Induction of Lipid Droplets in Fibroblasts of the Hamster Lung by a Diet High in Vitamin A

Abstract

To investigate the effect of vitamin A on the occurrence of lipid droplets in alveolar fibroblasts, light and electron microscopic studies were carried out on the lungs of Syrian golden hamsters fed on diets with a low, normal, or high vitamin A content for a period of 17 weeks. The feeding of the high vitamin A diet resulted in a considerable increase in size and number of lipid droplets in alveolar fibroblasts. These droplets also occurred in fibroblasts of the visceral pleura, and in fibroblasts of connective tissue around bronchioli and larger blood vessels. Most of the lipid-laden fibroblasts could be recognized as myofibroblasts. The significance of the droplets for the deposition of interstitial materials or for the synthesis of prostaglandins is discussed.

How common is the lipid body-containing interstitial cell in the mammalian lung?

“…For example, in vitro lipofibroblasts were shown to repair elastic fibers after treatment of an elastic fiber matrix with elastase (30). Furthermore, vitamin A is stored in lipofibroblasts (37,48) and increases the lipid content of lipofibroblasts in the adult hamster lung (48). As the treatment of emphysematous mice with vitamin A/retinoids resulted in reverse remodeling and the alleviation of the emphysema phenotype (27,19), considerable hopes for the translation of this treatment to patients with emphysema were raised although the regenerative potential of vitamin A/retinoic acid seems to depend on the type of emphysema mouse model or the pharmacogenetics of the mouse strains being used (13,18).…”

Modulation of retinoid signaling: therapeutic opportunities in organ fibrosis and repair

“…It is believed that lipofibroblasts may transfer neutral lipids to Type II cells to support surfactant and phospholipid synthesis (S. E. McGowan & Torday, 1997). The size of lipofibroblasts can be increased by vitamin A feeding suggesting that they are a significant storage site for retinoids in the lung (Okabe, Yorifuji, Yamada, & Takaku, 1984;Spit, 1983). Whereas α-SMA expression has been widely used to identify myofibroblasts, it has recently been shown that Tcf21 expression may identify the lipofibroblast lineage (distinct from myofibroblasts, interstitial fibroblasts, or adventitial fibroblasts) (Park et al, 2019).…”

Lung Mesenchymal Stromal Cells in Development and Disease: To Serve and Protect?

“…Additionally, lipofibroblasts can be found in primary septa of the alveoli, at the very base where secondary septa later grow outward (15, 16). Neonatal lipofibroblasts have been likened to the contractile interstitial cell (CIC), which has been described in the adult lung, based on their contractile phenotype (1,63,117). Although originally researchers reported that LIC were not able to differentiate into NLIC and vice versa (15), CICs are considered to be the progenitor cells of myofibroblasts (1).…”