**8. Serum levels of angiogenic growth factors are increased in ADPKD**

We have previously reported that serum levels of VEGF and Ang-2 are elevated in children and young adults with ADPKD compared to age, sex, and renal function matched young subjects with diabetes as shown in Table 2 (Reed et al., 2011). In these children and young adults renal function was normal, mean eGFR 128 ml/min/1.73m2. The level of VEGF detected in renal cyst fluid was comparable to the mean serum level. The plasma levels of the soluble VEGF receptor (sFlt1), an antagonist of VEGF, rise progressively with declining renal function in patients with CKD (Di Marco et al., 2009). The same study demonstrated an association between plasma sFlt1 level and endothelial dysfunction. In our own study we found that serum levels of sFlt1 ranged between <13-320 pg/ml in ADPKD patients, however normal healthy serum values were not available for comparison (unpublished data) (Table 2). It is important to note that both the circulating level of VEGF and level of the VEGF antagonist sFlt1 may play a role in implenting disease progression in ADPKD.

Angiogenesis and the Pathogenesis of Autosomal Dominant Polycystic Kidney Disease 101

early in ADPKD, this may increase angiopoietin production with further injurious effects on

Fig. 3. Potential Role of Angiogenic Growth Factor in Renal Injury in ADPKD.

**9. Serum levels of angiogenic growth factors correlate with renal and cardiac** 

Further evidence to support a role of angiogenic growth factors in the complications of ADPKD stems from our study in children and young adults (Reed et al., 2011). Measurement of VEGF, Ang-1 and Ang-2 in 71 children and young adults with ADPKD demonstrated strong correlations between log10 VEGF and both log10 total kidney volume and eGFR. (Table 3). In adult ADPKD patients no relationship between log10VEGF and total renal volume was found (N= 33). However, in adults there was a significant negative relationship between serum Ang-2 levels and eGFR (N = 85, p = 0. 04) that was not found in children and young adults. This indicates that VEGF may play a more significant role early in ADPKD, while Ang-2 may play a role in the progression of renal injury later in disease.

**IndependentVariable SE P SE P** 

Log10 VEGF 0.0511 0.0183 0.0073 NS Ang-1 0.0029 0.0014 0.0448 -0.00001 0.00001 NS Ang-2 NS NS

Log10 VEGF -0.0229 0.0080 0.0055 -0.0583 0.0307 0.06 Ang-1 -0.0010 0.0006 0.1058 NS Ang-2 NS -0.1380 0.0657 0.03

Table 3. Relationship of VEGF, Ang-1 and Ang-2 with renal structure and function.

 **Dependent Variable**  Log10 Total Renal Volume

eGFR

**Children Adults** 

the kidney vasculature and cyst growth.

**disease severity in ADPKD** 


Table 2. Mean serum, urine or cyst fluid levels of angiogenic growth factors.

Several recent studies have supported a role for an imbalance of angiogenic growth factor levels in disease processes including tumor growth, diabetes, CKD and cardiovascular disease (Augustin et al. 2009; David et al., 2009; Lim et al., 2005; Nadar et al., 2004; Nadar et al., 2005). Endothelial dysfunction is a common feature of patients with CKD and VEGF has been shown to play a crucial role in preservation of the microvasculature promoting vascular proliferation and repair in experimental renal disease (Chade et al., 2006; Iliescu et al., 2009; Zhu et al., 2004). The plasma level of Ang-2 is elevated in patients with diabetes and is associated with indices of endothelial damage and dysfunction (Lim et al., 2005). Likewise, abnormal levels of serum Ang-1 and Ang-2 in hypertension have been linked with target organ damage (Nadar et al., 2005), thus indicating a potential role for angiopoietins in exacerbation of the extrarenal complications of ADPKD, including LVH.

As the growing cysts in ADPKD kidneys result in compression of the vasculature with attendant ischaemia (Ecder et al., 2007) these conditions are conducive for upregulated angiopoietin expression. Furthermore, kidney expression of Ang-1 and Ang- 2 is known to be upregulated by angiotensin II in addition to hypoxia (Kitayama et al., 2006., Yamakawa et al., 2004). Thus, as activation of the renin-angiotensin-aldosterone system (RAAS) occurs

249 46 pg/ml (A) (Saito et al.,2009) 306 39 pg/ml (C) (Heshmat & El

39.0 9.9 ng/ml (A) (Park et al., 2009) 64.4 (23.5-101 ng/ml) (C) (Lovegrove et

1270 494 pg/ml (A) (Park et al., 2007) 68 (68-1330 pg/ml) (C) (Lovegrove et

Kerdany, 2007)

al., 2009)

al., 2009)

183.9 - 469.2 ng/24h (N=8)

**VEGF Mean SD or range (N)**  Adult ADPKD patients (serum) 5910 6188 pg/ml (N=46) Children and young adults with ADPKD (serum) 2997 5326 pg/ml (N=71)

Urine adults with ADPKD 82.7-277.2 pg/ml (N =8)

Renal cyst fluid 5940 6757 pg/ml (N=5)

Adult ADPKD patients (serum) 93.8 ± 63 pg/ml (N =38)

Adult ADPKD patients (serum) 37.54 19.54 ng/ml (N=85) Children and young adults with ADPKD (serum) 35.53 21.03 ng/ml (N=71)

Adult ADPKD patients (serum) 3002 1379 pg/ml (N=85) Children and young adults with ADPKD (serum) 2352 962 pg/ml (N=71)

Renal cyst fluid 1657 1035 pg/ml (N=5) Table 2. Mean serum, urine or cyst fluid levels of angiogenic growth factors.

exacerbation of the extrarenal complications of ADPKD, including LVH.

Several recent studies have supported a role for an imbalance of angiogenic growth factor levels in disease processes including tumor growth, diabetes, CKD and cardiovascular disease (Augustin et al. 2009; David et al., 2009; Lim et al., 2005; Nadar et al., 2004; Nadar et al., 2005). Endothelial dysfunction is a common feature of patients with CKD and VEGF has been shown to play a crucial role in preservation of the microvasculature promoting vascular proliferation and repair in experimental renal disease (Chade et al., 2006; Iliescu et al., 2009; Zhu et al., 2004). The plasma level of Ang-2 is elevated in patients with diabetes and is associated with indices of endothelial damage and dysfunction (Lim et al., 2005). Likewise, abnormal levels of serum Ang-1 and Ang-2 in hypertension have been linked with target organ damage (Nadar et al., 2005), thus indicating a potential role for angiopoietins in

As the growing cysts in ADPKD kidneys result in compression of the vasculature with attendant ischaemia (Ecder et al., 2007) these conditions are conducive for upregulated angiopoietin expression. Furthermore, kidney expression of Ang-1 and Ang- 2 is known to be upregulated by angiotensin II in addition to hypoxia (Kitayama et al., 2006., Yamakawa et al., 2004). Thus, as activation of the renin-angiotensin-aldosterone system (RAAS) occurs

Adult ADPKD patients (urine) Not detected

Renal cyst fluid None detected

Healthy adults (A) (serum) Healthy children (C) (serum)

**Soluble VEGF Receptor 1 (sFlt1)** 

Healthy adults (A) (serum) Healthy children (C) (serum)

Healthy adults (A) (serum) Healthy children (C) (serum)

**Angiopoietin 1** 

**Angiopoietin 2** 

early in ADPKD, this may increase angiopoietin production with further injurious effects on the kidney vasculature and cyst growth.

Fig. 3. Potential Role of Angiogenic Growth Factor in Renal Injury in ADPKD.
