Stephenson L A, Haney L B, Hussaini I M, Karns L R, Glass W F
Department of Pathology, Eastern Virginia Medical School, Norfolk 23501-1980, USA.
Kidney Int. 1998 Oct;54(4):1175-87. doi: 10.1046/j.1523-1755.1998.00101.x.
Mesangial cells during embryonic development and glomerular disease express smooth muscle alpha-actin (alpha-SMA). We were therefore surprised when cultured mesangial cells deprived of serum markedly increased expression of alpha-SMA. Serum-deprived mesangial cells appeared larger than serum-fed mesangial cells. We hypothesized that alpha-SMA expression may be more reflective of mesangial cell hypertrophy than hyperplasia.
Human mesangial cells were cultured in medium alone or with fetal bovine serum, thrombin, platelet-derived growth factor-BB (PDGF-BB) and/or transforming growth factor-beta1 (TGF-beta1). Alpha-SMA expression was examined by immunofluorescence, Western blot, and Northern blot analysis. Cell size was analyzed by forward light scatter flow cytometry.
Alpha-SMA mRNA was at least tenfold more abundant after three to five days in human mesangial cells plated without serum, but beta-actin mRNA was unchanged. Serum-deprived cells contained 5.3-fold more alpha-SMA after three days and 56-fold more after five days by Western blot. Serum deprivation also increased alpha-SMA in rat and mouse mesangial cells. The effects of serum deprivation on alpha-SMA expression were reversible. Mesangial cell mitogens, thrombin or PDGF-BB, decreased alpha-SMA, but TGF-beta1 increased alpha-SMA expression and slowed mesangial cell proliferation in serum-plus medium. Flow cytometry showed that serum deprivation or TGF-beta1 treatment caused mesangial cell hypertrophy. PDGF-BB, thrombin, or thrombin receptor-activating peptide blocked hypertrophy in response to serum deprivation.
We conclude that increased alpha-SMA expression in mesangial cells reflects cellular hypertrophy rather than hyperplasia.
系膜细胞在胚胎发育和肾小球疾病过程中表达平滑肌α-肌动蛋白（α-SMA）。因此，当培养的系膜细胞血清剥夺后α-SMA表达显著增加时，我们感到惊讶。血清剥夺的系膜细胞看起来比血清充足的系膜细胞更大。我们推测α-SMA表达可能更反映系膜细胞肥大而非增生。
人系膜细胞单独在培养基中培养或与胎牛血清、凝血酶、血小板衍生生长因子-BB（PDGF-BB）和/或转化生长因子-β1（TGF-β1）一起培养。通过免疫荧光、蛋白质印迹和Northern印迹分析检测α-SMA表达。通过前向光散射流式细胞术分析细胞大小。
在无血清培养的人系膜细胞中培养三到五天后，α-SMA mRNA丰度至少增加十倍，但β-肌动蛋白mRNA无变化。蛋白质印迹显示，血清剥夺的细胞在三天后α-SMA含量增加5.3倍，五天后增加56倍。血清剥夺也增加了大鼠和小鼠系膜细胞中的α-SMA。血清剥夺对α-SMA表达的影响是可逆的。系膜细胞有丝分裂原、凝血酶或PDGF-BB可降低α-SMA，但TGF-β1增加α-SMA表达并减缓血清充足培养基中系膜细胞的增殖。流式细胞术显示血清剥夺或TGF-β1处理导致系膜细胞肥大。PDGF-BB、凝血酶或凝血酶受体激活肽可阻止血清剥夺引起的肥大。
我们得出结论，系膜细胞中α-SMA表达增加反映细胞肥大而非增生。
