Justin Jacob1, Anjali Aggarwal2, Aditya Aggarwal3, Shalmoli Bhattacharyya4, Vishal Kumar5, Vinit Sharma6, Daisy Sahni7. 1. Department of Anatomy, Research Block B, Post Graduate Institute of Medical Education and Research, Chandigarh 160012, India. Electronic address: jjcruci67@gmail.com. 2. Department of Anatomy, Research Block B, Post Graduate Institute of Medical Education and Research, Chandigarh 160012, India. Electronic address: anjli_doc@yahoo.com. 3. Department of Orthopedics, Nehru Hospital, Post Graduate Institute of Medical Education and Research, Chandigarh 160012, India. Electronic address: adityadocpgi@gmail.com. 4. Department of Biophysics, Research Block B, Post Graduate Institute of Medical Education and Research, Chandigarh 160012, India. Electronic address: shalmoli2007@yahoo.co.in. 5. Department of Orthopedics, Nehru Hospital, Post Graduate Institute of Medical Education and Research, Chandigarh 160012, India. Electronic address: drkumarvishal@gmail.com. 6. Department of Anatomy, Research Block B, Post Graduate Institute of Medical Education and Research, Chandigarh 160012, India. Electronic address: vntsharma58@gmail.com. 7. Department of Anatomy, Research Block B, Post Graduate Institute of Medical Education and Research, Chandigarh 160012, India. Electronic address: daisy_sahni@rediffmail.com.
Abstract
OBJECTIVES: Despite the presence of chondrogenic progenitor cells (CPCs) in knee osteoarthritis patients they are unable to repair the damaged cartilage. This study aimed to evaluate the oxidative stress, cellular senescence, and senescence-associated secretory phenotype (SASP) in the CPCs derived from osteoarthritic cartilage and compare with the CPCs of healthy articular cartilage. METHODS: Isolated CPCs were characterized based on phenotypic expression of stem cell markers, clonogenicity, and tri-lineage differentiation assay. Production of ROS was measured using DCFDA assay. Cellular senescence in CPCs was assessed by senescence-associated beta-galactosidase assay and expression of senescence markers at the gene level using real-time PCR. Morphological features associated with senescent OA-CPCs were studied using scanning electron microscopy. To study SASP, the production of inflammatory cytokines was assessed in the culture supernatant using a flow-cytometer based cytometric bead array. RESULTS: OA-CPCs exhibited elevated ROS levels along with a relatively high percentage of senescent cells compared to non-OA CPCs, and a positive correlation exists between ROS production and senescence. The morphological assessment of senescent CPCs revealed increased cell size and multiple nuclei in senescent OA-CPCs. These results were further validated by elevated expression of senescence genes p16, p21, and p53. Additionally, culture supernatant of senescent OA-CPCs expressed IL-6 and IL-8 cytokines indicative of SASP. CONCLUSIONS: Despite exhibiting similar expression of stem cell markers and clonogenicity, CPCs undergo oxidative stress in diseased knee joint leading to increased production of intracellular ROS in chondrogenic progenitor cells that support cellular senescence. Further, senescence in OA-CPCs is mediated via the release of pro-inflammatory cytokines, IL-6 and IL-8.
OBJECTIVES: Despite the presence of chondrogenic progenitor cells (CPCs) in knee osteoarthritis patients they are unable to repair the damaged cartilage. This study aimed to evaluate the oxidative stress, cellular senescence, and senescence-associated secretory phenotype (SASP) in the CPCs derived from osteoarthritic cartilage and compare with the CPCs of healthy articular cartilage. METHODS: Isolated CPCs were characterized based on phenotypic expression of stem cell markers, clonogenicity, and tri-lineage differentiation assay. Production of ROS was measured using DCFDA assay. Cellular senescence in CPCs was assessed by senescence-associated beta-galactosidase assay and expression of senescence markers at the gene level using real-time PCR. Morphological features associated with senescent OA-CPCs were studied using scanning electron microscopy. To study SASP, the production of inflammatory cytokines was assessed in the culture supernatant using a flow-cytometer based cytometric bead array. RESULTS: OA-CPCs exhibited elevated ROS levels along with a relatively high percentage of senescent cells compared to non-OA CPCs, and a positive correlation exists between ROS production and senescence. The morphological assessment of senescent CPCs revealed increased cell size and multiple nuclei in senescent OA-CPCs. These results were further validated by elevated expression of senescence genes p16, p21, and p53. Additionally, culture supernatant of senescent OA-CPCs expressed IL-6 and IL-8 cytokines indicative of SASP. CONCLUSIONS: Despite exhibiting similar expression of stem cell markers and clonogenicity, CPCs undergo oxidative stress in diseased knee joint leading to increased production of intracellular ROS in chondrogenic progenitor cells that support cellular senescence. Further, senescence in OA-CPCs is mediated via the release of pro-inflammatory cytokines, IL-6 and IL-8.