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Early postnatal ablation of the microRNA-processing enzyme, Drosha, causes chondrocyte death and impairs the structural integrity of the articular cartilage.

ABSTRACT: In growth plate chondrocytes, loss of Dicer, a microRNA (miRNA)-processing enzyme, causes defects in proliferation and differentiation, leading to a lethal skeletal dysplasia. However roles of miRNAs in articular chondrocytes have not been defined in vivo. To investigate the role of miRNAs in articular chondrocytes and to explore the possibility of generating a novel mouse osteoarthritis (OA) model caused by intrinsic cellular dysfunction, we ablated Drosha, another essential enzyme for miRNA biogenesis, exclusively in articular chondrocytes of postnatal mice.First, to confirm that the essential role of miRNAs in skeletal development, we ablated the miRNA biogenesis pathway by deleting Drosha or DGCR8 in growth plate chondrocytes. Next, to investigate the role of miRNAs in articular cartilage, we deleted Drosha using Prg4-CreER(T) transgenic mice expressing a tamoxifen-activated Cre recombinase (CreER(T)) exclusively in articular chondrocytes. Tamoxifen was injected at postnatal days, 7, 14, 21, and 28 to ablate Drosha.Deletion of Drosha or DGCR8 in growth plate chondrocytes caused a lethal skeletal defect similar to that of Dicer deletion, confirming the essential role of miRNAs in normal skeletogenesis. Early postnatal Drosha deletion in articular chondrocytes significantly increased cell death and decreased Safranin-O staining. Mild OA-like changes, including surface erosion and cleft formation, were found in male mice at 6 months of age; however such changes in females were not observed even at 9 months of age.Early postnatal Drosha deficiency induces articular chondrocyte death and can cause a mild OA-like pathology.

SUBMITTER: Kobayashi T

PROVIDER: S-EPMC4470813 | biostudies-literature | 2015 Jul

REPOSITORIES: biostudies-literature

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Early postnatal ablation of the microRNA-processing enzyme, Drosha, causes chondrocyte death and impairs the structural integrity of the articular cartilage.

Kobayashi T T Papaioannou G G Mirzamohammadi F F Kozhemyakina E E Zhang M M Blelloch R R Chong M W MW

Osteoarthritis and cartilage 20150221 7

<h4>Objective</h4>In growth plate chondrocytes, loss of Dicer, a microRNA (miRNA)-processing enzyme, causes defects in proliferation and differentiation, leading to a lethal skeletal dysplasia. However roles of miRNAs in articular chondrocytes have not been defined in vivo. To investigate the role of miRNAs in articular chondrocytes and to explore the possibility of generating a novel mouse osteoarthritis (OA) model caused by intrinsic cellular dysfunction, we ablated Drosha, another essential e ...[more]

PMID: 25707934

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Project description:BackgroundArticular cartilage (AC) is the layer of tissue that covers the articulating ends of the bones in diarthrodial joints. Across species, adult AC shows an arcade-like structure with collagen predominantly perpendicular to the subchondral bone near the bone, and collagen predominantly parallel to the articular surface near the articular surface. Recent studies into collagen fibre orientation in stillborn and juvenile animals showed that this structure is absent at birth. Since the collagen structure is an important factor for AC mechanics, the absence of the adult Benninghoff structure has implications for perinatal AC mechanobiology. The current objective is to quantify the dynamics of collagen network development in a model animal from birth to maturity. We further aim to show the presence or absence of zonal differentiation at birth, and to assess differences in collagen network development between different anatomical sites of a single joint surface. We use quantitative polarised light microscopy to investigate properties of the collagen network and we use the sheep (Ovis aries) as our model animal.ResultsPredominant collagen orientation is parallel to the articular surface throughout the tissue depth for perinatal cartilage. This remodels to the Benninghoff structure before the sheep reach sexual maturity. Remodelling of predominant collagen orientation starts at a depth just below the future transitional zone. Tissue retardance shows a minimum near the articular surface at all ages, which indicates the presence of zonal differentiation at all ages. The absolute position of this minimum does change between birth and maturity. Between different anatomical sites, we find differences in the dynamics of collagen remodelling, but no differences in adult collagen structure.ConclusionsThe collagen network in articular cartilage remodels between birth and sexual maturity from a network with predominant orientation parallel to the articular surface to a Benninghoff network. The retardance minimum near, but not at, the articular surface at all ages shows that a zonal differentiation is already present in the perinatal animals. In these animals, the zonal differentiation can not be correlated to the collagen network orientation. We find no difference in adult collagen structure in the nearly congruent metacarpophalangeal joint, but we do find differences in the dynamics of collagen network remodelling.

Project description:BackgroundArticular cartilage undergoes an important maturation process from neonate to adult that is reflected by alterations in matrix protein organization and increased heterogeneity of chondrocyte morphology. In the horse, these changes are influenced by exercise during the first five months of postnatal life. Transcriptional profiling was used to evaluate changes in articular chondrocyte gene expression during postnatal growth and development.MethodsTotal RNA was isolated from the articular cartilage of neonatal (0-10 days) and adult (4-5 years) horses, subjected to one round of linear RNA amplification, and then applied to a 9,367-element equine-specific cDNA microarray. Comparisons were made with a dye-swap experimental design. Microarray results for selected genes (COL2A1, COMP, P4HA1, TGFB1, TGFBR3, TNC) were validated by quantitative polymerase chain reaction (qPCR).ResultsFifty-six probe sets, which represent 45 gene products, were up-regulated (p < 0.01) in chondrocytes of neonatal articular cartilage relative to chondrocytes of adult articular cartilage. Conversely, 586 probe sets, which represent 499 gene products, were up-regulated (p < 0.01) in chondrocytes of adult articular cartilage relative to chondrocytes of neonatal articular cartilage. Collagens, matrix-modifying enzymes, and provisional matrix non-collagenous proteins were expressed at higher levels in the articular cartilage of newborn foals. Those genes with increased mRNA abundance in adult chondrocytes included leucine-rich small proteoglycans, matrix assembly, and cartilage maintenance proteins.ConclusionDifferential expression of genes encoding matrix proteins and matrix-modifying enzymes between neonates and adults reflect a cellular maturation process in articular chondrocytes. Up-regulated transcripts in neonatal cartilage are consistent with growth and expansion of the articular surface. Expression patterns in mature articular cartilage indicate a transition from growth to homeostasis, and tissue function related to withstanding shear and weight-bearing stresses.

Project description:The degradation of proteoglycan was examined in cultured slices of pig articular cartilage. Pig leucocyte catabolin (10 ng/ml) was used to stimulate the chondrocytes and induce a 4-fold increase in the rate of proteoglycan loss from the matrix for 4 days. Material in the medium of both control and depleted cultures was mostly a degradation product of the aggregating proteoglycan. It was recovered as a very large molecule slightly smaller than the monomers extracted with 4M-guanidinium chloride and lacked a functional hyaluronate binding region. The size and charge were consistent with a very limited cleavage or conformational change of the core protein near the hyaluronate binding region releasing the C-terminal portion of the molecule intact from the aggregate. The 'clipped' monomer diffuses very rapidly through the matrix into the medium. The amount of proteoglycan extracted with 4M-guanidinium chloride decreased during culture from both the controls and depleted cartilage, and the average size of the molecules initially remained the same. However, the proportion of molecules with a smaller average size increased with time and was predominant in explants that had lost more than 70% of their proteoglycan. All of this material was able to form aggregates when mixed with hyaluronate, and glycosaminoglycans were the same size and charge as normal, indicating either that the core protein had been cleaved in many places or that larger molecules were preferentially released. A large proportion of the easily extracted and non-extractable proteoglycan remained in the partially depleted cartilage and the molecules were the same size and charge as those found in the controls. There was no evidence of detectable glycosidase activity and only very limited sulphatase activity. A similar rate of breakdown and final distribution pattern was found for newly synthesized proteoglycan. Increased amounts of latent neutral metalloproteinases and acid proteinase activities were present in the medium of depleted cartilage. These were not thought to be involved in the breakdown of proteoglycan. Increased release of proteoglycan ceased within 24h of removal of the catabolin, indicating that the effect was reversible and persisted only while the stimulus was present.

Dataset Information

Early postnatal ablation of the microRNA-processing enzyme, Drosha, causes chondrocyte death and impairs the structural integrity of the articular cartilage.

Publications

Early postnatal ablation of the microRNA-processing enzyme, Drosha, causes chondrocyte death and impairs the structural integrity of the articular cartilage.

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