PubMed Health⌕ Search

Biomedical subjects

D Nie

Publications and source records attributed to D Nie.

23 records · Page 2Linked to original sources
PubMed1998

Retinoic acid treatment elevates matrix metalloproteinase-2 protein and mRNA levels in avian growth plate chondrocyte cultures.

Matrix metalloproteinases (MMPs) play a crucial role in tissue remodeling. In growth plate (GP) cartilage, extensive remodeling occurs at the calcification front. To study the potential involvement of MMPs in retinoic acid (RA) regulation of skeletal development, we studied the effect of all-trans-RA on MMPs levels in mineralizing chicken epiphyseal chondrocyte primary cultures. When treated for 4 day periods on days 10 and 17, RA increased levels of an approximately 70 kDa gelatinase activity. The N-terminal sequence of the first 20 amino acid residues of the purified enzyme was identical to that deduced from chicken MMP-2 cDNA. Time-course studies indicated that RA elevated MMP-2 activity levels in the cultures within 16 h. This increase was inhibited by cycloheximide and was enhanced by forskolin. The increase in MMP-2 activity induced by RA was accompanied by an increase in MMP-2 mRNA levels and was abolished by treatment with cycloheximide. This upregulation of MMP levels by RA in GP chondrocytes is consistent with its effects on osteoblasts and osteosarcoma cells and opposite its inhibitory effects on fibroblasts and endothelial cells. It may well be related to the breakdown of the extracellular matrix in the GP and would be governed by the availability of RA at the calcification front where extensive vascularization also occurs.

Amino Acid Sequence↗
PubMed1997

Retinoic acid stimulates matrix calcification and initiates type I collagen synthesis in primary cultures of avian weight-bearing growth plate chondrocytes.

The effect of retinoic acid (RA) on primary cultures of growth plate chondrocytes obtained from weight-bearing joints was examined, Chondrocytes were isolated from the tibial epiphysis of 6- to 8-week-old broiler-strain chickens and cultured in either serum-containing or serum-free media. RA was administered at low levels either transiently or continuously after the cells had become established in culture. Effects of RA on cellular protein levels, alkaline phosphatase (AP) activity, synthesis of proteoglycan (PG), matrix calcification, cellular morphology, synthesis of tissue-specific types of collagen, and level of matrix metalloproteinase (MMP) activity were explored. RA treatment generally increased AP activity and stimulated mineral deposition, especially if present continuously. RA also caused a shift in cell morphology from spherical/polygonal to spindle-like. This occurred in conjunction with a change in the type of collagen synthesized: type X and II collagens were decreased, while synthesis of type I collagen was increased. There was also a marked increase in the activity of MMP. Contrasting effects of continuous RA treatment on cellular protein levels were seen: they were enhanced in serum-containing media, but decreased in serum-free HL-1 media. Levels of RA as low as 10 nM significantly inhibited PG synthesis and caused depletion in the levels of PG in the medium and cell-matrix layer. Thus, in these appendicular chondrocytes, RA suppressed chondrocytic (PG, cartilage-specific collagens) and enhanced osteoblastic phenotype (cell morphology, type I collagen, alkaline phosphatase, and mineralization).

Alkaline Phosphatase↗
PubMed1995

Defect in formation of functional matrix vesicles by growth plate chondrocytes in avian tibial dyschondroplasia: evidence of defective tissue vascularization.

Avian tibial dyschondroplasia (ATD), a disease characterized by an almost total lack of mineralization in affected areas of growth plate cartilage, may involve defective matrix vesicle (MV) mineralization. To explore the biochemical defect in ATD, both normal and diseased tissue were analyzed for the amount of isolatable MVs, their chemical composition, and their ability to induce mineral formation. We found significantly fewer MVs in ATD tissue, and in contrast to normal MVs, which rapidly mineralized when incubated in synthetic cartilage lymph, those isolated from ATD lesions induced only limited mineralization even after prolonged incubation. Analysis by detergent extraction revealed a nearly dysfunctional nucleational core in ATD MVs. Thus, in ATD tissue, there is a defect in the formation of MVs, and those that form are nearly inactive. There were also alterations in the lipid-dependent Ca2+(-)binding proteins (annexins) in ATD MVs. There were lower levels of annexins II and VI in endogenously produced collagenase-released matrix vesicles (CRMVs), but not in matrix vesicle-enriched microsomes (MVEMs) produced by tissue homogenization. These findings indicate that there is insufficient Ca2+ in ATD cells to enable incorporation of the annexins into MVs. Finally, there was evidence of phospholipid breakdown in ATD MVs, as well as in ATD tissue generally. This indicated that the ATD lesions were becoming necrotic. Taken together, these findings indicate that there is a defect in tissue vascularization such that the supply of mineral ions and nutrients to ATD cartilage is inadequate to support normal MV formation and subsequent mineralization.

Alkaline Phosphatase↗
PubMed1995

[Research on the different blood types umbilical cord blood hematopoietic progenitors mixed culture in vitro].

Using single layer agar culture method, we make a study on culture of human hematopoietic progenitor cell from umbilical cord blood. The result showed the mean value of the granulocyte macrophage progenitor cells (CFU-GM) from twenty neonates cord blood was 95.6 +/- 36.5/10(6) MNC. We compared the mixed culture of two different blood types neonates cord blood hematopoietic progenitors with single sample and found little difference between them in number and growth characteristics. This may provide a theoretical basis for clinical transplantation of mixed human cord progenitor cells.

Blood Group Antigens↗