Chronic kidney disease (CKD) is a major cause of illness in dogs, and it is commonly caused by glomerular diseases that result in proteinuria and a progressive decline in renal function. Despite the importance of glomerular lesions, tubulointerstitial fibrosis identified by histologic evaluation of renal biopsies correlates best with renal function. However, performing a renal biopsy is invasive. Most current non-invasive tests for renal function lack adequate sensitivity and specificity for renal disease. Proteinuria can be both a sensitive and specific marker for renal damage. However, its evaluation in veterinary medicine beyond determination of the magnitude of proteinuria (e.g., urine protein:creatinine ratio (UPC)) is limited. Therefore, in this report, further evaluation of the UPC was performed to aid in the monitoring of renal disease progression and response to treatment. In addition, qualitative evaluation of proteinuria was performed in dogs with progressive CKD in order to identify better non-invasive markers for tubulointerstitial injury. The day-to-day variability of the UPC was determined utilizing data obtained from female dogs that are carriers for X-linked hereditary nephropathy (XLHN). Despite an unchanging magnitude of proteinuria in these dogs, substantial variation in their UPC was observed. Using these results, guidelines were suggested to help assess whether disease progression or treatment leads to a significant change in UPC. Qualitative characterization of proteinuria in dogs with CKD was performed using urine from male dogs affected with XLHN, and results were correlated with clinical and histologic findings concerning renal function and damage. The two discovery proteomic techniques utilized (chromatographic chip array and two-dimensional gel electrophoresis) revealed several proteins that have not previously been implicated as markers for canine CKD, providing a basis for future studies. Specific assays for urinary biomarkers of renal injury were used to serially evaluate renal function in these dogs. All proteins evaluated proved to be sensitive markers for renal damage. However, only retinol binding protein provided clear evidence for renal disease progression. These results will provide the foundation for future studies aimed at monitoring urinary biomarkers in dogs with CKD, which will ultimately help veterinarians better diagnose and monitor proteinuric renal disease.

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Research Objective Patients with chronic kidney disease (CKD) are at increased risk for atherosclerosis and peripheral artery disease (PAD). PAD has received far less attention than coronary artery disease (CAD) in CKD patients. Few studies have examined risk factors for PAD in CKD. We studied the possible related risk factors and benefit of hypertension treatment in CKD patients with PAD. Data Sources We included 129 patients of both sexes with stages 3 to 5 of CKD, as described by the Kidney Outcome Quality Initiatives (K/DOQI ) classification, without receiving dialysis therapy, not previously diagnosed with PAD. Study Design The following information were collected within six month period, including demographic characteristics, history of hypertension, anti-hypertension drug, diabetes, smoking, and pre-existing cardiovascular disease, body mass index (BMI), fasting blood glucose, HbA1c, total cholesterol, triglyceride(TG), high density lipoprotein cholesterol (HDL), low density lipoprotein cholesterol(LDL), calcium (Ca), phosphate(P), Albumin, uric acid, urine protein. Ankle-brachial index (ABI) is a noninvasive diagnostic test that is efficient in detecting asymptomatic PAD with ABI <0.9. Findings There were 22 (17.7 %) participants with PAD. Higher systolic blood pressure (SBP), higher diastolic blood pressure (DBP), higher pulse pressure showed strong association with PAD in CKD patients. On further analysis, significant fewer patients treated with calcium channel blocker (CCB) in hypertensive CKD patients with PAD (£q2 =7.055, p =0.008). The multivariate logistic regression analysis in hypertensive patients demonstrated the risk factors for PAD was pulse pressure, and Calcium channel blocker treatment may correlate with decreasing PAD formation (odds ratio= 0.232, 95% CI=0.07-0.73, p =0.013) in CKD patients. Conclusion There is a high prevalence rate of PAD in population of CKD, especially those with hypertension. ABI should be routinely examined in these patients who can benefit earlier from therapeutic measures.

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Pea protein hydrolysate (PPH) has antihypertensive effects and prostanoids have been implicated in renal diseases. To investigate the role of PPH and prostanoids on renal and cardiovascular effects in cardio-renal disease, normal and diseased Han:SPRD-cy rats were given diets containing either 0, 0.5% or 1% PPH for 8 weeks. At termination, diseased rat kidneys displayed increased renal cyst growth, fibrosis, plasma creatinine and lower monocyte chemoattractant protein-1. Diseased rats also exhibited left ventricular (LV) hypertrophy, elevated systolic and diastolic blood pressures and LV end diastolic and systolic pressures. Four of five prostanoids were elevated in diseased rat kidneys. PPH attenuated systolic blood pressure, but not other components of the cardio-renal syndrome. PPH also increased select prostanoids in normal and diseased rats. Thus, dietary PPH attenuates hypertension in the Han:SPRD-cy rat, but does not ameliorate other components of disease, possibly due to increased prostanoid effects or an insufficient treatment length.

Current therapy for chronic kidney disease (CKD) is limited; however, recent studies have shown that a subpopulation of cells derived from the bone marrow, known as early outgrowth cells (EOCs), are able to attenuate kidney injury. Here we examined the efficacy of a modular tissue engineering system whereby the EOCs might be easily removed in the event of malignant change. While modular therapy mimicked the effects seen with standard EOC therapy, the modules degraded allowing the encapsulated EOCs to enter systemic circulation. Given the presumed egress of EOCs, we explored an alternative strategy for kidney protection. Here we investigated the long-term effectiveness of administering the conditioned medium (EOC-CM) that contains the factors the EOCs secrete, rather than the cells themselves. In these studies, repeated administration of EOC-CM attenuated the structural and functional manifestations of kidney injury suggesting that this approach may provide an effective and feasible, cell-free approach for CKD.

Current therapy for chronic kidney disease (CKD) is limited; however, recent studies have shown that a subpopulation of cells derived from the bone marrow, known as early outgrowth cells (EOCs), are able to attenuate kidney injury. Here we examined the efficacy of a modular tissue engineering system whereby the EOCs might be easily removed in the event of malignant change. While modular therapy mimicked the effects seen with standard EOC therapy, the modules degraded allowing the encapsulated EOCs to enter systemic circulation. Given the presumed egress of EOCs, we explored an alternative strategy for kidney protection. Here we investigated the long-term effectiveness of administering the conditioned medium (EOC-CM) that contains the factors the EOCs secrete, rather than the cells themselves. In these studies, repeated administration of EOC-CM attenuated the structural and functional manifestations of kidney injury suggesting that this approach may provide an effective and feasible, cell-free approach for CKD.

Since its discovery in 1988 the powerful vasoconstrictor endothelin-1 (ET-1) has been widely implicated in the pathophysiology of chronic kidney disease (CKD) as well as the cardiovascular disease with which it is associated. ET receptor antagonists have favourable effects in experimental models of these conditions and orally acting antagonists are now licensed for the treatment of pulmonary arterial hypertension. However, there is a paucity of human data regarding the role of ET-1 in CKD. In this thesis, I have therefore explored the utility of ET-1 as a biomarker in CKD, and, using selective ET receptor antagonists, the beneficial renal and cardiovascular effects of ET receptor antagonism in CKD. I have shown that as glomerular filtration rate (GFR) declines plasma ET-1 increases linearly whereas urinary ET-1 shows an exponential increase. Furthermore, urinary ET-1 may be a useful marker of disease activity in patients with lupus nephritis. Its levels are high in those with biopsy-proven active renal inflammation and these fall with treatment. I have shown that in subjects with stable non-diabetic proteinuric CKD, acute selective ETA receptor antagonism reduces blood pressure and arterial stiffness and that these systemic benefits are associated with an increase in renal blood flow and reduction in proteinuria. Importantly, these effects are seen on top of those achieved with maximal therapy with angiotensin converting enzyme inhibitors and/or angiotensin receptor blockers. Following a study confirming unchanged pharmacokinetics in CKD, I have used an oral selective ETA receptor antagonist to show that the reductions in BP, arterial stiffness and proteinuria seen in my acute studies are maintained longer term. This results of this study also suggest that the mechanism for the reduction in proteinuria is haemodynamic and relates to a reduction in GFR and filtration fraction. In summary, these studies suggest that ET-1 may act as a potential biomarker of renal inflammation, and confirm its role in the pathophysiology of the systemic and renal vasoconstriction seen in CKD. They also suggest that selective ETA receptor antagonism may provide a novel therapeutic approach in proteinuric CKD on top of standard therapies. Larger and longer term studies are now warranted to confirm this potential.

Bone’s ability to resist fracture is often ignored until a low-energy fracture occurs. Patients with Chronic Kidney Disease (CKD) or osteoporosis are at an increased risk of low-energy fracture. Generally, fracture risk is evaluated by using a bone mineral density (BMD) test. BMD values; however, do not fully predict bone’s ability to resist fracture. This suggests that other parameters may be involved. Bone quality is the term used to describe these parameters, which are categorized into three groups: structural, material, and microdamage. The aim of this dissertation research was to examine whether bone quality was altered in patients who: 1) had abnormal bone turnover (high or low) due to CKD, 2) suffered a low-energy fracture despite normal BMD, or 3) had osteoporosis and were treated with bisphosphonates. These studies used iliac crest bone specimens from Caucasian females aged 21 to 87 years. Bone’s material parameters were measured by Fourier transform infrared spectroscopy. The key finding from the turnover study was that high and low turnover was associated with altered bone quality. Specifically, bone with high turnover had a lower mineral-to-matrix ratio compared to normal and low turnover (p<0.05), while low turnover had a lower cancellous bone volume and trabecular thickness compared to normal or high turnover (p<0.05). The key finding from the fracture study was that patients with normal BMD and low-energy fractures had altered bone quality (greater collagen crosslinking ratio) compared to patients who had low-BMD with low-energy fractures and healthy subjects (controls) (p<0.05). Lastly, the key findings from the bisphosphonate studies were that osteoporosis patients treated with these drugs had altered bone quality (specifically, greater (p<0.05) mineral-to-matrix ratio) compared to untreated turnover-matched osteoporotic patients, and that were several positive linear correlations with the nanoindentation derived Young’s modulus and hardness of cortical and trabecular bone and the duration of bisphosphonate treatment (p<0.05). The findings presented provide further evidence that bone quantity is not the sole factor in determining bone’s ability to resist fractures and that bone quality is an essential factor.

The incidence of chronic kidney disease (CKD) is increasing. CKD is characterized by a gradual decrease in renal function leading to end stage renal disease (ESRD). Damage to the glomerular podocytes, is one of the first hallmarks of CKD. We hypothesized that podocyte prostaglandin E2 (PGE2) receptors contribute to the progression of glomerular injury in models of CKD. To test this hypothesis, transgenic mice were generated with either podocyte-specific overexpression or deletion of the PGE2 EP4 receptor (EP4pod+and EP4pod-/- respectively). Mice were next tested in the 5/6 nephrectomy (5/6 Nx) or angiotensin II (Ang II) models of CKD. These studies revealed increased proteinuria and decreased survival for EP4pod+ mice while EP4pod-/- mice were protected against the development of glomerular injury. Furthermore, our findings were supported by in vitro studies using cultured mouse podocytes where an adhesion defect was uncovered for cells overexpressing the EP4 receptor. Additionally, our investigations have demonstrated a novel synergy between angiotensin II AT1 receptors and prostaglandin E2 EP4 receptors. This was revealed by in vitro studies using isolated mouse glomeruli. There we were able to show that Ang II stimulation leads to increased expression of cyclooxygenase 2 (COX-2), the enzyme responsible for synthesis of PGE2, in a p38 mitogen activated protein kinase (MAPK) dependent fashion. Moreover increased PGE2 synthesis was measured in response to Ang II stimulation. We confirmed the presence of this synergy in our cultured mouse podocytes and showed an adhesion defect in response to Ang II stimulation which was COX-2 and EP4 dependent. These findings suggest that Ang II AT1 receptors and PGE2 EP4 receptors act in concert to exacerbate glomerulopathies. Studies using mice with either podocyte-specific overexpression of a dominant negative p38 MAPK or mice with global deletion of the EP1 receptor did not provide conclusive results as to their respective signaling involvement in podocyte injury. Altogether our findings provide novel insight for podocyte PGE2 EP4 and Ang II AT1 receptor signaling in models of CKD. These studies provide novel avenues for pursuing therapeutic interventions for individuals with progressive kidney disease.