Use of fresh frozen bone graft in rehabilitation of maxillar atrophy

AIM

Fresh frozen bone (FFB) is homologous bone obtained from human donors, provided by Tissue Banks. It is a graft material in reconstructive surgery; it is currently and widely used in orthopedic surgery and lately it has been introduced in oral and maxillofacial surgery. The purpose of this work was to show the use of fresh frozen homologous bone for bony augmentation of the maxilla and mandible in preparation for dental reconstruction with endosseous implants, as an effective alternative to harvesting and grafting autogenous bone from intra- or extra-oral donor sites.

METHODS

The case presented clinically demonstrates the use of FFB grafts in the vertical augmentation of a severe maxillary atrophy in general anesthesia, and the outpatient treatment with implants insertion and prosthetic restoration. Histologic evaluation of graft biopsy six months after surgery is added to clinical assessments.

RESULTS

Clinical outcome is shown with good volumetric and morphological reconstruction of the alveolar ridge without the need of a donor site. Excellent graft integration and bleeding newly formed bone was seen at the second surgical step (six months after FFB grafting), when fixation screws were removed and implant placement procedure was performed.

CONCLUSION

The use of FFB in major preprosthetic surgery may be an acceptable therapeutic alternative to the autogenous block graft (harvested from iliac crest or calvarium) for its success rate as graft material. Benefits include: surgical procedure with reduced discomfort and infection risk as a second operation field to harvest the graft is avoided; FFB is safe, cheap and available in programmed amounts, its use can significantly reduce operating time.

Stem cell factor enhances the adhesion of AML cells to fibronectin and augments fibronectin-mediated anti-apoptotic and proliferative signals

Acute myeloid leukaemia (AML) cells express the SCF receptor c-kit (CD117) on their cell surface and demonstrate enhanced adhesion to fibronectin (FN) following exposure to stem cell factor (SCF). Increased adhesion occurs within 5 min, is dose dependent, and persists beyond 2 h. Baseline and enhanced adhesion occur through the surface FN receptor very late antigen-5 (VLA-5, CD49e/CD29) which is expressed by AML cells. Unstimulated AML cells exposed to FN undergo less apoptosis than controls (inhibition 22.5 +/- 7.0%, P = 0.02, n = 8). Exposure to SCF alone without FN also inhibits AML cell apoptosis (by 19.0 +/- 7.7% compared to controls, P = 0.06, n = 8). Simultaneous exposure to SCF and FN increases the inhibition of AML cell apoptosis to 37.8 +/- 7.9% (P = 0.005 compared to control, P = 0.04 compared to FN alone, P = 0.06 compared to SCF alone) demonstrating that SCF not only enhances the propensity of AML cells to adhere to FN, but also results in an additive survival benefit following FN contact. Some but not all the reduction in apoptosis is mediated through VLA-5. The combination of SCF and FN also affects proliferation, resulting in a synergistic enhancement of AML cell proliferation in half the cases studied. When normal CD34+ human haemopoietic progenitors were studied, FN had little effect on their apoptosis and failed to enhance the anti-apoptotic effect of SCF. It did, however, synergise with SCF in promoting CD34+ cell proliferation. Exposure of AML cells to SCF and FN, both of which can be found in high concentration in the bone marrow stroma, inhibits apoptosis. Cytokines and extracellular matrix proteins augment each others' effects since SCF enhances adhesion to fibronectin, which in turn augments the survival signal delivered by the cytokine alone. Cytokine and adhesion receptors can combine to affect cell characteristics including proliferation and survival.

In vivo effect of granulocyte-macrophage colony-stimulating factor on the kinetics of human acute myeloid leukemia cells

Granulocyte-macrophage colony-stimulating factor, (GM-CSF) was given at 8 micrograms/kg daily by continuous i.v. infusion for 72 h to six patients with acute myeloid leukemia (AML) in expansion and one with chronic myeloid leukemia in blastic crisis to determine whether it was possible to augment the proliferative activity of the neoplastic population. The percentage of marrow blasts in S phase (labeling index, LI) was increased in five patients (1.3-, 1.5-, 1.9-, 2.3- and 3.2-fold change). The increase in LI was similar 24 and 48 h after beginning GM-CSF. The RNA Index also increased in patients who showed an increased LI, suggesting that GM-CSF had recruited quiescent neoplastic cells into the cell cycle. Forty eight hours after beginning GM-CSF, chemotherapy was started. The fate of S phase cells, labeled in vivo with bromodeoxyuridine (BrdU) immediately before cytostatic treatment, was monitored. BrdU positive cells were identified by fluorescent antibody for up to 28 days. A preferential killing of BrdU (S phase) cells was observed in 5/7 patients who obtained a complete remission, whereas this was not apparent in the two patients who achieved only a partial remission. Chemotherapy induced a rapid and profound aplasia; its duration, however, was not significantly different from that observed in historical controls. GM-CSF may have a potential role in the treatment of AML, as this study shows that it recruits leukemic cells into the cell cycle without adversely prolonging aplasia after cycle-specific therapy.

Effects of interferon alpha on autocrine growth factor loops in B lymphoproliferative disorders

The B lymphoproliferative disorders B chronic lymphocytic leukemia (B-CLL) and hairy cell leukemia (HCL) produce a number of autocrine growth factors, including tumor necrosis factor (TNF), interleukin 6 (IL-6), and IL-1, all of which may induce positive feedback growth loops. If such malignancies depend on these autocrine growth loops for survival, their interruption may be therapeutically valuable. Interferon alpha (IFN-alpha) abrogates TNF- or IL-6-induced proliferation of HCL and B-CLL cells in vitro and has therapeutic activity in these diseases. We have investigated the possibility that IFN-alpha may act by interrupting autocrine growth factor loops. If purified B-CLL or HCL cells are cultured in the presence of TNF, there is induction of mRNA for TNF, IL-1 alpha, IL-1 beta, and IL-6. However, culture in the presence of IFN-alpha in addition to TNF reduced the level of mRNA for all these cytokines, compared with cells cultured in TNF alone. While cytokine mRNA levels were diminished, levels of mRNA for the ribonuclease activator 2-5A synthetase were increased. Analysis of the kinetics of cytokine mRNA production showed that levels fall shortly after the rise of 2-5A synthetase mRNA. IFN-alpha may produce these effects by shortening the half-life of cytokine mRNA, since TNF mRNA half-life in B-CLL and HCL cells is substantially reduced when the cells are cultured with IFN-alpha. These data suggest that IFN-alpha may mediate its therapeutic effects in these malignancies by blocking autocrine growth factor loops.

Enhancement of monoclonal antibody dependent cell mediated cytotoxicity by IL2 and GM-CSF

Rodent monoclonal antibodies (MAb) directed against cells of the immune system may be used in vivo for applications including conditioning prior to marrow transplantation and treatment of lymphoid malignancies. Although some MAb may lyse targets by complement fixation, MAb dependent cell mediated cytotoxicity (MAb-DCC) appears to be an important additional effector mechanism. We have investigated the cellular basis of the phenomenon and the response of the effector cells to recombinant cytokines in an attempt to maximize the efficacy of MAb-DCC and thereby increase the therapeutic potency of MAbs. Blood mononuclear cells (PBM) coated with CAMPATH 1G (pan lymphocyte reactive rat IgG2b) MAb were used as targets (T) and autologous lymphocytes or granulocytes were used as effector (E) cells. We studied function in normal donors as well as patients 1 week before and 3-6 weeks after bone marrow transplantation (BMT). In the absence of CAMPATH 1G, specific 51Cr release from autologous PBM was less than 1% in all groups, even after pre-incubation of the effector cells with granulocyte-macrophage, colony stimulating factor (GM-CSF) or interleukin-2 (IL2). In the presence of 5 micrograms/ml of MAb, and at an E:T ratio of 50:1, lymphocytes from normal donors induced a low level (6.5%) of 51Cr release from auto PBM rising to 9% after pre-incubation of effector cells with IL2 (P = 0.02). Granulocytes had greater activity inducing 10% 51CR release (range 2-23%) which rose to 21.6% with GM-CSF (range 12-48%) (P less than 0.001). Pre-BMT, killing by lymphocytes and granulocytes was not significantly different from normal, and responded to IL2 and GM-CSF. In contrast, granulocyte killing after BMT was significantly impaired (51Cr release 3%) and showed no rise with GM-CSF. Killing by lymphocytes, however, remained normal, as did their IL2 response. Loss of granulocyte mediated MAb-DCC coincided with significant post-BMT impairment of oxidative metabolism; expression of Fc receptors II and III, however, was normal. Optimum therapeutic effect of MAb-DCC is likely to be achieved when MAb are given together with appropriate cytokines, the choice of which will depend upon the clinical circumstances.

Effects of recombinant interleukin-2 administration on cytotoxic function following high-dose chemo-radiotherapy for hematological malignancy

Activated killer cells, unrestricted by major histocompatibility (MHC) antigens circulate in the peripheral blood of patients who have undergone autologous and allogeneic bone marrow transplant (BMT) and may contribute to the reduced risk of leukemic relapse observed after these procedures. Interleukin-2 (IL-2) in vitro augments this cytotoxicity and used therapeutically might thereby promote the eradication of minimal residual disease. In order to assess whether these effects on cytotoxicity can be reproduced in vivo, we studied changes in number, phenotype, and MHC unrestricted cytotoxicity of peripheral blood mononuclear cells obtained from patients with hematologic malignancy receiving IL-2 infusions. Patients with acute myeloid leukemia and multiple myeloma were treated after cytotoxic chemotherapy or autologous BMT. IL-2 infusions produced an initial lymphopenia, followed by a progressive recovery in mononuclear cell numbers and a rebound lymphocytosis after the termination of treatment. This affected all lymphocyte subsets; in particular CD25 (IL-2 receptor) positive cell numbers rose sevenfold. Cells with the ability to kill a natural killer (NK)-resistant, lymphokine activated killer cell (LAK)-sensitive target appeared in the circulation during 16 of 19 infusions and mean LAK activity rose from 5.9% to 15.5% during infusion (E:T ratio, 50:1; P less than .001). During IL-2 infusion, cells present in the peripheral blood inhibited the growth of myeloid leukemia blasts in agar after overnight co-culture. Depletion experiments showed that LAK activity was mediated by cells of both CD3- CD16+ (NK derived) and CD3+ CD16- (T derived) subsets. LAK precursor activity in peripheral blood also significantly increased during IL-2 infusion. Increases in major histocompatibility complex (MHC) unrestricted cytotoxicity can be produced by IL-2 infusions in vivo and may result in improved relapse-free survival following chemotherapy or BMT.

A phase I clinical trial of recombinant interleukin 2 following high dose chemo-radiotherapy for haematological malignancy: applicability to the elimination of minimal residual disease

Biological response modifiers such as interleukin 2 (IL2) may be most effective in the setting of minimal residual disease. In a phase I-II clinical trial, IL2 was administered to 10 patients in remission of acute myeloid leukaemia and three with multiple myeloma 1-4 weeks after treatment with ablative chemotherapy or chemotherapy and autologous bone marrow transplantation. The aim was to assess the capacity of these patients to tolerate IL2 after intensive therapy and to determine whether regenerating lymphocytes were capable of responding to IL2 with the generation of anti-leukaemic effector cells. Toxicity was severe in two patients treated with escalating doses of IL2 and 19 subsequent infusions administered to 11 patients on a fixed dose schedule for periods of 3-5 days were well tolerated. Major toxicity was confined to hypotension (two courses) which responded rapidly to treatment cessation. No patients required intensive care unit support. IL2 infusions produced no significant adverse effects on marrow regeneration; while there were transient falls in platelet counts there were no episodes of clinical bleeding and neutrophil counts increased from a mean of 1.1 pre-infusion to 2.5 x 10(9)l-1 during the infusion (P = 0.004). A significant biochemical abnormality was hypokalaemia which responded rapidly to correction. Cells with activity against leukaemic progenitor cells appeared in peripheral blood within 48 h of beginning treatment. We conclude that IL2 may be used in minimal residual haematological malignancy, and by producing anti-neoplastic effector cells has the potential, as yet unproven, to prolong disease-free survival of patients entering remission.

In vivo induction of gamma interferon and tumor necrosis factor by interleukin-2 infusion following intensive chemotherapy or autologous marrow transplantation

Interleukin-2 (IL-2) therapy may improve immune reconstitution and reduce the risk of leukemic relapse in the setting of minimal residual disease by augmenting cytotoxic effector mechanisms directed at residual malignant cells. In addition, IL-2 in vitro promotes the release of cytokines including gamma-interferon (gamma-IFN) and tumor necrosis factor (TNF), which also possess antileukemic activity and can enhance granulocyte function. To determine if IL-2 infusion induces release of gamma-IFN and TNF in vivo in sufficient quantity to mediate these effects, we have measured serum levels of these cytokines and secretion by lymphocytes obtained from patients receiving this cytokine in a phase 1 trial. Serum gamma-IFN was undetectable pre-IL-2 and increased to 1.5 to 17 U/mL during IL-2 infusion (P less than .05). Culture of patient lymphocytes for 48 hours produced 1.2 U gamma-IFN/2 x 10(6) cells/mL pre-IL-2 rising to 50 U/2 x 10(6) cells/mL when the lymphocytes were obtained during therapy (P less than .05). Lymphocyte subset analysis showed that both CD3+ and CD16+ cells secreted gamma-IFN in response to IL-2. TNF secretion by lymphocytes also rose during IL-2 infusion from a mean of 5 U/mL to 14.4 U/mL (P less than .01) although no rise was seen in serum levels. The material secreted by IL-2-stimulated lymphocytes is bioactive as addition of supernatants from lymphocytes obtained during IL-2 therapy to cultures of myeloid blasts significantly inhibited clonogenic growth. IL-2-induced secretion of these cytokines mediated this inhibition as it could be partially blocked by either anti-gamma-IFN or anti-TNF antibodies. Preincubation of granulocytes with the same supernatants produced enhanced oxidative metabolism, measured by chemiluminescence in response to N-formyl-methionyl-leucyl-phenylalanine (FMLP). This effect also could be partially abrogated by anti-gamma-IFN and anti-TNF antibodies. Therefore, secondary cytokine secretion may boost granulocyte function and contribute to the antileukemic effects of IL-2 infusion in patients following bone marrow transplantation or chemotherapy.