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Tryptase β regulation of joint lubrication and inflammation via proteoglycan-4 in osteoarthritis

Nabangshu Das1,2,3,4, Luiz G N de Almeida2,3,4,5, Afshin Derakhshani2,3,4,5

  • 1Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada.

Nature Communications
|April 6, 2023
PubMed

Insights

Mast cell tryptase beta cleaves PRG4, reducing joint lubrication and activating inflammatory pathways. This cleavage is linked to osteoarthritis severity, highlighting tryptase beta as a key modulator of joint health.

Area of Science:

  • Biochemistry
  • Immunology
  • Orthopedics

Background:

  • PRG4 is an extracellular matrix protein crucial for joint homeostasis, providing lubrication and anti-inflammatory effects.
  • Dysfunctional PRG4 is implicated in joint inflammatory diseases like osteoarthritis.
  • Mast cell tryptase beta's role in joint pathophysiology is not fully understood.

Purpose of the Study:

  • To investigate the interaction between mast cell tryptase beta and PRG4.
  • To determine the functional consequences of PRG4 cleavage by tryptase beta.
  • To elucidate the role of this interaction in osteoarthritis pathogenesis.

Main Methods:

  • Enzymatic assays to confirm PRG4 cleavage by tryptase beta.
  • Silver stain gel electrophoresis and mass spectrometry for protein analysis.
  • Cellular assays measuring NF-κB activation in response to treated PRG4.
  • In vivo osteoarthritis model (destabilization of the medial meniscus) in rats.
  • Quantitative shotgun proteomics on human synovial fibroblasts.

Main Results:

  • Mast cell tryptase beta cleaves PRG4 in a dose- and time-dependent manner.
  • Cleaved PRG4 exhibits reduced lubricating properties.
  • Cleaved PRG4 enhances NF-κB activation in cells expressing TLRs.
  • Tryptase beta and PRG4 co-localize at injury sites in an osteoarthritis model, correlating with disease severity.
  • Proteomic analysis confirms NF-κB pathway activation in response to tryptase beta and PRG4 treatment.

Conclusions:

  • Mast cell tryptase beta directly cleaves PRG4, impairing its lubricating function.
  • PRG4 cleavage by tryptase beta promotes inflammation via NF-κB activation.
  • This enzymatic interaction is a significant factor in osteoarthritis development and progression.

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