Observation of the effect of platelet-rich plasma combined with cyclic adenosine monophosphate on the tendon morphology, IGF-1 and bFGF expression in rabbit models of Achilles tendinopathy
Authors: Qin Rui , Li Rui , Wu Hongli , Zhou Jihe , Fei Xi , Wang Shuai , Luo Shike , Du Chuanjia , Liu Hongjiang 
Published: May 2023

Objective:
This study aims to examine the effects of Platelet-Rich Plasma (PRP) and cyclic Adenosine Monophosphate (cAMP) on the morphology of tendon tissue, as well as the expression of insulin-like growth factor 1 (IGF-1) and basic fibroblast growth factor (bFGF) in a rabbit model of Achilles tendinopathy. The study also aims to investigate the possible mechanisms underlying the combined effects of PRP and cAMP on the repair of Achilles tendinopathy.
Methods:
In this study, a total of forty white rabbits were fed for a week and then randomly divided into two groups: the model group (N=32) and the blank control group (N=8). The model group was injected with prostaglandin E 21 times a week, for a period of four weeks, at a location about 2 cm above the heel node, to establish an animal model of Achilles tendinopathy. On the other hand, the blank control group was injected with an equal amount of saline. After the modeling process, the group was randomly divided into four groups: the PRP group (N=8), the cAMP group (N=8), the combined group (N=8), and the model control group (N=8). The PRP group was injected with autologous platelet-rich plasma, the cAMP group was injected with cAMP suspension, the combined group was injected with a mixture of the two, and the model control group was injected with an equal amount of saline, once every 3 weeks for a total of 2 injections, and the 6-week injection was completed. Afterwards, 40 rabbits were executed by air embolization, and the Achilles tendon tissue specimens were taken for histomorphological examination and detection of IGF-1 and bFGF.
Results:
(1) In the HE staining analysis, the fibers in the combined group appeared to be neatly arranged and tightly packed, with no noticeable wavy changes or signs of inflammatory cell infiltration. However, the fibers in the PRP and cAMP groups were slightly disordered and loosely arranged, with some wavy changes and clear signs of inflammatory cell infiltration. In contrast, the fibers in the model control group showed significant wavy changes and obvious inflammatory cell infiltration.
(2) Sirius picric acid staining: the fibers in the combined group were neatly arranged and the matrix was basically normal, closest to the blank control group; the collagen fibers in the PRP and cAMP groups were slightly damaged and showed longitudinal tear-like in some positions, and the matrix was slightly reduced; the fibers in the model control group were disorganized and disordered, with longitudinal tear-like and reduced matrix.
(3) IGF-1 level: the expression was significantly higher in the combined group compared with the model control group (P<0.05); although the expression was higher in the PRP and cAMP groups compared with the model control group (P<0.05), it was slightly lower in the PRP group compared with the cAMP group (P<0.05); in addition, the expression was slightly lower in the PRP group compared with the cAMP group.
(4) bFGF levels: the expression was significantly lower in the PRP group compared with the cAMP group, but slightly higher compared with the model control group (P<0.05); the expression was significantly higher in the combination group compared with the model control group (P<0.05); the expression was significantly lower in the PRP and cAMP groups compared with the combination group;
CONCLUSION:
he combination of PRP and cAMP can increase the expression levels of IGF-1 and bFGF, improve fiber arrangement, reduce inflammatory cell infiltration, and promote the repair of rabbit Achilles tendon injury.