Objective

2

To observe the effect of acupotomy on the articular cartilage in rabbits with knee osteoarthritis (KOA) and explore its mechanism for delaying cartilage degeneration based on the mechanosensitive Piezo1/p38 mitogen-activated protein kinase (p38MAPK)/extracellular signal-regulated kinase 5 (ERK5) signaling pathway.

Methods

2

Twenty-four New Zealand rabbits were randomly divided into a blank group

a model group

an acupotomy group

and an acupotomy+agonist group

with 6 rabbits in each group. Using a modified Videman method

KOA models were prepared in the model group

acupotomy group

and acupotomy+agonist group. In the acupotomy group

the conventional acupotomy was delivered

targeting nodules or cord-like tissues around the knee joint. In the acupotomy+agonist group

2 h before acupotomy

Piezo1-specific agonist Yoda1 (0.355 mg/mL

0.5 mL per injection) was injected into articular cavity

and the other procedures were same as the acupotomy group. The intervention was administered once weekly and for 3 consecutive weeks in each group. Before and after intervention

the Lequesne MG score was used to assess the improvements in the local knee joint symptoms

physical signs

and functions in each group. After intervention

safranin O-fast green staining was employed to observe the morphology of cartilage tissue of knee joint. The contents of cartilage degradation products

cartilage oligomeric matrix protein (COMP) and C-terminal telopeptide of type Ⅱ collagen (CTX-Ⅱ) in serum and synovial fluid of knee joint were detected by ELISA. Western blot was used to detect the protein expression levels of type Ⅱ collagen (Col-Ⅱ)

Aggrecan

Piezo1

p38MAPK

and ERK5 in the cartilage tissue.

Results

2

Before intervention

compared with the blank group

the Lequesne MG scores increased in the model

acupotomy

and acupotomy+agonist groups (

P

<

0.01). After intervention

compared with the blank group

the model group showed a higher Lequesne MG score (

P

<

0.01)

and when compared with the model group and acupotomy+agonist group

the acupotomy group exhibited a lower Lequesne MG score (

P

<

0.05). Compared with the blank group

the model group and acupotomy+agonist group showed the markedly reduced safranin O staining of the cartilage matrix

non-uniform and clustered distribution of chondrocytes

unclear cartilage structural layers

and disordered and blurred tidemarks. When compared with the model

group and acupotomy + agonist group

the acupotomy group demonstrated more uniform red safranin O staining of the cartilage matrix

relatively uniform and orderly distribution of chondrocytes

clearer cartilage structural layers

and restored tidemarks. In comparison with the blank group

the contents of COMP and CTX-Ⅱ in the serum and synovial fluid were elevated in the model group (

P

<

0.01). Compared with the model group and the acupotomy+agonist group

the acupotomy group showed the decrease in COMP and CTX-Ⅱ (

P

<

0.01). Compared with the blank group

the protein expression of Col-Ⅱ and Aggrecan in the cartilage decreased (

P

<

0.01)

while that of Piezo1

p38MAPK

and ERK5 increased (

P

<

0.01) in the model group. Compared with the model group

the acupotomy group and the acupotomy+agonist group showed the increase in the protein expression of Col-Ⅱ and Aggrecan (

P

<

0.01) and the decrease in the protein expression of Piezo1

p38MAPK

and ERK5 (

P

<

0.01). When compared with the acupotomy+agonist group

the acupotomy group demonstrated the higher protein expression of Col-Ⅱand Aggrecan (

P

<

0.01) and lower expression of Piezo1

p38MAPK

and ERK5 (

P

<

0.01).

Conclusion

2

Acupotomy can alleviate articular cartilage degeneration in KOA model rabbits. The mechanism may be associated with regulating the Piezo1/p38MAPK/ERK5 mechanosensitive pathway

exerting mechano-biological effect

inhibiting extracellular matrix degradation

maintaining articular cartilage metabolic homeostasis

thereby attenuating cartilage degeneration and injury

and promoting the repair of degenerated articular cartilage.