Local ZnCl2 accelerates fracture healing

The Significant Potential of Simonkolleite Powder for Deep Wound Healing under a Moist Environment: In Vivo Histological Evaluation Using a Rat Model

In the present work, simonkolleite powder consisting of Zn₅(OH)₈Cl₂·H₂O composition was proposed as a new candidate material for the healing of deep wounds in a moist environment. The powder was synthesized using a solution process and evaluated for wound-healing effects in rats. The pH value of physiological saline at 37 °C using the simonkolleite powder was 7.27, which was the optimal pH value for keratinocyte and fibroblast proliferation (range: 7.2-8.3). The amount of Zn²⁺ ions sustainably released from simonkolleite powder into physiological saline was 404 mmol/L below cytotoxic ion concentrations (<500 mmol/L), and the rhombohedral simonkolleite was accordingly converted to monoclinic Zn₅(OH)₁₀·2H₂O. To evaluate the wound-healing effect of simonkolleite powder, the powder was applied to a full-thickness surgical wound reaching the subcutaneous tissue in the rat's abdomen. The histological analysis of the skin tissues collected after 1, 2, and 4 weeks found that angiogenesis, collagen deposition, and maturation were notedly accelerated due to the Zn²⁺ ions released from simonkolleite powder. The simonkolleite regenerated collagen close to autologous skin tissue after 4 weeks. The hair follicles, one of the skin appendages, were observed on the regenerative skin in the simonkolleite group at 4 weeks but not in the control group. Therefore, simonkolleite was hypothesized to stimulate the early regeneration of skin tissue in a moist environment, compared with commercial wound dressing material. These results suggested that simonkolleite could offer great potential as new wound dressing material.

Hydrogel combined with antimicrobial protease dressing accompanied with emotional support to treat wounds of patients taking immunosuppressive agents: A longitudinal study

BACKGROUND

This study aimed to evaluate the healing process of chronic wounds treated with hydrogel combined with antimicrobial protease dressing and emotional support intervention in patients taking immunosuppressive agents.

CASES

The case series involved 8 patients treated at a tertiary public hospital for 12 weeks. Data were analysed by SPSS version 27.0. The intention-to-treat principle was carried out, without the loss or exclusion of the participants. The subjects had wounds for 70 (98) days, and they consisted of 50% (4/8) males with a mean age of 42.63 years (±16.94). All (100%) subjects had taken immunosuppressive agents, and 62.5% (5/8) had systolic hypertension. The mean initial area of all wounds was 19.54 (5.89) cm², and the mean final area was 3.0 cm², with a reduction rate of 89% over the 12 weeks of treatment. In addition, we found that tissue types of these wounds changed by using hydrogel combined with antibacterial protease dressings, especially devitalised tissue (P = 0.011). The amount of exudate did not statistically change (P = 0.083). No participant had severe or local adverse events during the study period. Hence, giving emotional support along with wound care for 12 weeks could significantly reduce anxiety scores (P = 0.012). These results suggested that hydrogel combined with antimicrobial protease dressing and emotional support intervention is a promising method for the healing of wounds in patients who suffer from immunosuppressive diseases or are receiving current immunosuppressive treatment.

Local zinc treatment enhances fracture callus properties in diabetic rats

The effects of locally applied zinc chloride (ZnCl₂ ) on early and late-stage parameters of fracture healing were evaluated in a diabetic rat model. Type 1 Diabetes has been shown to negatively impact mechanical parameters of bone as well as biologic markers associated with bone healing. Zinc treatments have been shown to reverse those outcomes in tests of nondiabetic and diabetic animals. This study is the first to assess the efficacy of a noncarrier mediated ZnCl₂ on bony healing in diabetic animals. This is a promising basic science approach which may lead to benefits for diabetic patients in the future. Treatment and healing were assessed through quantification of callus zinc, radiographic scoring, microcomputed tomography (µCT), histomorphometry, and mechanical testing. Local ZnCl₂ treatment increased callus zinc levels at 1 and 3 days after fracture (p ≤ 0.025). Femur fractures treated with ZnCl₂ showed increased mechanical properties after 4 and 6 weeks of healing. Histomorphometry of the ZnCl₂ -treated fractures found increased callus cartilage area at Day 7 (p = 0.033) and increased callus bone area at Day 10 (p = 0.038). In contrast, callus cartilage area was decreased (p < 0.01) after 14 days in the ZnCl₂ -treated rats. µCT analysis showed increased bone volume in the fracture callus of ZnCl₂ -treated rats at 6 weeks (p = 0.0012) with an associated increase in the proportion of µCT voxel axial projections (Z-rays) spanning the fracture site. The results suggest that local ZnCl₂ administration improves callus chondrogenesis leading to greater callus bone formation and improved fracture healing in diabetic rats.

Improved osteogenesis in rat femur segmental defects treated with human allograft and zinc adjuvants

Bone allograft is widely used to treat large bone defects or complex fractures. However, processing methods can significantly compromise allograft osteogenic activity. Adjuvants that can restore the osteogenic activity of processed allograft should improve clinical outcomes. In this study, zinc was tested as an adjuvant to increase the osteogenic activity of human allograft in a Rag2 null rat femoral defect model. Femoral defects were treated with human demineralized bone matrix (DBM) mixed with carboxy methyl cellulose containing ZnCl₂ (0, 75, 150, 300 µg) or Zn stearate (347 µg). Rat femur defects treated with DBM-ZnCl₂ (75 µg) and DBM-Zn stearate (347 µg) showed increased calcified tissue in the defect site compared to DBM alone. Radiograph scoring and µCT (microcomputed tomography) analysis showed an increased amount of bone formation at the defects treated with DBM-Zn stearate. Use of zinc as an adjuvant was also tested using human cancellous bone chips. The bone chips were soaked in ZnCl₂ solutions before being added to defect sites. Zn adsorbed onto the chips in a time- and concentration-dependent manner. Rat femur defects treated with Zn-bound bone chips had more new bone in the defects based on µCT and histomorphometric analyses. The results indicate that zinc supplementation of human bone allograft improves allograft osteogenic activity in the rat femur defect model.

Research status of biodegradable metals designed for oral and maxillofacial applications: A review

The oral and maxillofacial regions have complex anatomical structures and different tissue types, which have vital health and aesthetic functions. Biodegradable metals (BMs) is a promising bioactive materials to treat oral and maxillofacial diseases. This review summarizes the research status and future research directions of BMs for oral and maxillofacial applications. Mg-based BMs and Zn-based BMs for bone fracture fixation systems, and guided bone regeneration (GBR) membranes, are discussed in detail. Zn-based BMs with a moderate degradation rate and superior mechanical properties for GBR membranes show great potential for clinical translation. Fe-based BMs have a relatively low degradation rate and insoluble degradation products, which greatly limit their application and clinical translation. Furthermore, we proposed potential future research directions for BMs in the oral and maxillofacial regions, including 3D printed BM bone scaffolds, surface modification for BMs GBR membranes, and BMs containing hydrogels for cartilage regeneration, soft tissue regeneration, and nerve regeneration. Taken together, the progress made in the development of BMs in oral and maxillofacial regions has laid a foundation for further clinical translation.

Role of Zinc-Doped Bioactive Glass Encapsulated with Microspherical Gelatin in Localized Supplementation for Tissue Regeneration: A Contemporary Review

Gelatin, a natural polymer, provides excellent tissue compatibility for use in tissue rehabilitation. Bioactive glasses (BAG) offer superior capacity in stimulating a bioactive response but show high variability in uptake and solubility. To tackle these drawbacks, a combination of gelatin with BAG is proposed to form composites, which then offer a synergistic response. The cross-linked gelatin structure's mechanical properties are enhanced by the incorporation of the inorganic BAG, and the rate of BAG ionic supplementation responsible for bioactivity and regenerative potential is better controlled by a protective gelatin layer. Several studies have demonstrated the cellular benefits of these composites in different forms of functional modification such as doping with zinc or incorporation of zinc such as ions directly into the BAG matrix. This review presents a comprehensive perspective on the individual characteristics of BAG and gelatin, including the synthesis and mechanism of action. Further, adaptation of the composite into various applications for bone tissue engineering is discussed and future challenges are highlighted.

Accelerated Bone Regeneration by MOF Modified Multifunctional Membranes through Enhancement of Osteogenic and Angiogenic Performance

Owing to the insufficient guidance of new bone formation in orthopedic and craniomaxillofacial surgery, construction of a guided bone regeneration membrane to support vascularized bone regeneration remains a challenge. Herein, an electrospun asymmetric double-layer polycaprolactone/collagen (PCL/Col) membrane modified by metal-organic framework (MOF) crystals is developed. The optimization of the PCL/Col weight ratio (1:1 and 1:1.5) enables the composite membrane with a balanced tensile strength (only fell by 49.9% in wet conditions) and a controlled degradation rate (completely degraded at 12 weeks). The MOF crystals can provide a pH-responsive release of Zn²⁺ ions. In vitro experiments indicate that the barrier layer functions to prevent the infiltration of fibrous connective tissue. The MOF crystal layer functions to enhance osteogenesis and angiogenesis in vitro. Using a rat calvarial defect model, the MOF crystals exhibit a sign of osteoinductivity along with blood vessel formation after 8 weeks post-surgery. Strikingly, when assessed in a chick chorioallantoic membrane model, the MOF modified membrane demonstrates a significant angiogenic response, which can be envisaged as its outstanding merits over the commercially Col membrane. Therefore, the MOF crystals represent an exciting biomaterial option, with neovascularization capacity for bone tissue engineering and regenerative medicine.

Zinc chloride affects chondrogenesis via VEGF signaling

Insulin mimetics, including zinc containing compounds, have previously been shown to influence chondrogenesis as it relates to healing of fractures in various preclinical models. However, the mechanism by which these compounds drive chondrogenic differentiation is yet undefined. Here, via next-generation sequencing (NGS) and in vitro functional validation, we show that Zinc Chloride (ZnCl₂) induces expression of both chondrogenic genes (Sox9, Runx1, collagen) as well as genes associated with VEGF-mediated signal transduction, including VEGF receptors 1 and 2 and their ligands; VEGF-A and VEGF-B. Noticeably, although insulin was able to also induce expression of these pro-angiogenic and pro-chondrogenic genes, the impact of insulin on expression of VEGF receptor and ligand genes was marginal when compared to that of ZnCl_2. Furthermore, while the VEGFR antagonist, Axitinib, was able to attenuate the pro-chondrogenic effects of both insulin and ZnCl₂; a reduction in gene and protein expression was most profoundly observed when the antagonist was applied to cells treated with ZnCl_2. Taken together, these data suggest an important role for the VEGF-mediated signal transduction pathways in the positive effects observed when applying zinc-based compounds as adjuvants for chondrogenesis-mediated fracture healing. In this regard, further mechanistic evaluation of ZnCl₂ and other zinc-containing insulin mimetics may support rational design of therapies targeted for disease indications associated with impaired fracture healing.

The effect of zinc sulfate on penile corpus spongiosum after hypospadias repair in rats: A stereological study

Hypospadias repair involves correcting urethra defects and improving the wound healing process. Zinc has been well accepted as an effective agent in wound healing. This study aimed to investigate the effect of zinc on corpus spongiosum after experimental hypospadias in rats. The animals were divided into three groups. The control group rats underwent general anesthesia, but did not receive any surgeries and treatments. The second and third groups underwent surgeries and respectively received Distilled Water (DW, 2 ml) and zinc sulfate solution (2 ml, containing 4 mg zinc sulfate) by gavages twice a day for 14 days. Stereological methods were used to quantify the corpus spongiosum tissue. The volumes of corpus spongiosum, spongy tissue, urethral lumens, urethral epithelium, and collagen bundles and the number of fibroblasts were respectively amplified by 28%, 40%, 36%, 48%, 40%, and 29% in the surgery + zinc sulfate group in comparison to the surgery + DW group (p < 0.02). It can be concluded that consumption of 4 mg/day zinc sulfate for 14 days could improve the healing of hypospadias through increasing the population of fibroblasts, producing collagen bundles, and building a wider lumen and more epithelized urethra.

Zinc as a Therapeutic Agent in Bone Regeneration

Zinc is an essential mineral that is required for normal skeletal growth and bone homeostasis. Furthermore, zinc appears to be able to promote bone regeneration. However, the cellular and molecular pathways through which zinc promotes bone growth, homeostasis, and regeneration are poorly understood. Zinc can positively affect chondrocyte and osteoblast functions, while inhibiting osteoclast activity, consistent with a beneficial role for zinc in bone homeostasis and regeneration. Based on the effects of zinc on skeletal cell populations and the role of zinc in skeletal growth, therapeutic approaches using zinc to improve bone regeneration are being developed. This review focuses on the role of zinc in bone growth, homeostasis, and regeneration while providing an overview of the existing studies that use zinc as a bone regeneration therapeutic.

The effects of local and intraperitoneal zinc treatments on maxillofacial fracture healing in rabbits

OBJECTIVE

This study aimed to determine whether administration of topical and intraperitoneal zinc for maxillofacial fractures has any impact on the bone healing process.

MATERIAL AND METHOD

Thirty-two New Zealand rabbits were randomly assigned to four groups of eight each. The first group was the control group; fracture lines were fixed using titanium microplates and no medication was administered. The second group received fixations using zinc-coated titanium microplates. A single dose of 3 mg/kg zinc was administered intraperitoneally to the third group following fixations with titanium microplates. A single dose of 3 mg/kg zinc was administered intraperitoneally to the fourth group following fixations with zinc-coated titanium microplates. Zinc coating on to the titanium microplates was achieved using the physical vapor deposition technique. A fracture line was created in the nasal bones of all subjects and fixed with five-hole flat microplates and three 5-mm micro screws. All work groups were sacrificed at the end of the sixth week.

RESULTS

Histological examination showed that the number of osteoblasts were significantly higher in zinc-coated group (Group 2) than zinc uncoated, control group (Group 1), (415.6 ± 46.7 vs 366.3 ± 11.8) (p < 0.001). It was observed that intraperitoneal zinc treatment alone (Group 3) did not significantly increase in the osteoblast count compared to zinc un-coated group (Group 1), (390.6 ± 83.2 vs 366.3 ± 11.8), (p = 0.341). The immunoreactivity scores for IGF-1 were significantly higher in the zinc-coated group compared to control group (Group 2 vs 1), (9.3 ± 2.8 vs 3.7 ± 1.9) (p < 0.05). It was observed that intraperitoneal zinc treatment did not cause a significant difference in the aspect of IGF-1 for zinc-coated groups (Group 2 vs 4) (9.3 ± 2.8 vs 9.6 ± 2.2) (p = 0.791). The difference in the immunoreactivity score among whole groups for TGF-β was not statistically significant (Group 1 vs 2, 3.2 ± 1.7 vs 4.4 ± 2.3, p = 0.256; Group 1 vs 3, 3.2 ± 1.7 vs 3.8 ± 2.8, p = 0.524; Group 1 vs 4, 3.2 ± 1.7 vs 2.8 ± 1.3, p = 0.717; Group 2 vs 3, 4.4 ± 2.3, vs 3.8 ± 2.8, p = 0.610; Group 2 vs 4, 4.4 ± 2.3, vs 2.8 ± 1.3, p = 0.124; Group 3 vs 4, 3.8 ± 2.8, vs 2.8 ± 1.3, p = 0.311).

CONCLUSION

The local use of titanium microplates coated with zinc by PVD technique was found effective for fracture healing. Zinc coating of titanium microplates used in fracture treatment can accelerate fracture healing. It may be concluded that clinical studies should be performed now in order to explore if comparable results can be achieved in humans.

Blockade of the OGF-OGFr pathway in diabetic bone

Purpose: This research investigated the presence and integrity of the opioid growth factor (OGF)-opioid growth factor receptor (OGFr) regulatory pathway in type 1 diabetic (T1D) rats, and investigated whether modulation of this axis by naltrexone (NTX) altered the composition of normal bone or fractured femurs. Materials and Methods: Diabetes was induced by streptozotocin; controls rats received buffer. Hyperglycemic animals were subjected to femur osteotomy, with randomized cohorts receiving either topical NTX or sterile saline in calcium carbonate. In experiment 2, hyperglycemic rats were injected daily for 3 weeks with either 30 mg/kg NTX or sterile saline. Expression levels of OGF and OGFr were measured by immunohistochemistry, bone composition was assessed by histomorphometry, and bone integrity was evaluated by µCT and 3-point bending. Results: Relative to normoglycemic bones, OGF and OGFr expression levels were increased 95% and 84%, respectively, in T1D bone; serum levels of OGF in T1D rats were elevated 23%. Hyperglycemia decreased the strength (26%), osteocalcin expression (17%), and number of proliferative (Ki67+) cells (32%) in intact femur. Topical NTX treatment of fractured femurs reduced the percentage of granulation tissue and increased cartilage. Systemic NTX treatment of diabetic rats increased strength by 21% and energy absorbed by105% in bone relative to measurements in saline-treated diabetic rats. Conclusions: The OGF-OGFr pathway appears to be dysregulated in the bone of T1D rats. Topical NTX treatment of T1D fractured bone accelerated some aspects of delayed diabetic fracture repair, and systemic NTX protected against some elements of compromised bone composition.

Biodegradable zinc oxide composite scaffolds promote osteochondral differentiation of mesenchymal stem cells

Osteoarthritis (OA) involves the degeneration of articular cartilage and subchondral bone. The capacity of articular cartilage to repair and regenerate is limited. A biodegradable, fibrous scaffold containing zinc oxide (ZnO) was fabricated and evaluated for osteochondral tissue engineering applications. ZnO has shown promise for a variety of biomedical applications but has had limited use in tissue engineering. Composite scaffolds consisted of ZnO nanoparticles embedded in slow degrading, polycaprolactone to allow for dissolution of zinc ions over time. Zinc has well-known insulin-mimetic properties and can be beneficial for cartilage and bone regeneration. Fibrous ZnO composite scaffolds, having varying concentrations of 1-10 wt.% ZnO, were fabricated using the electrospinning technique and evaluated for human mesenchymal stem cell (MSC) differentiation along chondrocyte and osteoblast lineages. Slow release of the zinc was observed for all ZnO composite scaffolds. MSC chondrogenic differentiation was promoted on low percentage ZnO composite scaffolds as indicated by the highest collagen type II production and expression of cartilage-specific genes, while osteogenic differentiation was promoted on high percentage ZnO composite scaffolds as indicated by the highest alkaline phosphatase activity, collagen production, and expression of bone-specific genes. This study demonstrates the feasibility of ZnO-containing composites as a potential scaffold for osteochondral tissue engineering.

Effects of zinc and aprotinin on the healing of ulnar diaphyseal fractures in rabbits

The effects of zinc and aprotinin on fracture healing in experimentally induced fractures were investigated by means of histometric analyses and alkaline phosphatase histochemistry. Healthy 54 adult New Zealand White female rabbits were separated into three groups as control, zinc, and aprotinin treatment. The control animals did not receive any medicament; zinc sulphate was given orally to the rabbits in the Zn group for 15 days. Aprotinin was postoperatively infiltrated into the fracture area at the 3rdand 24thh following operation. Immobilization of fracture ends of all groups was similar throughout the experiment. The zinc administered group displayed the highest alkaline phosphatase positive cell level through the experiment. By day 30 after the operation, fibrocartilage and osseous tissues reached the highest levels in the zinc treated group. Based on the observation of augmented osseous tissue formation and increased alkaline phosphatase positive osteoblastic cell activity in the callus, it was conluded that Zn sulphate is a potent stimulator of bone formation by increasing mineralization in the fractured bone segments.

Zinc-Containing Hydroxyapatite Enhances Cold-Light-Activated Tooth Bleaching Treatment In Vitro

Cold-light bleaching treatment has grown to be a popular tooth whitening procedure in recent years, but its side effect of dental enamel demineralization is a widespread problem. The aim of this study was to synthesize zinc-substituted hydroxyapatite as an effective biomaterial to inhibit demineralization or increase remineralization. We synthesized zinc-substituted hydroxyapatite containing different zinc concentrations and analysed the product using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and energy dispersive spectrometer (EDS). The biological assessment of Zn-HA was conducted by CCK-8 assay and bacterial inhibition tests. pH cycling was performed to estimate the effect of Zn-HA on the enamel surface after cold-light bleaching treatment. The XRD, FTIR, and EDS results illustrated that zinc ions and hydroxyapatite combined in two forms: (1) Zn²⁺ absorbed on the surface of HA crystal and (2) Zn²⁺ incorporated into the lattice of HA. The results indicated that 2% Zn-HA, 4% Zn-HA, and 8% Zn-HA effectively inhibited the growth of bacteria yet showed poor biocompatibility, whereas 1% Zn-HA positively affected osteoblast proliferation. The XRD and scanning electron microscopy (SEM) results showed that the use of Zn-HA in pH cycling is obviously beneficial for enamel remineralization. Zinc-substituted hydroxyapatite could be a promising biomaterial for use in cold-light bleaching to prevent enamel demineralization.

Effects of local vanadium delivery on diabetic fracture healing

This study evaluated the effect of local vanadyl acetylacetonate (VAC), an insulin mimetic agent, upon the early and late parameters of fracture healing in rats using a standard femur fracture model. Mechanical testing, and radiographic scoring were performed, as well as histomorphometry, including percent bone, percent cartilage, and osteoclast numbers. Fractures treated with local 1.5 mg/kg VAC possessed significantly increased mechanical properties compared to controls at 6 weeks post-fracture, including increased torque to failure (15%; p = 0.046), shear modulus (89%; p = 0.043), and shear stress (81%; p = 0.009). The radiographic scoring analysis showed increased cortical bridging at 4 weeks and 6 weeks (119%; p = 0.036 and 209%; p = 0.002) in 1.5 mg/kg VAC treated groups. Histomorphometry of the fracture callus at days 10 and 14 showed increased percent cartilage (121%; p = 0.009 and 45%; p = 0.035) and percent mineralized tissue (66%; p = 0.035 and 58%; p = 0.006) with local VAC treated groups compared to control. Additionally, fewer osteoclasts were observed in the local VAC treated animals as compared to controls at day 14 (0.45% ± 0.29% vs. 0.83% ± 0.36% of callus area; p = 0.032). The results suggest local administration of VAC acts to modulate osteoclast activity and increase percentage of early callus cartilage, ultimately enhancing mechanical properties comparably to non-diabetic animals treated with local VAC. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2174-2180, 2017.

Local Zinc Chloride Release From a Calcium Sulfate Carrier Enhances Fracture Healing

BACKGROUND

This study examined the efficacy of calcium sulfate (CaSO4) as a carrier for intramedullary delivery of zinc chloride (ZnCl2) to treat fracture healing in a BB Wistar rat model. A non-carrier-mediated injection of 3.0 mg/kg of ZnCl2 has previously been shown to enhance fracture healing.

METHODS

A heterogeneous mixture of ZnCl2 and CaSO4 was administered into the intramedullary femoral canal and a mid-diaphyseal femur fracture was created unilaterally. Early and late parameters of fracture healing were assessed using biomechanical testing, radiographic scoring, quantitative histomorphometry (for percentage of new cartilage and bone within the fracture callus), and long-term histologic evaluation.

RESULTS

Fractures treated with 1.0 mg/kg of ZnCl2/CaSO4 demonstrated a significantly higher maximum torque to failure compared with both CaSO4 (P = 0.048) and saline (P = 0.005) controls at 4 weeks postfracture (396.4 versus 251.3 versus 178.7 N mm, respectively). Statistically significant increases in torsional rigidity, effective shear modulus, and effective shear stress were also found, as well as a 3.5 times increase in radiographic score (based on bone union). Histologic examination of the fracture callus indicated enhanced chondrogenesis at day 14 postfracture, with increased percent cartilage for the ZnCl2/CaSO4 group compared with saline (P = 0.0004) and CaSO4 (P = 0.0453) controls. Long-term radiographic and histologic evaluation revealed no abnormal bone formation or infection up to 12 weeks postoperatively.

CONCLUSIONS

The effective dose of ZnCl2 augmentation for the enhancement of fracture healing in rats was reduced 3-fold in this study compared with previous findings. Furthermore, CaSO4 acted synergistically with ZnCl2 to increase the mechanical strength and stability at the fracture site.

Promotive Effect of Zinc Ions on the Vitality, Migration, and Osteogenic Differentiation of Human Dental Pulp Cells

Zinc is an essential trace element for proper cellular function and bone formation. However, its exact role in the osteogenic differentiation of human dental pulp cells (hDPCs) has not been fully clarified before. Here, we speculated that zinc may be effective to regulate their growth and osteogenic differentiation properties. To test this hypothesis, different concentrations (1 × 10^-5, 4 × 10^-5, and 8 × 10^-5 M) of zinc ions (Zn²⁺) were added to the basic growth culture medium and osteogenic inductive medium. Cell viability and migration were measured by cell counting kit-8 (CCK-8) and transwell migration assay in the basic growth culture medium, respectively. The reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was used to detect the gene expression levels of selective osteogenic differentiation markers and zinc transporters. Alkaline phosphatase (ALP) activity analysis and alizarin red S staining were used to investigate the mineralization of hDPCs. Exposure of hDPCs to Zn²⁺ stimulated their viability and migration capacity in a dose- and time-dependent manner. RT-qPCR assay revealed elevated expression levels of osteogenic differentiation-related genes and zinc transporters genes in various degrees. ALP activity was also increased with elevated Zn²⁺ concentrations and extended culture periods, but enhanced matrix nodules formation were observed only in 4 × 10^-5 and 8 × 10^-5 M Zn²⁺ groups. These findings suggest that specific concentrations of Zn²⁺ could potentiate the vitality, migration, and osteogenic differentiation of hDPCs. We may combine optimum zinc element into pulp capping materials to improve their biological performance.

Accessing the biocompatibility of layered double hydroxide by intramuscular implantation: histological and microcirculation evaluation

Biocompatibility of layered double hydroxides (LDHs), also known as hydrotalcite-like materials or double metal hydroxides, was investigated by in vivo assays via intramuscular tablets implantation in rat abdominal wall. The tablets were composed by chloride ions intercalated into LDH of magnesium/aluminum (Mg2Al-Cl) and zinc/aluminum (Zn2Al-Cl). The antigenicity and tissue integration capacity of LDHs were assessed histologically after 7 and 28 days post-implantation. No fibrous capsule nearby the LDH was noticed for both materials as well any sign of inflammatory reactions. Sidestream Dark Field imaging, used to monitor in real time the microcirculation in tissues, revealed overall integrity of the microcirculatory network neighboring the tablets, with no blood flow obstruction, bleeding and/or increasing of leukocyte endothelial adhesion. After 28 days Mg2Al-Cl promoted multiple collagen invaginations (mostly collagen type-I) among its fragments while Zn2Al-Cl induced predominantly collagen type-III. This work supports previous results in the literature about LDHs compatibility with living matter, endorsing them as functional materials for biomedical applications.

Zinc has insulin-mimetic properties which enhance spinal fusion in a rat model

BACKGROUND CONTEXT

Previous studies have found that insulin or insulin-like growth factor treatment can stimulate fracture healing in diabetic and normal animal models, and increase fusion rates in a rat spinal fusion model. Insulin-mimetic agents, such as zinc, have demonstrated antidiabetic effects in animal and human studies, and these agents that mimic the effects of insulin could produce the same beneficial effects on bone regeneration and spinal fusion.

PURPOSE

The purpose of this study was to analyze the effects of locally applied zinc on spinal fusion in a rat model.

STUDY DESIGN/SETTING

Institutional Animal Care and Use Committee-approved animal study using Sprague-Dawley rats was used as the study design.

METHODS

Thirty Sprague-Dawley rats (450-500 g) underwent L4-L5 posterolateral lumbar fusion (PLF). After decortication and application of approximately 0.3 g of autograft per side, one of three pellets were added to each site: high-dose zinc calcium sulfate (ZnCaSO4), low-dose ZnCaSO4 (half of the high dose), or a control palmitic acid pellet (no Zn dose). Systemic blood glucose levels were measured 24 hours postoperatively. Rats were sacrificed after 8weeks and the PLFs analyzed qualitatively by manual palpation and radiograph review, and quantitatively by micro-computed tomography (CT) analysis of bone volume and trabecular thickness. Statistical analyses with p-values set at .05 were accomplished with analysis of variance, followed by posthoc tests for quantitative data, or Mann-Whitney rank tests for qualitative assessments.

RESULTS

Compared with controls, the low-dose zinc group demonstrated a significantly higher manual palpation grade (p=.011), radiographic score (p=.045), and bone formation on micro-CT (172.9 mm(3) vs. 126.7 mm(3) for controls) (p<.01). The high-dose zinc also demonstrated a significantly higher radiographic score (p=.017) and bone formation on micro-CT (172.7 mm(3) vs. 126.7 mm(3)) (p<.01) versus controls, and was trending toward higher manual palpation scores (p=.058).

CONCLUSIONS

This study demonstrates the potential benefit of a locally applied insulin-mimetic agent, such as zinc, in a rat lumbar fusion model. Previous studies have demonstrated the benefits of local insulin application in the same model, and it appears that zinc has similar effects.

Elcatonin attenuates disuse osteoporosis after fracture fixation of tubular bone in rats

BACKGROUND

Elcatonin (ECT) is used to prevent and treat osteoporosis. However, little is known about its effect on the disuse osteoporosis (DOP). The aim of this study is to evaluate the effect of ECT on DOP caused by fracture fixation.

METHODS

Forty-five male Sprague-Dawley (SD) rats, aged 6 weeks, were randomly allocated into three groups: the control group without surgery and elcatonin treatment (CTR, n = 15), the surgery group without elcatonin treatment (SUR, n = 15), and the surgery group which received elcatonin subcutaneously (SUR + ECT, n = 15). Surgery was produced by cutting the midshaft of the right femur transversely, fixing with stainless intramedullary needle, and immobilizing the right leg. All the proximal tibias from the random five rats in each group were harvested and investigated by evaluating bone mineral density (BMD), X-ray images, and histological staining respectively at the 4th, 8th, and 12th weeks after surgery.

RESULTS

Both of the SUR and SUR + ECT groups obviously exhibited lower BMD values compared to the CTR group; however, the SUR + ECT group showed significantly higher BMD values (p < 0.001, p < 0.05, and p < 0.05) than the SUR group at each time point after surgery. Moreover, similar changes were observed between these groups when examining the radiographs and hematoxylin and eosin (HE) staining.

CONCLUSIONS

Elcatonin attenuates disuse osteoporosis after fractures in rats, which may provide a new avenue to prevent and treat disuse osteoporosis after surgery in clinic.