Biochemical and Functional Changes of Rat Liver Spheroids During Spheroid Formation and Maintenance in Culture: I. Morphological Maturation and Kinetic Changes of Energy Metabolism, Albumin Synthesis, and Activities of Some Enzymes

Mingwen Ma, Jinsheng Xu, and Wendy M. Purcell
http://www3.interscience.wiley.com/cgi-bin/abstract/106563224/ABSTRACT?CRETRY=1&SRETRY=0

There have been many studies in the past observing how liver cells function when cultured on monolayers. Cells that aggregate into spheroids function much longer and superior (liver-like) to those cultured as monolayers in a dish. Spheroids are gobular formation of cells that form a three-dimensional, multicellular aggregate. Such a formation is favored for the cells will maintain cell-cell contact and maintain more liver-specific functions, as in secretions. Nevertheless, does spheroids really act like liver cells? The question is still being studied. Although spheroids can secrete, form (aggregate), and act as do liver cells, the cells may not be functional because it still undergoes a major environmental change, cultured in vitro. This paper describes how liver cells respond to the different environmental change of being cultured outside the body. It evaluates the liver cells/spheroids morphological formation and functional and biochemical parameters for 21 days. Spheroids grown in culture were compared to in vivo liver cells by measuring spheroid consumption, secretion, and activity.

Primary liver cells were obtained from rats and cultured into spheroids onto plates. Various biochemical assays were ran to compare how spheroids relate to in vivo liver cells. Total protein, glucose, galactose, albumin, pyruvate secretion were determined as well as LDH, g-GT, GPT, and GOT activity. Results were as following: galactose and pyruvate consumption was maintained at a relatively stable level throughout the assay. Glucose secretion and cellular GPT and GOT activities were higher in immature spheroids, then decreased up to maturity and remained stable after. g-GT and LDH activities were initially extremely low and increased as spheroids matured. Albumin secretion decreased rapidly before the formation of the spheroid and increased during maturity. Through the observations made throughout the 21 culture day, the group were able roughtly to divide liver spheroid formation into two days: immaturity (days 1-5) and maturity (> day 5). Throughout spheroid immaturity, the liver cells undergoes a period of biochemical and functional turbulence and after maturity, the spheroid tends to maintain relatively stable functions up to 21 days. As compared to liver cells cultured on monolayers, spheroids are much more related to in vivo liver cells. Nevertheless, it does not imply that spheriods grown in culture can be injected in vivo. Thus, in order to study how liver cells act in vitro, one should develop spheroids and observe them only after maturity, for when they mature, most of their functions have been recovered or maintained at relatively stable levels.

I chose this paper because it relates to the final project in this course. Since, the purpose of the final project can be to propose a method to create a bioartificial liver in a sense, it is crucial to understand the relationship between a liver grown in vitro to one in vivo. I have heard a lot about the importance of spheroids to mimic cells or organs in vivo. Nevertheless, one knows that it is noticeably different for the environment is completely different; the spheroids are grown in a dish. Nevertheless, despite the dramatic difference in environment, this study provides insight about how spheriods are similar and different than a liver. In addition, it gives insight as to parameters and techniques for comparing how well the spheroids mimic the a real liver. For instance, if one wants to observe or test spheroids, one must wait at least 5 days after plating the cells to allow the cells to aggregate and mature. After that, there are a variety of tests that display whether the cells are liver-like or still immature. As in the case for our final project, the amount of production of albumin indicates spheroid maturity and growing liver-like properties.