Allosensitization Following Bone Graft

Assessment and management of allosensitization following heart transplant in adults

Immunological injury to the allograft, specifically by antibodies to de novo donor specific human leukocyte antigen (dnDSA) and antibody mediated injury and rejection are the major limitations to graft survival after heart transplantation (HT). As such, our approach to allosensitization remains limited by the inability of contemporaneous immunoassays to unravel pathogenic potential of dnDSA. Additionally, the role of dnDSA is continuously evaluated with emerging methods to detect rejection. Moreover, the timing and frequency of dnDSA monitoring for early detection and risk mitigation as well as management of dnDSA remain challenging. A strategic approach to dnDSA employs diagnostic assays to determine relevant antibodies in conjunction with clinical presentation and injury/rejection of allograft to tailor therapeutics. In this review, we aim to outline contemporary knowledge involving detection, monitoring and management of dnDSA after HT. Subsequently, we propose a diagnostic and therapeutic approach that may mitigate morbidity and mortality while balancing adverse reactions from pharmacotherapy.

Characterization of immunologically detectable T-cell sensitization, Immunohistochemical detection of pro-inflammatory cytokines, and clinical parameters of patients after allogeneic intraoral bone grafting procedures: a prospective randomized controlled clinical trial in humans

BACKGROUND

The null hypotheses were tested that intraoral bone augmentation using two different allogeneic materials has no impact on the patient's blood levels of material-specific lymphocytes and on the immunohistochemical detection of pro-inflammatory cytokines IL-1α, IL1ß and TNF-α and T-cell markers CD4, CD8 in biopsies of the test groups.

METHODS

In this prospective RCT, 60 systemically healthy participants were randomly assigned to two allogeneic test groups (1: Maxgraft®, freeze-dried, multiple donors, and 2: Puros®, solvent-dehydrated, single donor) and an autologous control group (10 patients). Plasma samples were collected pre-(T1) and postoperatively (2 weeks (T2) and 4 months (T3)). The Lymphocyte Transformation Test (LTT) was used for analyzing levels of transformed lymphocytes for type IV immune reactions by 3H-thymidine activity. Bone biopsies were harvested at T3 and immunohistochemically analyzed for IL-1α, IL1ß, TNF-α, CD4, CD8 and correlated with the immunological and clinical findings.

RESULTS

A statistically significant difference between the tested materials was observed for LTT measurements at T3 (p = 0.033). Furthermore, three groups were identified: Group A (LTT negative T1-T3, n = 48), group B (LTT positive T1-T3, n = 7), group C (developing positive LTT at T2, n = 5). A highly significant elevation of IL-1α, IL1ß, TNF-α in patients of group C (p = 0.0001) and a significant elevation of CD4+ cells in patients of group B (p = 0.005) was shown.

CONCLUSION

Our data show that following allogeneic bone grafting, local and systemic immunological reactions can be detected in some patients. These findings were statistically significant for the timepoint T3 between the tested materials as well as for the groups B and C correlated with group A for both tested materials. Therefore, the null hypotheses were rejected. A preoperative compatibility test for allogeneic materials in order to improve patient safety and the predictability of these materials would be desirable.

TRIAL REGISTRATION

Ethical commission of the Ärztekammer Hamburg, Germany (PV5211) as well as by the German Registry of Clinical Studies (DRKS00013010) on 30/07/2018 ( http://apps.who.int/trialsearch/ ).

The allogeneic shell technique for alveolar ridge augmentation: a multicenter case series and experiences of more than 300 cases

PURPOSE

Allogeneic cortical bone plates (CP) might be used for alveolar ridge augmentation as an alternative to autogenous grafts (AG) and bone substitutes (BS). We report about a multicenter case series and our experiences of more than 300 cases using CP and the shell technique for reconstruction of the alveolar process to illustrate surgical key steps, variations, and complication management.

METHODS

Different types of alveolar ridge defects were augmented using the shell technique via CP. The space between the CP and the alveolar bone was filled with either autogenous or allogeneic granules (AUG, ALG) or a mixture of both. Implants were placed after 4-6 months. Microscopic and histological assessments were performed. In addition, space filling using AUG, ALG and bovine BS was discussed.

RESULTS

Scanning electron microscopy demonstrated the compact cortical structure of CP and the porous structure of ALG allowing micro-vessel ingrowth and bone remodeling. Histological assessment demonstrated sufficient bone remodeling and graft resorption after 4-6 months. In total, 372 CP cases and 656 implants were included to data analysis. The mean follow-up period was about 3.5 years. Four implants failed, while all implant failures were caused by peri-implantitis. Next, 30 CP complications were seen, while in 26 CP complications implant placement was possible. CP rehydration, stable positioning by adjusting screws, smoothing of sharp edges, and a tension-free wound closure were identified as relevant success factors. Space filling using ALG and a mixture of AUG/ALG resulted in sufficient bone remodeling, graft resorption and stability of the augmented bone.

CONCLUSIONS

CP and the shell technique is appropriate for alveolar ridge augmentation with adequate bone remodeling and low complication rates. Allografts can prevent donor site morbidity and therefore may decrease discomfort for the patient.

Donor-Specific Human Leukocyte Antigen Antibody Formation After Allograft Glenoid Reconstruction Occurs But Does Not Impact Clinicoradiographic Outcomes

BACKGROUND

Recurrent shoulder instability is a prevalent condition, with glenoid bone loss as a common cause. Arthroscopic repair using distal tibial allografts provides long-lasting treatment by restoring glenoid surface area and presumably avoids risks of sensitization against donor human leukocyte antigen (HLA). Two case studies have challenged this assumption, suggesting that small bone allografts are able to induce host adaptive immune responses to donor HLA. The incidence of small bone allograft HLA sensitization and its effects on resorption and patient outcomes are unclear.

PURPOSE/HYPOTHESIS

The purpose was to assess the rate of sensitization against donor HLA after distal tibial allograft procedures for shoulder instability due to glenoid bone loss and to find whether HLA sensitization negatively affects patient-reported and radiographic outcomes. We hypothesized that sensitized patients would have worse radiographic and self-reported outcomes compared with nonsensitized patients.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

A total of 71 patients with a mean age of 28.85 years (range, 13.58-61.31 years) were enrolled, with 58 patients submitting sufficient pre- and postoperative blood samples for HLA antibody testing. In patients who developed HLA antibodies postoperatively, donor HLA typing was used to confirm donor-specific sensitization. Pre- and postoperative computerized tomography scans (0.9 ± 0.8 years follow-up) were used to grade resorption based on the modified Zhu resorption grade classification (ie, grade 0 = no resorption; grade 1 = less than 25% resorption; grade 2 = between 25% and 50% resorption; and grade 3 = larger than 50% resorption). The Western Ontario Shoulder Instability Index outcome scores were obtained preoperatively and at regular postoperative appointments. Resorption and outcome data were compared between sensitized and nonsensitized patients using the Fisher exact test, independent 2-tailed Student t tests, and the Wilcoxon rank-sum test to determine the effect of HLA sensitization on radiographic and patient-reported outcomes.

RESULTS

A total of 7 (12.1%) patients with sufficient HLA samples were sensitized against donor HLA postoperatively. Sensitized patients did not have significantly higher rates of resorption (21.9% vs 14.3%, 21.9% vs 28.6%, 43.8% vs 28.6%, and 12.5% vs 28.6% for respective resorption grades 0-3; P = .67; α = .05). Self-reported outcomes were not statistically significant between sensitized and nonsensitized patients (24.9 ± 27.61 vs 40.16 ± 18.99; P = .37; α = .05) and did not differ significantly based on resorption grade (47.4 ± 0.0 vs 55.2 ± 18.8, 30.4 ± 15.8 vs 39.9 ± 20.9, 41.2 ± 0.0 vs 39.1 ± 13.1, and -24.9 ± 0 vs 24.4 ± 19.6 for resorption grades 0-3; P > .05; α = .05).

CONCLUSION

Sensitization against donor HLA after small bone graft allografting was not previously considered but has been brought to light as a possibility. Aside from potential complications for future organ transplants, HLA sensitization does not introduce a risk for adverse outcomes or higher grades of resorption compared with nonsensitized patients after small bone allografting for shoulder instability.

Customized Borosilicate Bioglass Scaffolds With Excellent Biodegradation and Osteogenesis for Mandible Reconstruction

Graft reconstruction of the mandible is an important approach that aims at improving the appearance and functionality of defected mandibles. The traditional implant materials are generally bioinert, non-degradable, and that they lack favorable pore structures for cell proliferation, which limit their clinical application. In this study, we used boron-containing bioactive glass which was combined with a three-dimensional (3D) printing technology to construct an osteoinductive implant scaffold, according to the imaging instructions of CT scan on bone defects. Here, the boron-containing bioglass scaffold (B-BGs) was prepared through sol-gel processing and a 3D print technique. Different boron content of borosilicate bioglass was prepared by incorporating B₂O₃ (molar: 19.4 and 38.8%) into 58S bioglass to replace parts of SiO₂. For fabricated mandible implants through three-dimensional 3D printing of B-BGs (size: 8 × 2 mm; pore size: 250 μm) modified with borosilicate bioglass powder and sodium alginate. Notably, the compressive strength of the B-BGs was about 3.8 Mpa, which supported mandibular activity. Subsequently, the excellent biocompatibility of B-BGs was confirmed using cytotoxicity in vitro studies. Finally, data from in vivo experiments demonstrated that the B-BGs could promote bone regeneration and they could almost get completely degraded within 4 weeks. Our results showed that the boron-containing bioglass could repair mandibular defects.

Developments in Antibiotic-Eluting Scaffolds for the Treatment of Osteomyelitis

Osteomyelitis is a devastating disease caused by the infection of bone tissue and is associated with significant morbidity and mortality. It is treated with antibiotic therapy and surgical debridement. A high dose of systemic antibiotics is often required due to poor bone penetration and this is often associated with unacceptable side-effects. To overcome this, local, implantable antibiotic carriers such as polymethyl methacrylate have been developed. However, this is a non-biodegradable material that requires a second surgery to be removed. Attention has therefore shifted to new antibiotic-eluting scaffolds which can be created with a range of unique properties. The purpose of this review is to assess the level of evidence that exists for these novel local treatments. Although this field is still developing, these strategies seem promising and provide hope for the future treatment of chronic osteomyelitis.

Osseous ingrowth in allogeneic bone blocks applied for vertical bone augmentation: a preclinical randomised controlled study

OBJECTIVES

The aim of the present study was the qualitative and quantitative evaluation of osseous graft consolidation using allogeneic bone blocks for vertical bone augmentation in an animal model.

MATERIAL AND METHODS

Standardised allogeneic and autologous bone blocks were fixed on the frontal skull of 20 adult female pigs and covered with a resorbable collagen membrane. Animals were sacrificed after 2 and 6 months. Specimens were histologically and histomorphometrically analysed focusing on the amount of vital bone, residual bone substitute material and connective tissue. Furthermore, the amount of expression of bone matrix proteins (collagen type I and osteocalcin) and de novo vessel formation (von Willebrand factor) were quantified by immunohistochemistry.

RESULTS

Significantly more allogeneic bone blocks failed for both evaluation time points (p < 0.05). Allogeneic blocks showed significantly less vital bone with more connective tissue formation compared to autologous bone blocks. Increased vessel formation could be detected for both evaluation time points in the contact area of autologous bone with local bone. The expression of collagen type I and osteocalcin was significantly lower in the allogeneic bone graft.

CONCLUSIONS

Allogeneic cancellous bone blocks showed a significantly higher failure rate compared to autologous bone blocks. Allogeneic bone blocks seemed to negatively affect bone formation or negatively influence the host in the long term, and increased connective tissue formation and block loss should be anticipated.

CLINICAL RELEVANCE

In order to maintain patient safety and treatment success clinicians should be persuaded to make a conscious choice of the applied biomaterials with regard to their components and structure.

Histological and immunohistochemical comparison of two different allogeneic bone grafting materials for alveolar ridge reconstruction: A prospective randomized trial in humans

Background

Preclinical studies have hypothesized a possible immunological reponse to allogeneic materials due to detection of remnants of potential immunogenic molecules. However, their impact on integration, bone remodeling and immunological reaction after the augmentation procedure is largely unknown and a direct correlation of analytical data and evaluation of human biopsies is missing.

Purpose

The present study aimed to compare two commercially available allogeneic materials regarding their content of cellular remnants as well as the bone remodeling, and integration and potential immunologic reactions on a histological and immunohistochemical level, integrating also in vitro analytical evaluation of the specific batches that were used clinically.

Materials and Methods

Twenty patients were randomly assigned to treatment with Maxgraft or Puros for lateral ridge augmentation in a two‐stage surgery. After a mean healing period of 5 months, implants were placed and biopsies were taken for histological, immunhistochemical, and histomorphometrical evaluation regarding bone remodeling and inflammation, protein concentrations in vitro and the presence of MHC molecules of the same batches used clinically.

Results

No differences in clinical outcome, histological, immunohistochemical, and in vitro protein analysis between the two bone grafting materials were observed. Active bone remodeling, amount of newly formed bone, and residual grafting material was independent of the materials used, but varied between subjects. MHC1 residues were not detected in any sample.

Conclusions

Within the limitations of this study, both tested materials yielded equivalent results in terms of clinical outcome, new bone formation, and lack of immunological potential on a histological and immunohistochemical level.

Impact of Regulatory T Cells on Innate Immune Cells in a Pre-Sensitized Heart Transplant Model

Background

Although our previous studies revealed the role of Tregs (regulatory T cells) and MDSCs (myeloid-derived suppressor cells) in a pre-sensitized cardiac transplant model, interplay between Tregs and NK cells, neutrophils, and macrophages remain undefined.

Material/Methods

Mice heart transplantation with skin pre-sensitization was performed, in which prolonged-cold ischemia time (PCI) was used for donor treatment. Syngeneic heterotopic heart transplant recipients with PCI were treated with PC61 (monoclonal anti-CD25 antibodies), adoptive cell transfer with Tregs, and rapamycin.

Results

We unveiled that both rapamycin treatment and adoptive transfer of Tregs could lead to a remarkable decrease of frequency of splenic Gr1+ cells (P=0.058 and P=0.016, respectively). Although administration of PC61 did not affect frequency of splenic Gr1+ cells, it dramatically increased frequency of splenic F4/80+ macrophages (P=0.052). Intriguingly, use of both exogenous PC61 and rapamycin induced a dramatic augmentation of frequency of Gr-1+ neutrophils in the grafts (PC61: P=0.00029; rapamycin: P=0.0096). Noticeably, all different regimens including PC61, rapamycin, and adoptive transfer of Tregs, consistently resulted in a remarked augmentation of frequency of F4/80+ macrophages within grafts (PC61, P=0.0013; rapamycin, P=0.015; Tregs transfer, P=0.013). Although rapamycin and adoptive transfer of Tregs did not affect frequency of NK1.1+ cells, administration of PC61 dramatically increased frequency of NK1.1+ cells within grafts (P=0.033).

Conclusions

Tregs depletion or Tregs induced by rapamycin or exogenous cell transfer could affect frequencies of both splenic and intragraft neutrophils, macrophages, and NK cells, but not splenic NK cells. Our data might shed light on understanding sensitized transplant biology.

Custom-milled individual allogeneic bone grafts for alveolar cleft osteoplasty-A technical note

INTRODUCTION

Bone grafts from the iliac crest are most commonly used for osteoplasties of the cleft alveolus. To preclude undue donoresite morbidity custom-milled allogeneic bone grafts might be an appropriate choice.

MATERIAL AND METHODS

This technical note showcases the repair of an alveolar cleft using an individualized allogeneic bone graft in a 36-year old female patient. She was asking for an alternative to the iliac crest bone grafting. Her alveolus was successfully build up by a custom-milled cancellous bone block allograft (maxgraft^® 80 bonebuilder).

RESULTS

Custom-milled cancellous bone block allografts can greatly facilitate alveolar cleft repair and may present an effective treatment option under the premise that resorption resistance corresponds to autografts.

CONCLUSION

Further clinical studies are needed to explore the potential of bone block allografts for alveolar cleft osteoplasty.