Table 5.
Podocyte Transcript Analysis
| Group | Podometric Parameters | Glomerular Transcript Values Expressed as % Compared with WT.2K.ALD | ||||||
|---|---|---|---|---|---|---|---|---|
| Podocyte Number per Glom | Podocyte Nuclear Density | Glepp1 Area Density | WT1 | Podocin | Nephrin | Ptpro (Glepp1) | Podocin/Nephrin Ratio | |
| TG.1K.ALD | 106.6±10.7 | 49.9±4.7a | 69.6±5.8a | 60.3±13.1a | 67.6±11.1b | 50.8±9.4a | 51.6±8.1a | 132.7±3.2a |
| TG.2K.ALD | 104.5±23.0 | 74.0±15.9 | 99.8±3.1 | 107.1±17.8 | 99.5±16.0 | 93.0±14.5 | 121.5±16.4 | 106.5±4.0 |
| TG.1K.CRD | 107.4±15.7 | 87.9±12.0 | 95.5±4.8 | 101.1±18.5 | 83.6±14.9 | 87.9±15.4 | 91.4±12.2 | 94.8±8.9 |
| TG.1K.ALD.Rapa | 92.9±13.8 | 102.7±6.4 | 94.5±2.7 | 30.4±10.1a | 33.1±9.0a | 24.3±8.9a | 34.5±11.9a | 140.9±18.5a |
| TG.1K.ALD.ACEi | 96.1±12.2 | 76.6±13.8 | 89.4±3.1 | 68.3±13.4b | 66.4±14.5b | 62.4±12.1a | 63.9±13.4a | 105.4±7.0 |
| WT.1K.ALD | 95.8±14.0 | 113±31.2 | 99.9±2.4 | 88.7±4.5 | 94.9±5.3 | 86.9±6.7 | 77.9±9.6 | 108.9±3.5 |
| WT.2K.ALD | 100±14.0 | 100±30.2 | 100±3.4 | 100±11.7 | 100±5.7 | 100±13.0 | 100±8.0 | 100±8.5 |
Comparison of glomerular podometric and transcriptomic parameters. All data are from isolated glomeruli obtained 3 weeks after nephrectomy or sham nephrectomy for the same groups as shown in Tables 1–3. Data shown in comparison with the wild-type sham-nephrectomized rats maintained on an ad libitum diet (WT.2K.ALD in bottom row at 100%). Podometric parameters are shown at left, relative transcriptomic expression in the middle, and podocyte transcript ratios at right. Nephrectomized TG rats maintained on an ad libitum diet (TG.1K.ALD) that developed FSGS are shown in the top row. In this group, although podocyte number per glomerulus was unchanged, podocyte nuclear density and Glepp1 cell area density were both decreased due to glomerular enlargement partially compensated for by podocyte cell hypertrophy. Podocyte transcripts (WT1, podocin, nephrin, and ptpro [Glepp1]) were all decreased in approximate proportion to the decreased podocyte density. The ratios of podocyte transcripts (podocin/nephrin previously), shown to be related to podocyte hypertrophic stress,6,7 were also increased in the TG.1K.ALD group that developed FSGS, but not in other groups. Rapamycin treatment itself markedly reduced podocyte transcript expression, thereby making interpretation of transcriptomic data in the setting of rapamycin difficult. ACE inhibition may have had minor effects on transcript levels that were not significant in the ratio data. These data show that there were two different reasons for podocyte transcript changes: (1) podocyte density was decreased due to accumulation of nonpodocyte glomerular cells, and (2) relative expression of podocyte genes was also altered compatible with podocytes undergoing hypertrophic stress in association with FSGS lesion development. Reduction in the podocyte transcriptomic signal was not due to preferential loss of podocytes from glomeruli. Data are shown as the mean±1 SD. Comparisons were performed by ANOVA using the Bonferroni correction. Glom, glomerulus; TG, Fischer344 TG rats; 1K/2K, nephrectomized/sham-nephrectomized; ALD, adlib diet; CRD, 40% calorie reduced diet; rapa, rapamycin-treated; ACEi, treated with the angiotensin II inhibitor enalapril; WT, wild-type Fischer344 rats.
P<0.05.
P<0.01.