Regeneration of immature tissue (fetal liver) functions utilizing a tissue-engineering approach

众所周知，胎儿肝脏具有肝脏和造血功能，含有大量未分化的细胞。本研究从组织工程的角度对胎儿肝细胞（FLCs）和骨髓细胞（BMCs）进行了长期三维培养，并研究了这些细胞的增殖和分化能力。采用多孔聚乙烯醇（PVF）树脂作为三维支架，进行三维培养和常规单层培养作为对照。在小鼠FLCs的长期三维培养中长达1个月，FLCs比单层培养更丰富和稳定地分泌白蛋白，这是一种具有代表性的肝脏特异性功能。此外，补充oncostatin M可显著刺激FLCs的增殖和白蛋白分泌，尤其是在三维培养中。在小鼠和猪FLCs的三维灌注培养中，这些细胞在普通灌注速率条件下很容易失去活力和功能，表明FLCs对介质流速非常敏感。然而，猪FLCs在这些灌注培养中比小鼠细胞更稳定，并且在低流速条件下表现出较长的白蛋白分泌能力。因此，利用三维培养的猪FLCs开发生物人工肝脏有望成为现实。考虑到造血功能，我们进行了小鼠骨髓干细胞的三维培养。在三维培养中，实现了bmc的高密度培养，这些细胞比单层培养中含有更丰富的祖细胞。此外，在三维培养中，无论是BMCs与基质细胞共培养，还是在较低的环境氧张力下培养，祖细胞的增殖都得到了显著改善。因此，bmmc的三维培养也被认为是一种有效扩增骨髓未成熟细胞的有前途的方法。少

Fetal livers are known to perform hepatic and hematopoietic functions, and contain undifferentiated cells abundantly. In the current study, long-term three-dimensional (3-D) cultures of fetal liver cells (FLCs) as well as bone marrow cells (BMCs) were performed from the tissue engineering viewpoints, and abilities of proliferation and differentiation of these cells were investigated.As a 3-D scaffold, porous polyvinyl formal (PVF) resin was adopted, and the 3-D cultures as well as conventional monolayer cultures as controls were performed. In the long-term 3-D cultures of murine FLCs for up to 1 month, the FLCs secreted albumin, a representative liver-specific function, more abundantly and stably than those in the monolayer cultures. Moreover, proliferation and albumin secretion of the FLCs were dramatically stimulated by supplementation of oncostatin M, especially in the 3-D cultures.In the 3-D perfusion cultures of the murine and porcine FLCs, these cells easily lost their viability … More and functions under conditions of ordinary perfusion rate, suggesting that FLCs are quite susceptible to medium flow rates. However, porcine FLCs were rather stable in these perfusion cultures than murine cells, and showed prolonged albumin secretion ability under a low flow rate condition. Therefore, the development of a bioartificial liver using 3-D cultured porcine FLCs is expected to be realistic.Respecting hematopoietic functions, 3-D cultures of murine BMCs were performed. In the 3-D cultures, high-density cultures of BMCs were achieved, and these cells contained progenitor cells more abundantly than in the monolayer cultures. Moreover, proliferation of the progenitor cells in the 3-D cultures was found to be considerably improved either by coculture of the BMCs with stroma cells or by cultures under a lowered ambient oxygen tension. From these facts, the 3-D cultures of BMCs were considered to be a promising method for effective expansion of the bone marrow immature cells as well. Less