ORIGINAL ARTICLE Hypertension modifies OPG, RANK, and RANKL expression during the dental socket bone healing process in spontaneously hypertensive rats Natalia Manrique & Cassiano Costa Silva Pereira & Eloá Rodrigues Luvizuto & Maria Del Pilar Rodriguez Sánchez & Tetuo Okamoto & Roberta Okamoto & Doris H. Sumida & Cristina Antoniali Received: 13 April 2014 /Accepted: 13 November 2014 # Springer-Verlag Berlin Heidelberg 2015 Abstract Objective The aim of this study was to evaluate the dental socket bone healing process by histomorphometric and im- munohistochemical analysis of osteoprotegerin (OPG), recep- tor activator of nuclear factor-κβ (RANK), and receptor acti- vator of nuclear factor-κβ ligand (RANKL) proteins in spon- taneously hypertensive rats (SHR). Materials and methods Under general anesthesia, 25 Wistar rats and 25 SHRs underwent upper right incisor extraction. Rats were euthanized after 7, 14, 21, 28, or 42 days of dental extractions. Histomorphometric and immunohistochemical analyses of OPG, RANK, and RANKL proteins were performed. Results Histomorphometric results showed decreased bone healing and reduced bone trabecular thickness in SHRs. Im- munohistochemical reactions showed intense RANKL and RANK immunolabeling at 14 and 28 postoperative days and mild OPG immunolabeling at 7, 14, and 21 days after surgery in SHRs. Conclusion The results of this study show that RANK, RANKL, and OPG immunolabeling was altered in SHRs, and these results are associated with bone healing delay and decreased trabecular thickness in SHRs. Clinical relevance Hypertension alters the expression of RANK, RANKL, and OPG and delays the socket bone healing process. These alterations could influence some dental procedures such as orthodontic treatment and implant placement. Keywords Extraction socket healing . Histomorphometry . Spontaneously hypertensive rats . OPG . RANK . RANKL Introduction Clinical and experimental studies have shown that hyperten- sion is associated with damaging effects on bone quality and density [1–3]. Several studies have demonstrated that sponta- neously hypertensive rats (SHRs) display important alter- ations in bone metabolism such as an increase in bone turn- over and reduction in cortical and trabecular bone mass [2, 4–6]. Osteoprotegerin (OPG), receptor activator of nuclear factor- κβ (RANK), and receptor activator of nuclear factor-κβ ligand (RANKL) proteins are mediators of several cell processes, including bone metabolism. In bone metabo- lism, osteoblasts modulate osteoclast formation and bone resorption by producing OPG and RANKL. OPG [7, 8] is able to bind to RANKL, preventing it from binding to RANK. By binding to RANKL, OPG inhibits osteoclast maturation, thus inhibiting osteoclastogenesis as well as lymphocyte de- velopment. Any imbalance in the communication between OPG, RANK, and RANKL proteins can lead to alterations in the quality of the formed mineralized tissue [9]. Luvizuto N. Manrique (*) Department of Pediatric and Social Dentistry, School of Dentistry of Araçatuba, UNESP—Univ Estadual Paulista, Araçatuba, SP, Brazil e-mail: namanrique@hotmail.com C. C. S. Pereira : E. R. Luvizuto : M. D. P. R. Sánchez Department of Surgery and Integrated Clinic, School of Dentistry of Araçatuba, UNESP—Univ Estadual Paulista, José Bonifácio 1193, CEP: 16015-050 Araçatuba, SP, Brazil T. Okamoto Graduate Research Department of Sacred Heart University—USC, Bauru, SP, Brazil R. Okamoto : D. H. Sumida : C. Antoniali Department of Basic Sciences, School of Dentistry of Aracatuba, UNESP—Univ Estadual Paulista, SP Araçatuba, Brazil Clin Oral Invest DOI 10.1007/s00784-014-1369-0