BACKGROUND:At present, the separation and culture technique of chondrocytes has been mature, but the chondrocytes grow slowly which are prone to degenerate using the present technique. It is not conducive to the fol ow-up test.
OBJECTIVE:To investigate and improve the separation and culture method of articular chondrocytes of New Zealand rats at 4 weeks of age.
METHODS:New Zealand rats aged 4 weeks were selected to take cartilage tissues from the bilateral knees that were resected under aseptic condition. Chondrocytes were isolated by type Ⅱ col agenase enzyme digestion and mechanical isolation method. The cells were cultured and passaged, and then identified by morphologic observation, toluidine blue staining and type Ⅱ col agen enzyme immunohistochemical methods. Growth curve was pictured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide method.
RESULTS AND CONCLUSION:Inverted microscope observation showed that the primary cultured chondrocytes adhered at 6 hours after cultivation. The monolayer formation occurred at 72 hours after cultivation, and the cells were ready to be passaged at 96 hours after cultivation. In the fourth generation, some cells represented a spindle-like appearance. In the fifth generation, most cells turned into irregular shape appearance, and cellproliferation capacity diminished. Toluidine blue staining showed that the nuclei of cultured chondrocytes were blue and cytoplasm was pale blue. Immunofluorescent staining showed that cultured chondrocytes had a positive expression of col agen type Ⅱ and the color was tawny. Proliferative rate of chondrocytes in the first to third generations had no differences (P<0.05), while differences were found compared with the fourth generation in 4-7 days (P<0.05) and the fifth generation in 1-7 days (P<0.05). The results indicate that type Ⅱ col agenase enzyme digestion and mechanical isolation method is successful for isolating, cultivating New Zealand rat articular chondrocytes in vitro, and the first to third generations can be the best choice for the experiments of knee osteoarthritis.

Objective : To investigate the protective effect of melatonin (MT) on formaldehyde (FA) inhalation-in- duced acute lung injury (ALI) in rats and its mechanism through the regulation of nuclear factor E2-related factor 2 (Nrf2) signaling pathway． Methods : Fifty female Wistar rats were randomly divided into Control group ，FA group，FA + MT 5 mg / kg group，FA + MT 10 mg / kg group and FA + MT 20 mg / kg group，with 10 rats in each group．Except for the Control group，all other groups inhaled 3 mg / m3 FA daily for 21 d consecutively to construct the tainted model，and then treated with different MT doses for 14 d．The tainting was continued during the MT treatment．Hematoxylin-eosin (HE) staining was used to observe the histopathological changes in lung tissue，lung water content and lung coefficient were weighed and measured，glutathione ( GSH) ，superoxide dismutase (SOD) and 8-hydroxydeoxyguanosine ( 8-OHdG) levels were measured by absorbance photometric method ，and enzyme linked immunosorbent assay(ELISA) was used to measure the levels of tumor necrosis factor-alpha (TNF-α) ，in- terleukin (IL) -6，and IL-1 β concentrations，Western blot to detect the protein expression levels of Nrf2，heme ox- ygenase-1 (HO-1) ，nuclear factor-κB ( NF-κB) ，and phosphorylated nuclear factor-κB ( p-NF-κB) in lung tis- sues，and quantitative polymerase chain reaction(qPCR) to detect the Nrf2，HO-1，and Kelch-like ECH-associated protein 1 (Keap1) mRNA expression levels. Results : Compared with the control group，lung injury was obvious in rats in the FA group ; lung tissue GSH and SOD levels were reduced ，and 8-OHdG levels were elevated ( P < 0. 05) ; alveolar lavage fluid TNF-α , IL-6，and IL-1 β levels were elevated (P＜0. 05) ; Nrf 2 and HO-1 protein expression levels were reduced in the lung tissue (P＜0. 05) ，and p-NF-κB protein expression levels were was ele- vated (P＜0. 05) ; the relative mRNA expression of Nrf2 and HO-1 in lung tissue was decreased，and the relative mRNA expression of Keap1 was elevated (P＜0. 05) ．Compared with the FA group，the lung injury of rats in the MT group was improved ; the levels of GSH and SOD in the lung tissue were increased (P＜0. 05) ，and the level of 8-OHdG was decreased (P＜0. 05) ; the levels of TNF-α , IL-6，and IL-1 β in the alveolar lavage fluid were de- creased (P＜0. 05) ; and the expression levels of the Nrf2 and HO-1 proteins in the lung tissue were increased (P ＜0. 05) ．p-NF-κB protein expression level was decreased (P ＜0. 05) ; the relative mRNA expression levels of Nrf2 and HO-1 in lung tissues were increased (P＜0. 05) ，and the relative mRNA expression level of Keap1 was decreased (P＜0. 05) in lung tissues，and all of them were in a dose-dependent manner． Conclusion MT can al- leviate oxidative stress and inflammatory responses and mitigate FA exposure-induced acute lung injury by regula- ting the Nrf2 / Keap1 / HO-1 signaling pathway.