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Updated: Jul 17, 2025
Isolation of Chondrocytes and Chondroprogenitors Using Fibronectin Adhesion and Migratory Assay
Published on: October 4, 2024
Adult Prg4+ progenitors repair long-term articular cartilage wounds in vivo
Mei Massengale1,2,3,4,5,6, Justin L Massengale7, Catherine R Benson2
1Spaulding Rehabilitation Network at Mass General Brigham, Cambridge, Massachusetts, USA.
Abstract:
The identity and origin of the stem/progenitor cells for adult joint cartilage repair remain unknown, impeding therapeutic development. Simulating the common therapeutic modality for cartilage repair in humans, i.e., full-thickness microfracture joint surgery, we combined the mouse full-thickness injury model with lineage tracing and identified a distinct skeletal progenitor cell type enabling long-term (beyond 7 days after injury) articular cartilage repair in vivo. Deriving from a population with active Prg4 expression in adulthood while lacking aggrecan expression, these progenitors proliferate, differentiate to express aggrecan and type II collagen, and predominate in long-term articular cartilage wounds, where they represent the principal repair progenitors in situ under native repair conditions without cellular transplantation. They originate outside the adult bone marrow or superficial zone articular cartilage. These findings have implications for skeletal biology and regenerative medicine for joint injury repair.
Insights
Researchers identified a novel skeletal progenitor cell type responsible for long-term joint cartilage repair after injury. These cells, crucial for in vivo articular cartilage regeneration, originate outside bone marrow or superficial cartilage zones.
Area of Science:
- Skeletal Biology
- Regenerative Medicine
- Cartilage Repair
Background:
- The source of stem/progenitor cells for adult joint cartilage regeneration is currently unknown.
- This knowledge gap hinders the development of effective therapeutic strategies for cartilage repair.
Purpose of the Study:
- To identify the specific stem/progenitor cells responsible for long-term articular cartilage repair in vivo.
- To investigate the origin and characteristics of these progenitor cells following simulated joint injury.
Main Methods:
- Utilized a mouse full-thickness joint injury model to simulate human microfracture surgery.
- Employed lineage tracing techniques to track progenitor cell behavior and contribution to repair.
- Analyzed gene expression (Prg4, aggrecan) and cell differentiation markers.
Main Results:
- Identified a distinct skeletal progenitor cell population enabling long-term (beyond 7 days) articular cartilage repair.
- These progenitors express Prg4 in adulthood, lack aggrecan initially, then differentiate to express aggrecan and type II collagen.
- The identified progenitors originate outside the adult bone marrow and superficial articular cartilage zones.
Conclusions:
- Discovered a novel progenitor cell type crucial for endogenous articular cartilage repair after injury.
- These findings provide critical insights into skeletal biology and pave the way for regenerative medicine strategies.
- Understanding these progenitors' origin and function is key for developing new joint injury treatments.
