The influence of the extracellular matrix (ECM) and ECM components on preadipocyte development was examined in primary cultures of adipose tissue stromal-vascular (S-V) cells. Extracellular matrix derived from Engelbreth-Holm-Swarm (EHS) cells or tumors enhanced several aspects of adipogenesis in vitro. In comparison to uncoated and fibronectin substrata, EHS-ECM substratum markedly increased attachment, spreading, and hypertrophy of preadipocytes while antagonizing spreading of non-preadipocytes. In addition, adipocyte number increased (P < .05) on these substrata despite no increase in total cell number: this resulted in a greater (P < .05) proportion of preadipocytes. These effects of EHS-ECM were also observed with laminin substrata per se, whereas types I and IV collagen and fibronectin had no influence. In contrast to all other substrata, adipocyte number decreased and total cell number increased 2.5-fold on ECM derived from corneal endothelial cells; this resulted in the lowest proportion of preadipocytes. Challenging cultures with adipogenic media (+serum) did not counter the inhibitory influence of corneal endothelial ECM, whereas dexamethasone partially neutralized the inhibitory influence of this ECM. These studies clearly show that source or type of the ECM dictated the influence of ECM substrata on preadipocyte development in primary S-V cultures. However, these studies indicated that the ECM and in particular laminin may play a critical role in morphological aspects of preadipocyte development.

It is well established that reproductive function is metabolically gated. However, the mechanisms whereby energy stores and metabolic cues influence appetite, energy homeostasis and fertility are yet to be completely understood. Adipose tissue is no longer considered as only a depot to store excess energy. Recent findings have identified numerous genes, several neurotrophic factors, interleukins, insulin-like growth factor binding protein-5, ciliary neurotrophic factor and neuropeptide Y (NPY) as being expressed by adipose tissue during pubertal development. These studies demonstrated for the first time the expression of several major adipokines or cytokines in pig adipose tissue which may influence local and central metabolism and growth. Leptin appears to be the primary metabolic signal and is part of the adipose tissue-hypothalamic regulatory loop in the control of appetite, energy homeostasis and luteinizing hormone (LH) secretion. Leptin's actions on appetite regulation are mediated by inhibition of hypothalamic NPY and stimulation of proopiomelanocortin. Its effects on gonadotropin-releasing hormone (GnRH)/LH secretion are mediated by NPY and kisspeptin. Thus, leptin appears to be an important link between metabolic status, the neuroendocrine axis and subsequent fertility in the gilt and sow.

No abstract

The relationships between adipocyte and muscle cell development within muscle are important in the study of factors or agents that may improve meat quality. Neonatal porcine muscle has the potential to yield both cell types for cell culture because it contains developing adipocytes and a high number of muscle satellite cells. Therefore, we modified a conventional collagenase-based procedure to digest neonatal porcine muscle and subsequently cultured the resultant muscle stromal-vascular (SV) cells on several substrata in basal and dexamethasone (DEX)-containing media. Developing myotubes and preadipocytes were present in muscle SV cell cultures on laminin substrata following seeding and plating with fetal bovine serum (FBS) with or without DEX. Myotube number was much higher (P < 0.05) on laminin substrata compared with all other substrata, whereas preadipocyte number in muscle SV cell cultures was independent of substrata, as we have shown previously. This approach can be used to establish co-cultures of differentiating adipocytes and myotubes from collagenase-digested neonatal pig muscle. Because the comparison is within the same culture dish, this method allows for a direct comparison of the responses of adipogenic and myogenic cells to growth and differentiation factors. For example, DEX did not alter myogenesis (i.e., 11 +/- 3 vs. 11 +/- 4 myotubes per unit area for control and DEX-treated cultures, respectively), but it has been shown to markedly increase preadipocyte number in muscle SV cell cultures.

No abstract