The emergence of cell-based regenerative therapy represents a significant approach to treating cartilage-related ailments, such as osteoarthritis (OA) and chondral defects1. These disorders, characterized by the breakdown or injury of cartilage within the joints, present substantial challenges during treatment. The self-repair of articular cartilage is reported to be limited due to its aneural architecture, avascularity, and low mitotic activity2.
The most utilized cells for cartilage tissue regeneration are Mesenchymal Stem Cells (MSCs) and chondrocytes3. However, several studies have reported limitations in using these cells for regeneration4. These limitations include the terminal differentiation of chondrocytes during extended in vitro expansion to achieve the required cell count and the hypertrophic tendency of MSCs. These factors can result in the formation of repair tissue with a suboptimal combination of fibrocartilage and hyaline5,6,7,8.
The discovery of Chondroprogenitor cells (CPCs) arose from the quest for alternative cells in articular cartilage9. They have generated immense interest due to their resemblance to MSCs and their superior chondrogenic potential, all while exhibiting reduced hypertrophy - an indispensable combination sought after10,11. In contrast to chondrocytes, these progenitor populations have been reported to exhibit enhanced replicative and telomerase activity, as well as increased expression of Neurogenic locus notch homolog protein 1 (NOTCH-1) and SRY-box transcription factor 9 (SOX-9)12,13,14,15. There are two standard methods to isolate CPCs reported both from cartilage and meniscus, including one based on their integrin receptor (CD49e/CD29) expression, isolated through a fibronectin adhesion assay - Fibronectin Adhesion Assay-derived Chondroprogenitors (FAA-CPs), and the other based on their heightened migratory potential from cartilage explants- Migratory Chondroprogenitors (MCPs)11,13,16,17,18,19. Numerous in vitro studies demonstrate the chondrogenic superiority and reduced hypertrophy of both FAA-CPCs and MCPs compared to chondrocytes and bone marrow (BM)-MSCs20,21,22,23.
Recent in vitro investigations comparing FAA-CPCs to MCPs have demonstrated the enhanced cartilage regeneration capacity of the latter progenitor population under normal oxygen conditions24. These optimistic in vitro results showcase a hyaline-like regeneration, encouraging further in vivo experiments. Nevertheless, both populations of CPCs have been reported to efficiently repair and regenerate cartilage in OA and other osteochondral disorders in animal models25,26,27,28,29.
Our laboratory has actively contributed to standardizing CPC isolation techniques and comparing their phenotypic characteristics with chondrocytes and MSCs. This article will provide a detailed protocol explaining the steps involved in isolating and culturing cartilage resident cells, namely chondrocytes, FAA-CPCs, and MCPs.