Distribution Of Hsp27 In Rat Molars And Their Development

Objective: To elucidate the role HSP27 during amelogenesis and odontogenesis in the teeth of limited growth by analyzing its expression in enamel organ of developing rat molar teeth and rat molar. Method: (1) To obtain embryos , a Wistar pregnant female on the day 17 of embryonic development was killed by cervical dislocation. Tissue including the tooth germs or primordial were dissected from the embryos and fixed in the ice-cold 4% paraformaldehyde in 0.1M phosphate buffer (PH 7.3) 24h at 4℃.(2)Twenty-eight Wistar female rats (1, 5, 11, 14, 21, 30, 100 days old,n=4 each)used were killed. The mandibule were removed and immersed in the same fixative 24h at 4℃.Following decalcification in 15% EDTA at 4℃for 1-10weeks.(3)Tooth germs from embryos and mandibules were made into paraffin section. Each section was processed for the SABC method using an anti-HSP27-polyclonal antibody. Immunohistochemical staining during different stages in ameloblast odontoblast and enamel free area cells were measured by the image analysis,the date of which was handled with SPSS11.5 software. Results: (1)During amelogenesis, Hsp27 immunoreactivity first appeared in the preameloblasts, and increased in immunoreactivity in secretory stage and maturation stage (1day,0.25048 ±0.007411; 5day ,0.29456±0.011328 ;11day,0.36398±0.008039 P<0.01 respectively). 14days after birth, the ameloblasts belong to late maturation stage. Hsp27 immunoreactivity were not different from those from 11days. (14day,. 0.36778±0.053316 ).(2)Hsp27 immunoreactivity positive staining was found in the the differentiating and differentiated odontoblasts. Following mature of odontoblasts , The coronal odontoblasts show intense Hsp27 immunoreactivity .At 21 days, the coronal odontoblasts retained intense hsp27 immunoreactivity, whereas the odontoblasts in the root and floor pulp where initially weak or negative. (21day, 0.15041±0.045361).But increased in immunoreativity in the later stages.(30day, 0.24151±0.007217;100day, 0.37384±0.044072 P<0.01 respectively). (3)Interestingly, the enamel free area cells, which essentially lack the ability for enamel formation, showed the Hsp27 immunoreactivity during 5-11days(5day, 0.35334 ±0.006531;11day, 0.36815±0.016382 P>0.05). but decreased in that immunoreactivity after 14 days following apoptosis(14day, 0.36778 ±0.053316 P<0.01). Conclusion: (1)Hsp27 might be a useful marker for distinguishing preameloblasts from inner enamel epithelial cells.(2) Expression of Hsp27 also reflects the differentiation status of odontoblasts.(3) Hsp27 has been shown to be a specific inhibitor of apopotosis, the enamel free area cells contribute to determine the outline of dentin at the cusped area.