TABLE 1

Comparison of advantages and disadvantages of various models for studying placental pathogens, particularly L. monocytogenesa

ModelHigh genetic variationRobust syncytiotrophoblastInvasive extravillous trophoblastsOrganization of tissue layersNo. of SYN layersGenetic manipulabilityGI L. monocytogenes inoculation (vs i.v.)No./exptMaternal immune cellsHuman L. monocytogenes sequelaeExpense
Choriocarcinoma cells+++NANA+++NA++++AbsentNA$
Mice++++++++Labyrinthine2++++++++++Present+++$$
Gerbils+++++++++Labyrinthine2++++++Present++$$$
Guinea pigs+++++++++++Labyrinthine1+++++++Present+++$$$$
Nonhuman primates+++++++++++Villous1+++++++Present++++$$$$$$$
Human placental explants++++++++++Villous1+NA++Mostly absentNA$$$$
  • a Models are evaluated on several aspects. Host genetic variation can be either an advantage or a disadvantage, depending on the desired application. Only fully in vivo models exhibit robust SYN; while SYN is present in explants, it may include breaks from physical damage, and syncytialized choriocarcinoma cells are patchy and possibly exhibit different gene expression. Invasive extravillous trophoblasts can be found in all in vivo models but are most extensive in villous placentas. +, low; ++, low intermediate; +++, high intermediate; ++++, high; NA, not applicable.