Tendon-Specific Dicer Deficient Mice Exhibit Hypoplastic Tendon Through the Downregulation of Tendon-Related Genes and MicroRNAs

CD1530, selective RARγ agonist, facilitates Achilles tendon healing by modulating the healing environment including less chondrification in a mouse model

Heterotopic ossification (HO) in Achilles tendon often arises due to endochondral ossification during the healing process following trauma. Retinoic acid receptor γ (RARγ) plays a critical role in this phenomenon. This study aims to elucidate the therapeutic effects of CD1530, an RARγ selective agonist, along with the contributing cells, in Achilles tendon healing, utilizing a cell lineage tracing system. Local injection of CD1530 facilitated histological tendon healing by inhibiting chondrification in a mouse Achilles rupture model. Resident Scleraxis (Scx)+ cells in Achilles tendon were not found to be actively involved in HO or　tendon healing following injury. Instead, these processes were primarily driven by tendon stem/progenitor cells (TSPC)-like cells. Furthermore, an in vitro assay revealed that CD1530 attenuated inflammation in injured Achilles tendon-derived tendon fibroblasts (iATF) and inhibited the chondrogenesis of iATF. This dual effect suggests the potential of CD1530 in effectively modulating the healing environment during tendon healing. Together, the present study demonstrated that the local administration of CD1530 accelerated tendon healing by modulating the healing environment, including reducing chondrification via targeting TSPC-like cells in a mouse Achilles tendon rupture model. These results suggest that CD1530 may have the potential to be a novel tendon therapy that offers benefits via the inhibition of chondrogenesis.

Response of a tenomodulin-positive subpopulation of human adipose-derived stem cells to decellularized tendon slices

The selection of appropriate cell sources is vital for the regeneration and repair of tendons using stem cell-based approaches. Human adipose-derived stem cells (hADSCs) have emerged as a promising therapeutic strategy for tendon injuries. However, the heterogeneity of hADSCs can lead to inconsistent or suboptimal therapeutic outcomes. In this study, we isolated and identified a tenomodulin (TNMD)-positive subpopulation from hADSCs (TNMD+hADSCs) using flow cytometry and then assessed the cellular response of this subpopulation to decellularized tendon slices (DTSs), including cell proliferation, migration, and tenogenic differentiation, using the CCK-8 assay, transwell migration assay, and quantitative real-time polymerase chain reaction. Our findings revealed that TNMD+hADSCs maintained the general characteristics of stem cells and exhibited significantly higher expressions of tendon-related markers compared to hADSCs. Importantly, DTSs significantly enhanced the proliferation, migration, and tenogenic differentiation of TNMD+hADSCs. This study provides preliminary experimental evidence for the translational application of ADSCs for tendon regeneration and repair.

Functional characteristics of Dicer genes in Plutella xylostella

BACKGROUND

Dicer is an endonuclease that belongs to the RNase III family and can specifically recognize and cleave double-stranded RNA (dsRNA). In most insects, there are two Dicer genes, Dicer-1 (Dcr-1) and Dicer-2 (Dcr-2), which are involved in the micro-RNA and small-interfering RNA pathways in many species, respectively. The function of Dicer in Plutella xylostella remains unknown.

RESULTS

The full-length open reading frames of P. xylostella Dicer-1 (PxDcr-1) and Dicer-2 (PxDcr-2) were cloned and sequenced. Dcr-1 and Dcr-2 proteins shared similar structural domains with the Dicer-Partner Binding Domain (Dicer-PBD) and the double-strand RNA binding domain (dsRBD) present only in Dcr-1. The phylogenetic trees showed that lepidopteran Dcr-1s or Dcr-2s clustered in one branch, with PxDcr-1 in the basal position and PxDcr-2 closest to Plodia interpunctella Dicer. Two homozygous knockout lines, ΔPxDcr-1 and ΔPxDcr-2, were obtained by using the CRISPR-Cas9 technique. The ΔPxDcr-1 strain exhibited a high mortality rate, a low eclosion rate, a low egg-laying rate, a low hatching rate, and a shriveled ovariole without mature eggs. The ΔPxDcr-2 strain showed no significant difference from the wild-type in terms of survival, development and reproduction, but the RNA interference (RNAi) efficiency caused by dsRNA was significantly reduced.

CONCLUSION

These findings demonstrate the involvement of PxDcr-1 in the development and reproduction of P. xylostella, specifically in the formation of ovarioles and eggs, and PxDcr-2 is indispensable for RNAi. These findings shed light on the function of Dcr-1 and Dcr-2 in Lepidoptera. © 2023 Society of Chemical Industry.

Senescence-accelerated mice prone 8 (SAMP8) in male as a spontaneous osteoarthritis model

BACKGROUND

Animal models of spontaneous osteoarthritis (OA) are sparse and not well characterized. The purpose of the present study is to examine OA-related changes and mechanisms in senescence-accelerated mouse prone 8 (SAMP8) that displays a phenotype of accelerated aging.  METHODS: Knees of male SAMP8 and SAM-resistant 1 (SAMR1) mice as control from 6 to 33 weeks of age were evaluated by histological grading systems for joint tissues (cartilage, meniscus, synovium, and subchondral bone), and µCT analysis. Gene expression patterns in articular cartilage were analyzed by real-time PCR. Immunohistochemistry was performed for OA-related factors, senescence markers, and apoptosis.

RESULTS

Starting at 14 weeks of age, SAMP8 exhibited mild OA-like changes such as proteoglycan loss and cartilage fibrillation. From 18 to 33 weeks of age, SAMP8 progressed to partial or full-thickness defects with exposure of subchondral bone on the medial tibia and exhibited synovitis. Histological scoring indicated significantly more severe OA in SAMP8 compared with SAMR1 from 14 weeks [median (interquartile range): SAMR1: 0.89 (0.56-1.81) vs SAMP8: 1.78 (1.35-4.62)] to 33 weeks of age [SAMR1: 1.67 (1.61-1.04) vs SAMP8: 13.03 (12.26-13.57)]. Subchondral bone sclerosis in the medial tibia, bone mineral density (BMD) loss of femoral metaphysis, and meniscus degeneration occurred much earlier than the onset of cartilage degeneration in SAMP8 at 14 weeks of age.

CONCLUSIONS

SAMP8 are a spontaneous OA model that is useful for investigating the pathogenesis of primary OA and evaluating therapeutic interventions.