Maintenance of Functional Human Cancellous Bone and Human Hematopoiesis in NOD/SCID Mice

Attempts were made to establish models to study interactions between marrow stromal cells and hematopoietic cells in vivo. The approach was to create a NOD-SCID-hu murine model of long-term human hematopoiesis by implantation of a human adult bone fragment. Nine to 12 weeks posttransplantation, human CD45+ cells were detected in the blood and the spleen of some mice. The histology of the human transplant showed that human bone fragment was viable at 9 weeks. Moreover, vessels of human origin, as assessed by immunohistochemical detection of human β2-microglobulin, were observed in the mouse tissue surrounding the transplanted human fragment.

[Bone allografts and the functions of bone banks]

The use of bone grafts is a common practice in musculoskeletal surgery to provide mechanical stability where there is a defect and it allows skeletal reconstruction. Classically auto and allografts have been used. The latter are the choice in large, complex defects. Allografts can be transplanted despite cell death, have osteoconduction and osteoinduction capacity, low antigenicity and biomechanical properties similar to the original bone. They can be obtained from living and death donors. They are stored by cryopreservation and lyophilization in entities called bone banks. This is a review about bone allografts and the organization and function of the bone banks.

[Clinical study of nanometer calcium phosphate ceramic artificial bone]

OBJECTIVE

To study the clinical effects and security of nanometer ceramics artificial bone transplantation to treat the bone defect.

METHODS

From March 2005 to November 2007, 32 patients (artificial bone group) with extremity bone defects applied nanometer ceramics artificial bone transplantations, included 19 males and 13 females, aged from 17 to 63 years old (averaged 31.4 years). The other 36 patients (internal fixation group) with extremity bone defects were treated by the internal fixation in the same period, included 21 males and 15 females, aged from 16 to 65 years old (averaged 32.6 years). Ca, P, B-ALP, IgG, IgA, IgM, CIC, C3, SL-2R and CD4+/CD8+ in the peripheral venous blood were measured in the 1st and 2th week and 1st, 3rd, 6th month after operation. All patients were followed up and the limb function was evaluated according to Enneking standard.

RESULTS

The wounds of all patients smoothly healed after operation. Every immunological indicators had no significant difference between two groups. Serum calcium and phosphorus content did not significantly increased. Serum B-ALP of all patients were increased after operation, fell to normal levels in the internal fixation group, but remained at a relatively high level in the artificial bone group. All patients were followed-up for from 9 to 24 months (averaged 15 months). All patients get the excellent physical function.

CONCLUSION

The artificial bone has no immunogenicity, no rejection,does not affect the blood calcium and phosphorus content, and has higher osteogenic activity. It is affirmed that nanometer ceramics artificial bone is used to treat the smaller bone defect on clinical.

Dissociation between peripheral blood chimerism and tolerance to hindlimb composite tissue transplants: preferential localization of chimerism in donor bone

BACKGROUND

Mixed chimerism induces donor-specific tolerance to composite tissue allotransplants (CTAs). In the present studies, we used a nonmyeloablative conditioning approach to establish chimerism and promote CTA acceptance.

METHODS

Wistar Furth (RT1A(u)) rats were conditioned with 600 to 300 cGy total body irradiation (TBI, day-1), and 100 x 10(6) T-cell-depleted ACI (RT1A(abl)) bone marrow cells were transplanted on day 0, followed by a 11-day course of tacrolimus and one dose of antilymphocyte serum (day 10). Heterotopic osteomyocutaneous flap transplantation was performed 4 to 6 weeks after bone marrow transplantation.

RESULTS

Mixed chimerism was initially achieved in almost all recipients, but long-term acceptance of CTA was only achieved in rats treated with 600 cGy TBI. When anti-alphabeta-T-cell receptor (TCR) monoclonal antibody (mAb) (day-3) was added into the regimens, donor chimerism was similar to recipients preconditioned without anti-alphabeta-TCR mAb. However, the long-term CTA survival was significantly improved in chimeras receiving more than or equal to 300 cGy TBI plus anti-alphabeta-TCR mAb. Higher levels of donor chimerism were associated with CTA acceptance. The majority of flap acceptors lost peripheral blood chimerism within 6 months. However, donor chimerism persisted in the transplanted bone at significantly higher levels compared with other hematopoietic compartments. The compartment donor chimerism may be responsible for the maintenance of tolerance to CTA. Long-term acceptors were tolerant to a donor skin graft challenge even in the absence of peripheral blood chimerism.

CONCLUSIONS

Mixed chimerism established by nonmyeloablative conditioning induces long-term acceptance of CTA, which is associated with persistent chimerism preferentially in the transplanted donor bone.

Human tissue allograft processing: impact on in vitro and in vivo biocompatibility

This work investigates the impact of chemical and physical treatments on biocompatibility for human bone/tendon tissues. Nontreated and treated tissues were compared. In vitro testing assessed indirect and direct cytotoxicity. Tissues were subcutaneously implanted in rats to assess the immunological, recolonization, and revascularization processes at 2-4 weeks postimplantation. No significant cytotoxicity was found for freeze-dried treated bones and tendons in comparison to control. The cellular adhesion was significantly reduced for cells seeded on these treated tissues after 24 h of direct contact. A significant cytotoxicity was found for frozen treated bones in comparison to freeze-dried treated bones. Tissue remodeling with graft stability, no harmful inflammation, and neo-vascularization was observed for freeze-dried chemically treated bones and tendons. Frozen-treated bones were characterized by a lack of matrix recolonization at 4 weeks postimplantation. In conclusion, chemical processing with freeze-drying of human tissues maintains in vitro biocompatibility and in vivo tissue remodeling for clinical application.

Histopathology of Cryopreserved Bone Allo- and Isografts: Pretreatment with Dimethyl Sulfoxide

Partial graft cell survival and enhanced graft revascularization have suggested fast freezing using the cryoprotective substance dimethyl sulfoxide (DMSO) as a promising means to improve the biologic function and immune tolerance of allograft bone. This study determines the presence of osteoblasts (cola(1)(I) mRNA), osteoclasts (TRAP), and cytotoxic T cells (CTLs; GrA mRNA) within pretreated bone grafts 12 days after transplantation. The grafts were transplanted either as isografts, allografts, or allografts in presensitized recipients. In fresh isografts, serving as control, well-formed blood vessels and the highest numbers of viable osteoblasts and osteoclasts were found. In fresh allografts, blood vessels were observed within the marrow cavity and the bone was partially covered by osteoblasts and osteoclasts accompanied by CTLs. In DMSO-pretreated frozen allografts, blood vessels together with osteoblasts were observed in three of five, but in none of five grafts frozen without DMSO. However, infiltration with CTLs was higher in DMSO-pretreated frozen allografts when compared to grafts frozen without DMSO. In presensitized allograft recipients, independent of the pretreatment, in none of the grafts were either blood vessels or osteoblasts found. Thus, fast cryopreservation of bone using DMSO improves vascularization and expression of cola(1)(I) mRNA (osteoblasts) after allografting when compared to cryopreservation alone, potentially improving graft incorporation. As these grafts were still invaded by CTLs, the long-term effect of DMSO pretreatment needs to be defined.

[Change of the expression level of Th1 and Th2 cytokines around the xenogeneic cancellous bone scaffold after transplantation: an experiment in rabbits]

OBJECTIVE

To observe the dynamic immunity of the porcine cancellous bone scaffold(PCBS) after transplantation and provide experimental evidences for amending and clinical use.

METHODS

The PCBS was gained through physical and chemical disposals to porcine cancellous bone and was implanted subcutaneously in rabbit. The histological investigation and the expression of Th1 (such as IL-2, IFN-gamma) and Th2 (such as IL-4, IL-10) mRNA were measured by HE, RT-PCR respectively in 1,2,4,8,12 week postoperation.

RESULTS

HE revealed: Inflammation cells (lymphocytes and monocytes) were shown abundantly in the surrounding tissue in 1 week and were decreased gradually since 2 week. At 12 week, there were few inflammation cells in the surrounding tissue. RT-PCR revealed: The mRNA expression level of Th1 cytokines such as IL-2, IFN-gamma was high in 1 week and began to fall since 2 week. At 12 week, the mRNA expression level of Th1 cytokines was low; The mRNA expression level of Th2 cytokines such as IL-4, IL-10 was low in 1 week, rose gradually since 2 week and reached tiptop in 8 week. At 12 week, the mRNA of Th2 cytokines maintained high level expression.

CONCLUSIONS

The porcine cancellous bone scaffold excitate immunoreaction was transitory inflammation after implantation.

Tissue Engineering and Tissue Repair in Immunocompetent Animals: Tissue Construction and Repair

Tissue engineering can regenerate autologous tissue using a biodegradable scaffold and in vitro expanded cells derived from small biopsy samples, and thus may have great potential for tissue repair and reconstruction in plastic and reconstructive surgery. As an important step towards a clinical application, research work in large animals is essential. This article presents our experience of tissue engineering and repair in large animals in the areas of bone, cartilage and tendon.

Grafting for periprosthetic femoral fractures: strut, impaction or femoral replacement

Peri-prosthetic fractures are technically demanding to treat, as they require the skills of revision arthroplasty as well as those of trauma surgery. [Lindahl H, Malchau H, Herberts P, Garellick G. Periprosthetic femoral fractures classification and demographics of 1049 periprosthetic femoral fractures from the Swedish National Hip Arthroplasty Register. J Arthroplasty 2005;20:857-65.] reporting on 1049 periprosthetic femoral fractures found that the annual incidence varied between 0.045% and 0.13% for all THAs performed in Sweden and that the accumulated incidence for the primary hip arthroplasties was 0.4% while for the revision arthroplasties was 2.1% [Lindahl H, Malchau H, Herberts P, Garellick G. Periprosthetic femoral fractures classification and demographics of 1049 periprosthetic femoral fractures from the Swedish National Hip Arthroplasty Register. J Arthroplasty 2005;20:857-65.]. The elderly population is particularly vulnerable to low energy periprosthetic fractures attributed to osteopenia or osteoporosis leaving limited reconstruction options to the hip revision surgeon. Bone grafting in the form of autograft has well recognized limitations and allograft represents the gold standard of bone augmentation in the majority of the cases. Allograft can be used as morselised in the form of impaction grafting, reconstructing the bone from within out, or in the form of structural allograft. In the latter case, strut onlay plates or whole proximal femoral allografts can be used to augment the deficient bone or to totally replace it respectively. Immune reaction and disease transmission along with delayed revascularization of the cortical allograft can cause failure of the construct in the long term; however, the results to date from their use are promising. We here present an overview of the literature on the use of available bone grafts in the treatment of periprosthetic femoral fractures.

[Changes in peripheral blood T lymphocyte subsets of rabbits in early stage after transplantation of tissue engineered bone constituted by biologically-derived scaffold]

OBJECTIVE

To observe the changes in the peripheral blood T lymphocyte subsets and the histomorphology of the transplanted tissues in the rabbits in the early stage after transplantation of the tissue engineered bone constituted by the biologically-derived scaffold and to confirm the feasibility of the biologically-derived materials as a scaffold in the bone tissue engineering.

METHODS

Forty-eight healthy New Zealand rabbits (weight, 2. 0-2.5 kg) with a 1-cm defect were equally and randomly divided into 4 groups: Groups A-D. The partial demineralized freeze-dried bone (PDFDB), the tissue engineered bone constructed by the osteoblasts derived from the lactant rabbit periosteum as a seeding cell, the xenogeneic cancellous bone undergoing the antigen self-digestion, partial demineralization and freeze-dried process as a scaffold, and the fresh xenogeneic allografting bone were respectively transplanted into the segmental defects of the rabbit radii in Groups A-D. To examine the effects of the 4 different materials, the flow cytometry was used to observe the changes in the T lymphocyte subsets in the rabbit peripheral blood at 1, 2, and 4 weeks after the operations and to examine the osteogenesis achieved by the 4 materials, the histological observations were also performed at 2, 4, 8, and 12 weeks after the operations.

RESULTS

Two weeks after the tissue engineered bone transplantation in Group B, the osteoblasts and chondroblasts were found in the apertures of the scaffold, the new bone formation could be observed, the osteoclasts could be seen in the peripheral zone, and some of the netlike frameworks were destroyed and absorbed. Four weeks after the operation, the histological observation revealed that the osteocartilagionous callus turned into a woven bone. The peripheral blood T lymphocyte subsets of CD4+ and CD8+ were significantly greater in number 1-2 weeks after the operations and in Groups A and B than before the operations and in the other groups (P<0. 05);4 weeks after the operations the T lymphocyte subset of CD4+ was only slightly greater in number than before the operations, but with no statistically significant difference (P>0.05). In Group C, the increase of the T lymphocyte subsets of CD4+ and CD8+ was not significant after the operation (P>0.05). The T lymphocyte subsets of CD4+ and CD8+ were significantly greater in number 1, 2 and 4 weeks after the operations and in Group D than before the operation and in the other groups (P<0.05).

CONCLUSION

The tissue engineered bone constructed by the partial demineralized freeze-dried bone as a scaffold does not cause a serious immunologic rejection in the early stage after the transplantation and does not affect its good ability to repair the bone defect. The biologically-derived bone can be used as a scaffold in the bone tissue engineering.

Trafficking of Donor-Derived Bone Marrow Correlates With Chimerism and Extension of Composite Allograft Survival Across MHC Barrier

We proposed to evaluate differences between recipient's immune response to vascularized skin and combined vascularized skin/bone allografts, under a 7-day alphabeta-TCR plus cyclosporine (CsA) treatment protocol. Thirty-six transplantations were performed in six groups: group I (isograft control-vascularized skin graft; n=6); group II (isograft control-combined vascularized skin/bone graft; n=6); group III (allograft rejection control group-vascularized skin graft; n=6); group IV (allograft rejection control-combined vascularized skin/bone graft; n=6); group V (allograft treatment-vascularized skin graft; n=6); and group VI (allograft treatment-combined vascularized skin/bone graft; n=6). Isograft transplantations were performed between Lewis rats and allografts were transplanted across the MHC barrier from Brown Norway to Lewis rats. In the allograft treatment group, a combined alphabeta-TCR+CsA protocol was applied for 7 days. All groups were compared clinically, immunologically and histologically. Statistical significance was determined with two-tailed Student's t test. Indefinite graft survival was achieved in the isograft control group (>300 days). Allograft rejection controls rejected within 5 to 9 days posttransplant; chimerism levels were undetectable (<.5%). Allografts under the alphabeta-TCR+CsA protocol had significantly extended survival when skin was combined with bone (61-125 days) compared to vascularized skin allografts (43-61 days). Lymphoid macrochimerism was significantly higher in group VI than group V. Histology confirmed skin and bone viability. Combined vascularized skin/bone allografts had higher and sustained levels of donor-specific chimerism and extended allograft survival.

Immunogenicity of unprocessed and photooxidized bovine and human osteochondral grafts in collagen-sensitive mice

Background

Autologous and allogeneic osteochondral grafts have been used to repair damaged or diseased cartilage. There are drawbacks to both of these methods, however. Another possible source for osteochondral grafting is photooxidized xenograft scaffolds. The purpose of this study was to evaluate the adaptive immune response to unprocessed and photooxidized xenogeneic osteochondral grafts in a collagen-sensitive mouse model.

Methods

Unprocessed and photooxidized bovine and human osteochondral grafts were used. The grafts were implanted subcutaneously in collagen-sensitive DBA/1LacJ mice for four or twelve weeks. ELISPOT assays were conducted with spleen cells to evaluate the number of collagen-specific T cells that produce IL-2, IL-4, IL-5 or IFN-γ. Serum was collected and ELISA assays were performed to determine the titers of collagen-specific and total IgG, IgG1, IgG2a, or IgM antibodies. Histology was conducted on the retrieved osteochondral grafts.

Results

Results indicated that, with respect to adaptive T cell immunity, the photooxidized bovine grafts, unprocessed human grafts and photooxidized human grafts did not induce a significant response to collagen. The unprocessed bovine grafts, however, were slightly more immunogenic, inducing a weak immune response. With respect to antibody production, the bovine grafts were less immunogenic than the human grafts. Bovine collagen-specific IgG antibodies were not induced by these grafts, but production of IgM after twelve weeks was observed with both the unprocessed and photooxidized bovine grafts. In contrast, photooxidized human osteochondral grafts induced IgG1 and IgG2a antibodies, while the unprocessed human grafts did not. Pre-existing human collagen-specific IgM antibodies were present in all mice, including sham-operated negative controls that did not receive an implant. Histological analysis revealed some degree of fibrous encapsulation and inflammatory infiltrations in both bovine and human implants, whether unprocessed or photooxidized.

Conclusion

Both bovine and human cartilage grafts showed weak, but clear immunogenicity in the DBA/1LacJ mice, indicating that immunogenic collagen was still contained in the grafts, even after cleaning and photooxidation. The process of photooxidation is still important in osteochondral grafting, since it stabilizes the surface of the cartilage by cross-linking the collagen fibers, and allows for immediate load bearing and joint resurfacing.

Biokompatibilitätstestung unterschiedlich sterilisierter bzw. desinfizierter allogener Knochentransplantate im Vergleich zum Goldstandard der autologen Knochenspende - Eine „In-vitro”-Analyse der Immunmodulation

INTRODUCTION

Repair of large skeletal defects using bone allografts has become a routine procedure in orthopaedic and trauma surgery. Different procedures of sterilisation (82.5 degrees C disinfection; 121 degrees C autoclaving; PES; Tutoplast; 25 kGy gamma irradiation) are available to inactivate bacteria and fungi, including their spores, as well as viruses in human bone allografts. The efficiency of these procedures has been proven. However, the effects on the cellular response are rarely investigated. This present in vitro study investigates the immunological answer of human bone marrow cells to human allogenous and autologous bone platelets which were sterilised by different methods.

MATERIALS AND METHODS

Human bone marrow cells and the bone platelets were harvested from patients undergoing a total hip replacement. All patients provided informed consent. Human bone platelets, 10 mm in diameter, 3 mm in height, were produced from femoral heads which were removed within the scope of total hip replacements. They were sterilised by different procedures or were disinfected (gamma radiotherapy, PES/ethanol treatment, Tutoplast procedure, 121 degrees C autoclaving, > 82.5 degrees C thermodisinfection). In addition, an autologous in vitro bone donation was simulated and compared with the allogenous bone grafts. Endobon was evaluated as a bovine hydroxyapatite ceramic. As control a human bone marrow cell culture without bone platelets was used. Over a period of four weeks the changes of the immunogenic cell populations were analysed in vitro (FACS analysis). Light and scanning microscopy were done to reveal morphological differences. As a vitality test the trypan-blue staining was performed.

RESULTS

Light and scanning microscopy demonstrated large differences between the various sterilisation and disinfection methods. After 4 weeks the autologous bone platelets were completely covered with homogenously distributed human osteoblast like cells. The heat-sterilised/disinfected transplants demonstrated similar effects compared to the autologous bone grafts while the irradiated bone platelets demonstrated less cell coverage. 2/3 of the cells were vital on average after four weeks, with the exception of the irradiated bone platelets. The FACS analysis revealed in comparison to the control group provable differences in the immunological answer for the autologous bone donation as well as for the differently sterilised or disinfected allogenous bone grafts. The heat sterilisation or, respectively, disinfection methods compared to the autologous bone donation demonstrated almost similar in vitro effects. By far the worst results, characterised by an excessively increased portion of cytotoxic T-cells and a decreased amount of viable cells, were seen in the 25 kGy gamma irradiation samples.

CONCLUSIONS

The results demonstrate the influence of the different sterilisation and disinfection procedures on the differentiation of human marrow cells (host). Similar in vitro effects were seen for the autologous and heat-treated bone platelets. The treatment of allogenous bone grafts with PES/ethanol and the Tutoplast procedures showed, just as Endobon, only low differences in comparison with the control cultures. The worse results in the case of the irradiated bone platelets may be explained by the production of free radicals which led to an excessive cell death.

The syringe technique for minimally invasive bone grafting

Standard techniques of bone grafting for nonunion involve extensive dissection of the soft tissues surrounding the nonunion site to gain exposure and facilitate placement of the graft. Successful minimally invasive grafting has been described; however, it can involve difficulties in graft placement or require the use of advanced, expensive technical equipment. We describe a simple, inexpensive technique in which the distal end of a standard syringe is trimmed to provide a conduit for minimally invasive delivery of bone graft material. Three illustrative case reports are discussed in which this technique achieved successful union without operative morbidity.

Immunological responses to bone soluble proteins in recipients of bone allografts

The significance of an immune response in complications of bone allograft procedures is not well understood. This study evaluates the immunological reaction to bone allografts in either cortical or cancellous form. Serological responses from osteoarthritis (OA) patients and normal individuals to soluble proteins extracted from allografts were assessed using Western blotting and ELISA techniques. A large number of patients expressed antibodies to bone proteins extracted from the washed bone as compared with normal controls. Antibodies were present in patients without the use of bone allografts, indicating that OA patients develop antibodies to bone soluble proteins. However, patients receiving allografts exhibited an increased immune reactivity against multiple bone proteins when compared with non-grafted patients. Protein characterization of the immunoreactive proteins revealed that the majority of antigenic targets were fragments of various collagen molecules. The data suggests that OA patients develop antibodies to bone soluble proteins prior to surgery, and these antibodies increase after revision surgery utilizing bone allografts. These findings support the implications that various collagen molecules as well as their degraded fragments represent potential immunogenic proteins within bone allografts. The removal of these antigenic proteins from the allografts prior to surgery may alleviate this immunological reactivity and improve graft outcome.

Immunologic testing of xeno-derived osteochondral grafts using peripheral blood mononuclear cells from healthy human donors

Background

One means of treating osteoarthritis is with autologous or allogeneic osteochondral grafts. The purpose of this study was to evaluate the innate immunological response in humans toward xeno-derived osteochondral grafts that have been partially or entirely treated by the photooxidation process.

Methods

The antigens tested included bovine, porcine, ovine and equine osteochondral samples that have been treated in successive steps of photooxidation. ELISPOT assays were used to evaluate the production of IL-1, IL-4, IL-6, IL-10, IL-12 and TNF-α by human monocytes in response to the antigens.

Results

Results indicated vigorous production of IL-1, IL-6, IL-10 and TNF-α in response to untreated bovine, porcine and equine specimens. This indicates that these samples are perceived as foreign, or stimulatory, by the human monocytes. There was no induction of IL-4 or IL-12, which is required for Th2 and Th1 immunity, respectively. In contrast, the processed bovine, porcine and equine samples did not induce significant activation of cells of the innate immune system. This occurred after the first step in processing (after cleaning in increasing strengths of ethanol). This suggests that the processing steps dramatically, if not completely, negated the immunostimulatory properties of the test sample. The results for the ovine samples indicate a reverse response.

Conclusion

The findings of the study suggest that photooxidized bovine, porcine or equine samples have the potential to be used as an osteochondral graft. Although the first step in processing reduced the immunological response, photooxidation is still necessary to retain the structure and mechanical integrity of the cartilage, which would allow for immediate joint resurfacing.

Human leukocyte antigen sensitization after structural cortical allograft implantations

The incidence and significance of a donor-specific human leukocyte antigen antibody response to massive fresh-frozen human bone allograft implantation is not established. This study was a prospective, multicenter study of a cohort of consecutive patients who self-randomized themselves into two groups based on their alloantibody response to allograft bone transplant. The study hypothesis was that donor-directed antibodies are an independent risk factor influencing incorporation of massive frozen bone allografts. Pretransplant and posttransplant human leukocyte antigen alloantibody analysis was performed and correlated to determine pre-existing and graft-induced antibodies. The surgical outcomes of the two groups of patients were compared to determine the relationship between alloantibody response and bone graft incorporation. Preliminary results revealed that donor-specific human leukocyte antigen sensitization occurred in 17 of 32 (53%) of previously nonsensitized patients. A survival analysis of time to healing based on human leukocyte antigen status showed no evidence of an association between human leukocyte antigen status and time to healing. Longer followup in additional patients will be required to determine if this sensitization is correlated with an alteration in the time to union or with the quality or type of bone graft incorporation.

LEVEL OF EVIDENCE

Therapeutic study, Level II. See the Guidelines for Authors for a complete description of levels of evidence.

[Experimental study of immunological tolerance induced by cytotoxic T lymphocyte-associated antigen 4 immunoglobulin in fresh bone allografts]

OBJECTIVE

To study the immunological tolerance induced by blocking the second signal of T cell with extrinsic cytotoxic T lymphocyte-associated antigen 4 immuno globulin (CTLA4-Ig).

METHODS

Fifty-four BALB/C mice, inbred strains, were employed as recipients of bone allografts, using a model of heterotopic muscle pouch. The 54 mice were divided into 3 groups and 18 for each group. The first group, in which the donor was C57BL/6 with intraperitoneal injection of L6 (as a control), was named AL group. The second group, also C57BL/6 with injection CTLA4-Ig, was named AC group. The third group, homologous BALB/C with injection of PBS buffer solution, was named AB group. The serum antibody, lymphocyte proliferation of the second stimulation by splenic cell and bone supernatant of donor, the analysis of lymphocyte subsets, a regraft experiment and histology were determined 2, 4 and 6 weeks after transplantation. The second transplantation was to regraft C57BL/6 (BC group) and C3H (BH group) mice respectively after first 12 mice being transplanted with C57BL/6 and injected with CTLA4-Ig as to detect donor-specificity of immunological tolerance.

RESULTS

Compared with AB group, AL group created more intensive immune rejection: CD4 T cell subsets (P<0.05), the serum antibody (P<0.05) and lymphocyte proliferation of the second stimulation by splenic cell and bone supernatant of donor (P<0.01 and 0.05) were significantly increased. However, the results of AC group showed that CTLA4-Ig significantly inhibited the immune rejection: CD4 T cell subsets (P>0.05), the serum antibody (P>0.05), and lymphocyte proliferation of the second stimulation (P>0.05) were similar to those of AB group. Histological observation of AC group showed that lymphocyte infiltration disappeared, cartilage and new bone formed, and bone marrow cavities emerged. A regraft experiment showed that CD4 T cell subsets (P<0.05) and lymphocyte proliferation of the second stimulation by splenic cell and bone supernatant of donor (P<0.05), BC group was significantly lower than those of BH group. So the immunological tolerance induced by CTLA4-Ig was of donor-specificity.

CONCLUSION

The immunological tolerance induced by CTLA4-Ig was prolonged for 6 weeks. This study provides a brand-new path for bone transplantation, which can be helpful to other organ transplantation.

[Changes of subtype T lymphocytes in blood after implanting with xenogeneic acellular bone matrix]

OBJECTIVE

To observe the changes of immune status in recipient after implanting with xenogeneic acellular bone matrix (ACBM).

METHODS

Twenty rabbits were randomly divided into 4 groups. Autograft, ACBM and bone soaked in alcohol were implanted into the 3 experimental groups separately, and No-treatment was done as control group. The CD4+, CD8+, CD25+ T lymphocytes in blood were detected by flow cytometer at 1, 2, 4 and 6 weeks after operation. After 2 and 6 weeks of implantation, the changes of bone and tissue were observed by histology.

RESULTS

After 2-6 weeks, CD4+ and CD8+ T cells were significantly higher in the implanted group of bone soaked in alcohol than that in the other 3 groups (P < 0.05) and there was no statistically significant difference in the other 3 groups (P > 0.05). After 2 weeks, CD25+ T cells were significantly higher in the implanted group of bone soaked in alcohol than that in the other groups. In the 2nd week, there were inflammatory infiltration with a predominance of granulocytes. In the 6th week, there were many fibroblasts instead of granulocytes with a few lymphocytes and cartilage island formed in the implanted groups of autograft and ACBM.

CONCLUSION

ACBM implanting has low influence on cellular immunity in recipient.

[Immune elimination and sterilization in homogeneous bone allografts]

Homogeneous bone allograft is most commonly used to treat bone defect. Immune elimination and sterilization are necessary measures to improve the outcome and to secure the reliability of homogeneous bone allografts. In this paper, we have given a brief introduction to the major methods of immune elimination and sterilization as well as the current researches on this subject.

Prolonged limb allograft survival with CD40 costimulation blockade, T-cell depletion, and megadose donor bone-marrow transfusion

The purpose of this study was to determine the efficacy of a treatment regimen consisting of CD 40 costimulation blockade, T-cell depletion, and megadose donor bone marrow transfusion in the limb allograft model. C57Bl/6 mice underwent limb transplantation from Balb/c mice and received MR1 (anti-CD 40 ligand monoclonal antibody), and CD4(+) and CD8(+) T cell-depleting antibodies with and without 120 x 10(6) donor bone-marrow transfusion. Recipients treated only with antibodies showed rejection at 51.4+/-17 (mean+/-SEM) days, while those who also received donor bone marrow had allograft survival of 67+/-16.4 days, with a range up to 91 days. Treated specimens with rejection had less lymphocytic infiltration than untreated controls. Recipients of donor bone marrow also demonstrated early mixed chimerism, which disappeared after 1 month. While allograft survival was prolonged, tolerance was not achieved, and the mechanism of rejection was more consistent with a chronic process.

The SCID-hu myeloma model

The severe combined immune deficient human (SCID-hu) myeloma model is the only available model in which primary myeloma cells grow in vivo in a human bone marrow micro environment. A SCID mouse receives an implanted human fetal bone into which myeloma cells are directly injected. Through interaction with the human bone marrow microenvironment, the myeloma cells induce typical myeloma manifestations in the SCID host, such as the appearance of M protein in the serum, and changes in the implanted human bone, which often result in osteolysis of the human bone. The model provides the only platform for in vivo investigation of the biology and therapy of primary human myeloma in a human microenvironment. This chapter describes in detail all the steps necessary to establish this model and evaluate its success.

Gradual graft-cell repopulation with recipient cells following vasularized bone and limb allotransplantation

Little is known about the fate of graft cells following vascularized bone allografting. This study was conducted to define the process of graft-cell repopulation with recipient cells. Sixty-five vascularized tibial bone and 50 limb allotransplantations were performed in rat sex-mismatched pairs. FK 506 was used for immunosuppression. The ratio of donor and recipient cells in the graft was evaluated by semiquantitative polymerase chain reaction, using the Y-chromosome primers. Allografted bones had no rejection episodes. In the vascularized bone allograft model, donor-derived cells were gradually replaced by cells of recipient origin, such that by 24 weeks, they comprised only 10% of total cells. In the limb allograft model, male recipient cells were detected in female grafts not at 1 week but at 48 weeks posttransplantation. The ratio of recipient cells was more than 10% in the femur and tibia. Recipient-derived cells gradually migrated into the grafted bone cells with the passage of time.

Immune response in patients receiving fresh osteochondral allografts

Immunologic response to cartilage-specific protein (CSP) antigens was tested in patients treated with fresh osteochondral allografts. Eight of 14 allograft recipients showed immune reactivity against CSP, whereas only 2 of 14 controls were reactive (P<.05). The molecular weights of the most common immunoreactive proteins were 220 kd and 95 kd. The precise identity of these proteins could not be determined using standard anticollagen antibodies. These data indicate the presence of antibodies to CSP--which supports the concept of immunologic response to the cartilage component of osteochondral allografts.

Effects of cessation of immunosuppression on skeleton reconstructed by vascularized bone allograft in rats

In the present study, we investigated the effects of cessation of immunosuppression on skeleton reconstructed by vascularized allogenic bone transplantation in a rat tibio-fibula graft model. Twelve-week-old male 25 Dark Agouti rats with the major histocompatibility antigen (MHC) RT1a were used as donors and age-matched male 25 Lewis rats with MHC RT1l were used as recipients. Among them, 20 rats were randomly allocated to 8-week cyclosporine A (CsA) followed by 8-week CsA vehicle group or continuous 16-week CsA group. The remaining 5 rats received CsA for 8 weeks followed by no further treatment for next 40 weeks (long-term observation group). In the CsA followed by vehicle group as well as the continuous CsA group, the structure of the reconstructed bones was maintained, though the transplanted bones in former group were found to be partly non-vital. The CsA followed by vehicle group had higher bone mineral density of the transplanted bones and stronger strength of the reconstructed bones than the continuous CsA group. In the long-term observation group, the structure of the reconstructed bones was still maintained and the transplanted bones were almost vital. These results suggest that long-term strong immunosuppression may not be necessary for successful reconstruction of large bone defect by vascularized bone allograft.

Living cells in 1 of 2 frozen femoral heads

Allogeneic, frozen bone is now the most commonly grafted tissue (Norman-Taylor and Villar 1997). Tissue banks collect bone material according to protocols developed with the aim of maintaining osseoinductive properties of grafts as well as preventing transmission of viral or bacterial diseases (Standards from the American Association of Tissue Banks (AATB) or from the European Association for Musculo-skeletal Transplanting (EAMST)). Standard procedures include cryopreservation of tissue at -80 degrees C, which is generally considered to devitalize the bone by killing all cells present, resulting in reduced immunogenicity of the graft. The osseoinductive properties of frozen, allogeneic bone grafts have therefore mainly been attributed to the dead bone matrix, that may provide osteoblast-stimulating growth factors and other essential proteins, and/or an osteoclast substrate to direct bone remodeling (Aspenberg et al. 1996, Kingsmill et al. 1999). Recently however, it was suggested that some cells in bone biopsies may survive standard bone bank freezing procotols. It is unclear whether vital cells are present in other bone banks and whether these cells can contribute to the clinical outcome of frozen allogeneic bone grafting. In this report, we show that frozen bone biopsies, obtained from the Erasmus Medical Center bone bank may contain living cells that can be cultured in vitro. These cultured cells were found to originate from the donor by genotyping.

The incorporation of different sorts of cancellous bone graft and the reaction of the host bone. A histomorphometric study in sheep

We performed a morphological and histomorphometric analysis of the use of either autografts, or of frozen or freeze-dried cancellous bone allografts in sheep. A cancellous bone defect was created in the lateral portion of the distal epiphysis of the left femur. Four groups of six animals were monitored for 3 months. In the first group, the cavity was filled with autograft, in the second with frozen allograft and in the third with freeze-dried allograft. In the last group, the cavity was not filled and served as control. A study of the host bone showed that the mean trabecular width of the peripheral osteoid was greatest in the control group, while the number of osteoblasts and osteoclasts was significantly lower in the freeze-dried allograft group. However, the different bone grafts that were used to fill the cavity showed a greater trabecular width and area in the autografts. Among the frozen allografts, these measurements were also greater than in the freeze-dried allograft group. The "erosion surface" of the freeze-dried allograft group was also found to be three times greater, and there were a larger number of osteoclasts and osteoclastic nuclei. We concluded that the "lyophilised" allografts were re-absorbed rapidly and that there were no major morphological differences between the frozen allografts and the autograft groups.

Immunologic and Osteogeneic Properties of Xenogeneic and Allogeneic Demineralized Bone Transplants

Xenografting is increasingly being developed as a response to the shortage of human tissues. However, antigenic components of bone material eliciting immune responses--particularly of cellular nature--are blamed for the reduction of the osteoinductive properties of bone and bone-derived implants. The aim of our study was to compare the immunologic response and osteogenesis induced by antigen-depleted allogeneic and xenogeneic bone-derived implants to that induced by partially antigen-depleted material heterotopically placed (muscular pouch) in rats. Wistar rats received bone-derived implants of different antigeneic condition, from both xenogeneic (rabbit) and allogeneic (rat) origin. After sacrifice, animals were evaluated for osteogenesis and immune response. New bone formation was observed around all bone-derived implants, whether fully or partially antigen-extracted, and from both xenogeneic and allogeneic origin. No significant humoral response resulted following bone implantation. Cellular response showed a similar pattern in partial and fully antigen-extracted bone of both allogeneic and xenogeneic origin. Xenogeneic antigen-extracted bone from safe donor sources could be a suitable solution to human tissue shortage in a near future.

Tumour necrosis factor receptor type II 196M/R genotype correlates with circulating soluble receptor levels in normal subjects and with graft-versus-host disease after sibling allogeneic bone marrow transplantation1

BACKGROUND

A single nucleotide polymorphism in the tumor necrosis factor type II receptor (TNFRII) gene, codon 196, results in the substitution of arginine (R allele) for methionine (M allele). The 196R allele is reportedly associated with an increased susceptibility to autoimmune disease, and donor 196R allele carriage correlates with increased severity of acute graft-versus-host disease (GVHD) after matched unrelated bone marrow transplantation (BMT).

METHODS

We investigated the impact of donor and recipient TNFRII genotype on GVHD incidence and severity among 104 adult recipients of myeloablative sibling BMTs.

RESULTS

196R allele frequency was 0.28 among recipients, donors, and controls. There was an increased incidence of acute GVHD among 196R-positive recipients (odds ratio [OR] 3.6, P=0.05). This association was confirmed in multivariate analysis (relative risk 4, P=0.04), correcting for previously established clinical and genetic risk factors. Donor 196R homozygosity was associated with an increased incidence of extensive chronic GVHD (OR 18.5, P=0.02). This association was also confirmed in multivariate analysis (OR 11, P=0.02). To investigate the functional impact of the TNFRII 196 M/R polymorphism, 79 volunteer blood donors were genotyped at this locus, by polymerase chain reaction and single-strand conformational polymorphism analysis, and plasma soluble TNFRII (sTNFRII) levels were measured by ELISA. Mean plasma sTNFRII levels (pg/mL: +/-SEM) were 1224 (+/-26) and 1063 (+/-65) for 196M-postive (196 M homozygous or heterozygous) individuals and 196R homozygotes, respectively (P=0.02).

CONCLUSIONS

Because sTNFRIIs can act as TNF antagonists, the association between recipient and donor TNFRII 196R allele status and acute or extensive chronic GVHD incidence, respectively, may reflect reduced circulating sTNFRII.

A New Concept of Stem Cell Disorders and Their New Therapy

The author previously proposed a new concept of categorizing stem cell disorders as: (1) stem cell aplasia (aplastic anemia), (2) monoclonal hematopoietic stem cell proliferative syndrome (leukemia and myelodysplastic syndrome), and (3) polyclonal hemopoietic stem cell proliferative syndrome (systemic and organ-specific autoimmune diseases). This review includes the following two stem cell disorders: mesenchymal stem cell disorders and organ-specific stem cell disorders. Age-associated diseases such as Alzheimer's disease, osteoporosis, and lung fibrosis belong to the former, whereas carcinosarcoma in the lung and adeno-endocrine cell carcinoma in the stomach belong to the latter. Recently, we have established a new method for allogeneic bone marrow transplantation using chimerism-resistant autoimmune-prone MRL/lpr mice. In this method, whole bone marrow cells containing a small number of T cells and mesenchymal stem cells are directly injected into the bone marrow cavity. MRL/lpr mice treated by injection of stem cells survived more than 2 years without showing symptoms of autoimmune disease. To apply this method to humans, we established a new method for bone marrow cell harvesting using cynomolgus monkeys. In this method, cells are harvested from the long bones using a perfusion method and are then injected directly into the bone marrow cavity of recipients. In this review, we show that this new method may become a powerful strategy for the treatment of various intractable diseases.

Blockade of the CD40/CD154 pathway enhances T-cell-depleted allogeneic bone marrow engraftment under nonmyeloablative and irradiation-free conditioning therapy

BACKGROUND

T-cell-depleted bone marrow transplantation (TDBMT) can prevent graft-versus-host disease (GvHD). However, depleting T cells from allogeneic bone marrow often results in failure of bone marrow engraftment under irradiation conditioning. It is not know whether donor T cells are essential for bone marrow engraftment and whether blocking the CD40/CD154 pathway promotes allogeneic TDBM engraftment under nonmyeloablative and irradiation-free fludarabine phosphate and cyclophosphamide conditioning therapy.

METHODS

Using fully major histocompatibility complex (MHC)-matched mouse models, we investigated whether donor T cells are essential for bone marrow engraftment under fludarabine phosphate and cyclophosphamide conditioning therapy. We also determined whether the barrier of allogeneic TDBM could be overcome by blocking the CD40/CD154 pathway. Donor chimerism was detected by flow cytometric analysis. Donor-specific tolerance through establishing mixed chimerism was tested in vivo by skin transplantation and in vitro by mixed leukocyte reaction and enzyme-linked immunospot (ELISPOT) assay.

RESULTS

Compared with unmodified bone marrow, TDBM resulted in poor engraftment when fully MHC-mismatched donors were used. However, anti-CD154 monoclonal antibody (mAb) treatment significantly enhanced donor TDBM engraftment. TDBM engraftment was also seen in CD154 knockout mice. A stable and high level of multilinage donor chimerism was achieved. Recovery of host CD3 T cells was suppressed, and recovery of donor CD3 T cells was promoted, after TDBMT and anti-CD154 mAb treatment. Donor chimerism was established by TDBMT induced donor-specific tolerance in vivo and in vitro.

CONCLUSION

Donor T cells facilitate bone marrow engraftment under nonmyeloablative and irradiation-free conditioning therapy, and the blocking the CD40/CD154 pathway can replace donor T cells to promote TDBM engraftment.

Bone transplantation

Bony deficiency, particularly loss of bone stock associated with failed joint replacements or tumours, is a challenging problem in orthopaedic surgery. Bone transplantation techniques provide solutions that can be tailored to the clinical problem. However, the risks of bone transplantation are well documented and the biology of allograft incorporation remains unpredictable and poorly understood.

IFN-gamma production is specifically regulated by IL-10 in mice made tolerant with anti-CD40 ligand antibody and intact active bone

We have developed a strategy to induce tolerance to allografts, involving cotransplantation of allogeneic intact active bone and transient anti-CD40 ligand mAb therapy. Tolerance induced by this approach in C57BL/6 mice receiving BALB/c hearts is not mediated by deletional mechanisms, but by peripheral regulatory mechanisms. Tolerance is associated with diminished ex vivo IFN-gamma production that is donor specific, and a reduction in the frequency of IFN-gamma-producing cells. Splenocytes from mice tolerant to BALB/c grafts, but sensitized to third-party C3H skin grafts, demonstrated normally primed ex vivo IFN-gamma responses to C3H stimulators. Neutralizing anti-IL-10 and anti-IL-10R, but not anti-TGF-beta, anti-IL-4, or anti-CTLA-4, Abs restored the ex vivo IFN-gamma response to BALB/c stimulators. There was no significant difference in IL-2 or IL-4 production between tolerant and rejecting mice, and anti-IL-10 mAbs had no effect on IL-2 or IL-4 production. The Cincinnati cytokine capture assay was used to test whether suppression of IFN-gamma production in vivo was also a marker of tolerance. In naive mice, we observed a dramatic increase in serum IFN-gamma levels following challenge with allogeneic BALB/c splenocytes or hearts. Tolerant mice challenged with allogeneic BALB/c splenocytes or hearts made significantly less or undetectable amounts of IFN-gamma. No IL-4 or IL-10 production was detected in tolerant or rejecting mice. Collectively, our studies suggest that active suppression of IFN-gamma production by IL-10 is correlated with, and may contribute to, tolerance induced with intact active bone and anti-CD40 ligand mAbs.

Cryopreservation of osteochondral allografts: dimethyl sulfoxide promotes angiogenesis and immune tolerance in mice

BACKGROUND

Although transplantation of cryopreserved bone allografts has become a routine procedure in orthopaedic surgery, biological and immunological impairment remains an unsolved problem that causes clinical failures. Experimental and clinical evidence has indicated that bone grafts that are revascularized early remain viable and contribute to union at the recipient site. Unprotected cryopreservation, used in most bone banks to reduce graft antigenicity, is associated with complete loss of graft viability, potentially contributing to graft failure. The differences in the survival of various cell types during cryopreservation with use of dimethyl sulfoxide, particularly the increased sensitivity of leukocytes to fast freezing, has resulted in a new approach to modulate immunogenicity. On the basis of this concept, it was proposed that a reduction in the immune response and enhanced revascularization of osteochondral allografts could be achieved by rapid cryopreservation with dimethyl sulfoxide. To test this hypothesis, angiogenesis and immune tolerance were quantified in a murine model with use of intravital microscopy.

METHODS

Fresh osteochondral tissue and osteochondral tissue that had been cryopreserved with and without dimethyl sulfoxide was transplanted into dorsal skinfold chambers as isografts and as allografts in presensitized and nonsensitized recipient mice. To quantify angiogenesis, the onset of hemorrhages in the vicinity of the grafts and the revascularization of the grafts were determined by means of intravital fluorescence microscopy. To determine the recipient's intravascular immune response to the grafts, the leukocyte-endothelium interaction was assessed on the twelfth day after transplantation.

RESULTS

Nine of nine fresh isografts were revascularized at a mean (and standard deviation) of 57 +/- 33 hours, eight of nine isografts that had been cryopreserved with dimethyl sulfoxide were revascularized at 98 +/- 50 hours, and zero of nine isografts that had been cryopreserved without dimethyl sulfoxide were revascularized. Seven of seven fresh allografts were revascularized at 53 +/- 6 hours, and ten of ten allografts that had been cryopreserved with dimethyl sulfoxide were revascularized at 82 +/- 29 hours. However, signs of revascularization faded in four of the seven fresh allografts whereas reperfusion was maintained in the majority (seven) of the ten grafts frozen in the presence of dimethyl sulfoxide. Similar to the findings associated with unprotected frozen isografts, zero of ten unprotected frozen allografts were revascularized. None of the allografts that had been transplanted into presensitized recipients were revascularized, regardless of whether they had been implanted fresh (nine grafts) or had been implanted after protected (eight grafts) or unprotected (nine grafts) freezing. Quantification of the leukocyte-endothelium interaction revealed a reduction in the intravascular immune response to frozen allografts (both protected and unprotected) compared with fresh allografts.

CONCLUSION

Osteochondral allografts that had been pretreated by cryopreservation with dimethyl sulfoxide demonstrated improved angiogenesis induction and enhanced immune tolerance compared with unprotected frozen grafts. A selective reduction in donor passenger leukocytes is the proposed mechanism underlying this phenomenon.

CLINICAL RELEVANCE

In the absence of presensitization, cryopreservation with dimethyl sulfoxide appears to reduce the immune response to allografts and to enhance their revascularization; in the presence of presensitization, alternatives to allograft transplantation should be considered since the allografts will be exposed to a deleterious immune response.

Intact active bone transplantation synergizes with anti-CD40 ligand therapy to induce B cell tolerance

Blockade of T cell costimulatory pathways can result in the prolongation of allograft survival through the suppression of Th1 responses; however, late allograft rejection is usually accompanied by an emerging allograft-specific humoral response. We have recently determined that intact active bone (IAB) fragments transplanted under the kidney capsule can synergize with transient anti-CD40 ligand (CD40L) treatment to induce robust donor-specific allograft tolerance and suppress the alloantibody response. In this study, we take advantage of the ability of galactosyltransferase-deficient knockout (GT-Ko) mice to respond to the carbohydrate epitope, galactose-alpha1,3-galactose (Gal), to investigate whether IAB plus transient anti-CD40L therapy directly tolerize B cell responses. GT-Ko mice tolerized to Gal-expressing C3H hearts and IAB plus transient anti-CD40L therapy were challenged with pig kidney membranes that express high levels of Gal. The anti-Gal IgM and IgG responses were significantly suppressed in IAB-tolerant mice compared with controls, while the non-Gal anti-pig Ab responses were comparable. The anti-pig T cell cytokine response (IFN-gamma and IL-4) was comparable in IAB-tolerant and control mice. The tolerant state for the anti-Gal IgM response could be reversed with repeated immunization, whereas the tolerant state for the IgG response was robust and resisted repeated immunization. These observations provide an important proof-of-concept that adjunct therapies can synergize with anti-CD40L Abs to tolerize B cell responses independent of their effects on T cells. This model, which does not require mixed chimerism, provides a unique opportunity for investigating the mechanism of peripheral tolerance in a clinically relevant population of carbohydrate-specific B cells.

Immune response to perforated and partially demineralized bone allografts

Immune responses have been shown to be involved in the pathogenesis of clinical complications of cortical bone allografts. In an attempt to reduce the immunogenicity of these allografts, we evaluated cortical bone allografts modified by laser perforation and partial demineralization transplanted orthotopically into sheep tibiae. The recipient animals were divided into three groups, of eight animals each, according to the type of cortical allograft that was transplanted: group 1, no treatment (control); group 2, demineralization only; and group 3, laser perforation and partial demineralization. All animals were tissue-typed by biochemical definition of MHC class I molecules, using unidimensional isoelectric focusing and Western blotting. Mismatches of donors and recipients were assessed by testing samples of each donor and recipient pair in parallel and by comparing their individual bands. Donor-specific alloantibodies were detected by a similar technique, using an enzyme-linked immunosorbent assay (ELISA) format. Negative controls were included in all tests. All grafts were poorly immunogenic, whether they were untreated, processed by partial demineralization, or processed by both laser perforation and partial demineralization. Only two recipient animals showed a transient, antibody-mediated donor-specific immune response. One of these animals had received a control allograft, whereas the other animal had received a laser-perforated and partially demineralized bone allograft. All of the grafts in this study, including control grafts, were stripped of soft tissues and their bone marrow was removed; cellular sources of alloantibody stimulation may have been eliminated by these processes. The results of this study suggest that immune responses to bone allografts may be reduced by removing the bone marrow and adjacent soft tissues. The processing of cortical bone allografts by laser perforation and partial demineralization appeared to have little effect on immune responses.

Shell osteochondral allografts of the knee: comparison of mr imaging findings and immunologic responses

PURPOSE

To define the magnetic resonance (MR) imaging appearance of shell osteochondral allografts of the knee and compare the MR findings with antibody responses.

MATERIALS AND METHODS

Thirty-six grafts were evaluated with a 1.5-T unit with T1-, intermediate-, and T2-weighted, and three-dimensional spoiled gradient-recalled MR imaging at 3, 6, 12, 24, and/or 36 months after surgery. Nineteen patients underwent imaging serially. Two osteoradiologists scored by consensus host marrow edema, thickness of graft-host interface, signal intensity of graft marrow, cyst formation, joint effusion, articular cartilage defects, and surface collapse. Patients were divided into antibody-positive (AP) (n = 11) and antibody-negative (AN) (n = 25) groups evenly distributed across the different time points on the basis of results of anti-human leukocyte antigen antibody screening. MR findings for the two groups were compared.

RESULTS

AP patients demonstrated greater mean edema (P<.002), thicker interface (P<.03), and more abnormal graft marrow (P<.04) than AN patients, and they had a higher proportion of surface collapse (P<.03).

CONCLUSION

Humoral immune responses were associated with more inflammation and less complete incorporation after allograft placement. MR imaging shows promise as a surrogate biomarker for success of shell osteochondral allograft implantation.

Comparison of long-term immunosuppression for limb transplantation using cyclosporine, tacrolimus, and mycophenolate mofetil: implications for clinical composite tissue transplantation

This study compared the efficacy of long-term intermittent immunosuppression in preventing the rejection of a limb transplant across the strongest histocompatibility barrier in ACI --> Lewis rats using the conventional immunosuppressive agent cyclosporine-A and the newer immunosuppressive agents FK-506 (tacrolimus) and RS-61443 (mycophenolate mofetil). The recipient animals were immunosuppressed daily for 14 days postoperatively, followed by long-term intermittent, twice-weekly immunosuppression using cyclosporine 25 mg/kg, RS-61443 30 mg/kg, or FK-506 2 mg/kg. All three immunosuppressive agents were able to prolong the rejection of the skin component of a limb transplant compared with nonimmunosuppressed controls. Eight of nine animals receiving cyclosporine immunosuppression showed signs of rejection of the skin component of the limb transplant while continuing to receive long-term immunosuppression and had a mean rejection time of 61.6 days. Seven of 10 animals immunosuppressed with RS-61443 also showed signs of rejection while still receiving immunosuppression, with a mean rejection time of 43.6 days. Nine of 10 animals receiving FK-506 immunosuppression showed no signs of skin rejection, but died of bacterial pneumonia between 273 and 334 days after transplantation, with a mean rejection time of 296.1 days. There was no statistically significant difference between intermittent immunosuppression with cyclosporine and RS-61443, but FK-506 was significantly superior to both cyclosporine and RS-61443. The implication of this study is that FK-506, but not cyclosporine or RS-61443, is probably the only single immunosuppressive agent capable of preventing rejection of the skin component of a composite tissue transplant. Combination immunosuppression with FK-506 and RS-61443, therefore, may be required to allow composite tissue transplantation to become a predictable clinical reality in the future.

Bone marrow-derived antigen-presenting cells are required for the generation of cytotoxic T lymphocyte responses to viruses and use transporter associated with antigen presentation (TAP)-dependent and -independent pathways of antigen presentation

Bone marrow (BM)-derived professional antigen-presenting cells (pAPCs) are required for the generation of cytotoxic T lymphocyte (CTL) responses to vaccinia virus and poliovirus. Furthermore, these BM-derived pAPCs require a functional transporter associated with antigen presentation (TAP). In this report we analyze the requirements for BM-derived pAPCs and TAP in the initiation of CTL responses to lymphocytic choriomeningitis virus (LCMV) and influenza virus (Flu). Our results indicate a requirement for BM-derived pAPCs for the CTL responses to these viruses. However, we found that the generation of CTLs to one LCMV epitope (LCMV nucleoprotein 396-404) was dependent on BM-derived pAPCs but, surprisingly, TAP independent. The study of the CTL response to Flu confirmed the existence of this BM-derived pAPC-dependent/TAP-independent CTL response and indicated that the TAP-independent pathway is approximately 10-300-fold less efficient than the TAP-dependent pathway.

Calcium sulfate bone void filler: a review and a look ahead

Bone grafting to augment skeletal healing has become one of the most common techniques in surgical practice. However, the morbidity and limited availability associated with autografts, and the potential for disease transmission, immunogenic response, and variable quality associated with allografts, have engendered a plethora of alternative materials. Such alternatives range from the simple, such as calcium sulfate and calcium phosphate materials, to the complex that contain allograft extracts, bone morphogenetic proteins, or other agents. Calcium sulfate has the distinction of being the alternative that is both one of the simplest as well as that which has the longest clinical history as a synthetic bone graft material--spanning more than 100 years. This article reviews the structure and function of calcium sulfate as a synthetic bone void filler and speculates on its future surgical role. It is anticipated that this foundation will also help assist in the understanding of how other bone graft alternatives may operate.

Neonatal induction of tolerance to skeletal tissue allografts without immunosuppression

Vascularized allogeneic skeletal tissue transplantation without the need for host immunosuppression would increase reconstructive options for treating congenital and acquired defects. Because the immune system of a fetus or neonate is immature, it may be possible to induce tolerance to allogeneic skeletal tissues by alloantigen injection during this permissive period. Within 12 hours after birth, 17 neonatal Lewis rats were injected through the superficial temporal vein with 3.5 to 5 million Brown Norway bone marrow cells in 0.1 ml normal saline. Ten weeks after the injection, peripheral blood from the Lewis rats was analyzed for the presence of Brown Norway cells to determine hemopoietic chimerism. The Lewis rats then received a heterotopic, vascularized limb tissue transplant (consisting of the knee, the distal femur, the proximal tibia, and the surrounding muscle on a femoral vascular pedicle) from Brown Norway rat donors to determine their tolerance to the allogeneic tissue. A positive control group (n = 6) consisted of syngeneic transplants from Lewis rats into naive Lewis rats to demonstrate survival of transplants. A negative control group (n = 6) consisted of Brown Norway transplants into naive Lewis rats not receiving bone marrow or other immunosuppressive treatment. The animals were assessed for transplant viability 30 days after transplantation using histologic and bone fluorochrome analysis. All the syngeneic controls (Lewis to Lewis) remained viable throughout the experiment, whereas all the Brown Norway to Lewis controls had rejected. Ten of the 17 allografts transplanted into bone marrow recipients were viable at 30 days, with profuse bleeding from the ends of the bone graft and the surrounding graft muscle. The percent of chimerism correlated with survival, with 3.31 percent (SD = 1.9) of peripheral blood, Brown Norway chimerism present in the prolonged survival groups and 0.75 percent (SD = 0.5) of Brown Norway chimerism in the rejected graft group. This study demonstrated prolonged survival of allogeneic skeletal tissue without immunosuppression after early neonatal injection of allogeneic bone marrow in a rat model.

Heterotopic sternum transplant in rats: A new model of a vascularized bone marrow transplantation

We introduced the heterotopic vascularized sternum transplant as a more simple and pure alternative to allogeneic hind limb transplantation for the study of bone marrow transplantation. We report the clinical and histopathological manifestations after transplantation of syngeneic and allogeneic sternal grafts with and without immunosuppression with FK-506. Syngeneic grafts maintained normal histology, whereas allografts showed rejection, which was prevented by FK-506. FK-506-treated allografts developed chimerism that was present throughout the observation period. Transplantation of the sternum may be a valuable model to study vascularized bone marrow transplantation and its effects on repopulation of bone marrow of the host, chimerism, and tolerance.

Biology of bone grafts

The terminology of bone transplantation is complicated by the various histologic types of bone grafts. A graft moved from one site to another within the same individual is an autograft; the corresponding adjective is autologous or autogenous. An allograft (adjective, allogeneic) is tissue transferred between two genetically different individuals of the same species. A xenograft (adjective, xenogeneic) is tissue from one species implanted into a member of a different species.

Long-term follow-up of patients with osteochondral allografts. A correlation between immunologic responses and clinical outcome

This article confirms immunologic responses in humans to histocompatibility antigens (Class I and II) presented by frozen osteochondral allografts. These observations include a correlation of immune responses with long-term clinical outcome. As found in animal models, matching of histocompatibility antigens, particularly to Class II, improves clinical and, presumably, biologic success following implantation of massive frozen bone allografts in humans. The presence of sensitization clearly does not preclude a satisfactory outcome, nor have other reconstructive alternatives (e.g., metallic implants) been shown to be superior in their long-term results.

Immune responses to osteoarticular allografts of the knee--cytokine studies

Immunological behaviour in correlation with bone allograft survival was studied in peripheral blood and synovial fluid from seven patients who had undergone large bone resection and allograft transplantation of the knee. Plasma and synovial fluid samples for cytokine measurements [interleukin (IL-1beta, IL-6) and tumour necrosis factor alpha (TNF-alpha)] were drawn from peripheral blood for diagnostic arthrocentesis. Two patients were monitored using consecutive sampling up to 12 months postoperatively. Graft survival was considered excellent, but local or diffuse resorption and also fatigue fractures were seen. These findings show that soluble products of T-cell, macrophage and osteoblast origin, produced as a response to the bone-graft antigens, might be responsible for the bone resorption seen in our material. The elevated IL-1beta and TNF-alpha levels detected support this statement.