慢性腎臟病是一個全球化的疾病，由於腎絲球過濾屏障的損壞，使得慢性腎臟病人伴隨著嚴重蛋白尿的症狀。腎絲球過濾屏障主要由三層結構組成，分別是腎絲球內皮細胞、基底膜，以及足細胞。其中足細胞是高度特化的上皮細胞，由一個細胞本體和以肌動蛋白為主的膜擴展稱之為足突所組成。遺傳變異或是疾病都會導致足細胞損傷，使得肌動蛋白發生重組，進而使足細胞形變而塌陷。Gelsolin (GSN) 是一個會與肌動蛋白結合的蛋白質，利用結核，加蓋和切斷的方式來調控肌動蛋白的狀態。許多文獻指出GSN參與在許多不同的疾病，包含了心血管疾病以及不同種類的癌症。
我們首先發現田寮地區老人族群血液中GSN的含量與他們的腎絲球過濾率呈現負相關。因此本研究的目的是想要找出GSN和足細胞中肌動蛋白之間的關係，以及找出慢性腎臟病導致足細胞受傷的機制。我們首先利用果蠅系統來測試GSN是否在維持足細胞正常功能上扮演重要的角色。昆蟲的腎元細胞是一個和足細胞相似的細胞，並且包含了狹小的過濾隔膜。果蠅腎元細胞的過濾功能是透過餵食果蠅一齡幼蟲添加硝酸銀的酵母菌食物後，觀察其存活率來檢驗。我們發現，GSN-knockdown 果蠅幼蟲在餵食硝酸銀後的存活率有顯著的下降。接著，利用足細胞的細胞培養方式來檢驗在處理puromycin aminonucleoside (PAN)藥物後，GSN和受損的足細胞間肌動蛋白機制，我們觀察到足細胞的表硬度會受到改變。GSN蛋白質以及調節肌動蛋白 RhoA 與 Rac1 的表現量會隨著PAN藥物處理濃度上升而增加。最後，我們的結果顯示，GSN會大量表現在慢性腎臟病小鼠動物模式的腎絲球結構中。
我們的研究結果顯示慢性腎臟病患體內過多的GSN蛋白扮演了不利的角色，可能使得足細胞受到破壞，進而使的腎絲球過濾屏障失去功能。

Chronic kidney disease (CKD) is a global health challenge and is usually associated with proteinuria, a symptom of a compromised glomerular filtration barrier (GFB). The three major components of the GFB are: glomerular endothelial cells, the basement membrane, and podocytes. Podocytes are differentiated epithelial cells that are highly specialized, and consist of a cell body and actin-based membrane extensions called foot processes. Podocyte injury caused by genetic causes or disease leads to reorganization of the actin cytoskeleton and podocyte effacement. Gelsolin (GSN) is an actin-binding protein that regulates actin dynamics through nucleating, capping and severing. Several reports have suggested that GSN may also play a role in numerous other diseases, e.g. cardiovascular diseases and different types of cancer.
In the first part of our clinical correlation study, we demonstrated that the plasma GSN levels of elderly people from Tianliao had a negative correlation with their eGFR. Our research aims to determine the relationship between GSN and podocyte, and thus the mechanism underlying podocyte injury caused by CKD. Firstly, we used Drosophila to test whether GSN has a physiological role in maintaining podocyte function. The insect nephrocyte is a podocyte-like cell with a filtration slit diaphragm. The survival rate of Drosophila larvae fed with AgNO3 was used to determine the physiological role of GSN. We found that survival of gelsolin-knockdown Drosophila larvae significantly decreased after AgNO3 consumption. Secondly, we used an in vitro model to determine how gelsolin affects actin assembly and found that podocyte stiffness was altered by treatment with puromycin aminonucleoside (PAN), which has been documented to cause podocyte injury. The protein expression of gelsolin and small GTPase RhoA and Rac1, which regulate actin dynamic increased with increasing PAN concentrations. Thirdly, we demonstrated that GSN was highly expressed in the glomeruli of mouse CKD animal models.
Our study results indicated that excess GSN level in CKD patients may represent damaged podocytes and advanced stages of CKD.

[1] J. H. Miner, "Podocyte biology in 2015: New insights into the mechanisms of podocyte health," Nat Rev Nephrol, vol. 12, pp. 63-4, Feb 2016.
[2] P. T. Brinkkoetter, C. Ising, and T. Benzing, "The role of the podocyte in albumin filtration," Nat Rev Nephrol, vol. 9, pp. 328-36, Jun 2013.
[3] V. Eremina, S. Cui, H. Gerber, N. Ferrara, J. Haigh, A. Nagy, et al., "Vascular endothelial growth factor a signaling in the podocyte-endothelial compartment is required for mesangial cell migration and survival," J Am Soc Nephrol, vol. 17, pp. 724-35, Mar 2006.
[4] N. Sachs and A. Sonnenberg, "Cell–matrix adhesion of podocytes in physiology and disease," Nature Reviews Nephrology, vol. 9, pp. 200-210, 2013.
[5] C. Faul, K. Asanuma, E. Yanagida-Asanuma, K. Kim, and P. Mundel, "Actin up: regulation of podocyte structure and function by components of the actin cytoskeleton," Trends Cell Biol, vol. 17, pp. 428-37, Sep 2007.
[6] F. Grahammer, C. Schell, and T. B. Huber, "The podocyte slit diaphragm--from a thin grey line to a complex signalling hub," Nat Rev Nephrol, vol. 9, pp. 587-98, Oct 2013.
[7] G. I. Welsh and M. A. Saleem, "The podocyte cytoskeleton--key to a functioning glomerulus in health and disease," Nat Rev Nephrol, vol. 8, pp. 14-21, Jan 2012.
[8] R. L. Cagan, "The Drosophila nephrocyte," Current Opinion in Nephrology and Hypertension, vol. 20, pp. 409-415, 2011.
[9] H. Weavers, S. Prieto-Sanchez, F. Grawe, A. Garcia-Lopez, R. Artero, M. Wilsch-Brauninger, et al., "The insect nephrocyte is a podocyte-like cell with a filtration slit diaphragm," Nature, vol. 457, pp. 322-6, Jan 15 2009.
[10] B. Denholm and H. Skaer, "Bringing together components of the fly renal system," Curr Opin Genet Dev, vol. 19, pp. 526-32, Oct 2009.
[11] F. Zhang, Y. Zhao, and Z. Han, "An in vivo functional analysis system for renal gene discovery in Drosophila pericardial nephrocytes," J Am Soc Nephrol, vol. 24, pp. 191-7, Feb 2013.
[12] Andrea H. Brand and N. Perrimon, "Targeted gene expression as a means of altering cell fates and generating dominant phenotypes," Development, pp. 401-415, 1993.
[13] D. A. Kimbrell, C. Hice, C. Bolduc, K. Kleinhesselink, and K. Beckingham, "The Dorothy enhancer has Tinman binding sites and drives hopscotch-induced tumor formation," Genesis, vol. 34, pp. 23-8, Sep-Oct 2002.
[14] S. J. Winder, "Actin-binding proteins," Journal of Cell Science, vol. 118, pp. 651-654, 2005.
[15] H. Q. Sun, M. Yamamoto, M. Mejillano, and H. L. Yin, "Gelsolin, a Multifunctional Actin regulatory protein," The Journal of biological chemistry, vol. 247, pp. 33179-33182, 1999.
[16] G. H. Li, P. D. Arora, Y. Chen, C. A. McCulloch, and P. Liu, "Multifunctional roles of gelsolin in health and diseases," Medicinal research reviews, vol. 32, pp. 999-1025, 2012.
[17] H. C. Yang, Y. Zuo, and A. B. Fogo, "Models of chronic kidney disease," Drug Discov Today Dis Models, vol. 7, pp. 13-19, 2010.
[18] Z. Wang, X. Wei, Y. Zhang, X. Ma, B. Li, S. Zhang, et al., "NADPH oxidase derived ROS contributes to upregulation of TRPC6 expression in PAN induced podocyte injury," 2009.
[19] Y. C. Ma, L. Zuo, J. H. Chen, Q. Luo, X. Q. Yu, Y. Li, et al., "Modified glomerular filtration rate estimating equation for Chinese patients with chronic kidney disease," J Am Soc Nephrol, vol. 17, pp. 2937-44, Oct 2006.
[20] F. Zhang, Y. Zhao, Y. Chao, K. Muir, and Z. Han, "Cubilin and amnionless mediate protein reabsorption in Drosophila nephrocytes," J Am Soc Nephrol, vol. 24, pp. 209-16, Feb 2013.
[21] M. Radmacher, R. W. Tillmann, M. Fritz, and H. E. Gaub, "From Molecules to Cells_ Imaging Soft Samples with the Atomic Force Microscope," Science, vol. 257, pp. 1900-1905, 1992.
[22] I. Dulinska, M. Targosz, W. Strojny, M. Lekka, P. Czuba, W. Balwierz, et al., "Stiffness of normal and pathological erythrocytes studied by means of atomic force microscopy," J Biochem Biophys Methods, vol. 66, pp. 1-11, Mar 31 2006.
[23] T. Yeung, P. C. Georges, L. A. Flanagan, B. Marg, M. Ortiz, M. Funaki, et al., "Effects of substrate stiffness on cell morphology, cytoskeletal structure, and adhesion," Cell Motil Cytoskeleton, vol. 60, pp. 24-34, Jan 2005.
[24] S. J. Shankland, J. W. Pippin, J. Reiser, and P. Mundel, "Podocytes in culture: past, present, and future," Kidney Int, vol. 72, pp. 26-36, Jul 2007.
[25] D. T. S. M. P. Jacobo, D. Billing, A. Rozkalne, S. D. Gage, T. Anagnostou, H. Pavenstädt, et al., "Antagonistic Regulation of Actin Dynamics and Cell Motility by TRPC5 and TRPC6 Channels," Science Signaling, vol. 3, pp. 1-13, 2010.
[26] N. Tapon and A. Hall, "Rho Rac and C42 GTPases regulate the organization of the actin cytoskeleton," Current Opinion in Cell Biology vol. 9, pp. 86-92, 1997.
[27] S. J. Shankland, "The podocyte's response to injury: role in proteinuria and glomerulosclerosis," Kidney Int, vol. 69, pp. 2131-47, Jun 2006.
[28] R. Kalluri, "Proteinuria with and without renal glomerular podocyte effacement," J Am Soc Nephrol, vol. 17, pp. 2383-9, Sep 2006.
[29] N. Peddada, A. Sagar, Ashish, and R. Garg, "Plasma gelsolin: a general prognostic marker of health," Med Hypotheses, vol. 78, pp. 203-10, Feb 2012.
[30] K. DJ, S. TP, O. SH, M. JE, C. HR, and Y. HL, "Plasma and cytoplasma gelsolin are encoded by a single gene and contain a duplicated actin binding domain," Nature vol. 323, pp. 455-458, 1986.
[31] K. DJ, M. R, I. S, N. G. B, and Y. HL, "Muscle Is the Major Source of Plasma Gelsolin," J Biol Chem, vol. 263, pp. 8239-8243, 1988.
[32] L. WM and G. RM, "The extracellular actin-scavenger system and actin toxicity," The New England Journal of MEdicine, vol. 326, pp. 1335-1341, 1992.
[33] N. Khatri, A. Sagar, N. Peddada, V. Choudhary, B. S. Chopra, V. Garg, et al., "Plasma gelsolin levels decrease in diabetic state and increase upon treatment with F-actin depolymerizing versions of gelsolin," J Diabetes Res, vol. 2014, p. 152075, 2014.
[34] P. S. Lee, K. Sampath, S. A. Karumanchi, H. Tamez, I. Bhan, T. Isakova, et al., "Plasma gelsolin and circulating actin correlate with hemodialysis mortality," J Am Soc Nephrol, vol. 20, pp. 1140-8, May 2009.
[35] T. Shimo, Y. Adachi, S. Yamanouchi, S. Tsuji, T. Kimata, K. Umezawa, et al., "A novel nuclear factor kappaB inhibitor, dehydroxymethylepoxyquinomicin, ameliorates puromycin aminonucleoside-induced nephrosis in mice," Am J Nephrol, vol. 37, pp. 302-9, 2013.