Discrimination of Two Fusogenic Properties of Aqueous Polyethylene Glycol Solutions

Abstract

Investigations on the dose response of cell fusion, induced by ionfree aqueous polyethylene glycol (PEG) solutions, reveal distinct lowest fusogenic PEG concentrations for different permanently growing mammalian cell lines. Part o f the requisite PEG can be replaced by carbo hydrates, preserving the fusogenity o f the solutions. This discriminates two effects o f PEG solutions causing cell fusion: a) cell shrinkage, the required hyperosmolality o f the solutions may be provided by PEG or by carbohydrates, is supposed to cause intracellular processes necessary for consolidating polycaryons; b) membrane alterations, which can not be induced by carbo hydrates, enable intimate cell-cell contact via particle-free membrane areas. Depending on cell line salts can not only raise the osmolality o f PEG solutions but are able to co-operate with PEG in generating membrane alterations.The polyethylene glycol-(PEG)-induced cell-cell fusion, as many other fusion events, consist of several distinct stages: (a) cells come to very close proximity, their adjacent membranes contact via particle-free lipid areas, (b) intercellular cytoplasm atic bridges develop at these contact sites and (c) the cytoplasm atic bridges expand and stable condi tions in m em brane and cytoplasma of the poly caryons are restored (for ref. see [1,2]). By which properties o f PEG solutions the necessary cell altera tions are induced was still an open question [1,3]. In this paper I demonstrate, how in ionfree fusogenic PEG solutions PEG can be replaced in part by carbohydrates an d /o r salts. These findings discrim i nate at least two properties of PEG solutions neces sary for cell fusion. There is evidence that one of them accounts for mem brane alterations enabling intim ate cell-cell contact via particle-free lipid areas whereas the other induces intracellular processes involved in consolidating polycaryons. The high affinity o f PEG molecules to water is supposed to be basicly responsible for all fusogenic properties of aqueous PEG solutions.C onfluent monolayers of permanently growing m am m alian cell lines (HeLa, HE, BT5C1, B IC R / M 1R-K) were used in standardized fusion experi ments carried out at first with ionfree aqueous PEG solutions [2]. Cytotoxic effects rem ained negligible in all experim ents presented. The fusion yield ex

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“…They studied the effect of different concentrations and molecular weights of the agents on cell aggregation. PEG causes cell shrinking and aggregation, and after removal of the PEG, cell fusion takes place (Robinson et al, 1979;Krahling, 1981;Hui et al, 1985). A direct interaction of PEG with membrane lipids is assumed to cause a decrease of the membrane fluidity (Ohno et al, 1981).…”