The Effects Of Melatonin On Fracture Healing In Aged Rats

Research backgroundOsteoporosis is a systemic skeletal disease.It can reduce bone mass and bone micro-structure characterized by degradation,resulting in increased bone fragility and fracture.As people's living standards improve,it speeds up the aging process of the society and population growth life expectancy.Osteoporosis,especially estrogen deficiency caused by osteoporosis has many mechanisms.The study founds women with osteoporosis in elderly patients is divided into acute and chronic stage.Acute phase is mainly caused by the lack of estrogen. While the chronic stage was mainly due to changes in calcium metabolism in vivo-induced calcium loss and secondary hyperthyroidism.Incidence of osteoporosis in elderly men is also mainly due to lower estrogen content,but at the same time it founds that secretion of endocrine hormone system function also play an important role。These hormones include growth hormone,insulin-like growth factor-1 and melatonin.Another Study founds that melatonin are closely related to the male and female aging caused by osteoporosis and blood concentration of melatonin may be the lower incidence of osteoporosis in postmenopausal important factor.Pineal melatonin secretion are a Indoles chemical substances,which widely used in neural - endocrine - immune regulation,biological rhythms,anti-aging and anti-free radical injury,sedation,analgesia hypnotic,anticonvulsant,but also for cardiovascular, kidney and other organs have a broad role.Recent studies have found that it influence the balance of bone metabolism through direct or indirect way.Melatonin on the market are now selling the main components of Melatonin which has been widely used in biological rhythm regulation,nervous system,immune system, endocrine system,anti-aging and anti-tumor.But its about osteoporosis and fracture healing research,both at home and abroad is still less reported.Objective To investigate the effects of Melatonin on osteoporotic fracture healing in aged rats.MethodsThe status of osteoporosis in 22-month-old male rats was confirmed by total body bone mineral density measurement.Fracture healing model was established by osteotomy with a wire saw and fixation with a Kirschner pin on left femur.70 model rats were randomized into two groups:35 for control group,and 35 for Melatonin group. Melatonin group was given daily by gastric gavage at dose of 50μg/100 g/d for total 10 days,while control group was given an equivalent volume of saline.The rats were scarified in 2,4,8 and 12 weeks after operation,the callus formation was monitored by histological and immunohistochemistry(osteoportegerin) assessment,the bone mineral density measurement of the callus and the right femur was taken,alkaline phosphatase(ALP) activity as an index of bone formation was arrayed.Normal radiographs were taken at 12 weeks.Get the measurement data to mean±standard deviation,the experimental group and the control group were few compared with the two samples of information t test,P＜0.05 for the difference statistically significant.Results1.The histomorphological analysis revealed that the process of cartilage forming and transforming were postponed in Melatonin group.The immunohistochemical results showed a increase of expression of OPG in Melatonin group.2.Melatonin group had higher bone mineral density.3.Melatonin produced a significant increase in serum ALP.4.Normal radiographs showed Melatonin group had more callus formation.ConclusionMelatonin enhancements the osteoporotic fracture healing in aged rats.The most contributing factor associated with the poor fracture healing was inhibition of OPG..