Peptide Enhanced Bone Graft Substitute Presents Improved Short-Term Increase in Bone Volume and Construct Stiffness Compared to Iliac Crest Autologous Bone in an Ovine Lumbar Interbody Fusion Model.

STUDY DESIGN: Preclinical ovine model. OBJECTIVE: To assess the in vivo efficacy and safety of the P-15 L bone graft substitute and compare its performance to autologous iliac crest bone graft (ICBG) for lumbar interbody fusion indications. METHODS: Thirty skeletally mature sheep underwent lumbar interbody fusion surgery. Half of the sheep received autologous ICBG and the other half the peptide enhanced bone graft substitute (P-15 L). Following termination at 1, 3, and 6 months after surgery, the operated segments were analyzed using micro computed tomography (µCT), histology, and destructive mechanical testing. Additional systemic health monitoring was performed for the P-15 L group. RESULTS: One month after surgery, there was only minor evidence of bone remodeling and residual graft material could be clearly observed within the cage. There was active bone remodeling between 1 and 3 months after surgery. At 3 months after surgery significantly denser and stiffer bone was found in the P-15 L group, whereas at 6 months, P-15 L and ICBG gave similar fusion results. The P-15 L bone graft substitute did not have any adverse effects on systemic health. CONCLUSIONS: The drug device combination P-15 L was demonstrated to be effective and save for lumbar interbody fusion as evidenced by this ovine model. Compared to autologous ICBG, P-15 L seems to expedite bone formation and remodeling but in the longer-term fusion results were similar.

Autologous fat processing via the Revolve system: quality and quantity of fat retention evaluated in an animal model.

BACKGROUND: Currently, fat graft viability and retention cannot be reliably predicted. The reasons for this variability are not fully understood, although fat processing has been implicated. OBJECTIVES: The authors compare the in vitro quantity and in vivo fat retention from lipoaspirate processed by the Revolve system (LifeCell, Bridgewater, New Jersey) compared with centrifugation and decantation. METHODS: Ten patients were enrolled in this prospective study. Lipoaspirate from each patient was processed by each of 3 methods: decantation, centrifugation, and the Revolve system. Biochemical characteristics and free oil, adipose, and aqueous phases of the processed fats were determined. Fat grafts were implanted in nude mice; volume retention and quality of the fat grafts were evaluated after 28 days. Viability of retained fat was demonstrated by intact adipocytes and neovascularization on histology. RESULTS: Of the 10 patients, 9 were women and 1 was a man. Mean patient age was 40.7 ± 8.9 years (range, 30-55 years). Fat tissue obtained from all methods had good physiological properties with neutral pH and isotonic salt concentrations. The Revolve system yielded significantly less blood cell debris, a higher percentage of adipose tissue, and a lower percentage of free oil compared with the other 2 methods. Fat tissue retention from Revolve samples was significantly higher (73.2%) than that from decanted samples (37.5%) and similar to that from centrifuged samples (67.7%). CONCLUSIONS: The Revolve system produced physiologically compatible, preinjection fat with reduced contaminants and free oil in conjunction with high fat content. In an animal model, volume retention of Revolve-processed fat grafts was significantly greater than decanted samples. The Revolve system presents a fat-processing option that was less time-consuming, easier to use, and more efficient in this study than standard centrifugation or decantation.

Implantation of a porcine acellular dermal graft in a primate model of rotator cuff repair.

BACKGROUND: Non-cross-linked xenogeneic extracellular matrix graft materials have typically elicited a hypersensitivity reaction when implanted into humans or other primates. The purpose of this study was to examine the histologic and immune response to a non-cross-linked porcine-derived dermal extracellular matrix graft processed to remove the α-gal epitope. MATERIALS AND METHODS: Eight African green monkeys were implanted with porcine acellular dermal matrix (Conexa Reconstructive Tissue Matrix; Tornier Inc, Edina, MN, USA) to repair and augment a partial excision defect of the supraspinatus tendon of the rotator cuff. Four animals each were sacrificed at 3 months and 6 months, and histologic samples were compared with tissues harvested from unoperated shoulders. RESULTS: Gross examination of grafted Conexa showed the appearance of integration proximally with tendon and distally with bone in each operated rotator cuff complex. Histologically, Conexa appeared to have remodeled to tendon-like architecture, with homogeneous distribution of fibroblast cells and parallel alignment of collagen fibers, with the direction of force evident by 3 months after implantation. Abundant vasculature observed at 3 months, which diminished to native tendon levels by 6 months, also indicated this to be a period of significant remodeling with an absence of significant inflammation, as evidenced by immunochemical methods and serum analysis. CONCLUSION: Conexa porcine acellular dermal matrix allows for incorporation of host tendon tissue without a hypersensitivity reaction in a primate model and should be a safe material for augmentation of human rotator cuff repair.

The use of acellular dermal matrix to prevent capsule formation around implants in a primate model.

BACKGROUND: Implant-based breast reconstruction is a popular option after mastectomy, but capsular contracture may detract from long-term outcomes. The authors have observed that breast implants covered with acellular dermal matrix (AlloDerm) are less likely to develop a capsule in the area where the implant is in direct contact with the acellular matrix. The authors tested this observation experimentally by comparing capsular formation around implants in the presence and absence of AlloDerm in primates. METHODS: Eight smooth-surfaced tissue expanders were implanted into eight African green monkeys. In four experimental animals, a sheet of AlloDerm was draped over the tissue expander so as to cover the implant. Four control animals underwent placement of a tissue expander only. Animals were killed after 10 weeks and specimens underwent histologic and immunohistochemical analysis. RESULTS: Hematoxylin and eosin staining of control specimens revealed the presence of a distinct layer of wavy, parallel arrays of collagen fibers consistent with capsule formation. Immunostaining identified abundant myofibroblasts, a profibrotic cell found in breast capsules. In the AlloDerm-covered specimens, no capsule layer was visible, and specimens stained weakly for myofibroblasts. The difference in myofibroblast staining intensity was statistically significant. CONCLUSIONS: The use of AlloDerm to partially enclose implants effectively prevented formation of a capsule in areas where AlloDerm contacted the implant at 10 weeks. Long-term studies will be required to determine whether this is a durable result that can be reproduced in humans.

Effects of e-beam radiation, storage, and hydration on osteoinductivity of DBM/AM composite.

E-beam irradiation is often used to sterilize medical devices including demineralized bone matrix (DBM) products. In this study, the effect of e-beam on osteoinductivity of a DBM product in hydrous and anhydrous configurations has been evaluated at 0-, 6- and 12-month ambient storage using a nude rat muscle pouch model. The thermal and structural stabilities of DBM and acellular dermal matrix (AM) composites were analyzed using differential scanning calorimetry (DSC) and trypsin digestion assay. Both hydrous and anhydrous DBM/AM composites exhibited osteoinductivity after e-beam irradiation of 15 kGy. After 12-month ambient storage, the osteoinductivity of hydrous DBM/AM was diminished, whereas the anhydrous DBM/AM retained its osteoinductive potential. However, the DSC and trypsin analysis revealed that the DBM in anhydrous DBM/AM was more vulnerable to damage from e-beam irradiation than its hydrous counterpart. This study has found that although the anhydrous DBM has more structural damage than hydrous DBM from e-beam irradiation, it has retained its osteoinductivity better after 1-year ambient storage.

Evaluation of bone regeneration at critical-sized calvarial defect by DBM/AM composite.

This study investigated the bone-regenerative potential of a demineralized bone and acellular matrix (DBM/AM) composite (AlloCraft DBM) in comparison with autologous bone using an in vivo model. Critical-sized calvarial defects (5 mm) were created in athymic rats. The defects were grafted with either the DBM/AM composite or the acellular human dermal matrix (AM), and compared with the defects filled with autologous bone (positive control) and the empty defect (negative control). Histological and radiographic assessments were carried out at 4 and 8 weeks after surgery to determine the biological healing, the amount and type of new bone formation and the percentage of new bone filled in the critical defects. At 4 weeks, DBM/AM composite group had the highest percentage of the defect filled with new bone (84%), which was significantly greater than autologous bone (62%), AM (41%), and untreated control (32%) groups. At 8 weeks, the DBM/AM continued to have the highest percentage of the defect filled with new bone (91%). The autologous bone group increased the percentage of bone fill to 83%. The defects either filled with AM or left untreated still had less of the defect filled with new bone, 57% and 33%, respectively. The total healing of defects grafted with DBM/AM was comparable with autologous bone group at 8 weeks. The results demonstrated that the DBM/AM composite promoted new bone formation more rapidly than autologous bone at calvarial defect in athymic rats. The study supports that DBM/AM is a potential substitute of autologous bone for bone repair.

T-complex polypeptide-1 interacts with the erythrocyte cytoskeleton in response to elevated temperatures.

Chaperonins are double ring complexes composed of highly conserved 60-kDa protein subunits that are divided into two subgroups. Group II chaperonins are found in archaea and the cytoplasm of eukarya and are believed to function like other chaperonins as part of a protein folding system. We report here that human erythrocytes contain the group II chaperonin T-complex polypeptide 1 (TCP-1) and that this complex translocates from the cytoplasm to the cytoskeleton in response to heat treatment in the absence of overt cell damage. Identification as TCP-1 was determined by immunodetection for TCP-1alpha and corroborated by mass spectroscopy peptide sequencing. Direct visualization by immunofluorescence confirmed peripherally localized TCP-1 in response to heat treatment. Temperatures ranging from 37-50 degrees C were demonstrated to have distinct kinetic profiles of induced translocation. Heat-induced binding was shown by Triton shell analysis to be specifically associated with the cytoskeletal proteins. Furthermore, the binding was reversible following removal of the stimulatory condition. A stabilizing process is hypothesized based on the known interactions of chaperonins.

Safety and efficacy of transfusions of autologous cryopreserved platelets derived from recombinant human thrombopoietin to support chemotherapy-associated severe thrombocytopenia: a randomised cross-over study.

BACKGROUND: The increasing demand for platelet products, and concern over the transfusion-associated risks of alloimmunisation and infections, have motivated a search for improved methods aimed at keeping exposure to donor antigens to a minimum. Transfusion of thrombopoietin-derived autologous platelets might provide an alternative strategy. We aimed to compare the safety and efficacy of this strategy with that of transfusion with fresh allogeneic platelets in patients with severe chemotherapy-induced thrombocytopenia. METHODS: 20 patients with gynaecological malignancies were treated with two doses of 1.2 microg/kg recombinant human thrombopoietin. From day 12, we aimed to collect 50 units of platelets from these patients by plateletpheresis. Harvested platelets were cryopreserved in ThromboSol and 2% dimethyl sulfoxide (DMSO) for use in subsequent autologous transfusions. Patients then received carboplatin for up to six cycles. Patients were randomly assigned to group A (n=10), which received allogeneic fresh platelets at the first instance of severe thrombocytopenia (platelet count <15,000/microL) and then autologous cryopreserved platelets at the next, or to group B (n=10), which received first autologous and then allogeneic platelets. In subsequent cycles, all patients received autologous platelets while available. The primary endpoint was platelet count increment corrected for the number of platelets transfused and the patients' body-surface area. Analysis was by intention to treat. FINDINGS: Treatment with recombinant human thrombopoietin significantly increased platelet count (median 2.3-fold [range 1.5-3.3], p<0.0001) in all but one patient in group A. The median number of platelets collected per patient was 53 units (14-66) in two collections (one to three). There was no significant difference in the corrected platelet count increments (CCIs) between the 19 paired transfusions of cryopreserved autologous platelets and fresh allogeneic platelets (median 1-h CCI 15.7 vs 19.8, p=0.398; median 24-h CCI 13.0 vs 18.1, p=0.398). 14 of the 19 patients had a good response (1-h CCI >7.5) to their first transfusion of allogeneic platelets. By contrast, all patients had a good response to their first transfusion of autologous platelets (p=0.063). Moreover, no significant decrease in the CCIs (p=0.405) was seen over six cycles after autologous platelet transfusions (n=63). No transfusion reactions or any serious adverse event was recorded during autologous platelet transfusions. INTERPRETATION: Recombinant human thrombopoietin facilitated collection of multiple units of platelets, which could be cryopreserved and reinfused to counteract severe thrombocytopenia during multicycle chemotherapy. Transfusion of autologous cryopreserved platelets derived from recombinant human thrombopoietin can provide a viable strategy to minimise the risks of allogeneic platelet transfusions and provide a long-lasting supply of platelet support.