PTH decreases in vitro human cartilage regeneration without affecting hypertrophic differentiation

Investigate the Regulatory Role of Parathyroid Hormone on Condylar Fibrocartilage Homeostasis

INTRODUCTION

Condylar fibrocartilage regeneration after injury has been hindered by its poor self-repair capacity. Injection of parathyroid hormone (PTH) has been proven to effectively delay cartilage damage in osteoarthritis. In this study, we investigated the regulatory effect of PTH on the homeostasis of condylar fibrocartilage.

METHODS

FCSCs were extracted and exposed to a high PTH environment from rats to analyze the transcriptional changes. The condyles of mice were cultured ex vivo and exposed to high PTH to observe changes in cartilage. Parathyroidectomy induced PTH-deficient rats were locally injected with PTH to observe its effects on cartilage homeostasis.

RESULTS

High PTH environment could promote chondrogenic differentiation of FCSCs early, while weakening at late phase. The ex vivo culture of mouse condyle under PTH stimulation enhanced the proliferation of chondrocytes early, which were replaced by hypertrophic chondrocytes. The degradation of cartilage matrix also grew distinct under high PTH. PTH deficiency induced osteoarthritis-like changes in rats, characterized by cartilage layers disorder, chondrocyte reduction, and matrix degradation. Exogenous PTH could reverse fibrocartilage degeneration.

CONCLUSION

The maintenance of PTH homeostasis is crucial for maintaining the function of temporomandibular condylar FCSCs. Exogenous PTH can ameliorate the characteristics associated with rat temporomandibular joint osteoarthritis.

Potential effects of teriparatide (PTH (1-34)) on osteoarthritis: a systematic review

Osteoarthritis (OA) is a common and prevalent degenerative joint disease characterized by degradation of the articular cartilage. However, none of disease-modifying OA drugs is approved currently. Teriparatide (PTH (1-34)) might stimulate chondrocyte proliferation and cartilage regeneration via some uncertain mechanisms. Relevant therapies of PTH (1-34) on OA with such effects have recently gained increasing interest, but have not become widespread practice. Thus, we launch this systematic review (SR) to update the latest evidence accordingly. A comprehensive literature search was conducted in PubMed, Web of Science, MEDLINE, the Cochrane Library, and Embase from their inception to February 2022. Studies investigating the effects of the PTH (1-34) on OA were obtained. The quality assessment and descriptive summary were made of all included studies. Overall, 307 records were identified, and 33 studies were included. In vivo studies (n = 22) concluded that PTH (1-34) slowed progression of OA by alleviating cartilage degeneration and aberrant remodeling of subchondral bone (SCB). Moreover, PTH (1-34) exhibited repair of cartilage and SCB, analgesic, and anti-inflammatory effects. In vitro studies (n = 11) concluded that PTH (1-34) was important for chondrocytes via increasing the proliferation and matrix synthesis but preventing apoptosis or hypertrophy. All included studies were assessed with low or unclear risk of bias in methodological quality. The SR demonstrated that PTH (1-34) could alleviate the progression of OA. Moreover, PTH (1-34) had beneficial effects on osteoporotic OA (OPOA) models, which might be a therapeutic option for OA and OPOA treatment.

Ectopic models recapitulating morphological and functional features of articular cartilage

BACKGROUND

Articular cartilage is an extremely specialized connective tissue which covers all diarthrodial joints. Implantation of chondrogenic cells without or with additional biomaterial scaffolds in ectopic locationsin vivo generates substitutes of cartilage with structural and functional characteristics that are used in fundamental investigations while also serving as a basis for translational studies.

METHODS

Literature search in Pubmed.

RESULTS AND DISCUSSION

This narrative review summarizes the most relevant ectopic models, among which subcutaneous, intramuscular, and kidney capsule transplantation and elaborates on implanted cells and biomaterial scaffolds and on their use to recapitulate morphological and functional features of articular cartilage. Although the absence of a physiological joint environment and biomechanical stimuli is the major limiting factor, ectopic models are an established component for articular cartilage research aiming to generate a bridge between in vitro data and the clinically more relevant translational orthotopic in vivo models when their limitations are considered.