Homandberg G A, Hui F
Department of Biochemistry, Rush Medical College at Rush-Presbyterian-St. Luke's Medical Center, Chicago, Illinois 60612-3864.
Arch Biochem Biophys. 1994 Jun;311(2):213-8. doi: 10.1006/abbi.1994.1229.
We reported earlier that Fn fragments (Fn-f) added to bovine articular cartilage cultured in serum-free DMEM cause marked elevated release of protease activity within a few days. This results in greatly elevated rates of release of proteoglycan (PG). We have now extended our studies to 4-week cultures of cartilage in the presence of 10% serum. We report here that cartilage cultured with 0.01, 0.1, and 1 microM of an amino terminal 29-kDa Fn-f in 10% serum accelerated the loss of PG from the tissue during the first few days in a concentration-dependent manner. However, beyond this period PG content decreased much more slowly. During this early period, the 29-kDa Fn-f decreased rates of protein and PG synthesis up to 50% in a concentration-dependent fashion. Beyond this period, the synthesis rates began to increase in a mode inversely related to 29-kDa Fn-f concentration, up to 135% of Fn-f free control values. However, during the entire culture period, cartilage cultured with 1 nM 29-kDa Fn-f had higher PG contents and had enhanced rates of protein and PG synthesis. Since 1 nM 29-kDa Fn-f stabilized cartilage against decreases in PG content, we tested its ability to block the activity of higher 29-kDa Fn-f concentrations. Cartilage was preincubated for 7 days with 1 nM 29-kDa Fn-f, and then the culture adjusted to 100 nM 29-kDa Fn-f to cause PG depletion. The preincubated cartilage showed markedly enhanced resistance to PG depletion. Since the protective effect was similar to known properties of IGF-1, the ability of 20 ng/ml IGF-1 to block against the effects of 100 nM Fn-f was tested and shown to be similar in magnitude to that of 1 nM 29-kDa Fn-f. We propose that the initial catabolic effects of higher concentrations of Fn-f, followed by the later anabolic effects, may aid in tissue repair. Also, the continuous anabolic effects of lower concentrations may be involved in tissue homeostasis.
我们之前报道过，将纤连蛋白片段（Fn-f）添加到在无血清DMEM中培养的牛关节软骨中，会在几天内导致蛋白酶活性的显著升高释放。这导致蛋白聚糖（PG）的释放速率大大提高。我们现在将研究扩展到在10%血清存在下的4周软骨培养。我们在此报告，在10%血清中用0.01、0.1和1微摩尔的氨基末端29-kDa Fn-f培养的软骨，在最初几天以浓度依赖的方式加速了PG从组织中的流失。然而，在此之后，PG含量下降得要慢得多。在这个早期阶段，29-kDa Fn-f以浓度依赖的方式使蛋白质和PG合成速率降低多达50%。在此之后，合成速率开始以与29-kDa Fn-f浓度呈反比的方式增加，高达无Fn-f对照值的135%。然而，在整个培养期间，用1纳摩尔29-kDa Fn-f培养的软骨具有更高的PG含量，并且蛋白质和PG合成速率增强。由于1纳摩尔29-kDa Fn-f使软骨对PG含量的降低具有稳定性，我们测试了其阻断更高浓度29-kDa Fn-f活性的能力。软骨先用1纳摩尔29-kDa Fn-f预孵育7天，然后将培养物调整到100纳摩尔29-kDa Fn-f以导致PG耗竭。预孵育的软骨对PG耗竭表现出明显增强的抵抗力。由于这种保护作用类似于已知的IGF-1特性，测试了20纳克/毫升IGF-1阻断100纳摩尔Fn-f作用的能力，结果显示其幅度与1纳摩尔29-kDa Fn-f相似。我们提出，较高浓度的Fn-f最初的分解代谢作用，随后是后期的合成代谢作用，可能有助于组织修复。此外，较低浓度的持续合成代谢作用可能参与组织稳态。
