In this study, we evaluated the effect of antibiotic on the intestinal microbial composition and the relationship between the gut microbiota dysbiosis and progression of osteoarthritis (OA). The concentration of serum OCN, TNF-α and IL-6, calcium was significantly decrease with a marked change in gut Flora in 8 weeks of oval antibiotic administration in OA. In contrast, the concentration of serum magnesium and estrogen were increased in antibiotic induced female mice. The results shown that antibiotic change intestinal bacterial and imply that antibiotic decrease the OA development, which may be caused by restrain its inflammatory reaction
Antibiotics alter the composition and functions of the microbiota and produce long-lasting effects for host[18],such as education of the immune system[32, 33], colonization resistance[34, 35] and allergic and metabolic syndromes[36]. In the intestinal, the gut microbiota catalyzes the conversion of drugs into absorbable, hydroxylation, and reduction[37]. We choose ampicillin and neomycin with less absorption in the intestine as an intervention. Another experiment of interfere with the intestinal flora is observe changes in osteoarthritis using germ-free mice. Ulici et.al found that GF mice will suppress the gut microbiota and decrease of development of OA after joint injury[16].
There are many methods to measure the severity of OA, such as OARSI, the Articular Cartilage Structure score, Safranin-O stains score and radiological test. Histopathology is currently the gold standard for assessing of OA in animal models[38]. This semi-quantitative scoring system proposed in this study was relatively easy and reproducibility to apply for both experienced and novices scores[39]. The micro-CT is another powerful technique utilized to study 3D structures reconstructed. Botter suggest that osteoarthritis in the murine knee using collagenase injections has been show significant changes in subchondral bone architecture could be detected and quantified in 3D with micro-CT analysis[40]. Soft X-ray apparatus also the important method to evaluate the severity of OA[41].
In early stages of OA in humans, elevated bone remodeling, subchondral bone loss and articular cartilage regression was observed, and was considered as a determinant of OA progression[42], subchondral sclerosis may be observed only during more advanced stages of OA[43]. In our studies, we found that antibiotic-induced dysbiosis for 8 weeks contribute more advanced stages of OA. There are three potential mechanisms by which the gut microbiota can influence bone tissues: 1)regulation of nutrient absorption at the gut epithelium, 2)regulation of the mucosal and systemic inflammation and immune system, 3)translocation of microbial contents across the gut endothelial barrier[44]. The overproduction of cytokines and growth factors is the important mediator in the pathophysiology of OA[45]. In OA pathogenesis particularly in synovial inflammation, activated chondrocytes and synovial fibroblasts (TNF-α and IL-6) have been identified as vital players[46]. Zhao et.al found that both spontaneous and surgically induced OA models indicated that TNF-α led to an accelerated OA-like phenotype[47]. TNF-α control the degeneration of articular cartilage matrix, which makes them prime targets for therapeutic strategies[48]. Latourte et.al found that IL-6 induces chondrocyte catabolism mainly via Stat3 signalling, a pathway activated in cartilage from joint subjected to DMM[49]. Intra-articular injections of IL-6 reproduced OA-like cartilage lesions in mice, and IL-6 knockout (KO) mice develop less severe posttraumatic OA lesions[50]. Lu J, et al investigated that correlation between the amount of intestinal flora and the number of CD4 + T lymphocytes and the levels of TNF-α and IL-6[51]. In our study, we found that antibiotics reduce the inflammatory response throughout the body after inhibiting the intestinal flora. This also provides new evidence for the intestinal flora-joint axis in osteoarthritis.
The role of the intestinal flora in the absorption of substances is very important, such as the absorption of inorganic and energy substances in the host. Scholz-Ahrens et.al studied that probiotic can increase the level of calcium prevented the decrease in bone metabolism in ovariectomized rats and the main mechanism of this process is increased intestinal absorptive bones and increased bowel microbial mass and reduced turnover of calcium in bones[52]. Whisner et.al studies the prebiotic increases calcium absorption, which may be mediated by the gut microbiota[53]. In our studies, we investigated that antibiotic decrease the total load of gut microbiota and it also mean that interaction mechanisms between intestinal flora and minerals[54]. Antibiotics perturbed gut microbial composition. Community diversity and richness were reduced, and the phyla Firmicutes/Bacteroidetes ratio was decreased by antibiotics[55]. This process leads to impaired gut barrier integrity and release of LPS from intestinal gram-negative bacteria for example Bacteroidetes into the bloodstream[56].Therefore, we found that the decrease of community diversity was increase the subchondral bone sclerosis and cartilage damage.
Gender was also reported specifically influence subchondral bone. Men are reported to have a higher prevalence of OA than women before the age of 50 years, but after this age the prevalence is higher in women, which coincides with menopause[57]. The estrogen replacement therapy exhibit a reduced risk of hip and knee OA in postmenopausal women[58]. Son et.al found that up of estrogen abrogates experimental OA via the estrogen-related receptor family of orphan nuclear receptor[59]. A lack of estrogens increases subchondral bone remodeling, and this bone remodeling has been suggested to ultimately induce osteoarthritis changes[60]. In general, acute loss of estrogens increases the levels of reactive oxygen species and activates nuclear factor-κB and pro-inflammatory cytokine production, indicating their predominant anti-inflammatory properties [61] .In our previous studies, we found that deficiency of estrogen can accelerate the development of OA which induced by ovariectomy[62]. What’s more, antibiotic-induced dysbiosis also increased the level of estrogen which may paly positive role in OA.
The role of osteocalcin in bone remodeling, specific expression and regulation in osteoblasts which is important biomarker in osteoporosis and level of reduced Osteocalcin expression were maintained in human osteoarthritic chondrocytes and represented a suitable biomarker of osteoarthritic chondrocyte activation[63]. Wagatsuma et.al found that diversity of gut microbiota affecting serum level of osteocalcin in patient[64]. It is means that the occurrence of osteoporosis causes uneven cartilage stress, which further aggravates joints and cartilage damage which make knee osteoarthritis more serious[57].At the same time, the exacerbation of osteoarthritis reduces the activity of mice and reduces stress stimuli which further aggravated osteoporosis[58]. In our studies, we found that antibiotic treatment of gut flora reduced the level of OCN which may contribute to development of OA and osteoporosis.
In addition, the effect of gut flora is also considered important factors for mice with sexual maturity[65]. However, the osteoarthritis after osteoporosis is also common in the clinical.