Telomerase Activity in Articular Chondrocytes Is Lost after Puberty

The effect of oral administration of undenatured type II collagen on monosodium iodoacetate-induced osteoarthritis in young and old rats

We investigated whether different doses of undenatured type II collagen (undenatured collagen, UC-II) help improve monosodium iodoacetate (MIA)-induced (osteoarthritis) OA in young and old rats. A total of 70 rats were divided into five groups: (1) control; (2) MIA (a single intra-articular injection of MIA); (3)-(5) MIA+ Undenatured Collagen with various oral doses (0.66, 1.33, and 2 mg/kg). The results showed that all doses of undenatured collagen in both age groups reduced knee diameter, while the two higher doses (1.33 mg/kg and 2 mg/kg) reduced the Mankin score and increased most gait measurements as early as day 14 compared to the MIA rats. However, the 2 mg/kg dose showed the best efficacy in improving Mankin score and gait measurements by 28 days post-OA induction. In young but not old rats, all doses of undenatured collagen reduced the Kellgren-Lawrence score compared to the MIA group. Undenatured collagen reduced the levels of most inflammatory and cartilage breakdown markers in serum and knee joint cartilage in both age groups. In conclusion, this data suggests that while all doses of undenatured collagen supplementation may ameliorate MIA-induced OA symptoms, the higher doses showed faster improvement in gait measurements and were more efficacious for overall joint health in rats.

Potential Methods of Targeting Cellular Aging Hallmarks to Reverse Osteoarthritic Phenotype of Chondrocytes

Osteoarthritis (OA) is a chronic degenerative joint disease that causes pain, physical disability, and life quality impairment. The pathophysiology of OA remains largely unclear, and currently no FDA-approved disease-modifying OA drugs (DMOADs) are available. As has been acknowledged, aging is the primary independent risk factor for OA, but the mechanisms underlying such a connection are not fully understood. In this review, we first revisit the changes in OA chondrocytes from the perspective of cellular hallmarks of aging. It is concluded that OA chondrocytes share many alterations similar to cellular aging. Next, based on the findings from studies on other cell types and diseases, we propose methods that can potentially reverse osteoarthritic phenotype of chondrocytes back to a healthier state. Lastly, current challenges and future perspectives are summarized.

Chondrocyte Aging: The Molecular Determinants and Therapeutic Opportunities

Osteoarthritis (OA) is a joint degenerative disease that is an exceedingly common problem associated with aging. Aging is the principal risk factor for OA, but damage-related physiopathology of articular chondrocytes probably drives the mechanisms of joint degeneration by a progressive decline in the homeostatic and regenerative capacity of cells. Cellular aging is the manifestation of a complex interplay of cellular and molecular pathways underpinned by transcriptional, translational, and epigenetic mechanisms and niche factors, and unraveling this complexity will improve our understanding of underlying molecular changes that affect the ability of the articular cartilage to maintain or regenerate itself. This insight is imperative for developing new cell and drug therapies for OA disease that will target the specific causes of age-related functional decline. This review explores the key age-related changes within articular chondrocytes and discusses the molecular mechanisms that are commonly perturbed as cartilage ages and degenerates. Current efforts and emerging potential therapies in treating OA that are being employed to halt or decelerate the aging processes are also discussed.

Feprazone Mitigates IL-1β-Induced Cellular Senescence in Chondrocytes

The proinflammatory cytokine interleukin-1 β (IL-1β)-mediated cellular senescence in chondrocytes is involved in the development and pathological progression of osteoarthritis (OA). Feprazone, a nonsteroidal anti-inflammatory drug (NSAID) and a cyclooxygenase (COX) inhibitor, is widely used in clinics. This study aims to investigate whether Feprazone has a protective effect against IL-1β-induced cellular senescence in human chondrocytes. In this study, C-28/I2 chondrocytes were stimulated with IL-1β (10 ng/mL) in the presence or absence of Feprazone (10 and 20 μM). Cellular senescence was assessed using senescence-associated β-galactosidase (SA-β-Gal) staining. The cell cycle was examined using flow cytometry. Gene and protein expressions were determined with real-time polymerase chain reaction (PCR) and western blot analysis. We found that treatment with Feprazone ameliorated IL-1β-induced increase in cellular senescence. Feprazone increased telomerase activity and prevented cell cycle arrest in the G0/G1 phase. We also found that Feprazone reduced the expressions of plasminogen activator inhibitor-1 (PAI-1) and p21, two important regulators of cellular senescence. Additionally, treatment with Feprazone reduced the expressions of matrix metalloprotein (MMP-13) and a disintegrin-like and metalloproteinase with thrombospondin type-1 motif-5 (ADAMTS-5). Interestingly, Feprazone prevented the activation of nuclear factor kappa-B (NF-κB) by preventing nuclear translocation of NF-κB p65 and the luciferase activity of the NF-κB promoter. The results also show that Feprazone increased nuclear levels of nuclear factor erythroid 2-related factor-2 (Nrf2) and reduced the production of reactive oxygen species (ROS). Importantly, silencing of Nrf2 abolished the protective effects of Feprazone against IL-1β-induced NF-κB activation and cellular senescence. These findings shed light on the potential use of Feprazone in the treatment of OA based on a novel mechanism.

The TERT rs2736100 Polymorphism and Susceptibility to Myeloproliferative Neoplasms: A Systematic Review and Meta-Analysis

Introduction: The classification of myeloproliferative neoplasms (MPN) is currently based on the genotype. Thus, to achieve better diagnostic and prognostic outcomes, it is necessary to further investigate the genetic spectrum underlying the pathogenesis of MPNs. The rs2736100A>C is a functional single nucleotide polymorphism in the telomerase reverse transcriptase (TERT) gene that has been previously reported to be associated with the risk of MPNs. Herein, we performed a meta-analysis to confirm the relationship between the TERT rs2736100A>C polymorphism and MPN susceptibility. Materials and Methods: Studies of case-control design were acquired from online databases with specific inclusion criteria. Odds ratios (ORs) with 95% confidence intervals (95% CI) were estimated to evaluate the association between the TERT rs2736100 polymorphism and MPN susceptibility using different genetic models. Results: Ten case-control studies involving 3488 cases and 57,948 controls were examined. Overall, there was a significant association between the TERT rs2736100 polymorphism and the risk of MPNs (allele model [C vs. A]: OR = 1.57 [95% CI: 1.47-1.69]; homozygous model [CC vs. AA]: OR = 3.00 [95% CI: 2.40-3.76]; heterozygous model [AC vs. AA]: OR = 2.17 [95% CI: 1.77-2.66]; dominant model [CC+AC vs. AA]: OR = 2.43 [95% CI: 2.00-2.95]; and recessive model [CC vs. AC+AA]: OR = 1.73 [95% CI: 1.47-2.04]). Conclusions: In this meta-analysis, we confirm an association between the TERT rs2736100A>C polymorphism and MPN susceptibility under all genetic models evaluated. The TERT rs2736100A>C allele increases the overall risk of MPN. Further studies are warranted to determine the functional role of the TERT rs2736100 polymorphism in MPN.

Characterization of polydactyly chondrocytes and their use in cartilage engineering

Treating cartilage injuries and degenerations represents an open surgical challenge. The recent advances in cell therapies have raised the need for a potent off-the-shelf cell source. Intra-articular injections of TGF-β transduced polydactyly chondrocytes have been proposed as a chronic osteoarthritis treatment but despite promising results, the use of gene therapy still raises safety concerns. In this study, we characterized infant, polydactyly chondrocytes during in vitro expansion and chondrogenic re-differentiation. Polydactyly chondrocytes have a steady proliferative rate and re-differentiate in 3D pellet culture after up to five passages. Additionally, we demonstrated that polydactyly chondrocytes produce cartilage-like matrix in a hyaluronan-based hydrogel, namely transglutaminase cross-linked hyaluronic acid (HA-TG). We utilized the versatility of TG cross-linking to augment the hydrogels with heparin moieties. The heparin chains allowed us to load the scaffolds with TGF-β1, which induced cartilage-like matrix deposition both in vitro and in vivo in a subcutaneous mouse model. This strategy introduces the possibility to use infant, polydactyly chondrocytes for the clinical treatment of joint diseases.

Study of Telomere Length in Preimplanted Cultured Chondrocytes

DESIGN

In the process of cell division, the extremes of the eukaryotic chromosomes are progressively shortening, and this phenomenon is related to cell degeneration and senescence. The treatment of cartilage lesions with autologous chondrocytes implies that cells proliferate in an artificial environment. We have studied the viability of cultured chondrocytes after measurement of their telomere length before implantation.

METHODS

Articular cartilage biopsies (B1, B2, and B3) were obtained from 3 patients (2 males and 1 female) with knee cartilage defects, who were going to be treated with chondrocyte implantation. Chondrocytes were cultured in DMEM with autologous serum. After the third passage, an aliquot of 1 million cells was removed to estimate the telomere length and the remaining cells were implanted. Telomere length was measured by quantitative fluorescent in situ hybridization (Q-FISH). Patients' clinical outcome was determined preoperatively, and 12 and 24 months postimplantation with the International Knee Documentation Committee (IKDC) questionnaire.

RESULTS

After chondrocyte implantation, IKDC score doubled at 12 and 24 months with regard to the basal value. After 3 passages, chondrocytes were cultured for a mean of 45.67 days, the mean duplication time being 4.53 days and the mean number of cell divisions being 10.04 during the culture period. The 20th percentile of telomere lengths were 6.84, 6.96, and 7.06 kbp and the median telomere lengths 10.30, 10.47, and 10.73 kbp, respectively. No significant correlation was found between IKDC score and telomere length.

CONCLUSION

Culturing autologous chondrocytes for implantation is not related to cell senescence in terms of telomere length.

Articular Cartilage Aging-Potential Regenerative Capacities of Cell Manipulation and Stem Cell Therapy

Changes in articular cartilage during the aging process are a stage of natural changes in the human body. Old age is the major risk factor for osteoarthritis but the disease does not have to be an inevitable consequence of aging. Chondrocytes are particularly prone to developing age-related changes. Changes in articular cartilage that take place in the course of aging include the acquisition of the senescence-associated secretory phenotype by chondrocytes, a decrease in the sensitivity of chondrocytes to growth factors, a destructive effect of chronic production of reactive oxygen species and the accumulation of the glycation end products. All of these factors affect the mechanical properties of articular cartilage. A better understanding of the underlying mechanisms in the process of articular cartilage aging may help to create new therapies aimed at slowing or inhibiting age-related modifications of articular cartilage. This paper presents the causes and consequences of cellular aging of chondrocytes and the biological therapeutic outlook for the regeneration of age-related changes of articular cartilage.

Physioxia Promotes the Articular Chondrocyte-Like Phenotype in Human Chondroprogenitor-Derived Self-Organized Tissue

INTRODUCTION

Biomaterial-based tissue engineering has not successfully reproduced the structural architecture or functional mechanical properties of native articular cartilage. In scaffold-free tissue engineering systems, cells secrete and organize the entire extracellular matrix over time in response to environmental signals such as oxygen level. In this study, we investigated the effect of oxygen on the formation of neocartilage from human-derived chondrogenic cells.

MATERIALS AND METHODS

Articular chondrocytes (ACs) and articular cartilage progenitor cells (ACPs) derived from healthy human adults were guided toward cell condensation by centrifugation onto plate inserts that were uncoated or coated with either agarose or fibronectin. Neocartilage discs were cultured at hyperoxic (20%) or physioxic (5%) oxygen levels, and biochemical, biomechanical, and molecular analyses were used to compare the cartilage produced by ACs versus ACPs.

RESULTS

Fibronectin-coated inserts proved optimal for growing cartilaginous discs from both cell types. In comparison with culture in hyperoxia, AC neocartilage cultured at physioxia exhibited a significant increase in chondrogenic gene expression, proteoglycan production, and mechanical properties with a concomitant decrease in collagen content. At both oxygen levels, ACP-derived neocartilage produced tissue with significantly enhanced mechanical properties and collagen content relative to AC-derived neocartilage. Both ACs and ACPs produced substantial collagen II and reduced levels of collagens I and X in physioxia relative to hyperoxia. Neocartilage from ACPs exhibited anisotropic organization characteristic of native cartilage with respect to collagen VI of the pericellular matrix when compared with AC-derived neocartilage; however, only ACs produced abundant surface-localized lubricin.

DISCUSSION AND CONCLUSIONS

Guiding human-derived cells toward condensation and subsequent culture in physioxia promoted the articular cartilage tissue phenotype for ACs and ACPs. Unlike ACs, ACPs are clonable and highly expandable while retaining chondrogenicity. The ability to generate large tissues utilizing a scaffold-free approach from a single autologous progenitor cell may represent a promising source of neocartilage destined for cartilage repair.

Autophagy promotes osteogenic differentiation of human bone marrow mesenchymal stem cell derived from osteoporotic vertebrae

Osteoporosis is one of the most prevalent age-related diseases worldwide, of which vertebral fracture is by far the most common osteoporotic fracture. Reduced bone formation caused by senescence is a main cause for senile osteoporosis, however, how to improve the osteogenic differentiation of osteoporotic bone marrow mesenchymal stem cells (BMSCs) remains a challenge. This study aimed to investigate the autophagic level changes in osteoporotic BMSCs derived from human vertebral body, and then influence osteogenesis through the regulation of autophagy. We found that hBMSCs from osteoporotic patients displayed the senescence-associated phenotypes and significantly reduced autophagic level compared to those derived from healthy ones. Meanwhile, the osteogenic potential remarkably decreased in osteoporotic hBMSCs, suggesting an inherent relationship between autophagy and osteogenic differentiation. Furthermore, rapymycin (RAP) significantly improved osteogenic differentiation through autophagy activatoin. However, the osteogenesis of hBMSCs was reversed by the autophagy inhibitor 3-methyladenine (3-MA). To provide more solid evidence, the hBMSCs pretreated with osteogenesis induction medium in the presence of 3-MA or RAP were implanted into nude mice. In vivo analysis showed that RAP treatment induced larger ectopic bone mass and more osteoid tissues, however, this restored ability of osteogenic potential was significantly inhibited by 3-MA pretreatment. In conclusion, our study indicated the pivotal role of autophagy for the osteo-differentiation hBMSCs, and offered novel therapeutic target for osteoporosis treatment.

High Quality of Infant Chondrocytes in Comparison with Adult Chondrocytes for Cartilage Tissue Engineering

BACKGROUND

Tissue engineering is used for the treatment of many diseases, and the ideal cell source for cartilage tissue engineering is chondrocytes. The main limitation of chondrocyte is the low number of cells in cartilage tissue engineering. This study investigated a suitable cell source with high proliferation rate to obtain a large number of chondrocytes.

METHODS

Adult cartilage tissue samples were obtained from adult patients undergoing surgical procedure, and infant cartilage tissue samples were obtained from polydactyly surgical waste. After isolation and expansion of chondrocytes, the proliferation rate was evaluated by calculating population doubling time (PDT) and MTT assay for both types of cells. Cartilage film was prepared with sheets of over confluent chondrocytes. The cartilage tissue film from infant and adult chondrocytes were evaluated histologically and by immunefluorescent staining collagen type 2.

RESULTS

PDT and MTT assays revealed that the growth rate of the infant chondrocytes was significantly higher than adult chondrocytes. Histological findings showed that sheets were thicker in the cartilage film of infant chondrocytes and they had more extracellular matrix between the sheets of cells than the cartilage film of adult chondrocytes. The findings of the immunofluorescent staining of cartilage film indicated that collagen type II film of polyductily was more positive than adult chondrocytes.

CONCLUSION

The recent study presented a new cell source to overcome the limitation of low number of chondrocytes for cell therapy of cartilage defects in adults and also sheets of cells able to overcome the problems of scaffolds.