Morphological, stereological and radiological changes in pinealectomized chicken cervical vertebrae

Abstract

Considerable evidence supports the hypothesis that melatonin plays an important role in osteogenesis. We carried out an experiment to investigate histological and radiological changes in the cervical vertebrae of pinealectomized chickens. Thirty new-hatched chicks were divided into two groups: pinealectomized group (n=15) and nonpinealectomized control (n=15). Surgical pinealectomies were performed in Hybro broiler chickens at the age of 3 days. At 8 wk, one animal from each group was examined using computed tomography scanner to obtain density histograms of four consecutive vertebrae between the 4th and 7th cervical vertebral segments of chickens. At the end of the study, all animals were killed for subsequent measurement of bone mineral density (BMD) and macroscopic, radiographic and histopathological evaluation of specimens. We found that the profile of the density histogram in nonpinealectomized control group showed a spike profile for the vertebral body, indicating an increase in the amount of higher density tissues in this region, while a plateau-shaped profile was obtained for the vertebral body in pinealectomy group, indicating the presence of heterogenous bone tissue. Accordingly, the mean value of BMD in pinealectomy group was significantly lower at the vertebral body in chickens compared with control subjects (P<0.001). At the end of the experiment, almost all of the chickens in pinealectomy group developed a scoliotic curvature and the mean weight and length of the cervical vertebral bodies of the pinealectomized chickens were significantly lower than those of control group (P<0.001). Although the numerical density of osteocytes and osteoblasts in pinealectomy group was significantly higher than that from the control group, total number of osteocytes but not osteoblasts in cervical vetrebrae from pinealectomized animals was significantly lower than that from nonpinealectomized control animals (P<0.05). In conclusion, the results of the current study demonstrated for the first time pinealectomy-induced histomorphometrical changes in chicken vertebral column using stereological methods, suggesting that pineal gland/melatonin may have an osteoinductive effect on bone formation, but further studies are needed to elucidate the relationship of our findings with some disorders such as postmenopausal and/or senile osteoporosis.

Melatonin inhibits fatty acid-induced triglyceride accumulation in ROS17/2.8 cells: implications for osteoblast differentiation and osteoporosis

“…An extreme form of bone loss is seen, of course, in the clinical condition of osteoporosis in humans, in which bone loss is so severe that bone fractures occur without obvious trauma, or with ordinarily trivial trauma, and vertebral deformities (compression or collapse) do alter skeletal spinal integrity. Similarly, pinealectomized animals (salmon, chicken, mice) that have a relative melatonin deficiency also develop spinal curvature and bone demineralization not unlike that seen in osteoporosis in the human (13,24,26,39).…”

Possible involvement of melatonin in tooth development: expression of melatonin 1a receptor in human and mouse tooth germs

“…Moreover, there are some reports that melatonin controls the secretion of human growth hormone (Forsling et al 1999) and adrenocortical hormones (Kostoglou-Athanassiou et al 1998;Cagnacci et al 1995). Furthermore, it has been reported that melatonin enhances the diVerentiation of osteoblasts in vitro and promotes bone formation in vivo (Roth et al 1999;Koyama et al 2002;Turgut et al 2005;Machida et al 2006;Nakade et al 1999;Satomura et al 2007). These data strongly suggest that melatonin is involved in the development and/or growth of other hard tissues as well as bone tissue.…”

“…There are many previous studies showing that melatonin has a variety of physiological actions such as control of circadian rhythms (Redman et al 1983;McArthur et al 1997), regulation of body temperature (Dollins et al 1994), activation of the immune system (Garcia-Maurino et al 2000;Raghavendra et al 2001;Guerrero and Reiter 2002), anti-tumor activity (Hill and Blask 1988;Martínez-Campa et al 2006;Sánchez-Barceló et al 2005), function as a free radical scavenger and antioxidant (León et al 2005;Tan et al 2007) and anabolic eVects on bone formation (Roth et al 1999;Koyama et al 2002;Turgut et al 2005;Machida et al 2006;Nakade et al 1999;Satomura et al 2007). However, no data are available about its eVect on tooth development.…”

Scientific Basis for the Potential Use of Melatonin in Bone Diseases: Osteoporosis and Adolescent Idiopathic Scoliosis

“…These facts and the above described effects of melatonin on bone physiology prompted studies on their possible utility as a complementary therapy for osteoporosis. Melatonin has been shown at the cell and tissue levels to promote osteogenesis and prevent bone deterioration in mammals [55], birds [56, 57], and fishes [21]. …”

“…In particular, the loss of melatonin induces a scoliotic curvature and reduces mean weight and length of cervical vertebrae, possibly due to a reduction in the total number of osteocytes. These results were interpreted to mean that melatonin may act to enhance osteocyte proliferation in the cervical vertebrae [57]. …”