Effect of osteogenic protein-1 on the development and mineralization of primary cultures of avian growth plate chondrocytes: Modulation by retinoic acid

Abstract

Osteogenic protein-1 (OP-1), a member of the TGF-beta family of proteins, induces endochondral bone formation. Here we studied the effect of OP-1 on the development of primary cultures of avian growth plate (GP) chondrocytes in either serum-free or serum-containing medium, in the absence or presence of retinoic acid (RA). OP-1 was added on day 7 of culture and continued for 7 days, or until the cultures were harvested, typically on day 21. Alone, OP-1 caused approximately 2-fold increase in proteoglycan synthesis into both the medium and the cell:matrix layer. Additionally, OP-1 caused a dosage-dependent increase in alkaline phosphatase (ALP) activity, and an increase in protein, when given from days 7-14 and examined on day 14. This stimulation was greater in cells grown in serum-free than in serum-containing media (3-5-fold vs. 2-3-fold increase in ALP; approximately 40% vs. approximately 20% increase in protein). Such stimulation of ALP activity and proteoglycan (PG) synthesis in cultured GP cells indicates that OP-1 elicits differentiation of chondrocytes. OP-1 minimally affected cell division (DNA content); however, a slight increase was seen when examined early in the culture. Alone, OP-1 increased mineral (Ca and Pi) content of the cultures by approximately 2-fold in both types of media. As early as day 14, clusters of mineral encircled many of the OP-1 treated cells. Thus, as in vivo, OP-1 strongly promoted mineral formation by the cultured GP chondrocytes. When present together, OP-1 and RA generally blocked the action of the other. Separately OP-1 and RA each stimulated protein synthesis, ALP activity, and Ca2+ deposition; together they were inhibitory to each. Also, RA blocked the stimulation of PG synthesis induced by OP-1; whereas OP-1 decreased cell division engendered by RA. Thus, this GP chondrocyte culture system is a good model for studying factors that influence differentiation and mineral deposition during bone growth in vivo.

Serum‐free media for periosteal chondrogenesis in vitro

“…However, the standard organ culture model to date involving whole explants of periosteum has required the addition of fetal bovine serum to the media. Numerous investigators have succeeded in culturing chondrocytes [23,68,69] and embryonic cells [49] in serum-free conditions [23,25] but there have been no studies focused on achieving a defined, serum-free media for culturing periosteum. The main goals of the present investigation were to determine if whole periosteal explants can be grown and produce cartilage in serum-free conditions, to define the minimum media supplements that would be conducive to chondrogenesis, and to begin examining combinations of factors that might further stimulate cartilage formation.…”

Cartilage‐derived morphogenetic proteins enhance the osteogenic protein‐1‐induced osteoblastic cell differentiation of C2C12 cells

“…Several BMPs exhibit multiple biological activities on different cell types (Dudley et al, 1995; Luo et al, 1995). For example, OP‐1 (Asahina et al, 1993; Chen et al, 1995; Wu et al, 1997; Klein‐Nulend et al, 1998), BMP‐2/BMP‐4 (Paralkar et al, 1992; Katagiri et al, 1994; Hogan, 1996) induces bone and cartilage formation in vivo and stimulates expression of the osteoblast phenotype in osteoprogenitor cells in vitro (Thies et al, 1992; Kawasaki et al, 1998). OP‐1 also appears to be involved in the development/differentiation of different organs, such as the neural system, the heart, the kidney, the eye, and the oral tissues.…”

Daily or Intermittent Calcitriol Administration during Growth Hormone Therapy in Rats with Renal Failure and Advanced Secondary Hyperparathyroidism

“…Several studies have reported that BMP-7 promoted mineral formation and terminal differentiation in avian chondrocytes and in mouse fetal bone explants (24,25). In the current study, phosphorus loading in nephrectomized rats diminished BMP-7 protein expression, which may suggest delay in chondrocyte maturation, although our previous experiments have shown that there were no changes in type X collagen expression in these animals.…”