Dataset Information

Conditional Deletion of the Phd2 Gene in Articular Chondrocytes Accelerates Differentiation and Reduces Articular Cartilage Thickness.

ABSTRACT: Based on our findings that PHD2 is a negative regulator of chondrocyte differentiation and that hypoxia signaling is implicated in the pathogenesis of osteoarthritis, we investigated the consequence of disruption of the Phd2 gene in chondrocytes on the articular cartilage phenotype in mice. Immunohistochemistry detected high expression of PHD2 in the superficial zone (SZ), while PHD3 and HIF-1? (target of PHD2) are mainly expressed in the middle-deep zone (MDZ). Conditional deletion of the Phd2 gene (cKO) in chondrocytes accelerated the transition of progenitors to hypertrophic (differentiating) chondrocytes as revealed by reduced SZ thickness, and increased MDZ thickness, as well as increased chondrocyte hypertrophy. Immunohistochemistry further revealed decreased levels of progenitor markers but increased levels of hypertrophy markers in the articular cartilage of the cKO mice. Treatment of primary articular chondrocytes, in vitro, with IOX2, a specific inhibitor of PHD2, promoted articular chondrocyte differentiation. Knockdown of Hif-1? expression in primary articular chondrocytes using lentiviral vectors containing Hif-1? shRNA resulted in reduced expression levels of Vegf, Glut1, Pgk1, and Col10 compared to control shRNA. We conclude that Phd2 is a key regulator of articular cartilage development that acts by inhibiting the differentiation of articular cartilage progenitors via modulating HIF-1? signaling.

SUBMITTER: Cheng S

PROVIDER: S-EPMC5368651 | biostudies-literature | 2017 Mar

REPOSITORIES: biostudies-literature

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Conditional Deletion of the Phd2 Gene in Articular Chondrocytes Accelerates Differentiation and Reduces Articular Cartilage Thickness.

Cheng Shaohong S Pourteymoor Sheila S Alarcon Catrina C Mohan Subburaman S

Scientific reports 20170328

Based on our findings that PHD2 is a negative regulator of chondrocyte differentiation and that hypoxia signaling is implicated in the pathogenesis of osteoarthritis, we investigated the consequence of disruption of the Phd2 gene in chondrocytes on the articular cartilage phenotype in mice. Immunohistochemistry detected high expression of PHD2 in the superficial zone (SZ), while PHD3 and HIF-1α (target of PHD2) are mainly expressed in the middle-deep zone (MDZ). Conditional deletion of the Phd2 ...[more]

PMID: 28349987

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Project description:Donor-site morbidity, limited numbers of cells, loss of phenotype during ex vivo expansion, and age-related decline in chondrogenic activity present critical obstacles to the use of autologous chondrocyte implantation for cartilage repair. Chondrocytes from juvenile cadaveric donors may represent an alternative to autologous cells. Hypothesis/The authors hypothesized that juvenile chondrocyte would show stronger and more stable chondrogenic activity than adult cells in vitro and that juvenile cells pose little risk of immunologic incompatibility in adult hosts.Controlled laboratory study.Cartilage samples were from juvenile (<13 years old) and adult (>13 years old) donors. The chondrogenic activity of freshly isolated human articular chondrocytes and of expanded cells after monolayer culture was measured by proteoglycan assay, gene expression analysis, and histology. Lymphocyte proliferation assays were used to assess immunogenic activity.Proteoglycan content in neocartilage produced by juvenile chondrocytes was 100-fold higher than in neocartilage produced by adult cells. Collagen type II and type IX mRNA in fresh juvenile chondrocytes were 100- and 700-fold higher, respectively, than in adult chondrocytes. The distributions of collagens II and IX were similar in native juvenile cartilage and in neocartilage made by juvenile cells. Juvenile cells grew significantly faster in monolayer cultures than adult cells (P = .002) and proteoglycan levels produced in agarose culture was significantly higher in juvenile cells than in adult cells after multiple passages (P < .001). Juvenile chondrocytes did not stimulate lymphocyte proliferation.These results document a dramatic age-related decline in human chondrocyte chondrogenic potential and show that allogeneic juvenile chondrocytes do not stimulate an immunologic response in vivo.Juvenile human chondrocytes have greater potential to restore articular cartilage than adult cells, and may be transplanted without the fear of rejection, suggesting a new allogeneic approach to restoring articular cartilage in older individuals.

Project description:Autologous chondrocyte implantation (ACI) is a regenerative procedure used to treat focal articular cartilage defects in knee joints. However, age has been considered as a limiting factor and ACI is not recommended for patients older than 40-50 years of age. One reason for this may be due to the reduced capacity of aged chondrocytes in generating new cartilage. Currently, the underlying mechanism contributing to aging-associated functional decline in chondrocytes is not clear and no proven approach exists to reverse chondrocyte aging. Given that chondrocytes in healthy hyaline cartilage typically display a spherical shape, believed to be essential for chondrocyte phenotype stability, we hypothesize that maintaining aged chondrocytes in a suspension culture that forces the cells to adopt a round morphology may help to "rejuvenate" them to a younger state, thus, leading to enhanced cartilage regeneration. Chondrocytes isolated from aged donors displayed reduced proliferation potential and impaired capacity in generating hyaline cartilage, compared to cells isolated from young donors, indicated by increased hypertrophy and cellular senescence. To test our hypothesis, the "old" chondrocytes were seeded as a suspension onto an agarose-based substratum, where they maintained a round morphology. After the 3-day suspension culture, aged chondrocytes displayed enhanced replicative capacity, compared to those grown adherent to tissue culture plastic. Moreover, chondrocytes subjected to suspension culture formed new cartilage in vitro with higher quality and quantity, with enhanced cartilage matrix deposition, concomitant with lower levels of hypertrophy and cellular senescence markers. Mechanistic analysis suggested the involvement of the RhoA and ERK1/2 signaling pathways in the "rejuvenation" process. In summary, our study presents a robust and straightforward method to enhance the function of aged human chondrocytes, which can be conveniently used to generate a large number of high-quality chondrocytes for ACI application in the elderly.

Dataset Information

Conditional Deletion of the Phd2 Gene in Articular Chondrocytes Accelerates Differentiation and Reduces Articular Cartilage Thickness.

Publications

Conditional Deletion of the Phd2 Gene in Articular Chondrocytes Accelerates Differentiation and Reduces Articular Cartilage Thickness.

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