Prolonged survival of musculoskeletal xenografts with combined cyclosporine and 15-deoxyspergualin

This study was undertaken to evaluate the feasibility of performing vascularized musculoskeletal xenografts between mice and rats using immunosuppression. Vascularized musculoskeletal grafts were harvested from the hind limb of C57BL/6J (B6) mice, transplanted heterotopically into Lewis rats, and revascularized by microanastomoses of the graft artery and the recipient femoral artery and the graft vein to the recipient femoral vein. Recipient rats were divided into four groups. Group 1 received no immunosuppression (n = 10), group 2 was treated with cyclosporine (10 mg/kg/day; n = 10), group 3 was treated with 15-deoxyspergualin (5 mg/kg/day; n = 10), and group 4 received both cyclosporine and 15-deoxyspergualin (n = 10). Graft survival was directly examined on postoperative days 4, 7, and 14. In vitro assays were performed using mixed lymphocyte reactions and anti-donor cytotoxic antibody assays to assess the recipient's immune response. Grafts were examined by histology and immunohistochemistry. All grafts in group 1 were rejected by day 4. In groups 2 and 3, all grafts were rejected by day 7. In group 4, however, 8 of 10 recipients had viable grafts on day 14. Data from mixed lymphocyte reactions showed that cell-mediated immune responses were uniformly suppressed in groups 2, 3, and 4 compared with group 1. However, anti-donor antibody production was only partly suppressed in groups 2 and 3, suggesting that graft rejection was primarily caused by circulating cytotoxic anti-donor antibodies in groups 1, 2, and 3. Histologic observations in groups 1, 2, and 3 confirmed the important role of the humoral mechanism in xenograft rejection. Furthermore, immunohistochemical results demonstrated that the small vessels in the rejected grafts showed anti-rat immunoglobulin and complement depositions. Only a combination therapy of cyclosporine and 15-deoxyspergualin attenuated the rejection of xenografts.

Adhesion of tissue-engineered cartilate to native cartilage

Reconstruction of cartilaginous defects to correct both craniofacial deformities and joint surface irregularities remains a challenging and controversial clinical problem. It has been shown that tissue-engineered cartilage can be produced in a nude mouse model. Before tissue-engineered cartilage is used clinically to fill in joint defects or to reconstruct auricular or nasal cartilaginous defects, it is important to determine whether it will integrate with or adhere to the adjacent native cartilage at the recipient site. The purpose of this study was to determine whether tissue-engineered cartilage would adhere to adjacent cartilage in vivo. Tissue-engineered cartilage was produced using a fibrin glue polymer (80 mg/cc purified porcine fibrinogen polymerized with 50 U/cc bovine thrombin) mixed with fresh swine articular chondrocytes. The polymer/chondrocyte mixture was sandwiched between two 6-mm-diameter discs of fresh articular cartilage. These constructs were surgically inserted into a subcutaneous pocket on the backs of nude mice (n = 15). The constructs were harvested 6 weeks later and assessed histologically, biomechanically, and by electron microscopy. Control samples consisted of cartilage discs held together by fibrin glue alone (no chondrocytes) (n = 10). Histologic evaluation of the experimental constructs revealed a layer of neocartilage between the two native cartilage discs. The neocartilage appeared to fill all irregularities along the surface of the cartilage discs. Safranin-O and toluidine blue staining indicated the presence of glycosaminoglycans and collagen, respectively. Control samples showed no evidence of neocartilage formation. Electron microscopy of the neocartilage revealed the formation of collagen fibers similar in appearance to the normal cartilage matrix in the adjacent native cartilage discs. The interface between the neocartilage and the native cartilage demonstrated neocartilage matrix directly adjacent to the normal cartilage matrix without any gaps or intervening capsule. The mechanical properties of the experimental constructs, as calculated from stress-strain curves, differed significantly from those of the control samples. The mean modulus for the experimental group was 0.74 +/- 0.22 MPa, which was 3.5 times greater than that of the control group (p < 0.0002). The mean tensile strength of the experimental group was 0.064 +/- 0.024 MPa, which was 62.6 times greater than that of the control group (p < 0.0002). The mean failure strain of the experimental group was 0.16 +/- 0.061 percent, which was 4.3 times greater than that of the control group (p < 0.0002). Finally, the mean fracture energy of the experimental group was 0.00049 +/- 0.00032 J, which was 15.6 times greater than that of the control group. Failure occurred in all cases at the interface between neocartilage and native cartilage. This study demonstrated that tissue-engineered cartilage produced using a fibrin-based polymer does adhere to adjacent native cartilage and can be used to join two separate pieces of cartilage in the nude mouse model. Cartilage pieces joined in this way can withstand forces significantly greater than those tolerated by cartilage samplesjoined only by fibrin glue.

A comparative study of nerve healing in adult, neonatal, and fetal rabbits

This experiment quantitatively compared the human equivalent of a nerve repair following surgical division in the fetal, adult, and early childhood period of development using a rabbit as an experimental animal model. Twelve time-dated pregnant New Zealand White rabbits at 24 days' gestation (term = 31 days) underwent hysterotomy; one hind limb was delivered through the uterine opening. The sciatic nerve was divided and repaired by primary neurorrhaphy using two 11-0 epineural sutures. Sciatic nerve repair was also performed in 10 neonatal and 10 adult New Zealand White rabbits. Following repair, each group was assessed using electromyography examination, measuring distal motor latency and amplitude at 1, 2, 3, and 4 months postrepair. There was no difference in any of the groups in distal motor latency. The amplitude rose incrementally in all groups, and the fetal group had significantly higher amplitudes (p < 0.02) at 1, 2, 3, and 4 months in comparison with the adult group. There was no statistically significant difference between fetal and neonatal nerve repairs at any of the time periods. At the completion of the study, the nerve repair sites were harvested for histologic estimation of mean myelinated fiber density and fiber diameter distribution distal and proximal to the repair site. A greater percentage of myelinated axons crossed the repair site in the fetal group (83 percent) in comparison with the adult group (63 percent) (p < 0.03). Our study also demonstrated significant increases in the number of larger myelinated fibers crossing the repair site in comparison with the neonatal and adult groups (p < 0.04). This study found that fetal nerve healing following surgical repair is superior to that found in adult animals and results in a higher number of larger myelinated fibers crossing the repair site in comparison with adult and neonatal repairs.

Skin allograft survival following intrathymic injection of donor bone marrow

BACKGROUND

Success has been reported using intrathymic injection in the preconditioning regimen to induce allograft tolerance. Although long-term stable tolerance has been achieved in numerous rodent vascularized solid organ allograft models, tolerance to skin transplants has only been achieved across minor antigenic or concordant species disparities. This study sought to induce tolerance across an allogeneic barrier in a rat model with a major genetic disparity.

MATERIALS AND METHODS

Lewis rats were injected intrathymically with 1 x 10(8) Brown-Norway (BN) bone marrow cells and intraperitoneally with 1.0 cc of rabbit anti-rat anti-lymphocyte serum (ALS). Twenty-one days later, BN skin grafts were placed on the injected animals. Control groups were included to isolate the effect of technique, thymic manipulation, strain specificity, and ALS.

RESULTS

Animals receiving both intrathymic bone marrow cells and ALS had a skin graft median survival time of 24 days versus 8 days for the control group (P = 0.003). Groups receiving anti-lymphocyte serum alone or intrathymic bone marrow cell injection alone exhibited no skin graft survival prolongation. Mixed lymphocyte reactions revealed normal responsiveness of tolerant animal lymphocytes to donor strain lymphocytes.

CONCLUSION

This protocol utilizing the intrathymic injection of donor bone marrow cells along with short-term immunosuppression with anti-lymphocyte serum produced markedly prolonged survival of skin allografts transplanted across a major histocompatibility barrier. Although tolerance was incomplete, significant prolongation has not previously been reported in genetic disparities of this degree. These results suggest that the application of this technique for central immune modulation may be beneficial for allograft tolerance induction and deserves further study in large animals models.

Biomechanical analysis of a chondrocyte-based repair model of articular cartilage

The objective of this study was to evaluate the biomechanical properties of newly formed cartilaginous tissue synthesized from isolated chondrocytes. Cartilage from articular joints of lambs was either digested in collagenase to isolated chondrocytes or cut into discs that were devitalized by multiple freeze-thaw cycles. Isolated cells were incubated in suspension culture in the presence of devitalized cartilage matrix for 3 weeks. Multiple chondrocyte/matrix constructs were assembled with fibrin glue and implanted subcutaneously in nude mice for up to 6 weeks. Testing methods were devised to quantify integration of cartilage pieces and mechanical properties of constructs. These studies showed monotonic increase with time in tensile strength, fracture strain, fracture energy, and tensile modulus to values 5-10% of normal articular cartilage by 6 weeks in vivo. Histological analysis indicated that chondrocytes grown on dead cartilage matrix produced new matrix that integrated individual cartilage pieces with mechanically functional tissue.

Injectable tissue-engineered cartilage using a fibrin glue polymer

The purpose of this study was to demonstrate the feasibility of using a fibrin glue polymer to produce injectable tissue-engineered cartilage and to determine the optimal fibrinogen and chondrocyte concentrations required to produce solid, homogeneous cartilage. The most favorable fibrinogen concentration was determined by measuring the rate of degradation of fibrin glue using varying concentrations of purified porcine fibrinogen. The fibrinogen was mixed with thrombin (50 U/cc in 40 mM calcium chloride) to produce fibrin glue. Swine chondrocytes were then suspended in the fibrinogen before the addition of thrombin. The chondrocyte/polymer constructs were injected into the subcutaneous tissue of nude mice using chondrocyte concentrations of 10, 25, and 40 million chondrocytes/cc of polymer (0.4-cc injections). At 6 and 12 weeks, the neocartilage was harvested and analyzed by histology, mass, glycosaminoglycan content, DNA content, and collagen type II content. Control groups consisted of nude mice injected with fibrin glue alone (without chondrocytes) and a separate group injected with chondrocytes suspended in saline only (40 million cells/cc in saline; 0.4-cc injections). The fibrinogen concentration with the most favorable rate of degradation was 80 mg/cc. Histologic analysis of the neocartilage showed solid, homogeneous cartilage when using 40 million chondrocytes/cc, both at 6 and 12 weeks. The 10 and 25 million chondrocytes/cc samples showed areas of cartilage separated by areas of remnant fibrin glue. The mass of the samples ranged from 0.07 to 0.12 g at 6 weeks and decreased only slightly by week 12. The glycosaminoglycan content ranged from 2.3 to 9.4 percent for all samples; normal cartilage controls had a content of 7.0 percent. DNA content ranged from 0.63 to 1.4 percent for all samples, with normal pig cartilage having a mean DNA content of 0.285 percent. The samples of fibrin glue alone produced no cartilage, and the chondrocytes alone produced neocartilage samples with a significantly smaller mass (0.47 g at 6 weeks and 0.46 g at 12 weeks) when compared with all samples produced from chondrocytes suspended in fibrin glue (p < 0.03). Gel electrophoreses demonstrated the presence of type II collagen in all sample groups. This study demonstrates that fibrin glue is a suitable polymer for the formation of injectable tissue-engineered cartilage in the nude mouse model. Forty million chondrocytes per cc yielded the best quality cartilage at 6 and 12 weeks when analyzed by histology and content of DNA, glycosaminoglycan, and type II collagen.

Transdermal photopolymerized adhesive for seroma prevention

The purpose of this study was to determine whether or not a synthetic photopolymerized tissue adhesive (polyethylene oxide hydrogel) is useful in seroma prevention using a well established rat mastectomy seroma model. Twenty-three Sprague-Dawley rats received mastectomies. The rats were randomly assigned to either the control group (n = 13) or the experimental group (n = 10). The control animals received 0.2 cc of saline into the wound before closure. The experimental group received either 0.2 cc (n = 5) or 0.4 cc (n = 5) of the polyethylene oxide polymer into their wounds before closure. The experimental animals were placed under an ultraviolet A lamp for 3 minutes to polymerize the adhesive. On postoperative day seven, the resultant seromas were quantified, and wound tissues were harvested for histologic evaluation. The rats in the control group had a mean seroma volume of 3.25 cc (SD = 2.41), whereas the rats treated with polymer had a mean seroma volume of 0.37 cc (SD = 0.51). A Student's t test was performed showing a statistically significant difference between the control and experimental groups (p < 0.005). The volume of polymer used (0.2 cc versus 0.4 cc) did not significantly impact the volume of the resultant seromas. This study demonstrates that photopolymerizable polyethylene oxide hydrogels can be used as a tissue adhesive and that such an adhesive significantly reduces seroma formation in the rat mastectomy model.

Use of swine model in transplantation of vascularized skeletal tissue allografts

Permanent tolerance to vascularized skeletal tissue allografts can be induced in miniature swine with minor antigen differences using a 12-day course of CsA. Demonstration of skeletal tissue allograft survival in a large animal model without long-term immunosuppression represents an important step toward transplantation of skeletal tissue allografts in humans.

Cell transplantation from limb allografts

A murine model of skeletal tissue transplantation was developed to study the allograft rejection process in mice for limb allograft transplantation. Muscle, bone, and skin have been shown to be strong antigenic stimuli in vascularized allograft models, and cells from these sources were used for transplantation. Using enzymatic digestion, keratinocytes, myocytes, and osteocytes were harvested from B10.A mice tissues, dissociated into single cells, and then grown in culture for 14 to 21 days. Each cell type was marked with an intracellular fluorescent marker before transplantation of the cells into pockets in the rectus abdominis muscle of a syngenic host. All cell types remained viable and were detectable 2 weeks following transplantation when examined histologically and observed under a fluorescent microscope. Transplanted osteocytes were found to produce bone 8 weeks following transplantation. These results demonstrate that individual cells transplanted into muscle pockets survive and have the ability to produce extracellular matrix in this mouse model of skeletal tissue transplantation. Use of this model will allow transplantation of the cellular components comprising limb allografts to study the relative antigenicities and the rejection of the separate cells with the advanced immunologic techniques available for mice. A better understanding of immunologic responses to these individual tissue components may enable specific donor tissue or host immune modification to achieve skeletal tissue transplantation without immunosuppression. These findings are particularly valuable to the field of tissue engineering where allogeneic cells may be used in cell/polymer constructs for reconstructive procedures.

Tissue engineered neocartilage using plasma derived polymer substrates and chondrocytes

This study demonstrates that fibrin monomers can be polymerized into moldable gels and used for the encapsulation of isolated chondrocytes. This biologically derived scaffold will maintain three-dimensional spatial support, allowing new tissue development in a subcutaneous space. Chondrocytes isolated from the glenohumeral and humeroradioulnar joints of a calf were combined with cyroprecipitate and polymerized with bovine thrombin to create a fibrin glue gel with a final cell density of 12.5 x 10(6) cells/ml. The polymer-chondrocyte constructs were implanted subcutaneously in 12 nude mice and incubated for 6 and 12 weeks in vivo. Histologic and biochemical analysis including deoxyribonucleic acid (DNA) and glycosaminoglycan quantitation confirmed the presence of actively proliferating chondrocytes with production of a well-formed cartilaginous matrix in the transplanted samples. Control specimens from 12 implantation sites consisting of chondrocytes alone or fibrin glue substrates did not demonstrate any gross or histologic evidence of neocartilage formation. Moldable autogenous fibrin glue polymer systems have a potential to serve as alternatives to current proprietary polymer systems used for tissue engineering cartilage as well as autogenous grafts and alloplastic materials used for facial skeletal and soft-tissue augmentation.

Monoclonal antibody to intercellular adhesion molecule 1 protects skin flaps against ischemia-reperfusion injury: an experimental study in rats

The purpose of this study was to evaluate the blockage of polymorphonuclear neutrophil endothelial adhesion by using a monoclonal antibody to the intercellular adhesion molecule 1 (ICAM-1) ligand to prevent ischemia-reperfusion injury in rat skin flaps. A skin and subcutaneous tissue flap (3.0 cm x 4.5 cm) supplied by the superficial epigastric artery and vein including the femoral vessels was isolated unilaterally in 45 male Sprague-Dawley rats and clamped for 9 hours (groups II and III) or 12 hours (groups IV and V) of ischemia. Five animals in group I were sham-operated only with 5 minutes of ischemia. Animals in groups II (n = 10) and IV (n = 10) received 0.05 mg of monoclonal antibody to ICAM-1 (0.20 mg/kg) in 0.5 ml of 0.9% normal saline intravenously 15 minutes before reperfusion; those in groups III (n = 10) and V (n = 10) received 0.5 ml of normal saline. The flaps were assessed histologically, by measuring viable and nonviable areas, and by diffuse reflectance spectroscopy to determine the ratio of oxyhemoglobin to deoxyhemoglobin. Flap measurements revealed that the average area of flap survival was 90.6 +/- 12.8 percent in group II and 18.3 +/- 19.6 percent in the control group (III) (p < 0.002). In the animals subjected to 12 hours of ischemia, those treated with monoclonal antibody to ICAM-1 (group IV) were 57.1 +/- 23.1 percent viable, which was significantly greater than the control animals (group V), in which only 0.3 +/- 1.0 percent of the flap was viable. Analysis of the diffuse reflectance spectra showed a hyperemic response during the first 10 minutes after reperfusion in animals treated with monoclonal antibody to ICAM-1. In group III, however, the spectra demonstrated a decreased amount of oxyhemoglobin, indicating decreased reperfusion of the flap after ischemia when compared with group II. Histopathologically, few inflammatory changes could be observed in groups I, II, and the viable areas of group IV. Marked damage was observed in groups III and V. We concluded that treating ischemic skin flaps with monoclonal antibody to ICAM-1 was effective for alleviating reperfusion injury after 9 or 12 hours of warm ischemia. The reactive hyperemic response determined by diffuse reflectance spectroscopy in groups II and IV correlated with areas of flap survival. Antibodies to particular adhesion molecules, such as ICAM-1, have potential clinical utility in that they could be administered, individually or together, to patients immediately before reestablishing perfusion after free-tissue transfer or replantation to block the adverse effects attributed to reperfusion injury.

Prolonged survival in fetal rabbit surgery

Timing and outcome of antenatal surgical intervention is being explored using fetal animal models. Models that are currently used range from larger animals with fewer offspring and higher cost to smaller animals with larger litters and lower cost. The rabbit is an ideal "small" animal model for experimentation in the third trimester, with a large litter, short gestation and a relatively large fetus. This paper reports methods by which prolonged survival (greater than 110 days) may be achieved in as many as 60% of operated fetuses following complex fetal surgery in the rabbit.

Bonding of cartilage matrices with cultured chondrocytes: an experimental model

The capacity of isolated chondrocytes to join separate masses of cartilage matrix was investigated with composites implanted in subcutaneous pouches in nude mice. Slices of articular cartilage were harvested from lambs and were devitalized by cyclic freezing and thawing. The slices were then either co-cultured with viable allogeneic lamb chondrocytes (experimental) or cultured without such chondrocytes (control). Composites of three slices were constructed with use of fibrin glue and were implanted in nude mice for periods ranging from 7 to 42 days. Bonding of the experimental matrices with viable chondrocytes was achieved at 28 and 42 days, as assessed by direct examination, histology, thymidine uptake, and fluorescence. No bonding occurred in the control composites without viable chondrocytes. We conclude that devitalized cartilage matrix is a scaffold to which isolated chondrocytes can attach and begin to repopulate.

Craniofacial skeletal fixation using biodegradable plates and cyanoacrylate glue

This study examined the feasibility of fixation of craniofacial bone using Lactosorb biodegradable plates adhered to bone with butyl-2-cyanoacrylate adhesive (Histoacryl) in a pig. The stability and bone-healing characteristics of this rigid fixation method were studied and compared with standard rigid fixation using metal plates and screws on osteotomy sites in the frontal bones and infraorbital rims. Rectangular osteotomies (2.0 x 3.0 cm) were performed on the right and left sides of the frontal bone and wedge-shaped osteotomies (1.5 x 1.7 cm) were made on the left and right infraorbital rims in seven Yorkshire pigs. Metal plates were applied with screws to the osteotomies on one side, and the other side was fixed with a biodegradable plate and butyl-2-cyanoacrylate. The animals were sacrificed at 8 weeks, and both sides were compared biomechanically and histologically. Radiographic, biomechanical, and histologic analyses were performed to evaluate skeletal stability, contour, accurate positioning of bony fragments, bone healing, and maximum torque to failure of the repair sites. Clinical and radiographic observations demonstrated stability of the bone fragments without any evidence of displacement. According to Student's t test for paired data, no statistical difference was found in the maximum torque to failure of fragments fixed with biodegradable plates and glue compared with those fixed with metal plates and screws (p > 0.05), whether or not a gap existed at the osteosynthesis site. Although the sample size was small, no differences were noted between the two types of treatment groups. This study demonstrates that rigid internal fixation of osteotomized cranial bone fragments using biodegradable plates and butyl-2-cyanoacrylate is as effective as metal plate and screw fixation in this animal model.

Prolonged general anesthesia for experimental craniofacial surgery in fetal swine

A protocol utilizing high preoperative doses of altrenogest (Regu-Mate) and a "balanced" general anesthesia regimen consisting of isoflurane at subanesthetic doses supplemented with intravenous doses of sodium thiopental was developed to prevent preterm labor, minimize intracranial fetal cerebral edema, and decrease postpartum mortality of fetal swine after undergoing complex in utero craniofacial procedures. A total of 20 fetal piglets at 75% gestation were exposed to prolonged (> 3 h) anesthesia conditions of which 7 piglets were randomly selected to undergo experimental craniofacial procedures consisting of periosteal stripping of frontal and parietal bone segments with/without extensive coronal suture fusion procedures. Neither sows nor piglets were lost to anesthetic complications during the initial laparotomy or subsequent cesarean delivery. None of the sows experienced uterine sepsis or underwent preterm labor. The overall survival rate for all piglets exposed to prolonged anesthesia conditions was 95% at 4 weeks and 45% at 11 weeks after surgery. The experimental group's survival was 85.7% at 4 weeks and 28.5% at 11 weeks after surgery.

Surgical model to assess the effects and optimal timing of craniofacial fixation

An in utero swine model of craniofacial deformity was developed as a potential alternative to neonatal models currently used for evaluating the optimal timing and long-term effects of rigid fixation techniques on a growing cranium. At 75% gestation, seven fetal piglets were randomly selected to undergo periosteal stripping of frontal and parietal bone segments with and without extensive coronal suture fusion procedures with cyanoacrylate adhesive. Fetal swine were killed postpartum at 4 and 11 weeks after fusion to assess craniofacial deformity. Piglets undergoing coronal fusion had slight deviation of the nose-snout toward the side of fusion and taller cranial vaults. The vertical cranial index of the experimental fusion group was 0.34 in comparison to a vertical index of 0.27 for the controls, suggesting abnormal vertical height expansion. There was no difference in the horizontal cranial index of either control or experimental fusion groups. Neither sows nor piglets were lost to anesthetic complications, uterine sepsis, or preterm labor during the initial laparotomy or subsequent cesarean delivery.

Injectable cartilage using polyethylene oxide polymer substrates

This study demonstrates that polyethylene oxide gels, which are biocompatible and biodegradable synthetic polymers, can be utilized for the encapsulation of isolated chondrocytes and maintenance of three-dimensional spatial support for new tissue development. Chondrocytes isolated from the glenohumeral and humeroradioulnar joints of a calf were added to a 20% polyethylene oxide solution in Ham's F-12 medium to generate a final cellular density of 10 x 10(6)/mL. The polymer-chondrocyte constructs were injected through a 22-gauge needle in 500-microliters aliquots subcutaneously in 12 nude mice and incubated for 6 and 12 weeks in vivo. Histologic and biochemical analyses including deoxyribonucleic acid and glycosaminoglycan quantitative analyses confirmed the presence of actively proliferating chondrocytes with production of a well-formed cartilaginous matrix in the transplanted samples. Control specimens from eight implantation sites consisting of chondrocytes alone or polyethylene oxide substrates did not demonstrate any gross or histologic evidence of neocartilage formation. These findings demonstrate the potential use of an injectable and moldable polymer substrate that can support cell proliferation and matrix synthesis after subcutaneous transplantation for neocartilage generation. The use of functional biologic tissue substitutes may serve as an alternative solution to current methods of augmentation or reconstruction of structural craniofacial contour deformities.

Prolonged survival of vascularized limb tissue allografts by donor irradiation

The clinical feasibility of transplantation of a vascularized limb tissue allograft depends upon reducing immunosuppression and its associated toxicity for the graft recipient. Donor or allograft irradiation would eradicate allogeneic marrow and provide a possible alternative or beneficial addition to host immunosuppression. The effect of irradiation on survival of limb tissue allograft was investigated in this study. In a rat model, knee allografts consisting of bone, cartilage, and soft tissues were transplanted across a strong histocompatibility barrier by femoral vascular microanastomoses. The grafts were harvested 1 and 2 weeks postoperatively for histologic and immunologic assays. Gamma irradiation of the graft immediately before transplant decreased graft rejection slightly. However, total body irradiation of the donor followed by a "waiting period" of 2 or more days before transplant significantly delayed rejection. After such a 6-day and a 2-day pretreatment protocol, the host cellular immune responses were not observed 1 and 2 weeks after transplantation and eventual progression toward graft rejection coincided with emergence of host antibody production. Rejection of vascularized limb tissue allografts after donor irradiation thus appeared to be mediated primarily through the humoral pathway. We conclude that donor irradiation is a potentially useful adjunct in prolonging survival of vascularized limb tissue allografts.

Augmented Becker versus modified Kessler tenorrhaphy in monkeys: dynamic mechanical analysis

The strength and gliding efficiency of an augmented Becker and Kessler tendon repair techniques were compared in fresh cadaver macaque monkey hands. Gliding efficiency was determined by comparing tendon work and load measurements made during tendon excursion to full fist with the same measurements made after tendon repair. Repair strength was then determined by tendon distraction to complete repair rupture. Data were gathered by computer controlled tensiometer and analyzed by factorial and repeated measures ANOVA. The augmented Becker repairs were significantly stronger than Kessler repairs. Repaired tendons required more load and work to bring the fingers into full fist; both repair types resulted in gliding efficiencies of 30% compared to intact controls. The augmented Becker repair is significantly stronger in situ than the modified Kessler and is recommended when early postoperative motion regimens are planned.

Experimental orthotopic transplantation of vascularized skeletal allografts: functional assessment and long-term survival

Vascularized skeletal tissue allografts would greatly expand the domain of reconstructive surgery. Few studies to date have examined the functional aspects of these allografts or their long-term fate. An orthotopic transplant model of rat distal femur and surrounding muscular cuff was developed to assess graft function in fracture healing and weight bearing. Isografts (RT1l to RT1l, n = 40), weak-barrier allografts (RT1l to RT1lv, n = 40), and strong-barrier allografts (RT1l to RT1n, n = 40) were transplanted. As the histocompatibility barrier increased between the donor and recipient animals, the graft viability and performance deteriorated according to radiographic, histologic, and immunologic analyses. Administration of cyclosporine led to survival of strong-barrier allografts similar to that of isografts. A long-term study of these allografts (RT1l to RT1n) was then performed on various immunosuppressive regimens. After an initial 10-week course of cyclosporine to achieve bony union and remodeling, subsequent cessation (n = 20) or intermittent "pulsing" (n = 20) of the immunosuppressant was insufficient in maintaining graft survival. However, graft viability and function were preserved through 1 year on continuous daily cyclosporine (n = 32). There was no evidence of host renal or hepatic toxicity by serum chemistry or histologic sections. Thus long-term survival of functional skeletal allografts was achieved in this orthotopic model without significant host toxicity from immunosuppression.

Vascularized growth-plate transplantation: a comparative study in the rat

The purpose of this study was to evaluate the influence of hormonal milieu on endochondral growth. This was achieved by transplanting hind limbs of juvenile rats to syngeneic adult rats. Because there is no potential for rejection, the limb can be transplanted between animals of different ages, to study the influence of hormonal maturity on stimulation and cessation of physeal growth and maturation. Tibial length and the histologic appearance of the physis were recorded. Whole vascularized hind-limb transplantation in syngeneic Lewis rats was used. Group 1: Thirty-five transplants between animals of the same age (three weeks old) were performed (isochronografts). Group 2: In 35 procedures, the age of the donor was three weeks old and of the recipient, 15 weeks (heterochronografts). In the first two study groups, the transplanted limb was placed on the dorsal flank of the recipient animal without nerve reconstruction. Controls were the contralateral hind limb of the donor animal. Because the limb was transplanted with loss of femoral and sciatic nerve supply to the dorsal flank position, the effects of denervation and lack of weight bearing were also evaluated. Group 3: Thirty-five limbs in three-week-old animals were transposed to the dorsal flank position, after severing the femoral and sciatic nerves. Analysis of variance of tibial length was used to compare study groups. Limbs transplanted to older animals (heterochronografts--Group 2) achieved the greatest length, 91 percent of normal, and significantly more when compared to Groups 1 (84 percent) and 3 (83 percent) (p less than .005). Growth of the limb was adversely affected by limb position and denervation.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunologic and ultrastructural changes during early rejection of vascularized bone allografts

This investigation evaluated ultrastructural changes during the earliest phase of immunologic rejection of vascularized bone allografts in a genetically defined rat model. These results were correlated with the cell-mediated and humoral immunologic responses during this time period. Employing a model for heterotopic allograft transplantation, 33 rats divided into four categories were evaluated. Group I consisted of ungrafted (naive) Lewis and Brown Norway rats; group II consisted of Lewis-to-Lewis vascularized bone isografts; group III consisted of Lewis-to-Brown Norway vascularized bone allografts; and group IV consisted of Lewis-to-Brown Norway vascularized bone allografts in rats receiving cyclosporine (10 mg/kg/day). Experimental animals were sacrificed at 3, 5, and 7 days. Immunologic analysis was performed using a cell-mediated lymphocytotoxicity assay and a complement-dependent cytotoxic antibody assay. The results of this study show that rejection of vascularized bone allografts appears as early as 3 days postoperatively, with osteocytes and vascular endothelium being the first elements affected. This early rejection is probably a manifestation of the humoral response. All changes secondary to rejection were arrested by cyclosporine.

The healing of facial bone fractures by the process of secondary union

The mechanism of healing of facial bone fractures was investigated in a rabbit model. Twelve New Zealand white rabbits underwent surgically induced fractures of the right infraorbital rim and fracture ostectomies (4 to 5 mm) of the left infraorbital rim. Animals were sacrificed 2, 4, and 8 weeks postfracture. Bone, including periosteum, obtained from each fracture or fracture osteoctomy site was divided longitudinally for hematoxylin and eosin staining, fluorescent microscopy, microangiography, and microradiography. Sequential fluorochrome labels of oxytetracycline (30 mg/kg), alizarin complexone (30 mg/kg), DCAF (20 mg/kg), and xylenol orange (90 mg/kg) were administered 24 hours preoperatively and at 1, 2, 4, and 8 weeks postfracture. All fracture and fracture ostectomy sites demonstrated vascular ingrowth, mineralization, and woven bone formation by 2 to 4 weeks postoperatively, beginning with a cartilage precursor. Subsequently, the woven bone was replaced with remodeled lamellar bone, resulting in complete bony healing by 8 weeks postoperatively. These steps were substantiated by microscopic, microradiographic, and radiologic examination of the specimens. This study demonstrates that fractures of the facial bones in a rabbit model heal by a process of new bone formation that resembles secondary union in endochondral bones.