Mitosis stimulating factor in serum of unilaterally nephrectomized rats

Age and Pre-operative HbA1c levels affect renal function compensation in living kidney donors

OBJECTIVES

About 90% of Japanese kidney transplantations are conducted from living donors, and their safety and the maintenance of their renal function are critical. This study aims to identify factors that affect the compensation of renal function in living kidney donors after donor nephrectomy.

METHOD

In a retrospective cohort study, we reviewed data from 120 patients who underwent nephrectomy as living kidney transplant donors in our department from 2012 to 2021. Univariable and multivariable linear regression analyses were performed for donor factors affecting renal function after donor nephrectomy.

RESULT

The multivariable linear regression model revealed that the donor's age (p = 0.025), preoperative estimated Glomerular Filtration Rate (eGFR) (p < 0.001), and hemoglobin A1c (HbA1c) (p = 0.043) were independent risk factors for eGFR at six months after nephrectomy. The eGFR deterioration was more strongly associated with age in females than in males, whereas higher HbA1c values were more strongly associated with eGFR deterioration in males. Higher donor age and higher HbA1c each enhance the deterioration of eGFR six months after living donor nephrectomy. The data suggest that old age in especially female donors and preoperative higher HbA1c in male donors have a harmful impact on their renal function compensation.

Compensatory renal hypertrophy following nephrectomy: When and how?

Following surgical removal of one kidney, the other enlarges and increases its function. The mechanism for the sensing of this change and the growth is incompletely understood but begins within days and compensatory renal hypertrophy (CRH) is the dominant contributor to the growth. In many individuals undergoing nephrectomy for cancer or kidney donation this produces a substantial and helpful increase in renal function. Two main mechanisms have been proposed, one in which increased activity by the remaining kidney leads to hypertrophy, the second in which there is release of a kidney specific factor in response to a unilateral nephrectomy that initiates CRH. Whilst multiple growth factors and pathways such as the mTORC pathway have been implicated in experimental studies, their roles and the precise mechanism of CRH are not defined. Unrestrained hypoxia inducible factor activation in renal cancer promotes growth and may play an important role in driving CRH.

Cytoprotective effects of nitrates in a cellular model of hydronephrosis

BACKGROUND

The earliest insult to the kidney following the onset of ureteral obstruction is a marked elevation in collecting system pressure. This imparts a mechanical stress that is transmitted directly from the collecting system to the kidney substance. Renal tubular injury is the principal functional and histological change encountered, with glomerular changes being less marked and occurring later. Nitric oxide (NO) has been shown to protect against renal injury in UO, but its mode of action has not been clearly defined.

METHODS

MDCK (canine) and HK-2 (human) renal tubular cells were grown under control conditions or subjected to mechanical strain for periods of 24 and 48 hours. Cells were studied treated with or without Fas-antibody, etoposide or diethyl maleate (DEM) alone or in combination with NG-monomethyl l-arginine (L-NMMA), sodium nitroprusside (SNP) or l-arginine. Cell proliferation and apoptosis was determined using propidium iodide DNA staining. NO production and inducible NO synthase (iNOS) expression were measured by the Griess reaction and Western blotting, respectively.

RESULTS

Cells subjected to mechanical strain displayed a decrease in the proportion of cells undergoing cell division. They also showed an increased susceptibility to apoptosis. Associated with this was a decrease in Bcl-2 expression. An increase in iNOS expression was seen in cells subjected to mechanical strain, but no increase in NO production. The cellular effects of mechanical strain were reversed by SNP and l-arginine.

CONCLUSIONS

Culture of renal tubule cells in an environment of mechanical strain results in an imbalance in homeostasis and a net cell loss. This can be reversed by the administration of an NO donor or precursor.

Unilateral nephrectomy induces the expression of the Wilms tumor gene in the contralateral kidney of the adult rat

PURPOSE

The tumor suppressor gene WT-1 encodes a nuclear deoxyribonucleic acid binding protein that is a transcriptional regulator. This gene is commonly deleted or defective in Wilms tumors and the Denys-Drash syndrome. Recently WT-1 was demonstrated to be essential for the development of the urogenital tract. We determined whether we could induce WT-1 expression in mature kidneys induced to grow by performing contralateral nephrectomy in mature rats.

MATERIALS AND METHODS

Northern analysis with a 32phosphorus-labeled antisense riboprobe synthesized by in vitro transcription of a 731 bp complementary deoxyribonucleic acid insert spanning exons 1 to 7 of the rat WT-1 in a pT7 Blue vector was used to demonstrate the expression of WT-1 in the developing and adult Sprague-Dawley rat kidney.

RESULTS

Transcript levels of WT-1 in the rat kidney decreased from day 0 (day of birth) to day 16, after which WT-1 transcripts were undetectable in the normal rat kidney. Unilateral nephrectomy in the adult male Sprague-Dawley rat (250 to 300 gm.) induced the expression of WT-1 ribonucleic acid in the contralateral kidney to detectable levels by Northern analysis 0.25 hours after nephrectomy. Subsequently levels of WT-1 ribonucleic acid decreased progressively to undetectable by 3 hours after nephrectomy. Expression of this gene was not detected in the normal kidneys of adult rats or sham operated adult rats.

CONCLUSIONS

These data suggest that the WT-1 gene product is involved in normal renal growth in the adult and developing rat kidney.

Rabbit and human renotropin are not epidermal growth factor

Sera obtained from rabbits and humans after unilateral nephrectomy (uni sera) compared with sera obtained preoperatively (control sera) significantly stimulate 3H-thymidine incorporation into the DNA of cultured renal tissue from the respective species. In contrast, rabbit liver cells in culture are not stimulated by the uni sera compared with control sera obtained from rabbits. Mouse epidermal growth factor (EGF) added to tissue cultures significantly stimulates both kidney and liver cells of rabbits and kidney cells of humans. Antiserum against EGF overcomes, at least to some extent, the enhancing effect of EGF under all circumstances, but does not influence the stimulatory ability of uni serum obtained from rabbit and human kidney cells from the respective species. In addition, the activity of EGF was not different in the presence of uni and control sera. This study corroborates the presence of renotropic activity in the sera of rabbits and humans after removal of functioning renal mass and shows that this activity is not derived from EGF, nor does it work by potentiating some aspect of the EGF system.

Expression of a Wilms tumor gene in porcine kidney during compensatory renal growth

Expression of the putative Wilms tumor gene (WT-1) was studied to investigate its role in renal growth. Compensatory renal growth was induced in 35-day-old Yorkshire-swine by unilateral nephrectomy. The contralateral kidney was removed 0.5 to 72 hours following the initial operation and analyzed for WT-1 gene expression by Northern analysis. Compensatory renal growth was detectable by wet weight measurements at 12 hours following contralateral nephrectomy. WT-1 gene expression was detectable in the contralateral kidney as early as 0.5 hours following unilateral nephrectomy. Expression of this gene was not detected in normal kidney from swine of this age group or from sham operated swine. In addition, we demonstrated the expression of this gene in newborn rat, pig and human kidneys, as well as human fetal kidney, indicating its role in nephrogenesis. These data suggest that expression of the WT-1 gene is involved in the regulatory mechanisms that control different types of renal growth.

The renotrophic factor, a persistent stimulus that crosses the placenta in mice

1. Twenty 7-week female mice underwent right nephrectomy and twenty others were sham operated. A week later all animals were made pregnant. Pregnancy was repeated five more times consecutively and various renal parameters were assessed in the pups. 2. Fractional fresh kidney weight (relative to body weight) was significantly increased in the pups of nephrectomized mothers while percentage renal water and protein content expressed as mg/g kidney weight were not statistically different in the two groups of pups. Thus dry kidney weight and amount of protein per kidney were increased in the experimental group. This was true for the newborns of all six pregnancies. 3. Renal morphometric studies performed in newborns of first pregnancies showed that the mean number of glomeruli per microscopic field, mean fractional cumulative glomerular area (relative to microscopic field area) and the mean number of cells per glomerulus were significantly greater in the experimental group. Mean glomerular radius was not statistically different in the two groups. 4. The results indicate that: (1) the renotrophic factor(s) crosses the placenta in mice; (2) its activity in maternal circulation following uninephrectomy is sustained for a relatively long period; and (3) fetal response to enhanced maternal renotrophin stimulation consists of increased renal dry weight and renal protein, formation of super-physiological numbers of glomeruli and cellular hyperplasia of the glomeruli.

Functional recovery in the irradiated kidney following removal of the contralateral unirradiated kidney

The right kidneys of seven Large White female pigs, approximately 14 weeks of age, were irradiated with single doses of 7-12.6 Gy of 250 kV X-rays. Sequential measurements of individual kidney glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were carried out using 99mTc-DTPA and [131I]hippuran renography for time periods up to 24 weeks after irradiation. From this data, kidneys receiving a dose of 7 Gy were found to be functioning (F), while kidneys which received greater than or equal to 8.8 Gy were assessed as having no significant function (NF). When the pigs were approximately 10 months of age the contralateral unirradiated kidney was removed; the left kidney of three age-matched unirradiated pigs was also removed. The response of the right kidney to unilateral nephrectomy (UN) in these animals was assessed in terms of changes in haemodynamics (i.e. GFR and ERPF) for periods up to 24 weeks after UN. At post-mortem, the length and weight of the remaining kidney was measured. A marked increase in renal length was observed in irradiated kidneys following UN. In addition, the weights of irradiated kidneys following UN were greater than those of irradiated kidneys in age-matched pigs where the unirradiated kidney had not been removed. Four weeks after UN there was a pronounced increase in GFR and, in particular, ERPF in previously NF irradiated kidneys. The mean increase in these parameters, measured at the end of the follow-up period, when compared with the pre-surgery values, was 350.1 +/- 84.3 and 781.8 +/- 151.0% respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of unilateral nephrectomy on growth of the Wistar/Furth Wilms' tumor

Compensatory renal growth, that is, renal growth following contralateral nephrectomy, is mediated by either the elaboration or the activation of a renotrophic growth factor. Since tumor growth may be modulated by various factors, we evaluated the effect of the renotrophic growth factor associated with compensatory renal growth on the Wistar/Furth rat Wilms' tumor. When compared to tumors grown in sham nephrectomized animals, tumors grown in animals who had undergone unilateral nephrectomy showed an increase in tumor weight and in DNA content. In addition, the rate of new cell formation as reflected by the uptake of tritiated thymidine into tumor cells was significantly higher and did not decline when tumors grown in animals who had undergone unilateral nephrectomy were compared to tumors from sham nephrectomized animals. Our studies therefore suggest that the renotrophic growth factor associated with compensatory renal growth may have ubiquitous growth regulating activity and that further studies may elucidate its role in the modulation of normal and neoplastic growth.

Renotrophic factors in urine

Our previous observations of increased renal protein synthesis in rats subjected to the constant intravenous reinfusion of half their urine output has suggested that the circulatory retention of renotrophic factors in urine is capable of stimulating renal growth. In the present studies, using this same model of "half-urine-reinfusion," which is designed to produce a selective halving of renal excretory function, we have demonstrated significant increases in total DNA content and the incorporation of tritiated thymidine in renal DNA. In addition, a bioassay method was developed in which an assay rat, given an intravenous infusion of urine from another rat, exhibited increases in the incorporation of thymidine into renal DNA and the incorporation of radiolabelled choline into renal phospholipid. This renotrophic activity in the urine was only minimally decreased by heating to 100 degrees C for 30 min and was confined to ultrafiltration fractions retained on a membrane with a nominal 10,000-dalton solute rejection. Removal of one kidney from the rats from which the urine was obtained led to only a modest and transient reduction in the excretion of renotrophic activity, suggesting that the urinary renotrophic factors are of circulatory, not renal, origin. Isolated renal cortical fragments incubated with an ultrafiltration retentate of urine displayed a dose-dependent increase in choline incorporation into phospholipid, suggesting a direct action of the factors on kidney tissue. Finally, no evidence of stimulation of either DNA or phospholipid synthesis could be seen in hepatic tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Renotropic growth factor found in cancer patient sera after removal of cancer-bearing kidney

We have used two sets of primary human kidney culture systems for assaying human renotropic growth factor in day 5 postnephrectomized human sera. The first set of primary kidney cell cultures was prepared from one hydronephrotic kidney and used for assaying the renotropic growth stimulating activity of six kidney cancer patients sera simultaneously. The level of renotropic growth-stimulating activity varies from patient to patient. The postnephrectomized sera of three patients showed rather small (27 to 68%) increase over their prenephrectomized sera. The postnephrectomized sera of the remaining three patients showed a much greater (2.69- to 3.19-fold) increase over their prenephrectomized sera. Variation in the growth-stimulating activities produced in these uninephrectomized kidney cancer patients is most probably due to different levels of renal function loss by removal of the cancer-bearing kidney. Each cancer-bearing kidney has a different proportion of healthy kidney region to diseased (nonfunctional) region. The second set of primary kidney cell cultures was prepared from a healthy noncancerous region of a cancer-bearing kidney and used to assay for renotropic growth-stimulating activities in two different unilaterally nephrectomized kidney transplantation donor sera. Increased levels of growth-stimulating activity are quite similar and high (4.19- to 4.79-fold increase above their prenephrectomized sera). These high and similar assay values of the renotropic growth factor produced in two healthy humans suggest the sensitivity and reliability of the assay method with the use of the noncancerous cells from the cancer-bearing kidney.

In vitro evidence from tissue cultures to prove existence of rabbit and human renotropic growth factor

When synchronized primary rabbit kidney monolayer cell cultures were incubated with a medium that contained uninephrectomized rabbit serum, the incorporation of tritiated thymidine into DNA was much greater than that with a medium that contained normal rabbit serum. The maximal growth-stimulating activity of uninephrectomized rabbit serum on thymidine incorporation into confluent monolayer cultures and sparsely cultured cells was increased approximately two- and fivefold, respectively, above that of normal serum. We conclude that uninephrectomized sera contain a growth-stimulating factor. Similarly, sera from a uninephrectomized human kidney donor and a cancer patient stimulated primary human kidney cell cultures to incorporate tritiated thymidine at levels far beyond those with their prenephrectomized sera. The maximal growth-stimulating activities of uninephrectomized human sera with confluent monolayer cultures and sparsely cultured cells were approximately six- and 13-fold, respectively, above those with the prenephrectomized sera. Thus, the maximal growth-stimulating activity in uninephrectomized human sera was much greater than that in uninephrectomized rabbit sera. Differences in the maximal growth-stimulating activities may be due to differences in the relative number of cell types, for example, epithelial versus fibroblast, present in these kidney cell cultures. By the use of primary cultured cells from other organs such as rabbit skin and human prostate and primary kidney cultures from three species (rabbit, human, and hamster), the growth-stimulating factor in uninephrectomized sera showed organ specificity, that is, renotropic and species specificity in this in vitro assay system.(ABSTRACT TRUNCATED AT 250 WORDS)

Serum renotropic activity and renal growth in spontaneously hypertensive rats

Studies performed in the 1950's suggested that a circulating factor controlling renal growth (renotropin) could contribute to hypertension. However, no assay was available to prove its existence. Recently, different assays have been able to demonstrate the presence of a circulating renotropic factor following unilateral nephrectomy in rats. Therefore, we investigated certain aspects of renal growth in SHR, especially serum renotropic activity, and compared these with the same parameters in three strains of normotensive rats (SD, NWR, and WKY). Renal slice and renal DNA synthesis in response to unilateral nephrectomy were not unusual in SHR compared to other strains previously studied. Sera and renal extracts from young SHR following unilateral nephrectomy compared to sera and renal extracts from sham-operated SHR stimulated 3H-thymidine incorporation into the DNA of renal fragments. This pattern was similar to findings when sera and renal extracts from unilaterally nephrectomized SD were investigated, but the sera and extracts from SHR may have shown greater overall stimulation. Interestingly, a relative increase in renotropic activity was found in the serum of untouched SHR (11.1% +/- 1.7 (SEM), P less than 0.001) but not untouched NWR, SD, and WKY. The greatest renotropic activity in SHR was found at 6 to 16 weeks of age (13.5% +/- 2.1 (SEM), P less than 0.001). The previously reported activator found in renal tissue after unilateral nephrectomy was not found to be increased in untouched SHR. No studies were performed on SHR greater than 25 weeks of age. As a first approximation, our investigations are consistent with a previously hypothesis that renotropin may play some role in hypertension.

Polyamine metabolism in compensatory renal growth

The aliphatic polyamines, putrescine, spermidine, and spermine, appear to play an important role in many forms of rapid growth including embryonic, regenerative, hormone-induced, and neoplastic. While the exact biochemical function of polyamines is unclear, current evidence suggests they are probably involved in the biosynthesis and accumulation of nucleic acids and proteins. Increased levels of polyamines and their biosynthetic enzymes are associated with augmented kidney growth stimulated by renal mass extirpation, as well as by various hormones, toxins, and carcinogens. These observations are reviewed and additional data is provided pertaining to alterations in polyamine metabolism during compensatory renal growth following unilateral nephrectomy (uni). To further explore the effect of growth stimuli on renal polyamine synthesis, an in vitro system was employed which previously provided evidence for a circulating renal growth factor after unilateral nephrectomy. These in vitro observations underscore the rapid inducibility of ornithine decarboxylase, the rate limiting enzyme for polyamine biosynthesis; illustrate the association of polyamine and nucleic acid synthesis during enhanced kidney growth; and support the existence of a circulating renal growth regulator which apparently contributes to compensatory responses following loss of functional renal parenchyma.

Growth stimulation following serum transfer from carcinogen-treated donors to normal rats: a new aspect of early carcinogen actions

Especially in their early phase of action carcinogens are strong inhibitors of cell proliferation. This is an apparent contradiction to the promoting activity of oncogens in the process of carcinogenesis. Because of obvious similarities between restorative and neoplastic growth processess on the tissue level we have studied the possibility, whether such similarities do exist also with regard to stimulatory activities in the serum. To overcome the non-specific inhibitory effect of a carcinogen, the serum of 2-acetylaminofluorene (AAF) treated male Sprague-Dawley rats was transferred to normal recipients. The results demonstrate that the proliferation of the same tissues (hepatocytes, adrenocortical cells, thymocytes) as in liver regenerating animals were stimulated by the serum of the carcinogen-treated rats. Whether the observed short-term effect corresponds to the so-called promoting activity of the carcinogen(s) is discussed. Nature and origin of the humoral stimulator(s) are still unknown.

Nephrocompensatory growth following thymectomy

Thymectomy performed 28 days before unilateral nephrectomy produced significant inhibition in compensatory renal growth (CRG) in 3-6-month-old rats. Sera from thymectomized animals are not deprived of their renotrophic activity, but thymectomy of serum recipients almost abolished the capability of renotrophic serum to produce CRG.

A renotropic system in rats

While plasma or sera obtained from rats 20 h after removal of one kidney (uninephrectomy) stimulated [3H] thyrmidine incorporation into the DNA of kidney tissue incubating in vitro, azotemic plasma or sera obtained from rats 20 h after removal of both kidneys had no apparent effect. Dialysis of this azotemic sera resulted in its ability to stimulate isotope incorporation into renal DNA to the same degree as sera from uninephrectomized rats. This stimulatory factor (renotropin) was found to rise significantly within the first 26 h after uninephrectomy. Renotropin worked only on renal tissue, and we found that a factor could be extracted in large amounts from the remaining kidney 20 h after uninephrectomy that would stimulate renal DNA synthesis in the presence of sera. Based on these findings and others, we postulate that after uninephrectomy there is an elevation in circulating renotropin as well as a tissue factor in the remaining kidney. Both factors together probably produce an excitor which enhances [3H] thymidine into DNA. The latter is tightly bound to renal tissue, and its production and/or activity is modified by circulating inhibitors that are especially prominent in azotemia.