Nano-crystalline diamond-coated titanium dental implants – A histomorphometric study in adult domestic pigs

Authors

Philipp Metzler, Cornelius von Wilmowsky, Bernd Stadlinger, Wolfgang Zemann, Karl Andreas Schlegel, Stephan Rosiwal, Stephan Rupprecht

Abstract

Promising biomaterial characteristics of diamond-coatings in biomedicine have been described in the literature. However, there is a lack of knowledge about implant osseointegration of this surface modification compared to the currently used sandblasted acid-etched Ti-Al6-V4 implants. The aim of this study was to investigate the osseointegration of microwave plasma-chemical-vapour deposition (MWP-CVD) diamond-coated Ti-Al6-V4 dental implants after healing periods of 2 and 5 months. Twenty-four MWP-CVD diamond-coated and 24 un-coated dental titanium-alloy implants (Ankylos®) were placed in the frontal skull of eight adult domestic pigs. To evaluate the effects of the nano-structured surfaces on bone formation, a histomorphometric analysis was performed after 2 and 5 months of implant healing. Histomorphometry analysed the bone-to-implant contact (BIC). No significant difference in BIC for the diamond-coated implants in comparison to reference implants could be observed for both healing periods. Scanning electron microscopy revealed an adequate interface between the bone and the diamond surface. No delamination or particle-dissociation due to shearing forces could be detected. In this study, diamond-coated dental titanium-alloy implants and sandblasted acid-etched implants showed a comparable degree of osseointegration.

Link to Article

http://dx.doi.org/10.1016/j.jcms.2012.11.020

Validation of histologic bone analysis following Microfil vessel perfusion

Authors

Sarhaddi, D; Poushanchi, B; Merati, M; Tchanque-Fossuo, C; Donneys, A; Baker, J; Buchman, S R

Abstract

The ability to examine bone vascularity using micro-computed tomography following vessel perfusion with Microfil® and to subsequently perform histologic bone analysis in the same specimen would provide an efficient method by which the vascular and cellular environment of bone can be examined simultaneously. The purpose of this report is to determine if the administration of Microfil precludes accurate histologic assessment of bone quality via osteocyte count and empty lacunae count. Sprague‐Dawley rats (n = 6) underwent perfusion with Microfil. Left hemi-mandibles were harvested, decalcified, and underwent vascular analysis via micro-computed tomography prior to sectioning and staining with Gomori’s trichrome. Quantitative histomorphometric evaluation was performed. Ninety-five percent confidence intervals (CIs) were used to determine statistical differences from an established set of controls (n = 12). Histologic analyses were successfully performed on specimens that had been perfused. Quantitative measures of bone cellularity of perfused versus control specimens revealed no statistical difference in osteocyte count per high-power field (95·33 versus 94·66; 95% CI: −7·64 to 6·30) or empty lacunae per high-power field (2·73 versus 1·89; 95% CI: −1·81 to 0·13). A statistical validation is reported that allows histologic analysis of cell counts in specimens which had been perfused with Microfil.

Link to Article

http://dx.doi.org/10.1179/2046023612Y.0000000012

The Effects of Delayed Puberty on the Growth Plate

Authors

Butler, Tiffiny A.; Yingling, Vanessa R

Abstract

Many athletes are beginning intense training before puberty, a time of increased bone accrual when up to 25% of total bone mineral accrual occurs. Female athletes experiencing late or delayed pubertal onset may have open epiphyseal plates that are vulnerable to injury. This investigation's purpose was to determine whether a delay in puberty (primary amenorrhea) affects the growth plate immediately postpuberty and at maturity. Forty-eight female Sprague-Dawley rats (23 d old) were randomly assigned to 4 groups (n=12); short-term control (C-ST), long-term control (C-LT), short-term GnRH antagonist (G-ST), and long-term GnRH antagonist (G-LT). At 25 days of age, daily gonadotropin-releasing hormone antagonist (GnRH-a) injections were administered delaying pubertal onset. Left tibias were analyzed. Stained frontal slices of proximal tibia (5 µm thick) were analyzed in hypertrophic, proliferative, and reserve zones for total height, zone height, and cell/column counts. All procedures were approved by Institutional Animal Care and Use Committee at Brooklyn College. Growth plate height was 19.7% wider in delayed puberty (G-ST) group and at maturity was 27.9% greater in G-LT group compared with control (C-LT) (P<0.05). No significant differences were found in short-term or long-term growth plate zone heights or cell/column counts between groups (P>0.05). Growth plate zone height normalized to total height resulted in 28.7% larger reserve zone in the short-term GnRH-a group but the proliferative zone was 8.5% larger in the long-term group compared with the control group (P<0.05). Normalized to growth plate height a significant decrease was found in column counts in proliferative zones of the short-term and long-term GnRH-a groups. Current data illustrate that delayed puberty using GnRH-a injections results in significant growth plate height and decreases proliferative column counts and zone height, thus potentially contributing to decreases in bone mass at maturity. Growth plate height increases indicate increased potential for growth and bone accrual. However, previous models report decreased bone volume following delayed puberty via GnRH-a injections that may have detrimental effects in the long term.

Link to Article

http://dx.doi.org/10.1097/BPO.0b013e31826a53f2

Sex and age modify biochemical and skeletal manifestations of chronic hyperparathyroidism by altering target organ responses to Ca2+ and PTH in mice

Authors

Zhiqiang Cheng, Nathan Liang, Tsui-Hua Chen, Alfred Li, Christian Santa Maria, Michael You, Hanson Ho, Fuqing Song, Daniel Bikle, Chialing Tu, Dolores Shoback, Wenhan Chang

Abstract

We studied mice with or without heterozygous deletion of the Casr in the parathyroid gland (PTG) [PTGCaSR(+/-)] to delineate effects of age and sex on manifestations of hyperparathyroidism (HPT). In control mice, aging induced a left-shift in the Ca2+/parathyroid hormone (PTH) set-point accompanied by increased PTG CaSR expression along with lowered serum Ca2+ and mildly increased PTH levels, suggesting adaptive responses of PTGs to aging-induced changes in mineral homeostasis. The aging effects on Ca2+/PTH set-point and CaSR expression were significantly blunted in PTGCaSR(+/-) mice who showed instead progressively elevated PTH levels with age, especially in 12-month-old females. These 12-month-old knockout mice demonstrated resistance to their high PTH levels in that serum 1,25-dihydroxyvitamin D (1,25-D) levels and RNA expression of renal Cyp27b1 and expression of genes involved in Ca2+ transport in kidney and intestine were unresponsive to the rising PTH levels. Such changes may promote negative Ca2+ balance, which further exacerbate the HPT. Skeletal responses to HPT were age-, sex-, and site-dependent. In control mice of either sex, trabecular bone in the distal femur decreased while cortical bone in the tibiofibular junction increased with age. In male PTGCaSR(+/-) mice, anabolic actions of the elevated PTH levels seemed to protect against trabecular bone loss at ≥3 months of age at the expense of cortical bone loss. In contrast, HPT produced catabolic effects on trabecular bone and anabolic effects on cortical bone in 3-month-old females; but these effects reversed by 12 months, preserving trabecular bone in aging mice. We demonstrate that the CaSR plays a central role in the adaptive responses of parathyroid function to age-induced changes in mineral metabolism and in target organ responses to calciotropic hormones. Restraining the ability of the PTG to upregulate CaSRs by heterozygous gene deletion contributes to biochemical and skeletal manifestations of HPT, especially in aging females.

Link to Article

http://dx.doi.org/10.1002/jbmr.1846

Transplantation of Human Umbilical Cord Blood-Derived Mesenchymal Stem Cells or Their Conditioned Medium Prevents Bone Loss in Ovariectomized Nude Mice

Authors

Jee Hyun An, Hyojung Park, Jung Ah Song, Kyung Ho Ki, Jae-Yeon Yang, Hyung Jin Choi, Sun Wook Cho, Sang Wan Kim, Seong Yeon Kim, Jeong Joon Yoo, Wook-Young Baek, Jung-Eun Kim, Soo Jin Choi, Wonil Oh, and Chan Soo Shin

Abstract

Umbilical cord blood (UCB) has recently been recognized as a new source of mesenchymal stem cells (MSCs) for use in stem cell therapy. We studied the effects of systemic injection of human UCB-MSCs and their conditioned medium (CM) on ovariectomy (OVX)-induced bone loss in nude mice. Ten-week-old female nude mice were divided into six groups: Sham-operated mice treated with vehicle (Sham-Vehicle), OVX mice subjected to UCB-MSCs (OVX-MSC), or human dermal fibroblast (OVX-DFB) transplantation, OVX mice treated with UCB-MSC CM (OVX-CM), zoledronate (OVX-Zol), or vehicle (OVX-Vehicle). Although the OVX-Vehicle group exhibited significantly less bone mineral density (BMD) gain compared with the Sham-Vehicle group, transplantation of hUCB-MSCs (OVX-MSC group) has effectively prevented OVX-induced bone mass attenuation. Notably, the OVX-CM group also showed BMD preservation comparable to the OVX-MSC group. In addition, microcomputed tomography analysis demonstrated improved trabecular parameters in both the OVX-MSC and OVX-CM groups compared to the OVX-Vehicle or OVX-DFB group. Histomorphometric analysis showed increased bone formation parameters, accompanied by increased serum procollagen type-I N-telopeptide levels in OVX-MSC and OVX-CM mice. However, cell-trafficking analysis failed to demonstrate engraftment of MSCs in bone tissue 48 h after cell infusion. In vitro, hUCB-MSC CM increased alkaline phosphatase (ALP) activity in human bone marrow-derived MSCs and mRNA expression of collagen type 1, Runx2, osterix, and ALP in C3H10T1/2 cells. Furthermore, hUCB-MSC CM significantly increased survival of osteocyte-like MLO-Y4 cells, while it inhibited osteoclastic differentiation. To summarize, transplantation of hUCB-MSCs could effectively prevent OVX-mediated bone loss in nude mice, which appears to be mediated by a paracrine mechanism rather than direct engraftment of the MSCs.

Link to Article

http://dx.doi.org/10.1089/ten.tea.2012.0047