Prenatal nicotine exposure increases osteoarthritis susceptibility in male elderly offspring rats via low-function programming of the TGFβ signaling pathway

Abstract

Epidemiological investigations indicate that effects related to prenatal adverse environments on the organs of the offspring could continue to adulthood. This study intends to confirm that prenatal nicotine exposure (PNE) increases the susceptibility of osteoarthritis (OA) in the male offspring, and to explore the potential intrauterine programming mechanism. During pregnancy, rats were divided into a PNE group and a control group. After birth, rats were given a high-fat diet for 6 months and long-distance running for 6 weeks. The rats were euthanized at 18 months after birth (PM18) and on gestational day 20 (GD20), respectively. Knee joints were collected for histochemistry, immunohistochemistry, and quantitative polymerase chain reaction (qPCR) assays. Histological analyses and the Mankin's score showed increased cartilage destruction and accelerated OA progression in adult offspring from the PNE group. Immunohistochemistry results showed decreased expression of transforming growth factor beta (TGFβ) signaling pathway. Furthermore, the expression of apoptosis factors (caspase-3 and caspase-8), inflammatory factors [interleukin (IL)-1, IL-6] and matrix degradation enzymes [matrix metalloproteinase (MMP)-3, MMP-13] were also significantly increased. Traced back to the intrauterine period, it was found that the number of chondrocytes and the contents of Col2A1 and aggrecan in the matrix in the PNE group were decreased. And, the expression of the TGFβ signaling pathway was inhibited. These results suggested that PNE enhanced the susceptibility of OA in male elderly offspring rats by down-regulating TGFβ signaling, which increased articular cartilage local inflammation, matrix degradation, and cell apoptosis. This study confirmed the developmental origin of OA, and clarified the congenital and the living environment impact on the occurrence and development of OA. Our findings provide a theoretical and experimental basis for OA early prevention.

Keywords: Inflammation; Intrauterine programming; Osteoarthritis; Prenatal nicotine exposure; TGFβ signaling pathway.