Group V secretory phospholipase A2 is involved in tubular integrity and sodium handling in the kidney

Group V (GV) phospholipase A2 (PLA2) is a member of the family of secreted PLA2 (sPLA2) enzymes. This enzyme has been identified in several organs, including the kidney. However, the physiologic role of GV sPLA2 in the maintenance of renal function remains unclear. We used mice lacking the gene encoding GV sPLA2 (Pla2g5−/−) and wild-type breeding pairs in the experiments. Mice were individually housed in metabolic cages and 48-h urine was collected for biochemical assays. Kidney samples were evaluated for glomerular morphology, renal fibrosis, and expression/activity of the (Na+ + K+)-ATPase α1 subunit. We observed that plasma creatinine levels were increased in Pla2g5−/− mice following by a decrease in creatinine clearance. The levels of urinary protein were higher in Pla2g5−/− mice than in the control group. Markers of tubular integrity and function such as γ-glutamyl transpeptidase, lactate dehydrogenase, and sodium excretion fraction (FENa+) were also increased in Pla2g5−/− mice. The increased FENa+ observed in Pla2g5−/− mice was correlated to alterations in cortical (Na+ + K+) ATPase activity/ expression. In addition, the kidney from Pla2g5−/− mice showed accumulation of matrix in corticomedullary glomeruli and tubulointerstitial fibrosis. These data suggest GV sPLA2 is involved in the maintenance of tubular cell function and integrity, promoting sodium retention through increased cortical (Na+ + K+)-ATPase expression and activity

Advances in the Knowledge about Kidney Decellularization and Repopulation

End-stage renal disease (ESRD) is characterized by the progressive deterioration of renal function that may compromise different tissues and organs. The major treatment indicated for patients with ESRD is kidney transplantation. However, the shortage of available organs, as well as the high rate of organ rejection, supports the need for new therapies. Thus, the implementation of tissue bioengineering to organ regeneration has emerged as an alternative to traditional organ transplantation. Decellularization of organs with chemical, physical, and/or biological agents generates natural scaffolds, which can serve as basis for tissue reconstruction. The recellularization of these scaffolds with different cell sources, such as stem cells or adult differentiated cells, can provide an organ with functionality and no immune response after in vivo transplantation on the host. Several studies have focused on improving these techniques, but until now, there is no optimal decellularization method for the kidney available yet. Herein, an overview of the current literature for kidney decellularization and whole-organ recellularization is presented, addressing the pros and cons of the actual techniques already developed, the methods adopted to evaluate the efficacy of the procedures, and the challenges to be overcome in order to achieve an optimal protocol

5-Lypoxygenase products are involved in renal tubulointerstitial injury induced by albumin overload in proximal tubules in mice.

The role of albumin overload in proximal tubules (PT) in the development of tubulointerstitial injury and, consequently, in the progression of renal disease has become more relevant in recent years. Despite the importance of leukotrienes (LTs) in renal disease, little is known about their role in tubulointerstitial injury. The aim of the present work was to investigate the possible role of LTs on tubulointerstitial injury induced by albumin overload. An animal model of tubulointerstitial injury challenged by bovine serum albumin was developed in SV129 mice (wild-type) and 5-lipoxygenase-deficient mice (5-LO(-/-)). The changes in glomerular morphology and nestin expression observed in wild-type mice subjected to kidney insult were also observed in 5-LO(-/-) mice. The levels of urinary protein observed in the 5-LO(-/-) mice subjected or not to kidney insult were lower than those observed in respective wild-type mice. Furthermore, the increase in lactate dehydrogenase activity, a marker of tubule damage, observed in wild-type mice subjected to kidney insult did not occur in 5-LO(-/-) mice. LTB4 and LTD4, 5-LO products, decreased the uptake of albumin in LLC-PK1 cells, a well-characterized porcine PT cell line. This effect correlated with activation of protein kinase C and inhibition of protein kinase B. The level of proinflammatory cytokines, tumor necrosis factor-α and interleukin (IL)-6, increased in mice subjected to kidney insult but this effect was not modified in 5-LO(-/-) mice. However, 5-LO(-/-) mice subjected to kidney insult presented lower macrophage infiltration and higher levels of IL-10 than wild-type mice. Our results reveal that LTs have an important role in tubulointerstitial disease induced by albumin overload

Renal Function Parameters.

<p>Renal Function Parameters.</p

Mild glomerular morphologic changes are observed in Pla2g5^−/− mice.

<p>PAS reagent was used for analysis of the mesangial surface of corticomedullary (A, B) and subcapsular glomeruli (C, D), as described in the Materials and Methods. Representative photomicrographs (magnification 40×) of (A) the corticomedullary glomerulus and (C) the subcapsular glomerulus. (B) Quantitative analysis of the corticomedullary and (D) subcapsular glomeruli (n = 6 per group). The results are expressed as means ± SE. *Statistically significant in relation to WT mice (P < 0.05).</p

Urinary tubular enzymes and collagen deposition, markers of tubular injury, are increased in <i>Pla2g-5</i>^{<i>−/−</i>} mice.

<p>(A) LDH (B) and γGT activities were measured in urine samples as markers of tubular injury (<i>n</i> = 8 per group). Collagen deposition in the renal cortex was visualized by Picrosirius Red staining. (C) Representative photomicrographs (magnification 40×) of collagen deposition in the renal cortex of WT and <i>Pla2g-5</i>^{<i>−/−</i>} mice. (D) Quantitative analysis of the collagen deposition (<i>n</i> = 6 per group). The results are expressed as means ± SE. *Statistically significant in relation to WT mice (<i>P</i> < 0.05).</p

GV sPLA₂ promotes sodium retention.

<p>(A) Urinary sodium excretion (U_Na⁺V), (B) clearance of sodium (C_Na⁺), (C) osmolar clearance, and (D) FE_Na⁺ in WT and Pla2g-5^−/− mice. The number of mice analyzed is given in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0147785#pone.0147785.t001" target="_blank">Table 1</a>. The results are expressed as means ± SE. *Statistically significant in relation to WT mice (P < 0.05).</p

GV sPLA2 upregulates activity and expression of cortical (Na+ + K+)-ATPase.

<p>Expression and activity of (Na⁺ + K⁺)-ATPase in WT and <i>Pla2g-5</i>^{<i>−/−</i>} mice. ATPase activity from the renal cortex (A) and medulla homogenate (C) was determinate by the colorimetric method. Immunoblotting was performed for the (Na⁺ + K⁺)-ATPase α1 subunit in (B) the renal cortex and (D) the medullar preparation of both WT and <i>Pla2g5</i>^{<i>−/−</i>} mice, as described in the Materials and Methods (<i>n</i> = 8 per group). The results are expressed as means ± SE. *Statistically significant in relation to WT mice (<i>P</i> < 0.05).</p

Nestin expression is increased in subcapsular and corticomedullary glomeruli of mice subjected to kidney injury.

<p>Mice were treated as described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0107549#pone-0107549-g001" target="_blank">Fig. 1</a> (<i>n</i> = 6 per group). (A) Representative immunohistochemical staining for nestin in the subcapsular glomerulus and (B) corticomedullary glomerulus of WT and 5-LO-deficient mice treated with saline or BSA (bars  = 20 µm). Quantitative analyses (C,D) were expressed as means ± SE. Statistically significant in relation to *WT+SAL (<i>p</i><0.05), #WT+BSA (<i>p</i><0.05), ⁺5-LO^–/–+SAL (<i>p</i><0.05).</p