Smoking delays chondrogenesis in a mouse model of closed tibial fracture healing

Abstract

Smoking delays the healing process and increases morbidity associated with many common musculoskeletal disorders, including long bone fracture. In the current study, a murine model of tibial fracture healing was used to test the hypothesis that smoking delays chondrogenesis after fracture. Mice were divided into two groups, a nonsmoking control group and a group exposed to cigarette smoke for 1 month prior to surgical tibial fracture. Mice were euthanized at 7, 14, and 28 days after surgery. The outcomes measured were immunohistochemical staining for type II collagen protein expression as a marker of cartilage matrix and proliferating cell nuclear antigen (PCNA) staining to measure proliferation at the site of injury. Toluidine blue staining and histomorphometry were used to quantify areas of cartilaginous and noncartilaginous fracture callus. Radiographs were analyzed for evidence of remodeling after injury. At day 7 after injury, mice exposed to cigarette smoke had a smaller fracture callus with less cartilage matrix compared to controls. Proliferation was present at high levels in both groups at this time point, but proliferating cells had a more immature morphology in the smoking group. At day 14, chondrogenesis was more active in smokers compared to controls, while a higher percentage of bone was present in the control animals. At day 28, X-ray analysis revealed a larger fracture callus remaining in the smoking animals. Together, these findings show that the chondrogenic phase of tibial fracture healing is delayed by smoking. This study represents, to our knowledge, the first analysis of molecular and cellular mechanisms of healing in a smoking mouse fracture model. ß

Regulation of chondrogenesis and chondrocyte differentiation by stress

“…Cartilage is an important target of cigarette smoke during fracture repair, and effects are observed on mesenchymal cell recruitment to the chondrocyte lineage and the later stages of endochondral bone formation. For example, exposure of mice to second-hand smoke caused delayed chondrogenesis in a tibial fracture model, as evidenced by reduced toluidine blue staining at day 7 after fracture and peak cartilage formation at day 14 when control calluses are mineralized (125). Work to identify which components of cigarette smoke are responsible for this inhibitory effect on chondrogenesis is important if the underlying molecular mechanisms are to be elucidated.…”

Effect of Smoking Cessation on Healing and Rehabilitation

“…The systematic review conducted by Rigotti, MWlafo and Stea~ (16] puplished 1n the Cochrane Collaboration fo~nd that intensive counseling for smoking cessation which continued at least one I?Onth after discharge was · able to maintain Principaf Inv~stigalor (Lewis, Pau l C) USU Project Number: HU0001-09-l-TS08 [18) confinned the cytotoxic effects of tobacco smoke on osteogenic activity which were also explored in the initial proposal. [19][20][21] Similar negative effects were found among in vivo research. Eleftherjou et al [22] evaluated the relationship between ~one structure and geometry with smoking among 723 young British military recruits.…”

Secretome analysis of human articular chondrocytes unravels catabolic effects of nicotine on the joint

“…A role for nicotine at high concentrations has been recently described on growth plate chondrocytes [14]. According to these observations, other authors suggest that smoking delays chondrogenesis in a mouse model of tibial fracture healing [15]. Finally, a recent report demonstrates that smoking and nicotine exposure delay development of collagen-induced arthritis in mice, and demonstrates a direct in vitro anti-inflamatory effect of this drug by diminishing IL-6 production [16].…”