Effects of losartan and atorvastatin on the development of early posttraumatic joint stiffness in a rat model

Abstract

Background

After a trauma, exuberant tissue healing with fibrosis of the joint capsule can lead to posttraumatic joint stiffness (PTJS). Losartan and atorvastatin have both shown their antifibrotic effects in different organ systems.

Objective

The purpose of this study was the evaluation of the influence of losartan and atorvastatin on the early development of joint contracture. In addition to joint angles, the change in myofibroblast numbers and the distribution of bone sialoprotein (BSP) were assessed.

Study design and methods

In this randomized and blinded experimental study with 24 rats, losartan and atorvastatin were compared to a placebo. After an initial joint injury, rat knees were immobilized with a Kirschner wire. Rats received either losartan, atorvastatin or a placebo orally daily. After 14 days, joint angle measurements and histological assessments were performed.

Results

Losartan increased the length of the inferior joint capsule. Joint angle and other capsule length measurements did not reveal significant differences between both drugs and the placebo. At cellular level both losartan and atorvastatin reduced the total number of myofibroblasts (losartan: 191±77, atorvastatin: 98±58, placebo: 319±113 per counting field, p<0.01) and the percentage area of myofibroblasts (losartan: 2.8±1.8% [p<0.05], atorvastatin: 2.5±1.7% [p<0.01], vs control [6.4±4%], respectively). BSP was detectable in equivalent amounts in the joint capsules of all groups with only a trend toward a reduction of the BSP-stained area by atorvastatin.

Conclusion

Both atorvastatin and losartan reduced the number of myofibroblasts in the posterior knee joint capsule of rat knees 2 weeks after trauma and losartan increased the length of the inferior joint capsule. However, these changes at the cellular level did not translate an increase in range of motion of the rats´ knee joints during early contracture development.

Keywords:

• posttraumatic joint stiffness
• knee joint contracture
• rat model
• myofibroblast
• antifibrotic drugs
• bone sialoprotein

Acknowledgments

The authors extend special thanks to Angelika Ackermann for technical support and Anke Grünow for graphic illustrations. We thank Dr Irene Schmidtmann from the Institute for Medical Biostatistics, Epidemiology and Informatics (IMBEI) for statistical consulting. Our research was funded in 2015 from the Johannes Gutenberg-University Mainz within the “Inneruniversitäre Forschungsförderung Stufe I” program and in 2016 from the German Society of Shoulder and Elbow Surgery (DVSE). The work was performed at the “Molekulares Forschungszentrum operativer Fächer (MFO)” of the University Medical Center Mainz.

Ethics approval

This study was approved by the local ethics committee “Landesuntersuchungsamt Rheinland-Pfalz” (ID 23 177-07/G 13-1-043). We have followed the German “Legal ordinance on the Protection of Animals Used for Experimental Purposes or for Other Scientific Purposes (Experimental Animal Welfare Regulation - TierSchVersV)” (https://www.gesetze-im-internet.de/tierschversv/BJNR312600013.html).

Data availability

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Abbreviations list

α-SMA, alpha smooth muscle actin; ACA, anti-α2Ct antibody; AT-1, angiotensin type 1; BSP, bone sialoprotein; CO_2, carbon dioxide; CTGF, connective tissue growth factor; DAB, 3,3′-diaminobenzidine; ECM, extracellular matrix; HIF-1, hypoxia-inducible factor 1; HMG-CoA, 3-hydroxy-3-methyl-glutaryl-coenzyme A; HO, heterotopic ossification; HRP, horseradish peroxidase; K-wire, Kirschner wire; MMP, matrix metalloproteinases; mRNA, messenger ribonucleic acid; P-ACA, PEGylated anti-α2Ct antibody; PTJS, posttraumatic joint stiffness; ROCK, Rho-associated coiled-coil-containing protein kinase; TRIS, tris(hydroxymethyl)aminomethane.

Author contributions

All authors made substantial contributions to conception and design, acquisition of data, or analysis and interpretation of data; took part in drafting the article or revising it critically for important intellectual content; gave final approval of the version to be published; and agree to be accountable for all aspects of the work.

Disclosure

Dr Andreas Baranowski reports grants from the Johannes Gutenberg-University Mainz and the German Society of Shoulder and Elbow Surgery (DVSE), during the conduct of the study. Dr Anja Klein reports grants from the German Society of Shoulder and Elbow Surgery (DVSE) and Inneruniversitäre Forschungsförderung Stufe I, during the conduct of the study. The authors report no other conflicts of interest in this work.