人高级别宫颈上皮内瘤变细胞的原代培养及其生物学特性的体外研究
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摘要
宫颈癌是威胁女性生命的首位生殖系统恶性肿瘤,近年来,随着宫颈癌筛查的有效开展,世界范围内宫颈癌的发病率和死亡率已经大幅下降,而宫颈癌前病变即宫颈上皮内瘤变(Cervical intraepithelial neoplasia, CIN)的检出率却越来越高。研究发现,宫颈癌发生发展过程中存在较长的、可逆转的癌前病变期,包括宫颈不典型增生和宫颈原位癌,它反映宫颈癌发生发展中的连续过程。宫颈上皮不典型增生表现为宫颈上皮层内出现异型细胞,即细胞大小不一,形状不规则,细胞核增大浓染,核浆比例增大,核分裂象增多,甚至有病理性核分裂,细胞极性紊乱等。根据细胞异常的程度及上皮累积范围又可将CIN分为三级,即CIN1级(轻度不典型增生),Ⅱ级(中度不典型增生)和Ⅲ级(重度不典型增生和原位癌)。根据对CIN的自然病史的研究,绝大多数的低级别CIN(即CINI)会自然消退,只有0.3%-1%会发展为浸润癌,而未经治疗的高级别CIN(即CIN II和CINIII)中20%-45%将发展为原位癌或浸润癌,故高级别CIN为潜在的宫颈癌前病变。由于CIN发展形成宫颈浸润癌的病程较长大约10年,因此,对CIN的患者及时早期发现、积极有效治疗是降低宫颈癌发病率的关键。目前认为人乳头瘤病毒(human papillomavirus, HPV)感染是CIN和宫颈癌发生的始动因素,在99%以上的宫颈癌及CIN中存在HPV DNA. HPV可分为高危型和低危型两大类,低危型多导致疣类病变和CIN1,而高危型则多导致CIN2-3及宫颈癌的发生。但是HPV不能进行常规的体外培养,而高危型HPV引起的疾病是一个漫长的过程。因此,对携带HPV的宫颈上皮内瘤变细胞进行原代培养并对其生物学特性进行研究,有利于更好的了解HPV感染宫颈上皮细胞的重要的意义,为高级别CIN和宫颈癌的进一步研究提供理论依据和实验基础。
目前,正常宫颈上皮细胞(Normal uterine cervix, NUC)及宫颈癌细胞的原代培养国内外已屡见报道,但是对于高级别CIN细胞这一潜在癌前病变的培养及其的生物学特性的研究国内外鲜有报道。众所周知,癌细胞的生物学特性主要包括：①形态特征：细胞异型性如癌细胞大小形态不一,核质比显著高于正常细胞；核形态不一,并可出现巨核、双核或多核现象；核分裂像常增多。②生理生化特征：细胞接触抑制丧失；具有迁移性和侵袭性等。但是,对于高级别CIN这一癌前期病变细胞却仅从形态学特征方面进行了描述,对于其生理生化特征却未见报道。单从宫颈癌细胞和高级别CIN细胞的形态特征来看,二者均具有异型性,故很难从形态学上对二者进行区分。但是癌细胞增殖活性强,具有非接触性抑制、迁移性及侵袭性,与人类肿瘤侵袭有关的MMP-2亦明显升高。高级别CIN细胞是否亦具有上述特性?高级别CIN细胞为何可以局限于上皮内多年或消失而不发生转移?基于此,本项目拟对高级别CIN细胞进行原代培养,探索一种快速、简便、有效的培养方法,同时对其生物学特性进行体外研究,为宫颈癌及其癌前病变的进一步研究提供理论及实验依据。
第一部分：一种新的正常人宫颈上皮细胞原代培养技术的建立
研究目的：
1.提供一种新型培养基,既能促进细胞的贴壁,又能减少成纤维细胞的污染。
2.从培养器皿方面,探索一种能协同促进宫颈上皮细胞贴壁的方法。
3.探索一种高纯度的宫颈上皮细胞的体外培养的方法。
研究方法：
1.取人正常宫颈上皮组织,用Ⅰ型胶原酶消化分解后得到宫颈上皮细胞悬液。
2.将细胞分别接种到以下培养瓶中：①未经鼠尾胶原包被,仅含无血清培养基(keratinocyte serum-free medium, K-SFM);②未经鼠尾胶原包被,含5%胎牛血清的K-SFM;③用鼠尾胶原包被,仅含K-SFM;④用鼠尾胶原包被,含5%胎牛血清的K-SFM.
3.待细胞贴壁后,首次换液,将培养基全部换成K-SFM.
4.采用细胞免疫荧光检测宫颈上皮基层角蛋白(Keratin, K)5、K14和K19的表达。
结果：
1.在含5%胎牛血清的培养基中,细胞的贴壁速度较无血清的培养基快(约30%和10%)。
2.用鼠尾胶原I型包被的培养瓶中,细胞的贴壁速度较未经鼠尾胶原包被的培养瓶中快(约60%和30%)。
3.联合使用含5%胎牛血清的培养基和经鼠尾胶原Ⅰ型包被的培养瓶是最理想的培养宫颈上皮细胞的方法。
4. K5, K14和K19几乎在所有细胞的细胞浆中均呈阳性表达,但K5表达很弱。
结论：
1.低浓度胎牛血清可以提高上皮细胞的贴壁能力,而无血清培养基抑制成纤维细胞的生长。
2.联合使用5%胎牛血清的培养基和经鼠尾胶原Ⅰ型包被的培养瓶是一种新颖、简便、有效的人宫颈上皮细胞的培养方法。
3.我们的方法可以从成人宫颈上皮组织中快速得到大量高纯度的正常宫颈上皮细胞。
第二部分：人高级别宫颈上皮内瘤变细胞的原代培养和鉴定研究目的：
建立一种人小块宫颈瘤变组织来源的自然感染HPV的高级别宫颈上皮内瘤变细胞的体外培养方法；为高级别上皮内瘤变细胞生物学特性的研究提供实验基础。
研究方法：
1.取小块人宫颈瘤变组织,取出一小部分行HPV DNA分型检测。
2.将剩余瘤变组织用I型胶原酶消化分解后制成类细胞悬液(未经细胞筛过滤)。
3.将类细胞悬液接种到含5%胎牛血清+K-SFM的、经鼠尾胶原包被的培养瓶中。
4.一组细胞培养3天后首次换液并更换K-SFM,收集未贴壁细胞并重新种植到新的培养瓶中继续培养3天。另一组细胞培养6天后首次换液并更换K-SFM.
5.将第三代细胞收集后行HPV DNA分型检测。
6.通过细胞免疫荧光检测宫颈上皮基底层K14和K19,宫颈干细胞K17和P63的表达,对CIN细胞进行鉴定。
结果：
1.细胞培养的第1、3和6天,分别有30%、60%和80%的高级别CIN细胞贴壁,未贴壁细胞在第3天重新收集并继续培养3天后仍然有30%的细胞贴壁,但由于细胞密度较低很难长满培养瓶并传代。
2.传代后高级别CIN细胞仍然保持其大小不等、形状异常的形态,没有明显分化现象。
3.传代后高级别CIN细胞的HPV分型检测结果同原代一致。
4.K14和K19几乎在所有NUC细胞和高级别CIN细胞的胞浆中表达；但是,K17和P63仅在高级别CIN细胞的胞浆中表达。
结论：
1.我们将“组织块培养法”与“酶消化法”相结合制备了类细胞悬液,不仅克服了“组织块培养法”中细胞因移动受到限制而造成的生长缓慢,而且节省细胞过滤过程中丢失的细胞,获得了更多的CIN细胞,克服了CIN培养过程中因标本过小而造成的困难。
2.高级别CIN细胞培养的第6天可作为最佳首次换液时间。
3.我们建立了一种从小块宫颈瘤变组织获取自然携带HPV的高级别宫颈上皮内瘤变细胞的简单而实用的培养方法,为CIN病变的体外研究提供了实验基础。
第三部分：人高级别宫颈上皮内瘤变细胞生物学特性的体外研究研究目的：
通过与NUC细胞及宫颈癌Caski细胞的对比,观察人高级别CIN细胞的生物学行为如生长增殖能力、肿瘤标志物的表达及迁徙和侵袭能力等,探讨高级别CIN细胞的生物学特性,为宫颈癌前病变及宫颈癌的进一步研究及治疗提供理论及实验依据。研究方法：
1.应用MTT实验测定高级别CIN细胞及对照组NUC细胞和宫颈癌Caski细胞的生长曲线。
2.应用细胞接触抑制试验检测高级别CIN细胞的生长活性。当细胞生长到约80%-90%融合时,继续培养3-5天,观察细胞有无接触性抑制现象。
3.应用流式细胞技术,检测高级别CIN细胞及对照组NUC细胞和Caski细胞的生长周期。
4.应用DNA倍体分析技术,检测高级别CIN细胞及对照组NUC细胞和Caski细胞的异倍体比例。
5.采用细胞免疫荧光技术,检测高级别CIN细胞及其对照组NUC细胞和Caski细胞中肿瘤标志物Ki-67和p16的表达情况。
6.在酶联免疫分析实验中,应用竞争性抑制法测定高级别CIN细胞及其对照组NUC细胞和Caski细胞分泌性及细胞内基质金属蛋白酶2(matrix metalloproteinase2,MMP-2)水平；应用双抗体夹心法测定基质金属蛋白酶抑制因子2(Tissue inhibitors of metalloproteinase2, TIMP-2)的水平。
7.应用Transwell小室技术,检测高级别CIN细胞及其对照组NUC细胞和Caski细胞的迁移和侵袭能力。
8. SPSS13.0统计软件对数据进行分析：生长曲线用重复测量资料的方差分析；计量资料统计结果以均数士标准差表示,三组之间的差异比较采用方差分析。
结果：
1.高级别CIN细胞、NUC细胞和宫颈癌Caski细胞的生长速度明显不同(P<0.01),Caski细胞的生长速度明显快于高级别CIN细胞和NUC细胞(P<0.01),高级别CIN细胞的生长速度明显快于NUC细胞(P<0.01)。高级别CIN细胞生长曲线的延缓期明显缩短,Caski细胞的生长曲线没有明显的延缓期。
2.高级别CIN细胞贴壁生长汇合成单层后即停止生长,存在接触抑制现象；Caski细胞贴壁生长汇合成单层后继续生长,接触抑制现象消失。
3.细胞周期检测实验显示S期细胞比率(SPF):Caski细胞组>高级别CIN细胞组>NUC细胞组(P<0.01)。
4.DNA倍体分析实验中,高级别CIN细胞组和Caski细胞组异倍体细胞所占比例均明显高于NUC细胞组(P<0.01),但高级别CIN细胞组和Caski细胞组之间异倍体细胞所占比例无显著性差异(P=0.392)。
5.细胞免疫荧光显示,在几乎所有NUC细胞、高级别CIN细胞和Caski细胞的细胞核中,均可见Ki-67呈弥漫的强阳性染色。p16在NUC细胞、高级别CIN细胞和Caski细胞的细胞核和细胞浆中均呈阳性表达。
6. Caski细胞组分泌性MMP-2的含量明显高于NUC细胞组和高级别CIN细胞组(P<0.05),NUC细胞组与高级别CIN细胞组之间无显著性差异(P>0.05),三组细胞之间细胞内MMP-2的含量无显著性差异(P>0.05)；三组细胞之间分泌性和细胞内TIMP-2的含量及MMP-2/TIMP-2的比值无显著性差异(P>0.05)。
7. Transwell体外迁移和侵袭实验均表明：高级别CIN细胞的迁移能力明显优于NUC细胞,但显著低于Caski细胞(P<0.01)；高级别CIN细胞有侵袭能力,但明显低于Caski细胞(P<0.001),NUC细胞无明显侵袭能力。
结论：
1.高级别CIN细胞的生长活力较NUC细胞明显增强,但仍然具有接触抑制现象。
2.高级别CIN细胞与宫颈癌Caski细胞在增殖的过程中均出现了大量的异倍体细胞,说明高级别CIN细胞的增殖能力较强；细胞周期中S期细胞比率的升高,进一步说明了高级别CIN细胞具有较强的生长活力。
3.肿瘤标志物Ki-67和p16在NUC细胞、高级别CIN细胞和Caski细胞均呈阳性表达,说明它们可能仅仅是细胞增殖的标记物。
4.高级别CIN细胞及其对照组细胞内MMP-2和TIMP-2的含量及其比值相似,但分泌性MMP-2的含量低于Caski细胞；同时,高级别CIN细胞具有较弱的侵袭能力,进一步说明了分泌性MMP-2在侵袭中的作用；而高级别CIN病变基底膜的完整性,说明在原位癌到侵袭癌的演进过程中,除了细胞本身的恶性潜能外,实质与间质之间的相互作用起了重要的作用。
Cervical cancer is the most common gynecological cancer in developing countries and the incidence significantly decrease with the wide application of cervical screening test in recent years. It was found out that cervical cancer usually proceeded by a long phase of pre-malignant disease. These pre-malignant changes represent a spectrum of histological abnormalities ranging from cervical intraepithelial neoplasia (CIN) I (mild dysplasia) to CIN2(moderate dysplasia) to CIN3(severe dysplasia/carcinoma in situ). CINI will regress spontaneously in most cases and only0.3%may progress to cervical cancer, whereas CIN II and III will persist and progress to cervical cancer in about20%-45%of untreated CIN II/III lesions. Therefore CINII and CINIII are regarded as high-grade lesions. Fortunately, it is appears that the mean interval for progression of cervical precursors to invasive cancer is about10years, therefore we have enough time to detect and manage this precancerous lesion, and cervical cancer may be prevented subsequently. It is well established that almost all high-grade CIN cases are caused by persistent oncogenic human papillomavirus (HPV) infection and long latency period of viral infection is needed for CIN progression. However, viruses do not have their own metabolism, and require a host cell to make new products. Therefore, HPV does not culture in a laboratory outside a host cell. Culture of naturally HPV-infected CIN keratinocytes has significant value in exploring biological behavior of high-grade CIN in vitro and in vivo then, as well as the transforming process of neoplastic cervical keratinocytes.
Studies on normal uterine cervix (NUC) and CIN keratinocyte cultures, as well as characteristics of CIN keratinocytes, are poorly available due to the numerous technical and methodological problems associated with the in vitro culturing of these cells. Dysplasia is characterized by four major pathological microscopic changes including cells of unequal size, abnormally shaped, hyperchromatism and presence of mitotic figures. The primary basis for assessing the specific grade of CIN is the ratio of nucleus to cytoplasm in a given cell, and higher ratios are associated with higher grades of CIN. However, it is very difficult to differentiate dysplastic cells from malignant cells in morphology to some extent. As we all known, loss of contact-dependent growth inhibition, migration and invasion ability are biological behavior of malignant cells, and we wonder if high grade CIN keratinocytes have such characteristics? Why such CIN keratinocytes are limited to intraepithelial and not broken through into the stroma? In this study, we plan to establish a novel method for culturing normal human cervical keratinocytes and naturally HPV-infected high-grade CIN keratinocytes starting from small pieces of neoplastic cervical tissues. Additionally, we intend to explore the in vitro biological behavior of high-grade CIN keratinocytes and provide an experimental basis for the further study of precancerous lesion of the cervix and cervical carcinoma.
Part I:Establishment of a Novel Method for Primary Culture of Normal Human Cervical Keratinocytes
Objectives:
1. To investigate a modified culture medium which could improve cervical keratinocytes attachment and constrain the fibroblast growth as well.
2. To explore a special culture plastics bottle which may help to improve cervical keratinocytes attachment.
3. To explore a method which could obtain highly purified keratinocytes from normal human cervical epithelium in vitro.
Methods
1. Normal cervical epithelial tissue pieces were obtained and digested with type I collagenase to dissociate the cells and a single cell suspension produced.
2. The cells were seeded on the following culture plastics:(1) Uncoated plastic tissue culture bottles containing keratinocyte serum-free medium (K-SFM) without5%fetal bovine serum (FBS).(2) Uncoated plastic tissue culture bottles containing modified K-SFM supplemented with5%FBS.(3) Plastic tissue culture bottles coated with collagen type I from rat tail containing K-SFM without5%FBS.(4) Plastic tissue culture bottles coated with collagen type I from rat tail containing modified K-SFM supplemented with5%FBS.
3. After attachment, the medium were replaced with K-SFM without FBS.
4. The expression of basal keratins (K) of the ectocervical epithelium, K5, K14and K19were assayed by immunofluorescence with monoclonal antibodies to identify the cell purity.
Results
1. Cells attached to the culture plastic bottles more quickly in K-SFM supplemented with5%FBS than in K-SFM alone
2. Cells attached to tissue culture plastic bottles coated with collagen type I more quickly than uncoated plastic bottles.
3. The modified medium composed of K-SFM and5%FBS combined with a specific tissue culture plastic bottles coated with collagen type I from rat tail was the best method for culture of normal cervical epithelial cells.
4. Diffuse and strong cytoplasmatic immunostaining for keratin14and19was obtained in nearly all cultured cervical epithelial cells. But these cells stained weakly for K5.
Conclusions:
1. In the modified medium, low concentration FBS could improve cervical keratinocyte attachment, whereas K-SFM may constrain the fibroblasts growth.
2. The modified medium composed of K-SFM and5%FBS combined with a specific tissue culture plastic coated with collagen type I from rat tail was a novel, simple and effective method for culture of normal cervical epithelial cells in vitro.
3. We could rapidly obtain highly purified keratinocytes from normal human cervical epithelium in this study.
Part II:Primary Culture and Identification of High-grade Cervical Intraepithelial Neoplasia Keratinocytes from Human Neoplastic Cervical Biopsies
Objectives:
To investigated a novel method for the in vitro culturing of naturally HPV-infected high-grade CIN keratinocytes from small-sized human neoplastic cervical biopsies. To provide an experimental basis for different research purposes, particularly the further study of the biological characteristics of high-grade CIN keratinocytes.
Methods:
1. A small tissue fraction from a CIN II-III sample was excised for DNA extraction.
2. Small pieces of neoplastic tissue were digested with0.2%type I collagenase and single cell suspensions were obtained.
3. The isolated cells were seeded into T25tissue culture plastic bottles, which was coated overnight with2μg/cm2collagen type I from the rat tail, in medium containing K-SFM supplemented with5%FBS.
4. On day3, the serum-supplemented K-SFM medium was replaced with K-SFM medium, and the unattached cells in group1were recovered, reseeded into new T25tissue culture plastic bottles coated with collagen type I from the rat tail, and allowed to attach for three days. The medium was replaced with K-SFM alone on day6, and the unattached cells in group2were discarded. The medium was changed twice a week.
5. For the HPV genotyping of the sub-cultured CIN keratinocytes, a small number of the third-generation cells were subjected to DNA extraction.
6. The expression of basal keratins of ectocervical epithelium including keratin K14and K19; markers for cervical stem cell including P63and K17were assayed by immunofluorescence with monoclonal antibodies to identify the presence of CIN keratinocytes.
Results:
1. Approximately20%,60%, and80%of the high-grade CIN keratinocytes were attached to the culture plastic bottles on days1,3, and6, respectively. Although the viability of the unattached cells on the third day was more than80%, only30%of the remaining cells attached to the new culture plastic bottles, and the attached cells were unable to survive well because of the low cell density in group1.
2. The passaged CIN keratinocytes maintained their original unequally sized, abnormally shaped morphology and did not undergo differentiation.
3. The passaged CIN keratinocytes exhibited the same HPV genotype detected in the original primary cells.
4. K14and K19were found to be expressed in nearly all of the normal and CIN keratinocytes, whereas K17and P63were expressed only in high-grade CIN keratinocytes.
Conclusions:
1. We combine "explant tissue culture method" with "digestion culture method" in this study, and obtain plenty of cells.
2. The6th day may be appropriate time for the first medium change for primary cultures of high-grade CIN keratinocytes.
3. Our study proposes a simple and practical method for rapidly obtaining highly purified naturally HPV-infected high-grade CIN keratinocytes from small-sized neoplastic cervical tissues, and provides an experimental basis for the further study of the biological characteristics of high-grade CIN keratinocytes.
Part Ⅲ In Vitro Study of Biological Behavior on Primary Cultured Human High-grade Cervical Intraepithelial Neoplasia Keratinocytes Objectives:
Compared with NUC keratinocytes and Caski cells, we sought to explore the in vitro biological behavior of high-grade CIN keratinocytes including cell growth curve, cell cycle and DNA aneuploidy, expression of p16and Ki-67, and migration and invasion ability. This study could serve as a basis for the further study of cervical cancer and precancerous lesion of the cervix.
Methods:
1. High-grade CIN cells growth curve was measured with MTT, NUC keratinocytes and Caski cells were used as controls.
2. Contact growth inhibition assay was used to determine the proliferation of high-grade CIN keratinocytes and its controls. When the cultures reached eighty percent confluence, the cells were cultured for further3-5days to test the existence of contact growth inhibition.
3. Flow cytometry analysis was used to detect the cell cycles of high-grade CIN keratinocytes group and its controls.
4. DNA ploidy analysis was used to detect the DNA aneuploidy among high-grade CIN keratinocytes group and its controls.
5. Ki-67and p16expression were examined by immunofluorescence assays among high-grade CIN keratinocytes group and its controls.
6. Competitive inhibition enzyme linked immunosorbent assay (ELISA) and solid phase ELISA was used to determine the concentrations of MMP-2and TIMP-2respectively among high-grade CIN keratinocytes group and its controls.
7. Transwell assay was employed to test cell migration and invasion of high-grade CIN keratinocytes and the controls.
8. Quantitative data were expressed as means±standard deviation (SD), the significance of the difference between groups was evaluated with analysis of variance (ANOVA). Cell growth curve was analyzed with repeated measures ANOVA. All calculations were performed using SPSS13.0statistical software.
Results:
1. Compared with NUC cells, the cells growth speed of high-grade CIN keratinocytes was significantly fast; however, it was significantly slower than Caski cells (P<0.001). After2days of incubation, high-grade CIN keratinocytes entered the logarithmic growth phase which was2days earlier than NUC keratinocytes. No apparent lag phase was observed in the growth curve of Caski cells.
2. Cell contact growth inhibition was identified in high-grade CIN keratinocytes, and Caski cells exhibited a character of uncontrolled cell proliferation with loss of cell contact inhibition.
3. Compared with NUC cells, the S phase fraction (SPF) of high-grade CIN keratinocyte group was significantly high, but was lower than Caski cell group (P＜0.01).
4. DNA aneuploidy ratios of high-grade CIN keratinocyte group and Caski cell group were significantly higher than NUC keratinocyte group (P＜0.01). However, no significant difference was seen between high-grade CIN keratinocyte group and Caski cell group (P=0.392).
5. Nuclear immunostaining for Ki-67was obtained in nearly all of the cultured high-grade CIN keratinocytes and the controls incuding NUC cells and Caski cells. In addition, p16were found to be expressed in nearly all of the high-grade CIN keratinocytes and the controls nuclear and cytoplasm.
6. The concentration of extracelluar matrix metalloproteinase2(MMP-2) in Caski cell group was higher than high-grade CIN and NUC keratinocyte groups (P<0.05), but no significant difference was seen between high-grade CIN and NUC keratinocyte groups (P>0.05). Additionally, the concentrations of extracelluar tissue inhibitors of metalloproteinase2(TIMP-2), intracellular MMP-2and TIMP-2, and the ratio of MMP-2/TIMP-2were insignificantly different among high-grade CIN keratinocyte, NUC keratinocyte and Caski cell groups (P>0.05).
7. Cell migration and invasion assays indicated that the migration ability of high-grade CIN keratinocytes was much higher than NUC keratinocytes, but it was significantly lower than Caski cells (P＜0.001). High-grade CIN keratinocytes had the ability of invasion, but the invasion power was much lower than Caski cells (P<0.001). NUC keratinocytes had no ability of invasion.
Conclusions:
1. Proliferation ability of high-grade CIN keratinocytes was much higher than NUC keratinocytes, but cell contact growth inhibition was still remained.
2. Plenty of DNA aneuploidy occurred during the course of proliferation of high-grade CIN keratinocytes and Caski cells, suggesting that high-grade CIN keratinocytes had the ability of high proliferation. Increased S phase fraction in cell cycle of high-grade CIN keratinocytes further supported this point.
3. Ki-67and p16were expressed not only in high-grade CIN keratinocytes and Caski cells, but also in NUC keratinocytes, suggesting that both Ki-67and p16were probably only markers of cell proliferation.
4. The relatively equal concentrations of extracelluar TIMP-2, intracellular MMP-2and TIMP-2among high-grade CIN keratinocyte group and it controls, the lower concentrations of extracelluar MMP-2and the mild ability of invasion in high-grade CIN keratinocytes, suggested that extracelluar MMP-2play an important role in the course of invasion. However, the basal membranes still keep intact in high-grade CIN lesions. Our study suggested that during the progression from carcinoma in situ to invasive cancer, the interaction of parenchyma and stroma play an important role in addition to to the malignant potential of the cell itself.
目前,正常宫颈上皮细胞(Normal uterine cervix, NUC)及宫颈癌细胞的原代培养国内外已屡见报道,但是对于高级别CIN细胞这一潜在癌前病变的培养及其的生物学特性的研究国内外鲜有报道。众所周知,癌细胞的生物学特性主要包括：①形态特征：细胞异型性如癌细胞大小形态不一,核质比显著高于正常细胞；核形态不一,并可出现巨核、双核或多核现象；核分裂像常增多。②生理生化特征：细胞接触抑制丧失；具有迁移性和侵袭性等。但是,对于高级别CIN这一癌前期病变细胞却仅从形态学特征方面进行了描述,对于其生理生化特征却未见报道。单从宫颈癌细胞和高级别CIN细胞的形态特征来看,二者均具有异型性,故很难从形态学上对二者进行区分。但是癌细胞增殖活性强,具有非接触性抑制、迁移性及侵袭性,与人类肿瘤侵袭有关的MMP-2亦明显升高。高级别CIN细胞是否亦具有上述特性?高级别CIN细胞为何可以局限于上皮内多年或消失而不发生转移?基于此,本项目拟对高级别CIN细胞进行原代培养,探索一种快速、简便、有效的培养方法,同时对其生物学特性进行体外研究,为宫颈癌及其癌前病变的进一步研究提供理论及实验依据。
第一部分：一种新的正常人宫颈上皮细胞原代培养技术的建立
研究目的：
1.提供一种新型培养基,既能促进细胞的贴壁,又能减少成纤维细胞的污染。
2.从培养器皿方面,探索一种能协同促进宫颈上皮细胞贴壁的方法。
3.探索一种高纯度的宫颈上皮细胞的体外培养的方法。
研究方法：
1.取人正常宫颈上皮组织,用Ⅰ型胶原酶消化分解后得到宫颈上皮细胞悬液。
2.将细胞分别接种到以下培养瓶中：①未经鼠尾胶原包被,仅含无血清培养基(keratinocyte serum-free medium, K-SFM);②未经鼠尾胶原包被,含5%胎牛血清的K-SFM;③用鼠尾胶原包被,仅含K-SFM;④用鼠尾胶原包被,含5%胎牛血清的K-SFM.
3.待细胞贴壁后,首次换液,将培养基全部换成K-SFM.
4.采用细胞免疫荧光检测宫颈上皮基层角蛋白(Keratin, K)5、K14和K19的表达。
结果：
1.在含5%胎牛血清的培养基中,细胞的贴壁速度较无血清的培养基快(约30%和10%)。
2.用鼠尾胶原I型包被的培养瓶中,细胞的贴壁速度较未经鼠尾胶原包被的培养瓶中快(约60%和30%)。
3.联合使用含5%胎牛血清的培养基和经鼠尾胶原Ⅰ型包被的培养瓶是最理想的培养宫颈上皮细胞的方法。
4. K5, K14和K19几乎在所有细胞的细胞浆中均呈阳性表达,但K5表达很弱。
结论：
1.低浓度胎牛血清可以提高上皮细胞的贴壁能力,而无血清培养基抑制成纤维细胞的生长。
2.联合使用5%胎牛血清的培养基和经鼠尾胶原Ⅰ型包被的培养瓶是一种新颖、简便、有效的人宫颈上皮细胞的培养方法。
3.我们的方法可以从成人宫颈上皮组织中快速得到大量高纯度的正常宫颈上皮细胞。
第二部分：人高级别宫颈上皮内瘤变细胞的原代培养和鉴定研究目的：
建立一种人小块宫颈瘤变组织来源的自然感染HPV的高级别宫颈上皮内瘤变细胞的体外培养方法；为高级别上皮内瘤变细胞生物学特性的研究提供实验基础。
研究方法：
1.取小块人宫颈瘤变组织,取出一小部分行HPV DNA分型检测。
2.将剩余瘤变组织用I型胶原酶消化分解后制成类细胞悬液(未经细胞筛过滤)。
3.将类细胞悬液接种到含5%胎牛血清+K-SFM的、经鼠尾胶原包被的培养瓶中。
4.一组细胞培养3天后首次换液并更换K-SFM,收集未贴壁细胞并重新种植到新的培养瓶中继续培养3天。另一组细胞培养6天后首次换液并更换K-SFM.
5.将第三代细胞收集后行HPV DNA分型检测。
6.通过细胞免疫荧光检测宫颈上皮基底层K14和K19,宫颈干细胞K17和P63的表达,对CIN细胞进行鉴定。
结果：
1.细胞培养的第1、3和6天,分别有30%、60%和80%的高级别CIN细胞贴壁,未贴壁细胞在第3天重新收集并继续培养3天后仍然有30%的细胞贴壁,但由于细胞密度较低很难长满培养瓶并传代。
2.传代后高级别CIN细胞仍然保持其大小不等、形状异常的形态,没有明显分化现象。
3.传代后高级别CIN细胞的HPV分型检测结果同原代一致。
4.K14和K19几乎在所有NUC细胞和高级别CIN细胞的胞浆中表达；但是,K17和P63仅在高级别CIN细胞的胞浆中表达。
结论：
1.我们将“组织块培养法”与“酶消化法”相结合制备了类细胞悬液,不仅克服了“组织块培养法”中细胞因移动受到限制而造成的生长缓慢,而且节省细胞过滤过程中丢失的细胞,获得了更多的CIN细胞,克服了CIN培养过程中因标本过小而造成的困难。
2.高级别CIN细胞培养的第6天可作为最佳首次换液时间。
3.我们建立了一种从小块宫颈瘤变组织获取自然携带HPV的高级别宫颈上皮内瘤变细胞的简单而实用的培养方法,为CIN病变的体外研究提供了实验基础。
第三部分：人高级别宫颈上皮内瘤变细胞生物学特性的体外研究研究目的：
通过与NUC细胞及宫颈癌Caski细胞的对比,观察人高级别CIN细胞的生物学行为如生长增殖能力、肿瘤标志物的表达及迁徙和侵袭能力等,探讨高级别CIN细胞的生物学特性,为宫颈癌前病变及宫颈癌的进一步研究及治疗提供理论及实验依据。研究方法：
1.应用MTT实验测定高级别CIN细胞及对照组NUC细胞和宫颈癌Caski细胞的生长曲线。
2.应用细胞接触抑制试验检测高级别CIN细胞的生长活性。当细胞生长到约80%-90%融合时,继续培养3-5天,观察细胞有无接触性抑制现象。
3.应用流式细胞技术,检测高级别CIN细胞及对照组NUC细胞和Caski细胞的生长周期。
4.应用DNA倍体分析技术,检测高级别CIN细胞及对照组NUC细胞和Caski细胞的异倍体比例。
5.采用细胞免疫荧光技术,检测高级别CIN细胞及其对照组NUC细胞和Caski细胞中肿瘤标志物Ki-67和p16的表达情况。
6.在酶联免疫分析实验中,应用竞争性抑制法测定高级别CIN细胞及其对照组NUC细胞和Caski细胞分泌性及细胞内基质金属蛋白酶2(matrix metalloproteinase2,MMP-2)水平；应用双抗体夹心法测定基质金属蛋白酶抑制因子2(Tissue inhibitors of metalloproteinase2, TIMP-2)的水平。
7.应用Transwell小室技术,检测高级别CIN细胞及其对照组NUC细胞和Caski细胞的迁移和侵袭能力。
8. SPSS13.0统计软件对数据进行分析：生长曲线用重复测量资料的方差分析；计量资料统计结果以均数士标准差表示,三组之间的差异比较采用方差分析。
结果：
1.高级别CIN细胞、NUC细胞和宫颈癌Caski细胞的生长速度明显不同(P<0.01),Caski细胞的生长速度明显快于高级别CIN细胞和NUC细胞(P<0.01),高级别CIN细胞的生长速度明显快于NUC细胞(P<0.01)。高级别CIN细胞生长曲线的延缓期明显缩短,Caski细胞的生长曲线没有明显的延缓期。
2.高级别CIN细胞贴壁生长汇合成单层后即停止生长,存在接触抑制现象；Caski细胞贴壁生长汇合成单层后继续生长,接触抑制现象消失。
3.细胞周期检测实验显示S期细胞比率(SPF):Caski细胞组>高级别CIN细胞组>NUC细胞组(P<0.01)。
4.DNA倍体分析实验中,高级别CIN细胞组和Caski细胞组异倍体细胞所占比例均明显高于NUC细胞组(P<0.01),但高级别CIN细胞组和Caski细胞组之间异倍体细胞所占比例无显著性差异(P=0.392)。
5.细胞免疫荧光显示,在几乎所有NUC细胞、高级别CIN细胞和Caski细胞的细胞核中,均可见Ki-67呈弥漫的强阳性染色。p16在NUC细胞、高级别CIN细胞和Caski细胞的细胞核和细胞浆中均呈阳性表达。
6. Caski细胞组分泌性MMP-2的含量明显高于NUC细胞组和高级别CIN细胞组(P<0.05),NUC细胞组与高级别CIN细胞组之间无显著性差异(P>0.05),三组细胞之间细胞内MMP-2的含量无显著性差异(P>0.05)；三组细胞之间分泌性和细胞内TIMP-2的含量及MMP-2/TIMP-2的比值无显著性差异(P>0.05)。
7. Transwell体外迁移和侵袭实验均表明：高级别CIN细胞的迁移能力明显优于NUC细胞,但显著低于Caski细胞(P<0.01)；高级别CIN细胞有侵袭能力,但明显低于Caski细胞(P<0.001),NUC细胞无明显侵袭能力。
结论：
1.高级别CIN细胞的生长活力较NUC细胞明显增强,但仍然具有接触抑制现象。
2.高级别CIN细胞与宫颈癌Caski细胞在增殖的过程中均出现了大量的异倍体细胞,说明高级别CIN细胞的增殖能力较强；细胞周期中S期细胞比率的升高,进一步说明了高级别CIN细胞具有较强的生长活力。
3.肿瘤标志物Ki-67和p16在NUC细胞、高级别CIN细胞和Caski细胞均呈阳性表达,说明它们可能仅仅是细胞增殖的标记物。
4.高级别CIN细胞及其对照组细胞内MMP-2和TIMP-2的含量及其比值相似,但分泌性MMP-2的含量低于Caski细胞；同时,高级别CIN细胞具有较弱的侵袭能力,进一步说明了分泌性MMP-2在侵袭中的作用；而高级别CIN病变基底膜的完整性,说明在原位癌到侵袭癌的演进过程中,除了细胞本身的恶性潜能外,实质与间质之间的相互作用起了重要的作用。
Cervical cancer is the most common gynecological cancer in developing countries and the incidence significantly decrease with the wide application of cervical screening test in recent years. It was found out that cervical cancer usually proceeded by a long phase of pre-malignant disease. These pre-malignant changes represent a spectrum of histological abnormalities ranging from cervical intraepithelial neoplasia (CIN) I (mild dysplasia) to CIN2(moderate dysplasia) to CIN3(severe dysplasia/carcinoma in situ). CINI will regress spontaneously in most cases and only0.3%may progress to cervical cancer, whereas CIN II and III will persist and progress to cervical cancer in about20%-45%of untreated CIN II/III lesions. Therefore CINII and CINIII are regarded as high-grade lesions. Fortunately, it is appears that the mean interval for progression of cervical precursors to invasive cancer is about10years, therefore we have enough time to detect and manage this precancerous lesion, and cervical cancer may be prevented subsequently. It is well established that almost all high-grade CIN cases are caused by persistent oncogenic human papillomavirus (HPV) infection and long latency period of viral infection is needed for CIN progression. However, viruses do not have their own metabolism, and require a host cell to make new products. Therefore, HPV does not culture in a laboratory outside a host cell. Culture of naturally HPV-infected CIN keratinocytes has significant value in exploring biological behavior of high-grade CIN in vitro and in vivo then, as well as the transforming process of neoplastic cervical keratinocytes.
Studies on normal uterine cervix (NUC) and CIN keratinocyte cultures, as well as characteristics of CIN keratinocytes, are poorly available due to the numerous technical and methodological problems associated with the in vitro culturing of these cells. Dysplasia is characterized by four major pathological microscopic changes including cells of unequal size, abnormally shaped, hyperchromatism and presence of mitotic figures. The primary basis for assessing the specific grade of CIN is the ratio of nucleus to cytoplasm in a given cell, and higher ratios are associated with higher grades of CIN. However, it is very difficult to differentiate dysplastic cells from malignant cells in morphology to some extent. As we all known, loss of contact-dependent growth inhibition, migration and invasion ability are biological behavior of malignant cells, and we wonder if high grade CIN keratinocytes have such characteristics? Why such CIN keratinocytes are limited to intraepithelial and not broken through into the stroma? In this study, we plan to establish a novel method for culturing normal human cervical keratinocytes and naturally HPV-infected high-grade CIN keratinocytes starting from small pieces of neoplastic cervical tissues. Additionally, we intend to explore the in vitro biological behavior of high-grade CIN keratinocytes and provide an experimental basis for the further study of precancerous lesion of the cervix and cervical carcinoma.
Part I:Establishment of a Novel Method for Primary Culture of Normal Human Cervical Keratinocytes
Objectives:
1. To investigate a modified culture medium which could improve cervical keratinocytes attachment and constrain the fibroblast growth as well.
2. To explore a special culture plastics bottle which may help to improve cervical keratinocytes attachment.
3. To explore a method which could obtain highly purified keratinocytes from normal human cervical epithelium in vitro.
Methods
1. Normal cervical epithelial tissue pieces were obtained and digested with type I collagenase to dissociate the cells and a single cell suspension produced.
2. The cells were seeded on the following culture plastics:(1) Uncoated plastic tissue culture bottles containing keratinocyte serum-free medium (K-SFM) without5%fetal bovine serum (FBS).(2) Uncoated plastic tissue culture bottles containing modified K-SFM supplemented with5%FBS.(3) Plastic tissue culture bottles coated with collagen type I from rat tail containing K-SFM without5%FBS.(4) Plastic tissue culture bottles coated with collagen type I from rat tail containing modified K-SFM supplemented with5%FBS.
3. After attachment, the medium were replaced with K-SFM without FBS.
4. The expression of basal keratins (K) of the ectocervical epithelium, K5, K14and K19were assayed by immunofluorescence with monoclonal antibodies to identify the cell purity.
Results
1. Cells attached to the culture plastic bottles more quickly in K-SFM supplemented with5%FBS than in K-SFM alone
2. Cells attached to tissue culture plastic bottles coated with collagen type I more quickly than uncoated plastic bottles.
3. The modified medium composed of K-SFM and5%FBS combined with a specific tissue culture plastic bottles coated with collagen type I from rat tail was the best method for culture of normal cervical epithelial cells.
4. Diffuse and strong cytoplasmatic immunostaining for keratin14and19was obtained in nearly all cultured cervical epithelial cells. But these cells stained weakly for K5.
Conclusions:
1. In the modified medium, low concentration FBS could improve cervical keratinocyte attachment, whereas K-SFM may constrain the fibroblasts growth.
2. The modified medium composed of K-SFM and5%FBS combined with a specific tissue culture plastic coated with collagen type I from rat tail was a novel, simple and effective method for culture of normal cervical epithelial cells in vitro.
3. We could rapidly obtain highly purified keratinocytes from normal human cervical epithelium in this study.
Part II:Primary Culture and Identification of High-grade Cervical Intraepithelial Neoplasia Keratinocytes from Human Neoplastic Cervical Biopsies
Objectives:
To investigated a novel method for the in vitro culturing of naturally HPV-infected high-grade CIN keratinocytes from small-sized human neoplastic cervical biopsies. To provide an experimental basis for different research purposes, particularly the further study of the biological characteristics of high-grade CIN keratinocytes.
Methods:
1. A small tissue fraction from a CIN II-III sample was excised for DNA extraction.
2. Small pieces of neoplastic tissue were digested with0.2%type I collagenase and single cell suspensions were obtained.
3. The isolated cells were seeded into T25tissue culture plastic bottles, which was coated overnight with2μg/cm2collagen type I from the rat tail, in medium containing K-SFM supplemented with5%FBS.
4. On day3, the serum-supplemented K-SFM medium was replaced with K-SFM medium, and the unattached cells in group1were recovered, reseeded into new T25tissue culture plastic bottles coated with collagen type I from the rat tail, and allowed to attach for three days. The medium was replaced with K-SFM alone on day6, and the unattached cells in group2were discarded. The medium was changed twice a week.
5. For the HPV genotyping of the sub-cultured CIN keratinocytes, a small number of the third-generation cells were subjected to DNA extraction.
6. The expression of basal keratins of ectocervical epithelium including keratin K14and K19; markers for cervical stem cell including P63and K17were assayed by immunofluorescence with monoclonal antibodies to identify the presence of CIN keratinocytes.
Results:
1. Approximately20%,60%, and80%of the high-grade CIN keratinocytes were attached to the culture plastic bottles on days1,3, and6, respectively. Although the viability of the unattached cells on the third day was more than80%, only30%of the remaining cells attached to the new culture plastic bottles, and the attached cells were unable to survive well because of the low cell density in group1.
2. The passaged CIN keratinocytes maintained their original unequally sized, abnormally shaped morphology and did not undergo differentiation.
3. The passaged CIN keratinocytes exhibited the same HPV genotype detected in the original primary cells.
4. K14and K19were found to be expressed in nearly all of the normal and CIN keratinocytes, whereas K17and P63were expressed only in high-grade CIN keratinocytes.
Conclusions:
1. We combine "explant tissue culture method" with "digestion culture method" in this study, and obtain plenty of cells.
2. The6th day may be appropriate time for the first medium change for primary cultures of high-grade CIN keratinocytes.
3. Our study proposes a simple and practical method for rapidly obtaining highly purified naturally HPV-infected high-grade CIN keratinocytes from small-sized neoplastic cervical tissues, and provides an experimental basis for the further study of the biological characteristics of high-grade CIN keratinocytes.
Part Ⅲ In Vitro Study of Biological Behavior on Primary Cultured Human High-grade Cervical Intraepithelial Neoplasia Keratinocytes Objectives:
Compared with NUC keratinocytes and Caski cells, we sought to explore the in vitro biological behavior of high-grade CIN keratinocytes including cell growth curve, cell cycle and DNA aneuploidy, expression of p16and Ki-67, and migration and invasion ability. This study could serve as a basis for the further study of cervical cancer and precancerous lesion of the cervix.
Methods:
1. High-grade CIN cells growth curve was measured with MTT, NUC keratinocytes and Caski cells were used as controls.
2. Contact growth inhibition assay was used to determine the proliferation of high-grade CIN keratinocytes and its controls. When the cultures reached eighty percent confluence, the cells were cultured for further3-5days to test the existence of contact growth inhibition.
3. Flow cytometry analysis was used to detect the cell cycles of high-grade CIN keratinocytes group and its controls.
4. DNA ploidy analysis was used to detect the DNA aneuploidy among high-grade CIN keratinocytes group and its controls.
5. Ki-67and p16expression were examined by immunofluorescence assays among high-grade CIN keratinocytes group and its controls.
6. Competitive inhibition enzyme linked immunosorbent assay (ELISA) and solid phase ELISA was used to determine the concentrations of MMP-2and TIMP-2respectively among high-grade CIN keratinocytes group and its controls.
7. Transwell assay was employed to test cell migration and invasion of high-grade CIN keratinocytes and the controls.
8. Quantitative data were expressed as means±standard deviation (SD), the significance of the difference between groups was evaluated with analysis of variance (ANOVA). Cell growth curve was analyzed with repeated measures ANOVA. All calculations were performed using SPSS13.0statistical software.
Results:
1. Compared with NUC cells, the cells growth speed of high-grade CIN keratinocytes was significantly fast; however, it was significantly slower than Caski cells (P<0.001). After2days of incubation, high-grade CIN keratinocytes entered the logarithmic growth phase which was2days earlier than NUC keratinocytes. No apparent lag phase was observed in the growth curve of Caski cells.
2. Cell contact growth inhibition was identified in high-grade CIN keratinocytes, and Caski cells exhibited a character of uncontrolled cell proliferation with loss of cell contact inhibition.
3. Compared with NUC cells, the S phase fraction (SPF) of high-grade CIN keratinocyte group was significantly high, but was lower than Caski cell group (P＜0.01).
4. DNA aneuploidy ratios of high-grade CIN keratinocyte group and Caski cell group were significantly higher than NUC keratinocyte group (P＜0.01). However, no significant difference was seen between high-grade CIN keratinocyte group and Caski cell group (P=0.392).
5. Nuclear immunostaining for Ki-67was obtained in nearly all of the cultured high-grade CIN keratinocytes and the controls incuding NUC cells and Caski cells. In addition, p16were found to be expressed in nearly all of the high-grade CIN keratinocytes and the controls nuclear and cytoplasm.
6. The concentration of extracelluar matrix metalloproteinase2(MMP-2) in Caski cell group was higher than high-grade CIN and NUC keratinocyte groups (P<0.05), but no significant difference was seen between high-grade CIN and NUC keratinocyte groups (P>0.05). Additionally, the concentrations of extracelluar tissue inhibitors of metalloproteinase2(TIMP-2), intracellular MMP-2and TIMP-2, and the ratio of MMP-2/TIMP-2were insignificantly different among high-grade CIN keratinocyte, NUC keratinocyte and Caski cell groups (P>0.05).
7. Cell migration and invasion assays indicated that the migration ability of high-grade CIN keratinocytes was much higher than NUC keratinocytes, but it was significantly lower than Caski cells (P＜0.001). High-grade CIN keratinocytes had the ability of invasion, but the invasion power was much lower than Caski cells (P<0.001). NUC keratinocytes had no ability of invasion.
Conclusions:
1. Proliferation ability of high-grade CIN keratinocytes was much higher than NUC keratinocytes, but cell contact growth inhibition was still remained.
2. Plenty of DNA aneuploidy occurred during the course of proliferation of high-grade CIN keratinocytes and Caski cells, suggesting that high-grade CIN keratinocytes had the ability of high proliferation. Increased S phase fraction in cell cycle of high-grade CIN keratinocytes further supported this point.
3. Ki-67and p16were expressed not only in high-grade CIN keratinocytes and Caski cells, but also in NUC keratinocytes, suggesting that both Ki-67and p16were probably only markers of cell proliferation.
4. The relatively equal concentrations of extracelluar TIMP-2, intracellular MMP-2and TIMP-2among high-grade CIN keratinocyte group and it controls, the lower concentrations of extracelluar MMP-2and the mild ability of invasion in high-grade CIN keratinocytes, suggested that extracelluar MMP-2play an important role in the course of invasion. However, the basal membranes still keep intact in high-grade CIN lesions. Our study suggested that during the progression from carcinoma in situ to invasive cancer, the interaction of parenchyma and stroma play an important role in addition to to the malignant potential of the cell itself.
引文
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