Understanding how a therapy will impact the injured kidney before being administered would be an asset to the clinical world. The work in this thesis advances the field of mathematical modeling of the kidneys to aid in this cause. The objectives of this work are threefold: 1) to develop and personalize a model to specific patients in different diseased states, via parameter estimation, in order to test therapeutic trajectories, 2) to use parameter estimation to understand the cause of different kidney diseases, differentiate between potential kidney diseases, and facilitate targeted therapies, and 3) to push forward the understanding of kidney physiology via physiology-based mathematical modeling techniques. To accomplish these objectives, we have developed two models of the kidneys: 1) a broad, steady-state, closed-loop model of the entire kidney with human physiologic parameters, and 2) a detailed, dynamic model of the proximal tubule, an important part of kidney, with rat physiologic parameters. To readily aid physicians, a human model would easily fit into the clinical workflow. Since there is a lack of invasive human renal data for validation and parameter estimation, we employ a minimal modeling approach. However, to aid in deeper understanding of renal function for future applications, targeted therapy testing, and potentially replace invasive measures, we develop a more detailed model. The development of such a model requires invasive data for validation and parameter estimation, and hence we model for rodents, where such invasive data are more readily available. The kidneys are composed of approximately one million functional units known as nephrons. The glomerular filtration rate (GFR) is the rate at which the kidney filters blood at the start of the nephron. This filtration rate is highly regulated via several control mechanisms and needs to be maintained within a small range in order to maintain a proper water and electrolyte balance. Hence, fluctuations of GFR are indicative of overall kidney health. In developing the human kidney model, we also sought to understand the relationship between blood pressure and GFR since many therapies affect blood pressure and subsequently GFR. This model describes steady-state conditions of the entire kidney, including renal autoregulation. Model validation is performed with experimental data from healthy subjects and severely hypertensive patients. The baseline model’s GFR simulation for normotensive and the manually tuned model’s GFR simulation for hypertensive intensive care unit patients had low root mean squared errors (RMSE) of 13.5 mL/min and 5 mL/min, respectively. These values are both lower than the error of 18 mL/min in GFR estimates, reported in previous studies. It has been shown that vascular resistance and renal autoregulation parameters are altered in severely hypertensive stages, and hence, a sensitivity analysis is conducted to investigate how changes in these parameters affect GFR. The results of the sensitivity analysis reinforce the fact that vascular resistance is inversely related to GFR and show that changes to either vascular resistance or renal autoregulation cause a significant change in sodium concentration in the descending limb of Henle. This is an important conclusion as it quantifies the mapping between hypertension parameters and two important kidney states, GFR and sodium urine levels. Glomerulonephritis is one of the two major intra-renal kidney diseases, characterized as a breakdown at the site of the glomerulus that affects GFR and subsequently other portions of the nephron. This disease accounts for 15% of all kidney injuries and one-fourth of end-stage renal disease patients. The human kidney model is used to estimate renal parameters of patients with glomerulonephritis. The model is an implicit system and in developing an optimization algorithm to use for parameter estimation, we modify in a novel way, the Levenberg-Marquardt optimization using the implicit function theorem in order to calculate the Jacobian and Hessian matrices needed. We further adapt the optimization algorithm to work for constrained optimization since our parameter values must be physiologically feasible within a certain range. The parameter estimation method we use is a three-step process: 1) manually adjusting parameters for the hypertension comorbidity, 2) iteratively estimating parameters that vary from person to person using no-kidney- injury (NKI) data, and 3) iteratively estimating parameters that are affected by glomerulonephritis using labeled diseased data. Such a process generates a model that is personalized to each given patient. This patient-specific model can then be used to simulate and evaluate outcomes of potential therapies (e.g., vasodilators) on the model in lieu of the patient, and observe how alterations in blood pressure or sodium level affect renal function. Parameter estimation in the presence of glomerulonephritis is a challenging task due to the complexity of the kidney physiology and the number of parameters to estimate. This is further complicated by comorbidities such as hypertension, cardiac arrythmia, and valvular disease, because they alter kidney physiology and hence, increase the number of parameters to estimate. We chose to focus on hypertension since it is very prevalent in hospitals and intensive care units. It was found that over all patients, average model estimates of GFR and urine output rate (UO) were within 9.2 mL/min and 0.71 mL/min for NKI data. These results are expectedly better than those achieved from the non-personalized model since the parameters are now specific to each patient. The results also demonstrate our ability to non-invasively estimate GFR with less error than the 18 mL/min currently possible. The estimations were validated by ensuring that the estimated parameter values were physiologically sound and matched the literature in terms of expected values for different demographic groups. It is vital for a properly functioning kidney to maintain solute transport throughout the nephron. Kidney diseases in the nephron can manifest themselves via the solute transport mechanisms. To understand how these diseases affect the kidney and to simulate transporter- targeting therapies, we have developed a detailed model, starting from the human model previously developed, of one portion of the kidneys, the proximal tubule. The proximal tubule is the site of the most active transport within the nephron and the target for several therapies. Our goal is to study and understand the dynamic behavior of the proximal tubule when solute transporters breakdown and to investigate treatment therapies targeting certain solute transporters. The proposed model is dynamic and includes several solutes’ transport mechanisms, with parameters for rats. We chose to investigate diabetic nephropathy and the associated sodium-transporter alteration (knockout) therapy. Diabetic nephropathy is characterized as kidney damage due to diabetes and affects 30% of diabetics. In terms of reducing hyperfiltration, a potential cause of diabetic nephropathy where an overabundance of solutes and fluid are filtered at the glomerulus, the model demonstrates that knockout of this transporter results in a reduction in sodium and chloride reabsorptions in the proximal tubule, thereby preventing hyperfiltration. Further, we conclude that vital flows for maintaining kidney homeostasis, fluid and ammonium reabsorptions, are corrected to healthy values by a 50% knockout (impairment) of the sodium-hydrogen transporter. Next, we use the dynamic model to detect different diseased states of the proximal tubule transporters. We have accomplished this task by using Bayesian estimation to estimate transporter density parameters (a metric for kidney health) using measured signals from the proximal tubule. This approach is validated with experimental rat data, while further investigations are conducted into the performance of the estimation in the presence of varied input signals, signal resolutions, and noise levels. Estimation accuracy within 20% of true transporter density and within 4% of true fluid and solute reabsorption was achieved for all combinations of diseased transporters. We concluded that including chloride and bicarbonate concentrations improved estimation accuracy, whereas including formic acid did not. This is an important conclusion as it can help physicians determine which blood tests to order for diagnosing kidney disease; to our knowledge, this is a first. It was also found that sodium and glucose proximal tubule concentrations are most affected by changes in the sodium-hydrogen and sodium-bicarbonate transporters. This conclusion provides insight into the interplay between solute transporter density and sodium and glucose concentrations in the proximal tubule. Such knowledge paves the way for new transporter targeted therapies.

Wang Ying. / "July 2003." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (p. 250-297). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

Diabetic nephropathy (DN) is one of the leading causes of end stage renal disease (ESRD) in western world and has a trend to spread in developing countries. Pathogenesis of DN is not fully elucidated. Studies of recent years showed that podocyte loss and activation of the rennin-angiotensin system (RAS), especially intra-renal RAS, played important roles in this process. Although renal biopsy is currently the most common way used to determine the expression pattern of podocyte and RAS associated molecules in DN, this invasive procedure has its own risk and is not practical for serial monitoring. We hypothesized that measurement of messenger ribonucleic acid (mRNA) expression of related genes in the urinary sediment might be a useful way to assess the severity of DN. / Firstly, we found that urinary mRNA expressions of podocyte-associated molecules nephrin, podocin, synaptopodin, Wilm's tumor-1 (WT-1) and alpha-actinin-4 were higher in patients with DN than in healthy controls, and urinary nephrin, podocin and synaptopodin expression was related to proteinuria and baseline renal function. In addition, there was a close relationship between urinary mRNA expression of type 2 angiotensin converting enzyme (ACE2), a key element of RAS, and the degrees of proteinuria, renal function and rate of decline of glomerular filtration rate (GFR). Urinary mRNA expression of ACE also inversely correlated with the rate of renal function decline. / In the next step, we studied the change in urinary mRNA expression of nephrin, podocin, synaptopodin, ACE and ACE2 in patients with DN treated with angiotensin converting enzyme inhibitor (ACEI) and addition of angiotensin receptor blocker (ARB). We found that urinary mRNA expression of podocin, synaptopodin and propably nephrin increased with disease progression, and percentage change in urinary podocin expression negatively correlated with rate of decline of GFR. Furthermore, serial measurement of urinary expression of nephrin and possibly synaptopodin may reflect therapeutic response to ARB in these patients. Urinary mRNA expression of ACE and ACE2, however, remained unchanged during the study duration and did not correlate with therapeutic response. / In this series of work, we investigated (i) the relation between the gene expression profile of podocyte-associated molecules and RAS related molecules in the urinary sediment and the severity of DN, including clinically defined parameter of disease severity, histological scarring, and the degree of intra-renal podocyte loss, (ii) the relation between urinary and intra-renal gene expression of patients with DN, (iii) the application of urinary gene expression on the monitoring of disease progression and therapy response of DN. The urinary mRNA expression of related genes was quantified by real-time quantitative polymerase chain reaction (RT Q-PCR). The intra-renal mRNA expression of related genes was studied from the histologic specimens of kidney biopsy by laser catapult microdissection (LCM) and RT Q-PCR. The degree of renal scarring was determined by morphometric analysis. Glomerular podocyte number was determined by stereological study on serial sections of renal biopsy specimen. / Taken together, our results suggest that although urinary mRNA expression of podocyte and RAS associated molecules is not related to intra-renal expression, urinary expression has the potential to be used as a non-invasive tool to assess the severity and progression of DN, and serial measurements of urinary gene expression of podocyte associated molecules may be used to reflect therapy response for patients with DN. Our findings also indicate that the information from urinary gene expression is supplementary to, but not a surrogate of, the data obtained from renal biopsy. / We then examined the relation between urinary gene expression and histological changes in the kidney. We found that urinary WT-1 expression correlated with the degree of kidney fibrosis. Unlike intra-renal expression, urinary mRNA expression of podocyte associated molecules did not correlate with glomerular podocyte number. There was also no association between urinary and intra-renal mRNA expression. / Wang, Gang. / Adviser: Cheuk Chen Szeto. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3423. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 156-180). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

BACKGROUND AND OBJECTIVES: Type 2 diabetes mellitus (T2DM) is a complex disease with genetic predisposition and histopathological characterization. Pancreatic islet amyloidosis, hyaline arteriolosclerosis, and diabetic glomerulopathy are histopathological hallmarks of T2DM at autopsy examination. The associations of genetic variants with diabetic amyloidosis, arteriosclerosis and glomerulopathy have not been fully elucidated. Several candidate genes including apolipoprotein E (ApoE), insulin degrading-enzyme (IDE) and glucose transporter-1 ( GLUT1) have been reported to increase risk of T2DM in human studies although results are not always consistent. Capitalizing on the pathological hallmarks of T2DM, I used autopsy specimens to investigate the risk associations of polymorphisms of ApoE (rs429358 and rs7412), IDE (rs6583813) and GLUT1 (rs710218) genes with clinical features and specific pathological changes in diabetic kidney and pancreas. I further explored the mechanisms of these associations by evaluating the histopathological changes and protein expression in pancreas and kidney. / CONCLUSIONS: These findings suggest that genetic factors have important effects in the development of tissue-specific changes and chronic complications in T2DM. Islet amyloidosis, arteriosclerosis and glomerulosclerosis in T2DM may share common pathogenetic processes as suggested by the coexistence of chaperone proteins, amyloid P and ApoE. Genetic--pathologic correlation studies are useful in advancing our understanding of the mechanisms of complex diseases such as T2DM. / METHODS AND MATERIALS: Genomic DNA was extracted from white blood cell-concentrated paraffin embedded formalin fixed spleen tissues. Genotyping for ApoE, IDE and GLUT1 polymorphisms was determined by polymerase chain reaction (PCR) and ligase detection reaction (LDR). The pathological changes were blindly assessed in pancreatic and kidney tissues of autopsy specimens. Protein expression of these genes was examined by immunostaining and quantified by using Metamorph image analysis system. / RESULTS: In a consecutive study population of 3693 autopsy specimens containing 328 T2DM and 209 control cases, the respective frequencies of genotypes were as follows: 1) TT of GLUT1 rs710218: 11.2% vs. 11.3%; 2) ApoE epsilon2: 19.4% vs. 10.9%; 3) ApoE epsilon4: 12.1% vs. 9.1% and 4) C carriers of IDE rs6583813: 51.2% vs. 47.9%. The key genotype-phenotype correlations were as follows. 1) In the T2DM cases, GLUT1 rs710218 IT genotype carriers (0% in TT genotype vs. 59.1% in AA genotype, P=0.0407) were less likely but ApoE epsilon 2 allele carriers (57.1% in epsilon2 allele carriers vs. 23.5% in epsilon3 allele carriers P=0.0382) were more likely to have diabetic glomerular hypertrophy than referential group. ApoE epsilon2 carriers showed increased glomerular ApoE protein expression with the immunoreactivity found mainly in the mesangial regions and nodular lesions. On the other hand, ApoE epsilon 3/epsilon4 cases had diffuse ApoE expression in glomerular capillaries. 2) ApoE epsilon4 carriers were more likely to have islet amyloidosis than non-carriers (62.5% in epsilon4 allele carriers vs. 23.6% in epsilon 3 allele carriers P=0.0232). There was immunolocalization of the chaperone proteins, amyloid P and ApoE in both islet amyloid deposits and arterial walls with hyaline arteriolosclerosis. 3) In T2DM cases, IDE rs6583813 C allele carriers had higher prevalence of vascular disorders [hypertension (67.4% vs. 43.6%, P=0.0332), death due to cardiovascular disease (58.1% vs. 25.6%, P=0.0479) and cerebral vascular accident (CVA) (20.9% vs. 2.4%, P=0.0412)1 than T allele carriers. / Guan, Jing. / Adviser: Chan Chung Ngor Juliana. / Source: Dissertation Abstracts International, Volume: 73-02, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 175-192). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

Nos últimos anos, evidências experimentais e clínicas tem sugerido a possibilidade de regressão de glomerulosclerose, em diversas formas de nefropatia progressiva, inclusive a diabética. No entanto, ainda não se sabe se lesões mais avançadas como glomerulosclerose acompanhada de sinéquias, podem ser revertidas com tratamento medicamentoso, ou se essa possibilidade só existe para lesões menos graves como expansão mesangial. Por outro lado, tem sido sugerido, recentemente, em diversas formas de nefropatia progressiva, que o efeito protetor dos bloqueadores do receptor AT-1 (BAT-1) é dose-dependente. Para avaliar a dose-dependência de um BAT-1 e a possibilidade de regressão de lesões glomerulares na nefropatia diabética (ND), ratos tornados diabéticos por estreptozotocina foram tratados com uma dose convencional e uma extremamente elevada de losartan (L). O tratamento com L reduziu a albuminúria e protegeu contra a glomerulosclerose e inflamação renal de forma semelhante com ambas as doses. Houve nítida regressão da expansão mesangial com o tratamento com L. Contudo, não foi observada regressão de glomerulosclerose. Os achados sugerem ausência de efeito protetor adicional com o uso de altas doses de L nesse modelo de ND. Os dados sugerem, ainda, que a regressão de lesões menos avançadas, como expansão de matriz mesangial, pode ser alcançada com o uso dos BAT-1 na ND. / Evidence of regression of glomerulosclerosis in diabetic nephropathy (DN) and other modalities of chronic kidney diseases has been provided in recent years. However, it remains unclear whether advanced lesions such as glomerular sinechiae can be reversed with pharmacological therapy, or whether this possibility exists only for relatively moderate damage such as mesangial expansion. Recently, the protective renal effect of AT-1 receptor blockers (ARBs) was shown to be dose-dependent in chronic nephropathies. To verify whether an ARB possess a dose-dependent renal effect and whether glomerular lesions can regress in DN, rats were made diabetic by streptozotocin and treated with a standard and an extremely high dose of losartan (L). L treatment reduced albuminuria and protected against glomerulosclerosis and glomerular inflammation, without an additional effect with high doses. There was regression of mesangial expansion with L. However, there was no regression in the frequency of glomerulosclerosis with sinechiae. These findings suggest no dose-dependent effect of L in this model of DN and that mesangial matrix removal is a feasible aim with ARBs in DN.

Zhao Hailu. / "June 2002." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (p. 192-210). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

Leung Yun Shing Wilson. / "May 2003." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (p. 157-184). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. Ann Arbor, MI : ProQuest dissertations and theses, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

published_or_final_version / Medicine / Master / Master of Research in Medicine

published_or_final_version / abstract / toc / Medicine / Master / Master of Philosophy

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2007. / Härtill 5 uppsatser.