Juan Rocabado - Academia.edu (original) (raw)

Papers by Juan Rocabado

Journal of Orthopaedic Surgery and Research, 2018

Background: Postmenopausal osteoporosis develops due to a deficiency of estrogen that causes a de... more Background: Postmenopausal osteoporosis develops due to a deficiency of estrogen that causes a decrease in bone mass and changes in the macro-and micro-architectural structure of the bone, leading to the loss of mechanical strength and an increased risk of fracture. Although the assessment of bone mineral density (BMD) has been widely used as a gold standard for diagnostic screening of bone fracture risks, it accounts for only a part of the variation in bone fragility; thus, it is necessary to consider other determinants of bone strength. Therefore, we aimed to comprehensively evaluate the architectural changes of the bone that influence bone fracture strength, together with the different sensitivities of cortical and trabecular bone in response to ovariectomy (OVX). Methods: Bone morphology parameters were separately analyzed both in cortical and in trabecular bones, at distal-metaphysis, and mid-diaphysis of OVX rat femurs. Three-point bending test was performed at mid-diaphysis of the femurs. Correlation of OVX-induced changes of morphological parameters with breaking force was analyzed using Pearson's correlation coefficient. Results: OVX resulted in a decline in the bone volume of distal-metaphysis trabecular bone, but an increase in distal-metaphysis and mid-diaphysis cortical bone volume. Tissue mineral density (TMD) remained unchanged in both the trabecular and cortical bone of the distal metaphysis but decreased in cortical bone of the mid-diaphysis. The OVX significantly increased the breaking force at mid-diaphysis of the femurs. Conclusions: OVX decreased the trabecular bone volume of the distal-metaphysis and increased the cortical bone volume of the distal-metaphysis and mid-diaphysis. Despite the reduction in TMD and increased cortical porosity, bone fracture strength increased in the mid-diaphysis after OVX. These results indicate that analyzing a single factor, i.e., BMD, is not sufficient to predict the absolute fracture risk of the bone, as OVX-induced bone response vary, depending on the bone type and location. Our results strongly support the necessity of analyzing bone microarchitecture and site specificity to clarify the true etiology of osteoporosis in a clinical setting.

Journal of Orthopaedic Surgery and Research, 2019

A multi-factorial analysis of bone morphology and fracture strength of rat femur in response to o... more A multi-factorial analysis of bone morphology and fracture strength of rat femur in response to ovariectomy," which was recently published in the Journal of Orthopaedic Surgery and Research [1], and very much appreciate the opportunity to respond. In the study, we aimed to comprehensively evaluate changes in the bone architecture that influence its fracture strength in response to estrogen deficiency of the ovariectomized (OVX) rat model. The changes in bone architecture induced by OVX varied at different sites, especially between trabecular and cortical bones. The OVX increased the external diameter of the cortical bone with a concomitant increase in bone strength at the mid-diaphysis, while the trabecular bone volume was decreased at the distalmetaphysis. One of the concerns raised was that the increased breaking force at the mid-diaphysis after OVX might be a consequence of the use of young rats, as we used rats that were 10 weeks old at the time of OVX and analyzed them at 18 weeks old. Considering the remodeling status and microarchitecture of the rat cortical bone, the use of aged rats (> 9 months old) and long observation periods (> 6 months) have been recommended for osteoporosis studies [2, 3]. However, it was reported that OVX still increases the external diameter of long bones with a concomitant increase in bone strength even in 9month-old rats [4]. Besides, due to the slow remodeling rate of the tissue, especially the cortical bone, sensitive detection approaches must be employed with aged-OVX models [5]. Note that fracture risk has not been reproduced in animal models, and the true degree of correspondence between bone changes in animal models and humans remains elusive [2]. Consequently, aged rats

PLOS ONE

Fibrillar type I collagen, the predominant organic component in bone, is stabilized by lysyl oxid... more Fibrillar type I collagen, the predominant organic component in bone, is stabilized by lysyl oxidase (LOX)-initiated covalent intermolecular cross-linking, an important determinant of bone quality. However, the impact of collagen cross-linking on the activity of bone cells and subsequent tissue remodeling is not well understood. In this study, we investigated the effect of collagen cross-linking on bone cellular activities employing a loss-of-function approach, using a potent LOX inhibitor, β-aminopropionitrile (BAPN). Osteoblastic cells (MC3T3-E1) were cultured for 2 weeks in the presence of 0-2 mM BAPN to obtain low cross-linked collagen matrices. The addition of BAPN to the cultures diminished collagen cross-links in a dose-dependent manner and, at 1 mM level, none of the major cross-links were detected without affecting collagen production. After the removal of cellular components from these cultures, MC3T3-E1, osteoclasts (RAW264.7), or mouse primary bone marrow-derived stromal cells (BMSCs) were seeded. MC3T3-E1 cells grown on low crosslink matrices showed increased alkaline phosphatase (ALP) activity. The number of multinucleate tartrate-resistant acid phosphatase (TRAP)-positive cells increased in RAW264.7 cells. Initial adhesion, proliferation, and ALP activity of BMSCs also increased. In the animal experiments, 4-week-old C57BL/6 mice were fed with BAPN-containing diet for 8 weeks. At this point, biochemical analysis of bone demonstrated that collagen cross-links decreased without affecting collagen content. Then, the diet was changed to a control diet to minimize the direct effect of BAPN. At 2 and 4 weeks after the change, histological samples were prepared. Histological examination of femur samples at 4 weeks showed a significant increase in the number of bone surface osteoblasts, while the bone volume and surface osteoclast numbers were not significantly affected. These results clearly demonstrated that the extent of collagen cross-linking of bone matrix affected the differentiation of bone cells, underscoring the importance of collagen cross-linking in the regulation of cell behaviors and tissue remodeling in bone. Characterization of collagen cross-linking in bone may be beneficial to obtain insight into not only bone mechanical property, but also bone cellular activities.

Implant Dentistry, 2015

To investigate the relationship between stress distributions and peri-implant bone reactions arou... more To investigate the relationship between stress distributions and peri-implant bone reactions around maxillary implants that support cantilevers in supraocclusal contact. After molar extraction, 16 Wistar rats received a titanium implant unilaterally. After healing, 8 rats (control group) were killed and the others received implant-supported cantilever superstructures in supraocclusion (loaded group). After 5 days, they were killed. The maxillae of all rats were scanned by microcomputed tomography (μ-CT). Based on the μ-CT images, bone volumes were measured. For the loaded group, 3D finite element models were created and analyzed under 20-N vertical and 5-N lateral forces, successively. After μ-CT scanning, sections were prepared and observed histologically. When compared with the controls, the bone volume tended to decrease in the loaded group, but the difference was not statistically significant. On average, marginal bone resorption and stresses tended to be higher in 2 rats that occluded on the cantilever arm than in the others, which occluded right on the implant, nevertheless, calculated stress did not surpass the maximum elastic stress (yielding strength) of rat bone. However, at the implant-bone interface of these samples, partial bone resorption surrounded by signs of active resorption was histologically found. These findings suggest that in this occlusally loaded rat model, the stress distributions correlated to some extent with bone volume and morphological changes observed on μ-CT images and histological sections.

Journal of Oral and Maxillofacial Surgery, 2014

Purpose: Clinically, bone marrow stromal cells (BMCs) are the most common source of osteoprogenit... more Purpose: Clinically, bone marrow stromal cells (BMCs) are the most common source of osteoprogenitor cells. Its harvest process, however, is invasive to patients. Previous reports have shown the potential advantages of using periosteum-derived cells (PDCs) as a source of cell-based transplant therapy. The objective of our study was to characterize the osteoblastic differentiation and mineralization ability of PDCs versus BMCs and osteoblasts (OBs).

Journal of Cellular Physiology, 2016

Considering the increased interest in cell-based bone regeneration, it is necessary to reveal the... more Considering the increased interest in cell-based bone regeneration, it is necessary to reveal the fate of transplanted cells and their substantive roles in bone regeneration. The aim of this study was to analyze the fate of transplanted cells and the effect of osteogenic cell transplantation on calvarial bone defect healing. An anti-apoptotic protein, heat shock protein (HSP) 27, was overexpressed in osteoblasts. Then, the treated osteoblasts were transplanted to calvarial bone defect and their fate was analyzed to evaluate the significance of transplanted cell survival. Transient overexpression of Hsp27 rescued MC3T3-E1 osteoblastic cells from H2 O2 -induced apoptosis without affecting osteoblastic differentiation in culture. Transplantation of Hsp27-overexpressing cells, encapsulated in collagen gel, showed higher proliferative activity, and fewer apoptotic cells in comparison with control cells. After 4-week of transplantation, both control cell- and Hsp27 overexpressed cell-transplanted groups showed significantly higher new bone formation in comparison with cell-free gel-transplantation group. Interestingly, the prolonged survival of transplanted osteoblastic cells by Hsp27 did not provide additional effect on bone healing. The transplanted cells in collagen gel survived for up to 4-week but did not differentiate into bone-forming osteoblasts. In conclusion, cell-containing collagen gel accelerated calvarial bone defect healing in comparison with cell-free collagen gel. However, prolonged survival of transplanted cells by Hsp27 overexpression did not provide additional effect. These results strongly indicate that cell transplantation-based bone regeneration cannot be explained only by the increment of osteogenic cells. Further studies are needed to elucidate the practical roles of transplanted cells that will potentiate successful bone regeneration. J. Cell. Physiol. 231: 1974-1982, 2016. © 2016 Wiley Periodicals, Inc.

Journal of cellular physiology, Jan 7, 2015

Type I collagen, a major extracellular component of the periodontal ligament (PDL), is post-trans... more Type I collagen, a major extracellular component of the periodontal ligament (PDL), is post-translationally modified by a series of specific enzymes. Among the collagen-modifying enzymes, lysyl oxidase (LOX) is essential to initiate collagen cross-linking and lysyl hydroxylases (LHs) to regulate the cross-linking pathways that are important for tissue specific mechanical properties. The purpose of this study was to investigate the effects of mechanical loading on the expression of collagen-modifying enzymes and subsequent tissue changes in PDL. Primary human PDL cells were subjected to mechanical loading in a 3D collagen gel, and gene expression and collagen component were analyzed. Wistar rats were subjected to excessive occlusal loading with or without intra-peritoneal injection of a LOX inhibitor, β-aminopropionitrile (BAPN). Upon mechanical loading, gene expression of LH2 and LOX was significantly elevated, while that of COL1A2 was not affected on hPDL-derived cells. The mechani...

Journal of Cellular Physiology, 2015

Type I collagen, a major extracellular component of the periodontal ligament (PDL), is post-trans... more Type I collagen, a major extracellular component of the periodontal ligament (PDL), is post-translationally modified by a series of specific enzymes. Among the collagen-modifying enzymes, lysyl oxidase (LOX) is essential to initiate collagen cross-linking and lysyl hydroxylases (LHs) to regulate the cross-linking pathways that are important for tissue specific mechanical properties. The purpose of this study was to investigate the effects of mechanical loading on the expression of collagen-modifying enzymes and subsequent tissue changes in PDL. Primary human PDL cells were subjected to mechanical loading in a 3D collagen gel, and gene expression and collagen component were analyzed. Wistar rats were subjected to excessive occlusal loading with or without intra-peritoneal injection of a LOX inhibitor, β-aminopropionitrile (BAPN). Upon mechanical loading, gene expression of LH2 and LOX was significantly elevated, while that of COL1A2 was not affected on hPDL-derived cells. The mechanical loading also elevated formation of collagen α-chain dimers in 3D culture. The numbers of LH2 and LOX positive cells in PDL were significantly increased in an excessive occlusal loading model. Notably, an increase of LH2-positive cells was observed only at the bone-side of PDL. Intensity of picrosirius red staining was increased by excessive occlusal loading, but significantly diminished by BAPN treatment. These results demonstrated that mechanical loading induced collagen maturation in PDL by up-regulating collagen-modifying enzymes and subsequent collagen cross-linking which are important for PDL tissue maintenance. J. Cell. Physiol. 9999: 1-8, 2015. © 2015 Wiley Periodicals, Inc.

Journal of Oral and Maxillofacial Surgery, 2014

Purpose: Clinically, bone marrow stromal cells (BMCs) are the most common source of osteoprogenit... more Purpose: Clinically, bone marrow stromal cells (BMCs) are the most common source of osteoprogenitor cells. Its harvest process, however, is invasive to patients. Previous reports have shown the potential advantages of using periosteum-derived cells (PDCs) as a source of cell-based transplant therapy. The objective of our study was to characterize the osteoblastic differentiation and mineralization ability of PDCs versus BMCs and osteoblasts (OBs).

Journal of Functional Foods, 2014

Collagen crosslink Type I collagen Lysyl hydroxylase A B S T R A C T Royal jelly (RJ) is an essen... more Collagen crosslink Type I collagen Lysyl hydroxylase A B S T R A C T Royal jelly (RJ) is an essential food for queen bees, and it reportedly has estrogen-like activity. The objective of this study was to evaluate the effect of RJ intake on bone quality with a focus on the posttranslational modifications of type I collagen. RJ was fed to ovariectomized (OVX) rats for 12 weeks. RJ intake did not affect OVX-induced reduction in bone volume at the femur epiphysis; however, the reduction of collagen crosslinks (pyridinoline and deoxypyridinoline), which represent an aspect of bone quality, were significantly mitigated. In cultured MC3T3-E1osteoblasts, RJ treatment did not affect cell proliferation, cell differentiation, matrix formation, or mineralization. However, RJ treatment did stimulate expression of plods, which encode lysyl hydroxylase isoforms that control the collagen crosslinking pathway, and it also affected collagen crosslinking. These results indicate that oral intake of RJ could improve bone quality by modulating the posttranslational modification of type I collagen.

Implant Dentistry, 2015

To investigate the relationship between stress distributions and peri-implant bone reactions arou... more To investigate the relationship between stress distributions and peri-implant bone reactions around maxillary implants that support cantilevers in supraocclusal contact. After molar extraction, 16 Wistar rats received a titanium implant unilaterally. After healing, 8 rats (control group) were killed and the others received implant-supported cantilever superstructures in supraocclusion (loaded group). After 5 days, they were killed. The maxillae of all rats were scanned by microcomputed tomography (μ-CT). Based on the μ-CT images, bone volumes were measured. For the loaded group, 3D finite element models were created and analyzed under 20-N vertical and 5-N lateral forces, successively. After μ-CT scanning, sections were prepared and observed histologically. When compared with the controls, the bone volume tended to decrease in the loaded group, but the difference was not statistically significant. On average, marginal bone resorption and stresses tended to be higher in 2 rats that occluded on the cantilever arm than in the others, which occluded right on the implant, nevertheless, calculated stress did not surpass the maximum elastic stress (yielding strength) of rat bone. However, at the implant-bone interface of these samples, partial bone resorption surrounded by signs of active resorption was histologically found. These findings suggest that in this occlusally loaded rat model, the stress distributions correlated to some extent with bone volume and morphological changes observed on μ-CT images and histological sections.

Journal of Orthopaedic Surgery and Research, 2018

Background: Postmenopausal osteoporosis develops due to a deficiency of estrogen that causes a de... more Background: Postmenopausal osteoporosis develops due to a deficiency of estrogen that causes a decrease in bone mass and changes in the macro-and micro-architectural structure of the bone, leading to the loss of mechanical strength and an increased risk of fracture. Although the assessment of bone mineral density (BMD) has been widely used as a gold standard for diagnostic screening of bone fracture risks, it accounts for only a part of the variation in bone fragility; thus, it is necessary to consider other determinants of bone strength. Therefore, we aimed to comprehensively evaluate the architectural changes of the bone that influence bone fracture strength, together with the different sensitivities of cortical and trabecular bone in response to ovariectomy (OVX). Methods: Bone morphology parameters were separately analyzed both in cortical and in trabecular bones, at distal-metaphysis, and mid-diaphysis of OVX rat femurs. Three-point bending test was performed at mid-diaphysis of the femurs. Correlation of OVX-induced changes of morphological parameters with breaking force was analyzed using Pearson's correlation coefficient. Results: OVX resulted in a decline in the bone volume of distal-metaphysis trabecular bone, but an increase in distal-metaphysis and mid-diaphysis cortical bone volume. Tissue mineral density (TMD) remained unchanged in both the trabecular and cortical bone of the distal metaphysis but decreased in cortical bone of the mid-diaphysis. The OVX significantly increased the breaking force at mid-diaphysis of the femurs. Conclusions: OVX decreased the trabecular bone volume of the distal-metaphysis and increased the cortical bone volume of the distal-metaphysis and mid-diaphysis. Despite the reduction in TMD and increased cortical porosity, bone fracture strength increased in the mid-diaphysis after OVX. These results indicate that analyzing a single factor, i.e., BMD, is not sufficient to predict the absolute fracture risk of the bone, as OVX-induced bone response vary, depending on the bone type and location. Our results strongly support the necessity of analyzing bone microarchitecture and site specificity to clarify the true etiology of osteoporosis in a clinical setting.

Journal of Orthopaedic Surgery and Research, 2019

A multi-factorial analysis of bone morphology and fracture strength of rat femur in response to o... more A multi-factorial analysis of bone morphology and fracture strength of rat femur in response to ovariectomy," which was recently published in the Journal of Orthopaedic Surgery and Research [1], and very much appreciate the opportunity to respond. In the study, we aimed to comprehensively evaluate changes in the bone architecture that influence its fracture strength in response to estrogen deficiency of the ovariectomized (OVX) rat model. The changes in bone architecture induced by OVX varied at different sites, especially between trabecular and cortical bones. The OVX increased the external diameter of the cortical bone with a concomitant increase in bone strength at the mid-diaphysis, while the trabecular bone volume was decreased at the distalmetaphysis. One of the concerns raised was that the increased breaking force at the mid-diaphysis after OVX might be a consequence of the use of young rats, as we used rats that were 10 weeks old at the time of OVX and analyzed them at 18 weeks old. Considering the remodeling status and microarchitecture of the rat cortical bone, the use of aged rats (> 9 months old) and long observation periods (> 6 months) have been recommended for osteoporosis studies [2, 3]. However, it was reported that OVX still increases the external diameter of long bones with a concomitant increase in bone strength even in 9month-old rats [4]. Besides, due to the slow remodeling rate of the tissue, especially the cortical bone, sensitive detection approaches must be employed with aged-OVX models [5]. Note that fracture risk has not been reproduced in animal models, and the true degree of correspondence between bone changes in animal models and humans remains elusive [2]. Consequently, aged rats

PLOS ONE

Fibrillar type I collagen, the predominant organic component in bone, is stabilized by lysyl oxid... more Fibrillar type I collagen, the predominant organic component in bone, is stabilized by lysyl oxidase (LOX)-initiated covalent intermolecular cross-linking, an important determinant of bone quality. However, the impact of collagen cross-linking on the activity of bone cells and subsequent tissue remodeling is not well understood. In this study, we investigated the effect of collagen cross-linking on bone cellular activities employing a loss-of-function approach, using a potent LOX inhibitor, β-aminopropionitrile (BAPN). Osteoblastic cells (MC3T3-E1) were cultured for 2 weeks in the presence of 0-2 mM BAPN to obtain low cross-linked collagen matrices. The addition of BAPN to the cultures diminished collagen cross-links in a dose-dependent manner and, at 1 mM level, none of the major cross-links were detected without affecting collagen production. After the removal of cellular components from these cultures, MC3T3-E1, osteoclasts (RAW264.7), or mouse primary bone marrow-derived stromal cells (BMSCs) were seeded. MC3T3-E1 cells grown on low crosslink matrices showed increased alkaline phosphatase (ALP) activity. The number of multinucleate tartrate-resistant acid phosphatase (TRAP)-positive cells increased in RAW264.7 cells. Initial adhesion, proliferation, and ALP activity of BMSCs also increased. In the animal experiments, 4-week-old C57BL/6 mice were fed with BAPN-containing diet for 8 weeks. At this point, biochemical analysis of bone demonstrated that collagen cross-links decreased without affecting collagen content. Then, the diet was changed to a control diet to minimize the direct effect of BAPN. At 2 and 4 weeks after the change, histological samples were prepared. Histological examination of femur samples at 4 weeks showed a significant increase in the number of bone surface osteoblasts, while the bone volume and surface osteoclast numbers were not significantly affected. These results clearly demonstrated that the extent of collagen cross-linking of bone matrix affected the differentiation of bone cells, underscoring the importance of collagen cross-linking in the regulation of cell behaviors and tissue remodeling in bone. Characterization of collagen cross-linking in bone may be beneficial to obtain insight into not only bone mechanical property, but also bone cellular activities.

Implant Dentistry, 2015

To investigate the relationship between stress distributions and peri-implant bone reactions arou... more To investigate the relationship between stress distributions and peri-implant bone reactions around maxillary implants that support cantilevers in supraocclusal contact. After molar extraction, 16 Wistar rats received a titanium implant unilaterally. After healing, 8 rats (control group) were killed and the others received implant-supported cantilever superstructures in supraocclusion (loaded group). After 5 days, they were killed. The maxillae of all rats were scanned by microcomputed tomography (μ-CT). Based on the μ-CT images, bone volumes were measured. For the loaded group, 3D finite element models were created and analyzed under 20-N vertical and 5-N lateral forces, successively. After μ-CT scanning, sections were prepared and observed histologically. When compared with the controls, the bone volume tended to decrease in the loaded group, but the difference was not statistically significant. On average, marginal bone resorption and stresses tended to be higher in 2 rats that occluded on the cantilever arm than in the others, which occluded right on the implant, nevertheless, calculated stress did not surpass the maximum elastic stress (yielding strength) of rat bone. However, at the implant-bone interface of these samples, partial bone resorption surrounded by signs of active resorption was histologically found. These findings suggest that in this occlusally loaded rat model, the stress distributions correlated to some extent with bone volume and morphological changes observed on μ-CT images and histological sections.

Journal of Oral and Maxillofacial Surgery, 2014

Purpose: Clinically, bone marrow stromal cells (BMCs) are the most common source of osteoprogenit... more Purpose: Clinically, bone marrow stromal cells (BMCs) are the most common source of osteoprogenitor cells. Its harvest process, however, is invasive to patients. Previous reports have shown the potential advantages of using periosteum-derived cells (PDCs) as a source of cell-based transplant therapy. The objective of our study was to characterize the osteoblastic differentiation and mineralization ability of PDCs versus BMCs and osteoblasts (OBs).

Journal of Cellular Physiology, 2016

Considering the increased interest in cell-based bone regeneration, it is necessary to reveal the... more Considering the increased interest in cell-based bone regeneration, it is necessary to reveal the fate of transplanted cells and their substantive roles in bone regeneration. The aim of this study was to analyze the fate of transplanted cells and the effect of osteogenic cell transplantation on calvarial bone defect healing. An anti-apoptotic protein, heat shock protein (HSP) 27, was overexpressed in osteoblasts. Then, the treated osteoblasts were transplanted to calvarial bone defect and their fate was analyzed to evaluate the significance of transplanted cell survival. Transient overexpression of Hsp27 rescued MC3T3-E1 osteoblastic cells from H2 O2 -induced apoptosis without affecting osteoblastic differentiation in culture. Transplantation of Hsp27-overexpressing cells, encapsulated in collagen gel, showed higher proliferative activity, and fewer apoptotic cells in comparison with control cells. After 4-week of transplantation, both control cell- and Hsp27 overexpressed cell-transplanted groups showed significantly higher new bone formation in comparison with cell-free gel-transplantation group. Interestingly, the prolonged survival of transplanted osteoblastic cells by Hsp27 did not provide additional effect on bone healing. The transplanted cells in collagen gel survived for up to 4-week but did not differentiate into bone-forming osteoblasts. In conclusion, cell-containing collagen gel accelerated calvarial bone defect healing in comparison with cell-free collagen gel. However, prolonged survival of transplanted cells by Hsp27 overexpression did not provide additional effect. These results strongly indicate that cell transplantation-based bone regeneration cannot be explained only by the increment of osteogenic cells. Further studies are needed to elucidate the practical roles of transplanted cells that will potentiate successful bone regeneration. J. Cell. Physiol. 231: 1974-1982, 2016. © 2016 Wiley Periodicals, Inc.

Journal of cellular physiology, Jan 7, 2015

Type I collagen, a major extracellular component of the periodontal ligament (PDL), is post-trans... more Type I collagen, a major extracellular component of the periodontal ligament (PDL), is post-translationally modified by a series of specific enzymes. Among the collagen-modifying enzymes, lysyl oxidase (LOX) is essential to initiate collagen cross-linking and lysyl hydroxylases (LHs) to regulate the cross-linking pathways that are important for tissue specific mechanical properties. The purpose of this study was to investigate the effects of mechanical loading on the expression of collagen-modifying enzymes and subsequent tissue changes in PDL. Primary human PDL cells were subjected to mechanical loading in a 3D collagen gel, and gene expression and collagen component were analyzed. Wistar rats were subjected to excessive occlusal loading with or without intra-peritoneal injection of a LOX inhibitor, β-aminopropionitrile (BAPN). Upon mechanical loading, gene expression of LH2 and LOX was significantly elevated, while that of COL1A2 was not affected on hPDL-derived cells. The mechani...

Journal of Cellular Physiology, 2015

Type I collagen, a major extracellular component of the periodontal ligament (PDL), is post-trans... more Type I collagen, a major extracellular component of the periodontal ligament (PDL), is post-translationally modified by a series of specific enzymes. Among the collagen-modifying enzymes, lysyl oxidase (LOX) is essential to initiate collagen cross-linking and lysyl hydroxylases (LHs) to regulate the cross-linking pathways that are important for tissue specific mechanical properties. The purpose of this study was to investigate the effects of mechanical loading on the expression of collagen-modifying enzymes and subsequent tissue changes in PDL. Primary human PDL cells were subjected to mechanical loading in a 3D collagen gel, and gene expression and collagen component were analyzed. Wistar rats were subjected to excessive occlusal loading with or without intra-peritoneal injection of a LOX inhibitor, β-aminopropionitrile (BAPN). Upon mechanical loading, gene expression of LH2 and LOX was significantly elevated, while that of COL1A2 was not affected on hPDL-derived cells. The mechanical loading also elevated formation of collagen α-chain dimers in 3D culture. The numbers of LH2 and LOX positive cells in PDL were significantly increased in an excessive occlusal loading model. Notably, an increase of LH2-positive cells was observed only at the bone-side of PDL. Intensity of picrosirius red staining was increased by excessive occlusal loading, but significantly diminished by BAPN treatment. These results demonstrated that mechanical loading induced collagen maturation in PDL by up-regulating collagen-modifying enzymes and subsequent collagen cross-linking which are important for PDL tissue maintenance. J. Cell. Physiol. 9999: 1-8, 2015. © 2015 Wiley Periodicals, Inc.

Journal of Oral and Maxillofacial Surgery, 2014

Purpose: Clinically, bone marrow stromal cells (BMCs) are the most common source of osteoprogenit... more Purpose: Clinically, bone marrow stromal cells (BMCs) are the most common source of osteoprogenitor cells. Its harvest process, however, is invasive to patients. Previous reports have shown the potential advantages of using periosteum-derived cells (PDCs) as a source of cell-based transplant therapy. The objective of our study was to characterize the osteoblastic differentiation and mineralization ability of PDCs versus BMCs and osteoblasts (OBs).

Journal of Functional Foods, 2014

Collagen crosslink Type I collagen Lysyl hydroxylase A B S T R A C T Royal jelly (RJ) is an essen... more Collagen crosslink Type I collagen Lysyl hydroxylase A B S T R A C T Royal jelly (RJ) is an essential food for queen bees, and it reportedly has estrogen-like activity. The objective of this study was to evaluate the effect of RJ intake on bone quality with a focus on the posttranslational modifications of type I collagen. RJ was fed to ovariectomized (OVX) rats for 12 weeks. RJ intake did not affect OVX-induced reduction in bone volume at the femur epiphysis; however, the reduction of collagen crosslinks (pyridinoline and deoxypyridinoline), which represent an aspect of bone quality, were significantly mitigated. In cultured MC3T3-E1osteoblasts, RJ treatment did not affect cell proliferation, cell differentiation, matrix formation, or mineralization. However, RJ treatment did stimulate expression of plods, which encode lysyl hydroxylase isoforms that control the collagen crosslinking pathway, and it also affected collagen crosslinking. These results indicate that oral intake of RJ could improve bone quality by modulating the posttranslational modification of type I collagen.

Implant Dentistry, 2015

To investigate the relationship between stress distributions and peri-implant bone reactions arou... more To investigate the relationship between stress distributions and peri-implant bone reactions around maxillary implants that support cantilevers in supraocclusal contact. After molar extraction, 16 Wistar rats received a titanium implant unilaterally. After healing, 8 rats (control group) were killed and the others received implant-supported cantilever superstructures in supraocclusion (loaded group). After 5 days, they were killed. The maxillae of all rats were scanned by microcomputed tomography (μ-CT). Based on the μ-CT images, bone volumes were measured. For the loaded group, 3D finite element models were created and analyzed under 20-N vertical and 5-N lateral forces, successively. After μ-CT scanning, sections were prepared and observed histologically. When compared with the controls, the bone volume tended to decrease in the loaded group, but the difference was not statistically significant. On average, marginal bone resorption and stresses tended to be higher in 2 rats that occluded on the cantilever arm than in the others, which occluded right on the implant, nevertheless, calculated stress did not surpass the maximum elastic stress (yielding strength) of rat bone. However, at the implant-bone interface of these samples, partial bone resorption surrounded by signs of active resorption was histologically found. These findings suggest that in this occlusally loaded rat model, the stress distributions correlated to some extent with bone volume and morphological changes observed on μ-CT images and histological sections.