Institute of Pathology, Medical Faculty, RWTH Aachen University, 52074 Aachen, Germany.
Differentiation. 2010 Mar;79(3):182-93. doi: 10.1016/j.diff.2010.01.005. Epub 2010 Feb 11.
During early embryogenesis, mesenchymal cells arise from the primitive epithelium and can revert to an epithelial phenotype by passing through mesenchymal-to-epithelial transition (MET). Mesenchymal stem cells (MSC) of the Wharton's Jelly of the umbilical cord (UC-MSC) express pluripotency markers underlining their primitive developmental state. As mesenchymal stem cells from bone marrow (BM-MSC) possess a strong propensity to ameliorate mesenchymal tissue damage, UC-MSC might also be able to differentiate into cells apart from the mesoderm, allowing replacement of ectodermal and mesodermal tissues. In this study, we analysed the possible epidermal differentiation of UC-MSC on dermal equivalents (DEs) consisting of collagen I/III with dermal fibroblasts and subjected to the culture conditions for tissue engineering of skin with keratinocytes. The culture conditions were further modified by pre-treating the cells with 5-azacytidine or by supplementing the medium with all trans retinoic acid. Interestingly, a subpopulation of UC-MSC (29%) co-expressed pan-cytokeratin (epithelial marker; pan-CK) and vimentin (mesenchymal marker) after isolation. Under the three-dimensional conditions of skin, the number of pan-CK(+)-cells increased to >30% after 21 days of cultivation, while under osteogenic culture conditions the cells were pan-CK-negative, thus showing the influence of the artificial niche. Nevertheless, the pan-CK-expression was neither accompanied by typical epithelial morphology nor expression of other epidermal markers. The pan-CK-detection can be explained by the expression of cytokeratins in myofibroblasts. UC-MSC expressed alpha-smooth muscle actin after isolation and displayed all features of functional myofibroblasts like morphology, cell-mediated contraction of a collagen gel and production of components of the extracellular matrix (ECM). The treatment with all trans retinoic acid or 5-azacytidine could neither induce an epidermal differentiation nor enhance the myofibroblastic differentiation. Concluding, UC-MSC might be an interesting cell source to support the regeneration of wounds by their differentiation into myofibroblasts and their extensive synthesis of ECM components.
在胚胎早期，间充质细胞从原始上皮细胞中产生，并通过间质上皮转化（MET）可恢复为上皮表型。脐带华通氏胶（UC-MSC）的间充质干细胞在表达多能性标记物的情况下表现出原始发育状态。由于骨髓间充质干细胞（BM-MSC）具有强烈改善间充质组织损伤的倾向，因此 UC-MSC 也可能能够分化为除中胚层以外的细胞，从而替代外胚层和中胚层组织。在这项研究中，我们分析了 UC-MSC 在真皮等效物（DE）上分化为表皮细胞的可能性，真皮等效物由 I/III 型胶原蛋白组成，其中包含真皮成纤维细胞，并在角质形成细胞的皮肤组织工程培养条件下进行培养。通过用 5-氮杂胞苷预处理细胞或在培养基中补充全反式视黄酸，进一步修改了培养条件。有趣的是，UC-MSC 的一个亚群（29%）在分离后同时表达广谱细胞角蛋白（上皮标记物；pan-CK）和波形蛋白（间充质标记物）。在皮肤的三维条件下，培养 21 天后，pan-CK（+）细胞的数量增加到超过 30%，而在成骨培养条件下，细胞为 pan-CK 阴性，表明人工基质的影响。然而，pan-CK 的表达既没有伴随典型的上皮形态，也没有表达其他表皮标记物。pan-CK 的检测可以通过肌成纤维细胞中细胞角蛋白的表达来解释。UC-MSC 在分离后表达α-平滑肌肌动蛋白，并显示出功能肌成纤维细胞的所有特征，如形态、细胞介导的胶原蛋白凝胶收缩以及细胞外基质（ECM）成分的产生。用全反式视黄酸或 5-氮杂胞苷处理既不能诱导表皮分化，也不能增强肌成纤维分化。总之，UC-MSC 可能是一种有趣的细胞来源，可以通过分化为肌成纤维细胞和广泛合成 ECM 成分来支持伤口再生。
