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Lipopolysaccharide alters aggrecan metabolism in the growth plate
1Department of Nutritional Sciences, Rutgers University, Cook College, New Brunswick, New Jersey 08903-0231, USA.
Insights
Lipopolysaccharide (LPS) disrupts aggrecan metabolism and structure in chick growth plates, affecting proteoglycan synthesis and monomer size. This disruption may negatively impact longitudinal bone growth.
Area of Science:
- Biochemistry
- Developmental Biology
- Animal Science
Background:
- Growth plate cartilage is crucial for longitudinal bone growth.
- Aggrecan is the major proteoglycan in cartilage, essential for its structural integrity.
- Lipopolysaccharide (LPS) is a component of Gram-negative bacteria known to induce inflammatory responses.
Purpose of the Study:
- To investigate the effects of lipopolysaccharide (LPS) on aggrecan metabolism and structure in the avian growth plate.
- To determine if LPS exposure, both in vivo and in vitro, alters proteoglycan synthesis, breakdown, and structural integrity.
Main Methods:
- In vivo administration of LPS to 10-day-old broiler chicks, followed by growth plate analysis.
- In vitro culture of growth plate explants with and without LPS to assess proteoglycan synthesis and breakdown.
- Analysis of proteoglycan structure using Sepharose CL2B chromatography to evaluate monomer size and aggregation.
Main Results:
- In vivo LPS exposure decreased proteoglycan synthesis and resulted in smaller aggrecan monomers with reduced aggregation.
- In vitro LPS treatment of growth plate explants significantly reduced proteoglycan synthesis and increased breakdown.
- LPS-treated explants released smaller proteoglycans with impaired aggregation capabilities.
Conclusions:
- Lipopolysaccharide (LPS) disrupts normal aggrecan metabolism and structural organization in the growth plate.
- These disruptions in aggrecan may adversely affect longitudinal bone growth.
- The findings highlight a potential mechanism by which bacterial components can impact skeletal development.
Abstract:
In this study, we examined the influence of lipopolysaccharide (LPS) on aggrecan metabolism and structure in the growth plate. Two experimental approaches were used: (i) in vivo administration of LPS to 10-day-old chicks; and (ii) in vitro addition of LPS to explant culture of normal chick growth plate. Twelve-day-old male broiler chicks were killed 48 hr after intravenous injection of LPS (3 mg/kg) or saline (control), and growth plate from the femur or tibia was cultured or frozen. Tissue for explant culture was (i) cultured for 5 days with daily medium change (glycosaminoglycan release into the medium estimates proteoglycan breakdown rates), or (b) incubated with 35SO4 to determine the rate of proteoglycan synthesis. Proteoglycan structure was determined by associative (0.5 M sodium acetate) and dissociative (4 M guanidine HCl) Sepharose CL2B chromatography. Explant culture of growth plate from LPS-injected chicks (in vivo) showed a decrease (P < 0.05) in the rate of proteoglycan synthesis. There were a greater proportion of small monomers and a reduced ability to aggregate in growth plate from LPS-injected chicks. In vitro addition of LPS (100 micrograms/ml) to explant culture medium reduced proteoglycan synthesis (P < 0.02), and the rate of release was increased (P < 0.001). In addition, the total and newly synthesized proteoglycans released into the medium from LPS-treated explant culture had a reduced aggregation and a majority of monomers that were smaller than control. These results demonstrate that LPS disrupts the normal metabolism and structure of growth plate aggrecan, and we hypothesize that this may adversely influence longitudinal growth.