Immunosuppression with FK506 has no influence on fracture healing in the rat

Local FK506 delivery induces osteogenesis in rat bone defect and rabbit spine fusion models

Bone grafting procedures are commonly used for the repair, regeneration, and fusion of bones in a wide range of orthopaedic surgeries, including large bone defects and spine fusion procedures. Autografts are the clinical gold standard, though recombinant human bone morphogenetic proteins (rhBMPs) are often used, particularly in difficult clinical situations. However, treatment with rhBMPs can have off-target effects and increase surgical costs, adding to patients' already high economic and mental burden. Recent studies have identified that FDA-approved immunosuppressant drug, FK506 (Tacrolimus), can also activate the BMP pathway by binding to its inhibitors. This study tested the hypothesis that FK506, as a standalone treatment, could induce osteogenic differentiation of human mesenchymal stromal cells (hMSCs), as well as functional bone formation in a rat segmental bone defect model and rabbit spinal fusion model. FK506 enhanced osteogenic differentiation and mineralization of hMSCs in vitro. Standalone treatment with FK506 delivered on a collagen sponge produced consistent bone bridging of a critically sized rat femoral defect with functional mechanical properties comparable to naïve bone. In a rabbit single level posterolateral spine fusion model, treatment with FK506 delivered on a collagen sponge successfully fused the L5-L6 vertebrae at rates comparable to rhBMP-2 treatment. These data demonstrate the ability of FK506 to induce bone formation in human cells and two challenging in vivo models, and indicate FK506 can be utilized to treat a variety of spine disorders.

Topical Tacrolimus and Mycophenolic Acid Therapy Synergizes with Low Dose Systemic Immunosuppression to Sustain Vascularized Composite Allograft Survival

AIM

The goal of this study was to evaluate whether topical administration of tacrolimus (TAC) and mycophenolic acid (MPA) at the transplant site enables vascularized composite allograft (VCA) survival with significant minimization of the dose and adverse effects of systemic TAC (STAC) immunosuppression.

MATERIALS AND METHODS

Lewis (Lew) rats received orthotopic hind limb allotransplants from fully mismatched Brown Norway (BN) donors. Group 1 (Controls) received no treatment. Other groups were treated with STAC at a dose of 1 mg/kg/day for 7 days. On post-operative day (POD) 8, the STAC dose was dropped to 0.1 mg/kg/day for Group 2 and maintained at 1 mg/kg for Group 3. Group 4 received topical application of TAC and MPA on the transplanted (Tx) limb starting POD 8 without STAC. Group 5 received topical TAC and MPA on the contralateral non-Tx limb and Group 6 received topical TAC and MPA on the Tx limb starting POD 8 along with low dose STAC (0.1 mg/kg/day). Treatment was continued until the study end point was reached, defined as either grade 3 rejection or allograft survival exceeding 100 days. .We conducted sequential LC-MS/MS measurements to assess TAC and MPA concentrations in both blood/plasma and allograft tissues. Additionally, we evaluated markers indicative of organ toxicity associated with STAC immunosuppression.

RESULTS

Compared to controls, topical therapy with TAC+MPA significantly prolonged allograft survival beyond 100 daysat very low dose STAC (0.1 mg/kg/day) (Group 6). The histopathological assessment of the grafts was consistent with the clinical outcomes. .Drug levels in blood/plasma remained low or undetectable, while allograft tissues showed higher drug concentrations compared to contralateral limb tissues (P<0.05). . Urinary creatinine clearance remained within the normal range at 2.5 mL/min.

CONCLUSION

Combination therapy with topical TAC and MPA synergizes with a very low dose, corticosteroid- free-STAC regimen and facilitates rejection-free, prolonged VCA survival without morbidity.

Tacrolimus, FK506, promotes bone formation in bone defect mouse model

OBJECTIVES

Some studies have reported that tacrolimus (FK506), an immunosuppressant, may have positive effects on bone formation. However, the precise effects of FK506 on bone repair or osteoblasts remain inadequately elucidated, and limited research has explored the outcomes of its use in an in vivo mouse model. This study aims to examine the effects of FK506 on bone repair and osteoblast functions using bone defect and BMP-2-induced ectopic ossification mouse models, as well as cultured primary mouse osteoblasts treated with FK506.

METHODS

We established mouse models of femur bone defect and BMP-2-induced ectopic ossification to evaluate the effect of FK506 on new bone formation, respectively. Additionally, primary mouse osteoblasts were cultured with FK506 and examined for gene expressions related to osteoblast differentiation.

RESULTS

While FK506 promoted the repair of bone defect areas in the femur of the bone defect mouse model, it also led to widespread abnormal bone formation outside the intended area. Additionally, following the implantation of a collagen sponge containing BMP-2 into mouse muscle tissue, FK506 was found to promote ectopic ossification and enhance BMP-2-induced osteoblast differentiation in vitro. Our findings also revealed that FK506 increased the number of immature osteoblasts in the absence of BMP-2 without affecting osteoblast differentiation. Furthermore, direct effects were observed, reducing the ability of osteoblasts to support osteoclastogenesis.

CONCLUSIONS

These results indicate that FK506 increases new bone formation during bone repair and influences the proliferation of immature osteoblasts, as well as osteoblast-supported osteoclastogenesis.

Local FK506 delivery induces osteogenesis in in vivo rat bone defect and rabbit spine fusion models

Bone grafting procedures are commonly used for the repair, regeneration, and fusion of bones in in a wide range of orthopaedic surgeries, including large bone defects and spine fusion procedures. Autografts are the clinical gold standard, though recombinant human bone morphogenetic proteins (rhBMPs) are often used, particularly in difficult clinical situations. However, treatment with rhBMPs can have off-target effects and significantly increase surgical costs, adding to patients' already high economic and mental burden. Recent studies have identified that FDA-approved immunosuppressant drug, FK506 (Tacrolimus), can also activate the BMP pathway by binding to its inhibitors. This study tested the hypothesis that FK506, as a standalone treatment, could induce osteogenic differentiation of human mesenchymal stromal cells (hMSCs), as well as functional bone formation in a rat segmental bone defect model and rabbit spinal fusion model. FK506 potentiated the effect of low dose BMP-2 to enhance osteogenic differentiation and mineralization of hMSCs in vitro. Standalone treatment with FK506 delivered on a collagen sponge, produced consistent bone bridging of a rat critically-sized femoral defect with functional mechanical properties comparable to naïve bone. In a rabbit single level posterolateral spine fusion model, treatment with FK506 delivered on a collagen sponge successfully fused the L5-L6 vertebrae at rates comparable to rhBMP-2 treatment. These data demonstrate the ability of FK506 to induce bone formation in human cells and two challenging in vivo models, and indicate FK506 can be utilized either as a standalone treatment or in conjunction with rhBMP to treat a variety of spine disorders.

FK506 increases susceptibility to musculoskeletal infection in a rodent model

Background

Delayed fracture healing caused by soft tissue loss can be resolved by the administration of a Th1 immunosuppressant, such as FK506. Additionally, open fractures are at high risk for infection. We hypothesized that the inclusion of an immunosuppressant to a subject at risk for a musculoskeletal infection will increase the likelihood of infection.

Methods

A rat model of musculoskeletal infection was used. Sprague Dawley rats received a stabilized femur defect and were inoculated with 10⁴ CFU Staphylococcus aureus via a collagen matrix. Six hours after inoculation, the wounds were debrided of collagen and devitalized tissue and irrigated with sterile saline. The animals were randomized into two groups: carrier control and FK506, which were administered daily for 14 days and were euthanized and the tissues harvested to measure local bioburden.

Results

The dosing regimen of FK506 that restored bone healing increased the bioburden in the bone and on the fixation implant compared to the carrier control animals. As expected, the administration of FK506 decreased circulating white blood cells, lymphocytes, neutrophils, and monocytes. Additionally, the red blood cell count, hematocrit, and body weight were lower in those animals that received FK506 compared to carrier control.

Conclusions

FK506 administration decreased the systemic immune cell counts and increased the bacterial bioburden within a model of musculoskeletal infection. Collectively, these outcomes could be attributed to the overall T cell suppression by FK506 and the altered antimicrobial activity of innate cells, thereby allowing S. aureus to thrive and subsequently leading to infection of severe, musculoskeletal injuries. These observations reveal the crucial continued investigation for the clinical use of FK506, and other immunosuppressant compounds, in trauma patients who are at increased risk of developing infections.

Kidney Transplantation, Immunosuppression and the Risk of Fracture: Clinical and Economic Implications

Rationale & Objective

Disorders of bone and mineral metabolism frequently develop with advanced kidney disease, may be exacerbated by immunosuppression after kidney transplantation, and increase the risk of fractures.

Study Design

Retrospective database study.

Setting & Participants

Kidney-only transplant recipients aged ≥18 years from 2005 to 2016 in the United States captured in US Renal Data System records, which integrate Organ Procurement and Transplantation Network/United Network for Organ Sharing records with Medicare billing claims.

Exposures

Various immunosuppression regimens in the first 3 months after kidney transplantation.

Outcomes

The development of fractures, as ascertained using diagnostic codes on Medicare billing claims.

Analytical Approach

We used multivariable Cox regression with inverse propensity weighting to compare the incidence of fractures >3 months-to-3 years after kidney transplantation associated with various immunosuppression regimens compared to a reference regimen of antithymocyte globulin (TMG) or alemtuzumab (ALEM) with tacrolimus + mycophenolic acid + prednisone using inverse probability treatment weighting.

Results

Overall, fractures were identified in 7.5% of kidney transplant recipients (women, 8.8%; men, 6.7%; age < 55 years, 5.9%; age ≥ 55 years, 9.3%). In time-varying regression, experiencing a fracture was associated with a substantially increased risk of subsequent death within 3 months (adjusted hazard ratio [aHR], 3.06; 95% confidence interval [CI], 2.45-3.81). Fractures were also associated with increased Medicare spending (first year: $5,122; second year: $10,890; third year: $11,083; [P < 0.001]). Induction with TMG or ALEM and the avoidance or early withdrawal of steroids significantly reduced the risk of fractures in younger (aHR, 0.63; 95% CI, 0.54-0.73) and older (aHR, 0.83; 95% CI, 0.74-0.94) patients. The avoidance or early withdrawal of steroids with any induction was associated with a reduced risk of fractures in women.

Limitations

This was a retrospective study which lacked data on immunosuppression levels.

Conclusions

Fractures after kidney transplantation are associated with significantly increased mortality risk and costs. The early avoidance or early withdrawal of steroids after induction with TMG or ALEM reduces the risk of fractures after kidney transplantation and should be considered for patients at high-risk of this complication, including older adults and women.

Effects of FK506 on the healing of diaphyseal, critical size defects in the rat femur

There is much interest in understanding the influence of the immune system on bone healing, including a number of reports suggesting a beneficial effect of FK506 (tacrolimus) in this regard. The influence of FK506 in a rat, femoral, critical size defect was examined using locally implanted, recombinant, human (rh) BMP-2 and adenovirally-transduced, autologous, adipose-derived mesenchymal stromal cells (AD-MSCs) expressing BMP-2. FK506 was delivered systemically using an implanted osmotic pump. Empty defects and those implanted with unmodified AD-MSCs did not heal in the presence or absence of FK506. Defects treated with rhBMP-2 healed with a large callus containing thin cortices and wispy trabeculae; this, too, was unaffected by FK506. A third of defects implanted with adenovirally-transduced AD-MSCs healed, but this improved to 100 % in the presence of FK506. New bone formed in response to BMP-2 synthesised endogenously by the genetically modified cells had a slimmer callus than those healed by rhBMP-2, with improved cortication and advanced reconstitution of marrow. These results suggest that FK506 may have had little effect on the intrinsic biology of bone healing, but improved healing in response to adenovirally-transduced cells by inhibiting immune responses to the first-generation adenovirus used here. Because the genetically modified cells produced bone of higher quality at far lower doses of BMP-2, this approach should be explored in subsequent research.

[Immunosuppressive treatment and bone healing]

Due to demographic changes in the population and the development of novel immunosuppressive agents, an increasing number of trauma and orthopedic patients are taking concomitant immunosuppressive medication. These drugs might interfere with the healing process and can possibly retard or prevent wound and fracture healing and lead to a higher risk of infections. In these complex situations a structured and interdisciplinary process during hospital admission should preoperatively evaluate the possibility of interrupting immunosuppressive medications for the perioperative treatment period without risking a relapse of the underlying disease and which surgical approach should be individually selected for the patient.

Diagnosis and Management of Polytraumatized Patients With Severe Extremity Trauma

Multiply injured patients with severe extremity trauma are at risk of acute systemic complications and are at high risk of developing longer term orthopaedic complications including soft-tissue infection, osteomyelitis, posttraumatic osteoarthritis, and nonunion. It is becoming increasingly recognized that injury magnitude and response to injury have major jurisdiction pertaining to patient outcomes and complications. The complexities of injury and injury response that affect outcomes present opportunities to apply precision approaches to understand and quantify injury magnitude and injury response on a patient-specific basis. Here, we present novel approaches to measure injury magnitude by adopting methods that quantify both mechanical and ischemic tissue injury specific to each patient. We also present evolving computational approaches that have provided new insight into the complexities of inflammation and immunologic response to injury specific to each patient. These precision approaches are on the forefront of understanding how to stratify individualized injury and injury response in an effort to optimize titrated orthopaedic surgical interventions, which invariably involve most of the multiply injured patients. Finally, we present novel methods directed at mangled limbs with severe soft-tissue injury that comprise severely injured patients. Specifically, methods being developed to treat mangled limbs with volumetric muscle loss have the potential to improve limb outcomes and also mitigate uncompensated inflammation that occurs in these patients.

Impairment of early fracture healing by skeletal muscle trauma is restored by FK506

Background

Heightened local inflammation due to muscle trauma or disease is associated with impaired bone regeneration.

Methods

We hypothesized that FK506, an FDA approved immunomodulatory compound with neurotrophic and osteogenic effects, will rescue the early phase of fracture healing which is impaired by concomitant muscle trauma in male (~4 months old) Lewis rats. FK506 (1 mg/kg; i.p.) or saline was administered systemically for 14 days after an endogenously healing tibia osteotomy was created and fixed with an intermedullary pin, and the overlying tibialis anterior (TA) muscle was either left uninjured or incurred volumetric muscle loss injury (6 mm full thickness biopsy from middle third of the muscle).

Results

The salient observations of this study were that 1) concomitant TA muscle trauma impaired recovery of tibia mechanical properties 28 days post-injury, 2) FK506 administration rescued the recovery of tibia mechanical properties in the presence of concomitant TA muscle trauma but did not augment mechanical recovery of an isolated osteotomy (no muscle trauma), 3) T lymphocytes and macrophage presence within the traumatized musculature were heightened by trauma and attenuated by FK506 3 days post-injury, and 4) T lymphocyte but not macrophage presence within the fracture callus were attenuated by FK506 at 14 days post-injury. FK506 did not improve TA muscle isometric torque production

Conclusion

Collectively, these findings support the administration of FK506 to ameliorate healing of fractures with severe muscle trauma comorbidity. The results suggest one potential mechanism of action is a reduction in local T lymphocytes within the injured musculoskeletal tissue, though other mechanisms to include direct osteogenic effects of FK506 require further investigation.

Electronic supplementary material

The online version of this article (doi:10.1186/s12891-017-1617-y) contains supplementary material, which is available to authorized users.

The role of imaging in patient selection, preoperative planning, and postoperative monitoring in human upper extremity allotransplantation

Objective. To describe the role of imaging in vascular composite allotransplantation based on one institution's experience with upper extremity allotransplant patients. Methods. The institutional review board approved this review of HIPAA-compliant patient data without the need for individual consent. A retrospective review was performed of imaging from 2008 to 2011 on individuals undergoing upper extremity transplantation. This demonstrated that, of the 19 patients initially considered, 5 patients with a mean age of 37 underwent transplantation. Reports were correlated clinically to delineate which preoperative factors lead to patient selection versus disqualification and what concerns dictated postoperative imaging. Findings were subdivided into musculoskeletal and vascular imaging criterion. Results. Within the screening phase, musculoskeletal exclusion criterion included severe shoulder arthropathy, poor native bone integrity, and marked muscular atrophy. Vascular exclusion criterion included loss of sufficient arterial or venous supply and significant distortion of the native vascular architecture. Postoperative imaging was used to document healing and hardware integrity. Postsurgical angiography and ultrasound were used to monitor for endothelial proliferation or thrombosis as signs of rejection and vascular complication. Conclusion. Multimodality imaging is an integral component of vascular composite allotransplantation surgical planning and surveillance to maximize returning form and functionality while minimizing possible complications.

Cell lineage in vascularized bone transplantation

BACKGROUND

The biology behind vascularized bone allotransplantation remains largely unknown. We aim to study cell traffic between donor and recipient following bone auto-, and allografting.

METHODS

Vascularized femoral transplantation was performed with arteriovenous bundle implantation and short-term immunosuppression. Twenty male Piebald Virol Glaxo (PVG; RT1(c) ) rats received isotransplants from female PVG (RT1(c) ) rats and 22 male PVG rats received allografts from female Dark Agouti rats (DA, RT1(a) ), representing a major histocompatibility mismatch. Both groups were randomly analyzed at 4 or 18 weeks. Bone remodeling areas (inner and outer cortical samples) were labeled and laser capture microdissected. Analysis of sex-mismatch genes by real-time reverse transcription-polymerase chain reaction provided the relative Expression Ratio (rER) of donor (female) to recipient (male) cells.

RESULTS

The rER was 0.456 ± 0.266 at 4 weeks and 0.749 ± 0.387 at 18 weeks (p = 0.09) in allotransplants. In isotransplants, the rER was 0.412 ± 0.239 and 0.467 ± 0.252 at 4 and 18 weeks, respectively (p = 0.21). At 4 weeks, the rER at the outer cortical area of isotransplants was significantly lower in isotransplants as compared with allotransplants (0.247 ± 0.181 vs. 0.549 ± 0.184, p = 0.007). Cells in the inner and outer cortical bone remodeling areas in isotransplants were mainly donor derived (rER < 0.5) at 18 weeks, whereas allotransplants contained mainly recipient-derived cells (rER > 0.5) at 18 weeks.

CONCLUSIONS

Applying novel methodology, we describe detailed cell traffic in vascularized bone transplants, elaborating our comprehension on bone transplantation.

Immunosuppressant prograf® (tacrolimus) induces histopathological disorders in the peritubular tissue of rat testes

Treatment with tacrolimus (FK-506) has been shown to induce a significant decrease in the number of spermatocytes, spermatids, and Sertoli cells. Regarding the importance of the peritubular tissue for the maintenance of Sertoli cells, the integrity of the cellular and extracellular components of the peritubular tissue was evaluated in adult rats that were treated with 1 mg/kg/day of FK-506 for 30 and 60 days. Testicular sections were used for a quantitative analysis of the peritubular cells (PCs) and were submitted to the PAS method. Paraffin sections were submitted to the TUNEL method and to immunohistochemistry for the detection of caspase-3. Several testicular fragments were analyzed under a transmission electron microscope (TEM). A weak PAS reaction was noted in the peritubular tissue of the tacrolimus-treated animals. Next to the damaged peritubular tissue, the Sertoli cell nuclei were absent or dislocated from the basement membrane. In the treated animals, the number of PCs decreased significantly compared to the control animals, and these cells showed apoptotic features, were TUNEL positive, and were caspase-3 immunolabeled. Using the TEM, apoptosis was confirmed in myoid cells; moreover, the thickness and undulation of the basal laminae and an enlargement of the collagen I layer adjacent to the myoid cells was observed. Long-term treatment with the immunosuppressor induced peritubular myoid cell death by apoptosis and disarrangement of the peritubular extracellular layers. Future studies are necessary to confirm whether the structural alterations in the seminiferous epithelium are related to the effect of FK-506 on peritubular tissue.

Host-derived neoangiogenesis with short-term immunosuppression allows incorporation and remodeling of vascularized diaphyseal allogeneic rabbit femur transplants

The purpose of this study was to demonstrate that living bone allotransplants can incorporate, remodel, and maintain mechanical properties without long-term immunosuppression in a fashion comparable to living autotransplants. For this, viability is maintained by repair of nutrient vessels and neovascularization from implanted host-derived vasculature. Microsurgically revascularized femoral diaphysis allotransplants were transferred from young male New-Zealand-White (NZW) into 4 groups of male Dutch-Belted (DB) rabbits. Short-term immunosuppression by tacrolimus (IS, groups 4 and 5) and host-derived neovascularization (NV) from implanted fascial flaps was used to maintain viability (groups 3 and 5) as independent variables. Group 2 received neither IS nor NV. Vascularized pedicled autotransplants were orthotopically transplanted in group 1. After 16 weeks, transplants were evaluated using radiologic, histologic, biomechanical, and histomorphometric parameters. Vascularized bone allotransplants treated with both short-term IS and host-derived NV (group 5) healed in a fashion similar to pedicled autotransplants (group 1). Their radiographic scores were higher than other groups. Groups with patent fascial flaps (3 and 5) showed significantly greater neoangiogenesis than ligated controls (2 and 4). Tacrolimus administration did not affect neoangiogenesis. Elastic modulus and ultimate stress were significantly greater in autogenous bone than in allotransplanted femora. Biomechanical properties were not significantly different among allotransplants. Bone turnover was decreased with IS, but increased with NV by the implanted fascial flaps. Living allogeneic femoral allotransplants treated with short-term IS and host-derived neoangiogenesis can lead to stable transplant incorporation in this rabbit model. The combination of both factors optimizes bone healing. Transplant mineralization is improved with neoangiogenesis but diminished with IS.

Structural alterations in the seminiferous tubules of rats treated with immunosuppressor tacrolimus

BACKGROUND

Tacrolimus (FK-506) is an immunosuppressant that binds to a specific immunophilin, resulting in the suppression of the cellular immune response during transplant rejection. Except for some alterations in the spermatozoa, testicular morphological alterations have not been described in rats treated with tacrolimus. In the present study, we purpose to evaluate if the treatment with tacrolimus at long term of follow-up interferes in the integrity of the seminiferous tubules.

METHODS

Rats aging 42-day-old received daily subcutaneous injections of 1 mg/kg/day of tacrolimus during 30 (T-30) and 60 (T-60) days; the rats from control groups (C-30 and C-60) received saline solution. The left testes were fixed in 4% formaldehyde and embedded in glycol methacrylate for morphological and morphometric analyses while right testes were fixed in Bouin's liquid and embedded in paraffin for detection of cell death by the TUNEL method. The epithelial and total tubular areas as well as the stages of the seminiferous epithelium and the number of spermatocytes, spermatids and Sertoli cells (SC) per tubule were obtained.

RESULTS

In the treated groups, seminiferous tubules irregularly outlined showed disarranged cellular layers and loss of germ cells probably due to cell death, which was revealed by TUNEL method. In addition to germ cells, structural alterations in the SC and folding of the peritubular tissue were usually observed. The morphometric results revealed significant decrease in the number of SC, spermatocytes, spermatids and significant reduction in the epithelial and total tubular areas.

CONCLUSION

Tacrolimus induces significant histopathological disorders in the seminiferous tubules, resulting in spermatogenic damage and reduction in the number of Sertoli cells. A careful evaluation of the peritubular components will be necessary to clarify if these alterations are related to the effect of FK-506 on the peritubular tissue.

Rapamycin affects early fracture healing in mice

BACKGROUND AND PURPOSE

The immunosuppressive drug rapamycin (RAPA) prevents rejection in organ transplantation by inhibiting interleukin-2-stimulated T-cell division. Rapamycin has also been suggested to possess strong anti-angiogenic activities linked to a decrease in production of vascular endothelial growth factor (VEGF). Angiogenesis and VEGF are thought to play a crucial role in fracture healing and as osteoporotic and traumatic fractures are common complications in immunosuppressed, organ transplantation patients, we conducted this study to analyze the effect of rapamycin treatment on bone repair.

EXPERIMENTAL APPROACH

We investigated the effect of rapamycin treatment on bone repair in a murine closed femur fracture model using radiological, histomorphometric, immunohistochemical, biomechanical and protein biochemical analyses.

KEY RESULTS

X-ray analyses demonstrated that rapamycin treatment inhibits callus formation after two weeks of fracture healing. The radiologically observed lack of callus formation was confirmed by histomorphometric analyses, which revealed a significantly diminished callus size and a reduced amount of bone formation when compared with vehicle-treated controls. Biomechanical testing further demonstrated that rapamycin significantly reduces torsional stiffness of the callus. Interestingly, this effect was associated with decreased vessel formation; a diminished proliferation of osteoblasts, endothelial cells and periosteal cells; and a reduced VEGF expression in hypertrophic chondrocytes. After five weeks treatment, however, the negative impact of rapamycin on fracture healing was overcome.

CONCLUSIONS AND IMPLICATIONS

Thus, rapamycin initially delays fracture healing, most probably by inhibiting cell proliferation and neovascularization in the callus. These undesirable effects should be considered when rapamycin is administered to patients sustaining bone fractures.

Biochemical evaluation of glycemic levels of long-term tacrolimus therapy in rats

One of the more serious complications following transplantation is the development of post-transplantation diabetes mellitus (PTDM), which has a major impact on the quality of life, with effects ranging from the control of glycemia times to increased susceptibility to infections and cardiovascular complications. It has been suggested that immunosuppressive therapy, mainly tacrolimus therapy, may be an important factor in the development of PTDM. There is a lack of studies that explore the effects of long-term tacrolimus on PTDM in animal protocols. The objective of this study was therefore to evaluate the effects of long-term therapy with tacrolimus in rats. One group was treated with tacrolimus, injected subcutaneously, in a daily dose of 1 mg/kg of body weight. The chosen dose was sufficient to achieve therapeutic tacrolimus serum levels. The experimental periods were 60, 120, 180 and 240 days. One group was used as control and received daily subcutaneous injections of saline solution during all periods. A tendency towards increased glycemia levels during the initial periods (60 and 120 days) was observed. However, at 180 and 240 days, the glycemia levels were not statistically different from that of the control group of the same period. It may thus be concluded that the deleterious effects of tacrolimus therapy on glycemia may be a time-related side effect.

Protective effects of Tacrolimus, a calcineurin inhibitor, in experimental periodontitis in rats

OBJECTIVE

Periodontitis is a well-appreciated example of leukocyte-mediated bone loss and inflammation with pathogenic features similar to those observed in other inflammatory diseases, such as arthritis. Since Tacrolimus, is an immunomodulatory drug used for the treatment of some cases of arthritis, we hypothesized that it may modulate periodontal disease.

DESIGN

Using a murine model of ligature-induced periodontal disease, we assessed the effects of daily administrations of Tacrolimus (1mg/kg body weight) on bone loss, enzymatic (myeloperoxidase) analysis, differential white blood cells counts, airpouch exudate and cytokine expression for 5-30 days.

RESULTS

Radiographic, enzymatic (myeloperoxidase) and histological analysis revealed that Tacrolimus reduced the severity of periodontitis. More specifically, Tacrolimus suppressed the expression of serum interleukin (IL-1beta), tumour necrosis factor (TNF-alpha), IL-6, airpouch exudate PGE(2) and leukocytosis usually observed after the induction of periodontitis. Tacrolimus treatment in periodontitis-induced rats conferred protection against the inflammation-induced tissue and bone loss associated with periodontitis, through a mechanism involving IL-1beta, TNF-alpha and IL-6.

CONCLUSIONS

The effects of Tacrolimus on periodontal disease pathogenesis may provide clues to a novel approach to host modulation therapy in destructive periodontal disease.