Kumar V, Abbas AK, Aster JC, editors. Robbins and Cotran pathologic basis of disease. 9th ed. Philadelphia, PA: Elsevier/Saunders; 2015. 

5 Venturi S, Venturi M. Iodine in evolution of salivary glands and oral health. Nutr Health. 2009;20(2):119–34.

6 Oka Y, Orth DN. Human plasma epidermal growth factor/beta-urogastrone is associated with blood platelets. J Clin Invest. 1983;72(1): 249–59. 

7 Harris RC, Chung E, Coffey RJ. EGF receptor ligands. Exp Cell Res. 2003;284(1):2–13. 

8 Carpenter G, Cohen S. Epidermal growth factor. Annu Rev Biochem. 1979;48:193–216. 

9 Kim BW, Kim SK, Heo KW, Bae KB, Jeong KH, Lee SH, et al. Association between epidermal growth factor (EGF) and EGF receptor gene polymorphisms and end-stage renal disease and acute renal allograft rejection in a Korean population. Ren Fail. 2020;42(1):98–106. 

10 Herbst RS. Review of epidermal growth factor receptor biology. Int J Radiat Oncol Biol Phys. 2004;59(2 Suppl):21–6.

#cistanche #cistanchedeserticola #cistanchetubulosa #cistanchesalsa #glycoside #echinacoside #verbascoside #acteoside #ニクジュヨウ #肉蓯蓉 #ベルバスコシド #アクテオシド #クサギニン #エキナコシド #肉蓯蓉 #CistancheManufacturer #CistancheExtract #HerbalExtractsSupplier #CistancheTubulosa #CistancheDeserticola #TraditionalChineseMedicine #HerbalSupplements 

Supportive Service Of Wecistanche-The largest cistanche exporter in the China:

Email:wallence.suen@wecistanche.com 

Whatsapp/Tel:+86 15292862950