Proliferation and differentiation of rat adipose precursor cells in chemically defined medium: Differential action of anti‐adipogenic agents

Abstract

Primary rat adipose precursor cells, maintained in the minimal chemically defined medium (ITT medium) able to promote differentiation, have been used to investigate the ability of several agents to modulate their proliferation and their differentiation. Fetuin and fibroblast growth factor (FGF), which exhibited a strong and a weak mitogenic activity, respectively, do not significantly affect the proportion of differentiated cells as indicated by glycerol-3-phosphate dehydrogenase (GPDH) activity values. In contrast, carbaprostacyclin (cPGI2), a stable analogue of prostacyclin, behaves as a true adipogenic factor leading to a 4 to 5-fold increase in GPDH-specific activities with no significant effect on cell growth. Submaxillary gland kallikrein (SMGK), transforming growth factor-beta (TGF-beta) and tumor necrosis factor-alpha (TNF-alpha) behave as growth-promoting agents but at the same time elicit a dose-dependent inhibition of differentiation. Epidermal growth factor (EGF) and prostaglandin F2 alpha (PGF2 alpha) do not show any effect on cell proliferation at concentrations which exert a maximal inhibitory action on differentiation. Upon removal of EGF from the culture medium, complete resumption of differentiation occurs, whereas upon removal of PGF2 alpha or SMGK, complete resumption only takes place when differentiation is triggered by cPGI2. Upon removal of TNF-alpha, a partial resumption of differentiation is observed, whereas no subsequent differentiation is observed upon TGF-beta removal. These results emphasize the adipogenic, nonmitogenic role of cPGI2 and also allow the distinction between the various adipogenic/mitogenic factors which affect adipose cell differentiation.

The adipose conversion process: regulation by extracellular and intracellular factors

“…Similar results were reported for rat, porcine and human primary preadipocytes [179,185,186,247]. As suggested for PDGF and FGF, this negative effect appears to be independent on a proliferative action [185,240].…”

“…Studies on 3T3-L1 cells revealed that EGF increases adipose conversion in serum-free medium [15] whereas negative effect were obtained in serum-containing medium [3]. Furthermore, EGF increases the differentiation of porcine preadipocytes [27], whereas it inhibits the adipose conversion of rodent and human preadipose cells cultured in similar conditions [107,198,247]. Transforming growth factor α, that can be expressed by preadipose cells, exhibits antiadipogenic activities when tested on 3T3-F442A and rat preadipose cells [154,198,199].…”

“…In serumcontaining medium, FGF was shown to decrease the differentiation of TA1 cells [166,167]. In contrast, FGF had no or a poor effect on the adipose conversion of 3T3-L1 cells or of human and rat primary preadipocytes cultured in serum-free medium [107,195,200,247]. Recently, FGF-10 was shown to be produced by rat preadipocytes and to ensure their growth without affecting differentiation [263].…”

“…Tumor necrosis factor α, interferon γ, and interleukins 1 and 11 strongly decrease adipose conversion in cell lines as well as in rat, porcine and human primary cells [22,27,56,91,133,178,240,247]. The mechanism of action of TNFα has been largely investigated.…”

“…Because this PG can stimulate the synthesis of TGFα in rat preadipocytes, the existence of an amplification mechanism between these two differentiation inhibitors has been postulated [199]. By contrast, carbaprostacyclin (cPGI 2 ), a stable analogue of PGI 2 , is recognized as a strong auto-/paracrine adipogenic agent for Ob1771 cells as well as for primary rodent and human preadipocytes [40,170,245,247]. In addition to PGI 2 , PGD 2 and its derivative PG 15-deoxy-J 2 may be endogenous ligands for PPARγ [117,142].…”