两种体外培养兔膀胱变移上皮细胞方法的比较

目的 比较组织贴块法和酶消化法体外培养兔膀胱变移上皮细胞的优缺点,探索简单、高效培养膀胱变移上皮细胞的方法,为膀胱组织工程种子细胞的培养提供实验基础。方法 采用组织贴块法和酶消化进行兔膀胱变移上皮细胞体外培养,相差显微镜下观察其生长特点,应用细胞免疫荧光染色对细胞进行鉴定,测定细胞生长曲线了解细胞生长的基本规律。结果 培养的细胞具有上皮细胞的典型形态,生长曲线呈“S”形,角蛋白（CKAE1/AE3）单克隆抗体免疫荧光染色阳性,波形蛋白染色阴性。结论 组织贴块法和酶消化法均能成功培养出兔膀胱变移上皮细胞。组织贴块法原代培养时间长,但是成功率高。酶消化法可以在较短时间内获取大量细胞,但是操作步骤多,细胞容易污染或损伤。     

上皮细胞条件培养液对BMSCs分化的影响

目的 探讨上皮细胞条件培养液(epithelial cell conditioned medium,ECCM)体外诱导犬BMSCs向上皮细胞分化的可行性.方法 成年健康雄性比格犬1只,体重10 kg.于犬髂后上棘采用骨髓穿刺法取骨髓5 mL,分离培养BMSCs.取犬口腔黏膜下组织,剪成约4 mm×4 mm大小,制备ECCM.取第2代BMSCs以2×104个/孔细胞密度接种,实验组于ECCM中培养,对照组于低糖DMEM完全培养基中培养.观察两组细胞形态特征,MTT法绘制生长曲线,诱导培养21 d免疫组织化学染色鉴定上皮细胞特异性标志物--细胞角蛋白19(cytokeratinl9,CK-19)和细胞角蛋白AE1/AE3,透射电镜观察细胞超微结构.结果 倒置相差显微镜下见两组细胞均呈长梭形,均匀分布,折光性较强,增殖迅速.两组细胞生长曲线均呈"S"形,实验组生长曲线较对照组右移,提示ECCM对细胞增殖有抑制作用.实验组CK-19和细胞角蛋白AE1/AE3免疫组织化学染色均呈阳性反应,对照组呈阴性.透射电镜下实验组细胞胞浆内可见紧密连接.结论 ECCM体外有诱导同种BMSCs向上皮细胞分化的作用.     

人类肥大乳房乳腺上皮细胞的原代培养

目的 探讨人类肥大乳房乳腺上皮细胞的原代培养方法.方法 采用胶原酶消化培养法,在体外进行人类肥大乳房乳腺上皮细胞的分离培养,用倒置显微镜观察、细胞爬片、HE染色和细胞角蛋白免疫组织化学染色的方法对分离培养的细胞进行形态学观察和鉴定.结果 倒置显微镜下观察细胞形态呈鹅卵石型或多角型,部分形态不规则,增殖的过程中形成岛屿状闭合型的细胞群,细胞之间连接紧密.细胞HE染色可见细胞胞质呈粉红色或浅紫色,细胞核呈蓝紫色,圆形或椭圆形,核中可见深蓝色的染色体.免疫组化鉴定结果显示,培养的细胞胞浆内可见棕黄色的细胞角蛋白着色,表达上皮细胞特异的细胞角蛋白18.结论 应用酶消化法和条件培养液可以获得纯度较高的人类肥大乳房乳腺上皮细胞.     

输尿管种子细胞分离及组织工程输尿管网状支架构建

目的 探讨输尿管上皮种子细胞的分离培养和增殖规律,以及构建种植种子细胞输尿管组织工程网状支架的可行性.方法 采用自制输尿管翻转分离器,分离实验用小型猪输尿管上皮种子细胞.体外培养并鉴定输尿管上皮种子细胞.观察输尿管种子细胞形态变化,噻唑蓝(MTT)比色法检测原代、第3代、第5代和第7代种子细胞增殖特性.后将输尿管种子细胞种植到电纺丝输尿管网状支架,于支架孵育第1、3、5、7、9天检测种子细胞增殖活性,并绘制细胞生长曲线.结果 成功分离培养输尿管上皮种子细胞,角蛋白抗体和尿路上皮特异抗体UroplakinⅡ证实为输尿管尿路上皮细胞.输尿管上皮种子细胞接种24 h基本贴壁,呈多角形团簇样生长,8d时细胞融合70％以上,呈铺路石状排列.输尿管上皮种子细胞在电纺丝输尿管网状支架上生长增殖良好.结论 改良输尿管上皮细胞分离方法可获得大量纯化的输尿管上皮种子细胞,其在输尿管网状支架上生长增殖良好,成功构建输尿管组织工程网状支架有望应用于输尿管损伤替代修复.     

阻塞性黄疸猪胃粘膜表皮生长因子受体的免疫组化研究

探讨阻塞性黄疸时胃粘膜上皮细胞表皮生长因子受体的变化及其在胃粘膜病变机制中的作用。方法 采用免疫组化技术，辅以光镜及电子显微镜观察，研究阻塞性黄疸时猪胃粘膜上皮细胞表上生长受体的表达。结果 阻塞性黄疸猪胃粘上皮细胞表皮生长因子受本明显减少，呈弱阳性或阴性，正常对照组为强阳性。     

体外诱导骨髓间充质干细胞分化为上皮细胞的初步实验研究

目的:探讨表皮生长因子(EGF)体外诱导骨髓间充质干细胞(MSCs)分化为上皮细胞的可行性.方法:抽取小型香猪的骨髓,经密度梯度离心分离纯化MSCs,培养扩增后,用含EGF不同介质诱导,观察细胞形态的变化,免疫组织化学染色和流式细胞仪鉴定角蛋白的表达.结果:免疫组织化学染色显示EGF诱导后3dMSCs角蛋白表达较弱,7d角蛋白表达增强.流式细胞仪检测发现EGF诱导后3d表达角蛋白的MSCs较少,7d表达角蛋白的细胞数量明显增加.结论:MSCs在体外EGF诱导下可能分化为上皮细胞.     

在体诱导骨髓间充质干细胞分化为表皮细胞的初步研究

目的探讨骨髓间充质干细胞(MSCs)分化为表皮细胞的可行性.方法抽取小型香猪的骨髓,经密度梯度离心分离、纯化间充质干细胞及培养扩增后,应用5-溴脱氧尿嘧啶(BrdU)标记技术进行细胞标记.将已标记的细胞以注射方式回植到提供骨髓的猪的皮内及皮下,分别于注射后1、2、4周取材,常规石蜡包埋,行BrdU和角蛋白免疫荧光双染色,激光共聚焦显微镜观察.结果大多数BrdU阳性细胞聚集在真皮中的小血管周围.但有少数BrdU阳性标记细胞出现在表皮的棘层和颗粒层,并同时表达角蛋白.结论在皮肤微环境下骨髓间充质干细胞具有分化为表皮细胞的潜能.     

组织工程化膀胱壁复层结构的体外构建

目的 探讨膀胱缺损组织工程修复方法.方法 机械法去除膀胱黏膜层、肌层和浆膜层,仅保留膀胱黏膜下层.经SDS、Trixon-100和三蒸水处理去除细胞结构,制备获得膀胱脱细胞基质移植物(BAMG)作为支架材料.取成年猪膀胱壁,机械法分离膀胱肌层和黏膜层.以酶消化法分别获取膀胱尿路上皮细胞和平滑肌细胞.常规细胞传代和扩增后,将膀胱平滑肌细胞和尿路上皮细胞分别接种在BAMG浆膜面和黏膜面.细胞-材料复合物体外培养4周并行组织学鉴定.结果 HE和Masson染色鉴定发现,BAMG以胶原成分为主,内部未见明显细胞残留.免疫荧光方法鉴定结果显示,膀胱尿路上皮细胞uroplakin Ⅱ阳性,膀胱平滑肌细胞α-平滑肌肌动蛋白阳性.体外培养4周后,BAMG浆膜面和黏膜面分别形成连续的复层结构尿路上皮层和膀胱平滑肌层,免疫组化显示平滑肌层α-平滑肌肌动蛋白表达阳性,尿路上皮层广谱角蛋白表达阳性.结论 以膀胱脱细胞材料作为支架,尿路上皮细胞和膀胱平滑肌细胞作为种子细胞,能够在体外构建形成包含膀胱黏膜层及平滑肌层的复层膀胱壁结构.细胞-材料复合物的体外构建将为体内膀胱缺损的组织工程修复提供实验依据.     

膀胱移行上皮细胞的体外培养研究

目的：探索并建立大鼠膀胱移行上皮细胞的体外培养方法，为膀胱癌相关研究提供实验依据。方法：获取Wistar大鼠膀胱粘膜，采用Dispase酶消化法收集上皮细胞。动态观察细胞形态变化、生长增殖情况；对培养细胞进行细胞周期检测及超微结构观察，并行免疫组织化学鉴定。结果：培养细胞为二倍体移行上皮细胞，无成纤维细胞混杂生长。免疫组织化学证实角蛋白染色阳性。结论：膀胱移行上皮细胞体外培养为体外研究提供了理想的模型。     

人脂肪间充质干细胞诱导分化尿路上皮细胞的研究

目的 探讨间接共培养法诱导人脂肪间充质干细胞向尿路上皮细胞定向分化的可行性.方法 人脂肪间充质干细胞提取自吸脂术患者的废弃脂肪组织中,经流式细胞法来鉴定人脂肪间充质干细胞的表型.应用Transwell培养系统构建间接共培养模型,上层种植输尿管上皮细胞(1×l04/cm2),下层种植脂肪间充质干细胞(0.5×104/cm2),共培养14 d.采用免疫荧光方法鉴定尿路上皮标志物[细胞角蛋白-18 (CK-18),尿斑蛋白2(UP2)]表达.将诱导后的细胞种植于Ⅰ型胶原+聚乳酸混合电纺丝输尿管支架材料上,体外培养7d,免疫荧光法鉴定诱导后的细胞在输尿管支架材料上尿路上皮标志物表达.苏木素-伊红(HE)染色、Livedead法检测观察诱导后细胞生长.结果 共培养7d后,诱导后的细胞形态呈现尿路上皮细胞样,14 d后,免疫荧光检测表明,40％～50％的干细胞表达尿路上皮标志物(CK-18及UP2).诱导后的细胞种植在输尿管支架材料上,细胞增殖生长良好,呈铺展状态生长,活细胞占总数的90％以上(Livedead),并且表达尿路上皮标志物.结论 使用间接共培养法能成功诱导人脂肪间充质于细胞向尿路上皮细胞分化,为输尿管等泌尿系统组织工程研究提供了一种新的种子细胞.     

Aldosterone induces collagen synthesis via activation of extracellular signal-regulated kinase 1 and 2 in renal proximal tubules

Aim: Aldosterone plays a crucial role in renal fibrosis by inducing mesangial cell proliferation and promoting collagen synthesis in renal fibroblasts. However, renal proximal tubule involvement in aldosterone-induced collagen synthesis has not yet been identified. The aim of this study was to examine the potential role of aldosterone in collagen expression and its possible mineralocorticoid receptor (MR)-dependent pathway, mediated by activation of extracellular signal-regulated kinase 1 and 2 (ERK1/2) in cultured human renal proximal tubular epithelial (HKC) cells. Methods: After HKC cells were stimulated by aldosterone with different concentrations for various time and periods, the gene expression and protein synthesis of collagen I, II, III and IV were measured by real-time polymerase chain reaction and western blot, respectively. ERK1/2 activation, α-smooth muscle actin (α-SMA), and E-cadherin were also detected by western blot. Results: Aldosterone can increase ERK1/2 phosphorylation of human renal proximal tubular epithelial cells in a time- and dose-dependent manner. Although aldosterone had no effect on collagen I and II expression, it increased expression of α-SMA and collagen III and IV and decreased that of E-cadherin in HKC cells after 48 h. These effects could be prevented by a ERK pathway inhibitor, U0126, or by a selective MR antagonist, spironolactone. Conclusion: The results suggest that aldosterone plays a pivotal role in tubulointerstitial fibrosis by promoting tubular epithelial–mesenchymal transition and collagen synthesis in proximal tubular cells. The process is MR-dependent, and mediated by ERK1/2 mitogen-activated protein kinase pathway.     

Growth of Differentiated Ovine Tracheal Epithelial Cells In Vitro

Culture of ovine tracheal epithelial cells is a useful tool for conducting various in vitro studies. We describe herein an in vitro technique and the conditions for culturing primary epithelial cells derived from tracheas of adult sheep. Ovine tracheas were surgically removed from 2‐ to 3‐month‐old healthy sheep and tracheal epithelial cells were isolated by 0.15% pronase digestion. After epithelial cells isolation, a Millicell insert with porous membrane was coated with 0.05% human placental collagen and the epithelial cells were added to the membrane. To create an air–liquid interface environment for the cells, the apical compartment of the membrane containing the tracheal epithelial cells was left exposed to 5% CO₂ at 37°C for 2 days then increased to 9% CO₂ while cells in the basolateral compartment underneath the membrane contained the growth medium necessary for cells nourishment. Pepsin digestion was more effective in reducing the number of fibroblasts than other procedures. Cells were allowed to grow for 6–7 days to form a confluent monolayer and nearly 21 days for cilia formation on the apical surface as determined by light microscopy of haematoxylin and eosin‐stained sections of membranes. In order to further confirm the epithelial origin of cells, cells were stained for cytokeratin antigen by immunohistochemistry. Most ciliated epithelial cells were immunoreactive for cytokeratin. This is the first report of differentiated ovine tracheal epithelial cells growth and isolation. This technique can be used in numerous in vitro investigative studies in ovine species as an animal model for human disease.     

Transplantation of tracheal epithelial cells onto a prefabricated capsule pouch with fibrin glue as a delivery vehicle

OBJECTIVE: The purpose of this study was to investigate whether in vitro cultured tracheal epithelial cells can be transplanted onto a prefabricated capsule surface in vivo for possible use in tracheal reconstruction. METHODS: Tracheal epithelial cells from 12 donor inbred rats were harvested for culture and expansion. In 16 recipient inbred rats, 2 sterile cylinders made of silicone rubber were implanted in each rat bilaterally in the folds of both the left and right anterior rectus sheath by wrapping the sheaths around the cylinders to induce a capsule formation. Ten days later, the cell cultures were divided and suspended in 1 of 2 delivery vehicles (standard culture medium or fibrin glue) and implanted onto the capsule surface. To compare the 2 delivery vehicles, we used fibrin glue on one side and the standard culture medium on the other. RESULTS: After 2 (group 1, n = 8) and 4 (group 2, n = 8) weeks, histologic findings, immunohistochemical staining, and electron microscopy demonstrated the capsule to be covered with a tracheal neoepithelium in group 1 and additional ciliated cells and secretory cells in a confluent layer in group 2 but only on the side with fibrin glue as the delivery vehicle. No viable epithelial cells were identified on the side with the standard culture medium in either group. CONCLUSION: We conclude that cultured epithelial cells can be successfully transplanted onto a prefabricated capsule surface with fibrin glue, which will differentiate into morphologic, nearly normal epithelium, showing potential for tracheal reconstruction.     

Age effect of type I collagen on morphogenesis of Mardin-Darby canine kidney cells

BACKGROUND: Mardin-Darby canine kidney (MDCK) cells cultured in hydrated collagen gels develop simple epithelial cysts or branching tubules, depending on the presence of hepatocyte growth factor (HGF). Constituents of extracellular matrix can modulate the morphogenesis of MDCK cells. Collagen is one of the few well-defined structural entities that display gross structural changes with aging. This study was conducted to delineate the effects of age-induced changes of collagen on the morphogenesis of MDCK cells cultured in collagen gel. METHODS: We employed Y224 and MDCK clone II 3B5 cells to study cystogenesis and branching tubulogenesis, respectively. Cells were cultured in three-dimensional collagen gels prepared from 1-, 4-, 8-, and 16-month-old rat tail tendons, and their capacity to develop cysts or branching tubules was assessed. We also analyzed the compositions and physical structures of collagen of various ages. RESULTS: Y224 cells developed generally larger spherical cysts in collagen gels prepared from rats that were more than four months old. The ratio of apoptosis of cells cultured in one-month-old collagen gel was markedly higher than in the gel of older ages. The results were consistent with the observations that collagen gel overlay-induced apoptosis of Y224 cells in one-month-old collagen was higher than that in older collagen. On the other hand, 3B5 cells exhibited a remarkable scattering morphology when cultured in one- or four-month-old collagen gel with HGF. In contrast, 3B5 cells exhibited more intercellular adhesion and were organized into branching tubule structures only in the collagen gel that was more than eight months old. The differences in morphogenesis could be explained by the observations that collagen of younger ages exerted markedly higher HGF-triggered migration capability than collagen of older ages. CONCLUSIONS: Age-related alterations in collagen influence epithelial cell morphogenesis via regulation of cell apoptosis, proliferation, and/or motility.     

组织工程颌下腺细胞与胶原海绵复合培养的实验研究

目的研究大鼠颌下腺细胞在胶原海绵材料支架上的生长情况。方法取8d龄Wistar大鼠颌下腺细胞，传代培养至第2代细胞，按2×10^4／ml注射法接种于5mm×5mm×2mm胶原海绵表面进行培养。术后1、2、3周行组织学观察、扫描电镜观察胶原海绵上接种颌下腺细胞形态结构特点；取复合培养3周的颌下腺细胞行免疫组织化学细胞角蛋白（cytokratin8．13，CK8．13）、α-平滑肌肌动蛋白（α-smooth muscular actin，α-SMA）染色，透射电镜观察细胞超微结构，鉴定细胞来源。分别取复合培养1d，1、2、3周的培养上清，用Amano法测定淀粉酶含量，检测与胶原海绵复合培养的颌下腺细胞功能。结果细胞接种后第1周细胞分散于材料表面，无细胞突起形成；第2周细胞数量有所增加、细胞突起形成并锚定于胶原海绵表面；第3周时附着的细胞数目增多，可见细胞表层有丝状纤维形成。免疫组织化学染色观察复合培养的颌下腺细胞上皮细胞特异性抗体CK8。13呈强阳性，肌上皮细胞特异性抗体α-SMA染色呈阳性。透射电镜下颌下腺上皮细胞表面可见微绒毛、胞浆皱褶和细胞顶部的酶原颗粒，胞核大卵圆形，胞质内见线粒体和粗面内质网。随着接种后培养时间的延长，与胶原海绵复合培养的颌下腺细胞分泌的淀粉酶含量有不同程度的增加。结论胶原海绵具有良好的细胞相容性，颌下腺细胞与胶原海绵复合培养，细胞可保持增殖分化能力及分泌功能，有望成为颌下腺细胞的载体应用于组织工程支架材料。     

Puromycin aminonucleoside suppresses integrin expression in cultured glomerular epithelial cells

Puromycin aminonucleoside (PAN)-induced nephrosis is a well-described model of human idiopathic nephrotic syndrome, but the mechanism of PAN's effect is not completely understood. Because PAN injection into rats results in retraction of glomerular epithelial cell foot processes and glomerular epithelial cell detachment, it was hypothesized that PAN might alter the contacts between these cells and the glomerular basement membrane. The major integrin expressed by glomerular epithelial cells is alpha3beta1, which mediates attachment of these cells to extracellular matrix proteins including type IV collagen. T-SV 40 immortalized human glomerular epithelial cells were used to study PAN's effects on alpha3beta1 expression, as well as that of podocalyxin and the slit diaphragm component ZO-1. Glomerular epithelial cells were seeded into plastic flasks and allowed to attach and proliferate for 48 h. The cells were then incubated for another 48 h in media containing 0, 0.5, or 5.0 microg/ml PAN. PAN exposure resulted in dose-dependent decreases in alpha3 and beta1 expression, both at the protein level and at the mRNA level. This was accompanied by a significant decrease in the adhesion of glomerular epithelial cells to type IV collagen. PAN did not affect ZO-1 protein expression. Treatment with PAN increased the expression of podocalyxin at the protein and mRNA levels. Reduced glomerular epithelial cell expression of alpha3beta1 integrins and impaired adhesion to type IV collagen may contribute to the glomerular epithelial cell detachment from glomerular basement membrane seen in the PAN nephrosis model.     

Proliferation and differentiation of rat dorsal prostatic epithelial cells in collagen gel matrix culture, focusing upon effects of adipocytes

BACKGROUND: Prostatic epithelial cells organize functional acinus structures under epithelial extracellular matrix and epithelial-stromal cell interactions. Recently, the adipose tissue, which surrounds and even exists within the prostate, has been suggested to affect the differentiation and proliferation of some cell types. Therefore, tissue fragments, which consist mainly of epithelial and fibromuscular stromal cells, were cultured in three-dimensional collagen gel matrix culture with adipocytes. METHODS: Tissue fragments of rat dorsal prostate, including both epithelial and fibromuscular stromal components, were cultured in collagen gel with or without adipocytes. Epithelial cell differentiation was evaluated with the reconstruction of acinus-like structures and with immunohistochemistry of rat dorsal prostate-specific proteins, dorsal protein-1 and probasin. The proliferation was examined by uridine uptake. RESULTS: Under coculture of the fragments and adipocytes, epithelial cells reconstructed more differentiated acinus-like structures surrounded by fibromuscular stromal cells than tissue fragment culture without adipocytes. Dorsal protein-1 and probasin expressions of epithelial cells in this coculture system were the same as in rat prostate in vivo. In the coculture, epithelial cells had a higher proliferation activity. CONCLUSION: These results indicate that adipocytes promote proliferation and differentiation of prostatic epithelial cells. Our new culture model with adipocytes suggests the importance of cell-cell interactions, including those of epithelial cells and adipocytes.     

终末期糖基化终产物通过转化生长因子依赖和非依赖途径介导NRK52E细胞转分化和胶原Ⅰ的合成

目的探讨终末期糖基化终产物（AGEs）介导肾小管上皮细胞转分化和胶原（Col）Ⅰ合成的分子机制。方法体外培养正常大鼠近端肾小管上皮细胞系（NRK52E），应用自制的AGE-牛血清白蛋白（BSA）刺激NRK52E细胞。免疫细胞化学方法检测不同时间磷酸化（P）Smad2／3核转位情况。ELISA方法检测细胞培养上清TGF-β1的水平。RT-PCR方法检测α-平滑肌肌动蛋白（SMA）、E-钙黏着糖蛋白（cadherin）和ColⅠmRNA表达。Western印迹检测α-SMA、E-cadherin和ColⅠ蛋白的表达。同时观察TGF-β1中和抗体对AGE-BSA上述效应的阻断作用。结果基础状态下，NRK52E细胞存在低水平p-Smad2／3核表达（16％）。与BSA对照组比较，AGE—BSA以时间依赖方式上调NRK52E细胞p-Smad2／3核转位，其高峰出现在30min（68％比30.5％，P〈0．01）和24h（76％比31．3％，P〈0．01）。AGE—BSA显著上调α-SMA和ColⅠmRNA和蛋白表达；下调E-cadherin mRNA和蛋白的表达；并能促进NRK52E细胞合成和分泌TGF-β1。TGF-β1中和抗体能明显抑制AGE—BSA介导的24hp-Smad2／3核转位（25．2％，P〈0．01），但不能阻抑30min活化高峰；能明显抑制AGE-BSA介导的α-SMA和ColⅠmRNA和蛋白表达．以及显著地上调E-cadherin mRNA和蛋白的表达。结论AGEs通过TGF-β依赖和非依赖途径诱导肾小管上皮细胞Smads信号通路活化，促进其向肌成纤维母细胞转分化和ColⅠ的合成。     

Porcine small intestinal submucosa (SIS): a bioscaffold supporting in vitro primary human epidermal cell differentiation and synthesis of basement membrane proteins

The growth pattern of human epidermal cells, fibroblasts or Swiss mouse 3T3/J2 fibroblasts cultured upon the extracellular matrix (ECM) derived from small intestinal submucosa (SIS) was evaluated. The cell/SIS composites were grown submerged, then maintained in air/liquid interface for 2, 7, 10 or 14 days. The presence of differentiation-related keratins 10, 14 and 16, FN, laminin, collagen type VII and collagen type IV was determined by immunohistochemical methods in SIS alone and in the SIS/cell composite. Only FN could be detected in SIS alone. SIS supported the formation of an epithelial structure with suprabasal expression of K16 and regional suprabasal expression of K10. The epidermal cells were K14 positive and tended to 'invade' the SIS to various degrees. Following the growth of epidermal cells and fibroblasts on the SIS substratum, immunolabeling of FN, laminin, collagen type VII and collagen type IV was observed in a cell-associated pattern. The fibroblasts commonly invaded the SIS, when co-cultivated with epidermal cells on the opposite side of the SIS. The ability of SIS to support epidermal cell/fibroblast attachment, migration and/or proliferation and differentiation with deposition of basement membrane (BM) components indicates that the composite model may be useful for studying cell-matrix interactions and for investigation as a dermal substitute.