Effects of colony stimulating factor-1 on human extravillous trophoblast growth and invasion

Abstract

Colony stimulating factor (CSF)-1 has been localized in a variety of tissues and shown to influence proliferation and differentiation of numerous cell types. Messenger RNA and protein products of CSF-1 and its receptor (c-fms) have been identified in the human placenta and decidua. We examined whether CSF-1 and c-fms mRNA and protein are expressed by normal human first trimester invasive extravillous trophoblast (EVT) cells propagated in culture and whether CSF-1 influences proliferation and/or invasion of these cells. CSF-1 mRNA and protein expression was determined by RT-PCR and immunofluorescence microscopy. Proliferation was assessed by the cellular uptake of tritiated thymidine and invasion was evaluated by Matrigel invasion assay as well as Northern blot analysis of mRNA expression for invasion-associated enzymes and their inhibitors. Results revealed that normal invasive EVT cells in culture express both CSF-1 and c-fms mRNA and protein. Under serum-free conditions, exogenous CSF-1 greatly stimulated the proliferation of these cells. CSF-1 neutralizing and c-fms receptor blocking antibody (Ab) each abolished the growth stimulatory effects of CSF-1, indicating that CSF-1 and c-fms interaction was responsible for these effects. In fact, c-fms Ab alone reduced proliferation to below background levels. While exogenous CSF-1 failed to influence EVT cell invasiveness, Northern blot analysis of mRNA indicated a slight upregulation of the invasion-associated enzyme 72 kDa type IV collagenase as well as its natural inhibitor tissue inhibitor of metalloprotease (TIMP)-1, so that the balance between the two remained unaltered. These findings suggest that CSF-1 may represent an autocrine (and possibly paracrine) growth stimulatory factor for the invasive trophoblast cells in situ with no net effect on their invasiveness.

Comment: Response to an article by Hamilton et al. on 'Effects of colony stimulating factor-1 on human extravillous trophoblast growth and invasion'

“…In serum-free medium, EVT incorporated 400-1000 c.p.m./6 h (Hamilton et al 1998). TCL-1 cells incorporated about 300 000 dpm/h (our unpublished data), a rate substantially greater.…”

“…Table 1 shows the similarities and differences between the observations made in the two papers (Lewis et al 1996, Hamilton et al 1998 which have investigated the roles of colony-stimulating factor-1 (CSF-1) and its receptor (c-fms) in human extravillous cytotrophoblast (EVCT). Both types of EVCT show the components of a CSF-1/ c-fms autocrine loop, and it is clear that there is no role for CSF-1 in controlling EVCT invasion (Table 1).…”

“…Both types of EVCT show the components of a CSF-1/ c-fms autocrine loop, and it is clear that there is no role for CSF-1 in controlling EVCT invasion (Table 1). However, in primary cells (designated EVT), CSF-1 was a positive regulator of cell proliferation (Hamilton et al 1998), whereas in immortalised TCL-1 cells (and in BeWo choriocarcinoma) CSF-1 appeared to be an inhibitor of such proliferation (Lewis et al 1996).…”

“…We wish to comment on the article by Hamilton et al 1998. Table 1 shows the similarities and differences between the observations made in the two papers (Lewis et al 1996, Hamilton et al 1998 which have investigated the roles of colony-stimulating factor-1 (CSF-1) and its receptor (c-fms) in human extravillous cytotrophoblast (EVCT).…”

“…(1) EVT were obtained by culture of adherent cells and explants from minced first trimester villi (Hamilton et al 1998), whereas TCL-1 were from chorionic membranes and immortalised with the SV40 large-T antigen (Lewis et al 1996). There may be a change in trophoblast response to CSF-1 depending on gestational age, intrauterine location or, as described by Hamilton et al, the fact that TCL-1 were immortalised.…”