Biomedical subjects

Mark A Randolph

Publications and source records attributed to Mark A Randolph.

At least 19 recordsLinked to original sources

PubMed2006

An allogenic cell-based implant for meniscal lesions.

BACKGROUND: Meniscal tears in the avascular zones do not heal. Although tissue-engineering approaches using cells seeded onto scaffolds could expand the indication for meniscal repair, harvesting autologous cells could cause additional trauma to the patient. Allogenic cells, however, could provide an unlimited amount of cells. HYPOTHESIS: Allogenic cells from 2 anatomical sources can repair lesions in the avascular region of the meniscus. STUDY DESIGN: Controlled laboratory study. METHODS: Both autologous and allogenic chondrocytes were seeded onto a Vicryl mesh scaffold and sutured into a bucket-handle lesion created in the medial menisci of 17 swine. Controls consisted of 3 swine knees treated with unseeded implants and controls from a previous experiment in which 4 swine were treated with suture only and 4 with no treatment. Menisci were harvested after 12 weeks and evaluated histologically for new tissue and percentage of interface healing surface; they were also evaluated statistically. RESULTS: The lesions were closed in 15 of 17 menisci. None of the control samples demonstrated healing. Histologic analysis of sequential cuts through the lesion showed formation of new scar-like tissue in all experimental samples. One of 8 menisci was completely healed in the allogenic group and 2 of 9 in the autologous group; the remaining samples were partially healed in both groups. No statistically significant differences in the percentage of healing were observed between the autologous and allogenic cell-based implants. CONCLUSION: Use of autologous and allogenic chondrocytes delivered via a biodegradable mesh enhanced healing of avascular meniscal lesions. CLINICAL RELEVANCE: This study demonstrates the potential of a tissue-engineered cellular repair of the meniscus using autologous and allogenic chondrocytes.

Absorbable Implants↗

PubMed2006

Influence of gel properties on neocartilage formation by auricular chondrocytes photoencapsulated in hyaluronic acid networks.

The objective of this study was to determine how changes in the network structure and properties of hyaluronic acid (HA) hydrogels, due to variations in the macromer molecular weight (50-1,100 kDa) and macromer concentration (2-20 wt %), affect neocartilage formation by encapsulated auricular chondrocytes. To investigate tissue formation, swine auricular chondrocytes were photoencapsulated in the various networks, implanted subcutaneously in the dorsum of nude mice, and explanted after 6 and 12 weeks for biochemical and histological analysis. After 12 weeks, the various constructs were 81-93% water, contained between 0.1 x 10(6) and 0.6 x 10(6) chondrocytes per sample, and consisted of 0-0.049 microg chondroitin sulfate/mug wet weight (glycosaminoglycan (GAG) content) and 0.002-0.060 microg collagen/microg wet weight. Histological staining showed an even distribution of chondrocytes and GAGs in addition to minimal type I collagen staining and intense and uniform type II collagen staining in the constructs with greatest neocartilage production. Hydrogels fabricated from 2 wt % of the 50 kDa HA macromer most resembled the properties of native cartilage and show the greatest promise for continued development for cartilage regeneration.

Animals↗

PubMed2006

Isolated perfusion of a tubed superficial epigastric flap in a rodent model.

BACKGROUND: Isolated perfusion models can yield important data regarding metabolism of the skin. An effective model must remain stable during perfusion but respond appropriately to metabolic and vascular stimuli. We describe the design and characterization of a tubed superficial epigastric isolated perfusion flap. MATERIALS AND METHODS: Tubed superficial epigastric flaps were created in 20 male Sprague Dawley rats. Forty-eight hours later the femoral vessels were cannulated and the flaps were perfused using a Krebs-Heinseleit buffer containing albumin for a period of 2 h. In five of the flaps norepinephrine and acetylcholine were added sequentially to the perfusate to determine vascular reactivity. In a further four flaps insulin (20 U/liter) and iodoacetate (5 mM) were added to the perfusate to confirm that the flap was metabolically active and reactive. Venous outflow was collected at regular intervals and analyzed for electrolytes, lactate, and glucose content. Vascularity and skin perfusion were characterized using barium microangiography and methylene blue dye injection. RESULTS: This flap model was found to be stable in terms of arterial pressure, electrolyte levels, and lactate production over the perfusion period. Norepinephrine caused a sharp increase in vascular resistance, which was reversed by administration of acetylcholine. Lactate production increased appropriately with the addition of insulin to the perfusate with a rapid decline following addition of the glycolysis inhibitor iodoacetate. There was no leakage of perfusate or significant swelling of the flap during the perfusion. CONCLUSIONS: The tubed superficial epigastric artery flap makes an effective model for isolated perfusion studies of the skin with a wide range of experimental applications.

Acetylcholine↗

PubMed2006

Healing potential of transplanted allogeneic chondrocytes of three different sources in lesions of the avascular zone of the meniscus: a pilot study.

UNLABELLED: Successful treatment of tears to the avascular region of the meniscus remains a challenge. Current repair techniques, such as sutures and anchors, are effective in stabilizing the peripheral, vascularized regions of the meniscus, but are not adequate for promoting healing in the avascular region. The purpose of this study was to demonstrate the healing ability of a tissue-engineered repair technique using allogenic chondrocytes from three different sources for the avascular zone of the meniscus. MATERIAL AND METHODS: Articular, auricular, and costal chondrocytes were harvested from 3-month-old Yorkshire swine. A 1-cm bucket-handle lesion was created in the avascular zone of each three swine. A cell-scaffold construct, composed of a single chondrocyte cell type and Vicryl mesh, was implanted into the lesion and secured with two vertical mattress sutures. Controls consisted of each three sutured unseeded mesh implants, suture only, and untreated lesions. The swine were allowed immediate post-operative full weight bearing. Menisci and controls were harvested after 12 weeks. RESULTS: In all experimental samples, lesion closure was observed. Gross mechanical testing with two Adson forceps demonstrated bonding of the lesion. Histological analysis showed formation of new tissue in all three experimental samples. None of the control samples demonstrated closure and formation of new matrix. CONCLUSION: We present preliminary data that demonstrates the potential of a tissue-engineered, allogenic cellular repair to provide successful healing of lesions in the avascular zone in a large animal model.

Animals↗

PubMed2006

A histologic analysis of the effects of stainless steel and titanium implants adjacent to tendons: an experimental rabbit study.

PURPOSE: The current trend is to treat distal radius fractures with open reduction and internal fixation with either titanium or stainless steel plates. Both provide stable fixation; however, there is minimal evidence concerning the soft-tissue response to these materials. Our objective was to evaluate the response of adjacent extensor tendons to titanium and stainless steel in a rabbit in vivo model and to evaluate the influence of time. METHODS: Forty rabbits were divided into 5 groups of 8 rabbits each. Groups I and II had unilateral osteotomy of the distal radius followed by dorsal fixation with titanium and stainless steel plates, respectively. Groups III and IV had fixation with titanium and stainless steel, respectively, but without osteotomy. Group V had surgical dissection without osteotomy or plates. Two animals per group were killed at 1, 4, 12, and 24 weeks. The specimens (distal radius, plate, overlying soft tissue, and extensor tendon) were harvested en bloc for histologic analysis. For interface preservation between implant and tissues the specimens were embedded in methylmethacrylate, sectioned, and stained with hematoxylin-eosin. RESULTS: Histologic analysis showed a fibrous tissue layer formed over both implants between the plate and the overlying extensor tendons in the groups treated with plating independently of the material and the presence or absence of osteotomy. This fibrous layer contained the majority of debris. Metallic particles were not observed in the tendon or muscle substance of any animals; however, they were visualized in the tenosynovium. Hematoxylin-eosin-stained sections of groups I through IV showed proliferative fibroblasts and metallic particles; however, this layer was not observed in group V. Statistical analysis did not show differences between the groups regarding the number of cells or metallic particles. CONCLUSIONS: Our results indicate that both implants generated adjacent reactive inflammatory tissue and particulate debris. There was no difference in cell or particle number produced by both materials. There is a statistically significant increase in inflammatory cells with increasing time of implantation.

Animals↗

PubMed2006

Tissue engineered cartilage integration to live and devitalized cartilage: a study by reflectance mode confocal microscopy and standard histology.

This study investigated the in vivo formation of engineering cartilage within living or devitalized cartilage discs using reflectance mode confocal microscopy and conventional light microscopy. Pig articular chondrocytes were suspended in fibrin glue and placed between two cartilage discs. Four experimental groups were prepared: in groups 1 and 2, the cell-hydrogel composite was placed between two live or between two devitalized cartilage discs, respectively; in groups 3 and 4, acellular fibrin glue was placed between two live or between two devitalized cartilage discs, respectively. Samples were implanted in the back of nude mice and analyzed after 2, 5, and 8 weeks. Results showed that engineered cartilage seems to grow more homogenously when the cell-seeded gel was placed between devitalized cartilages than when it was placed between live cartilage matrices. Confocal microscopy provides valuable information on the integration of tissue-engineered cartilage with native tissue and could be useful for nondestructive imaging in vivo.

Animals↗

PubMed2006

Review of injectable cartilage engineering using fibrin gel in mice and swine models.

More than a decade of work has been devoted to engineering cartilage for articular surface repair. This review covers the use of fibrin gel polymer as an injectable scaffold for generating new cartilage matrix from isolated articular chondrocytes beginning with studies in mice and culminating in an applied study in swine joints. These studies began with developing a formulation of fibrin that was injectable and promoted cartilage matrix formation. Subsequent studies addressed the problems of volume loss after the scaffolds were placed in vivo by adding lyophilized cartilage matrix. Additional studies focused on the ability of isolated chondrocytes to heal and repair cartilage in a model that could be biomechanically tested. In conclusion, this series of studies demonstrated that fibrin gel is a suitable polymer gel for generating new cartilage matrix from articular chondrocytes. The new matrix is capable of forming mechanical bonds between cartilage disks and can lead to healing and integration. Armed with these results, implantation of fibrin-cell constructs into defects in swine knees showed new cartilage formation and filling of the defects. Continuing work in these models with fibrin and other polymerizable hydrogels could result in a suitable cell-based therapy for articular cartilage lesions.

Animals↗

PubMed2006

Effects of auricular chondrocyte expansion on neocartilage formation in photocrosslinked hyaluronic acid networks.

The overall objective of this study was to examine the effects of in vitro expansion on neocartilage formation by auricular chondrocytes photoencapsulated in a hyaluronic acid (HA) hydrogel as a next step toward the clinical application of tissue engineering therapies for treatment of damaged cartilage. Swine auricular chondrocytes were encapsulated either directly after isolation (p = 0), or after further in vitro expansion ( p = 1 and p = 2) in a 2 wt%, 50-kDa HA hydrogel and implanted subcutaneously in the dorsum of nude mice. After 12 weeks, constructs were explanted for mechanical testing and biochemical and immunohistochemical analysis and compared to controls of HA gels alone and native cartilage. The compressive equilibrium moduli of the p = 0 and p = 1 constructs (51.2 +/- 8.0 and 72.5 +/- 35.2 kPa, respectively) were greater than the p = 2 constructs (26.8 +/- 14.9 kPa) and the control HA gel alone (12.3 +/- 1.3 kPa) and comparable to auricular cartilage (35.1 +/- 12.2 kPa). Biochemical analysis showed a general decrease in glycosaminoglycan (GAG), collagen, and elastin content with chondrocyte passage, though no significant differences were found between the p = 0 and p = 1 constructs for any of the analyses. Histological staining showed intense and uniform staining for aggrecan, as well as greater type II collagen versus type I collagen staining in all constructs. Overall, this study illustrates that constructs with the p = 0 and p = 1 auricular chondrocytes produced neocartilage tissue that resembled native auricular cartilage after 12 weeks in vivo. However, these results indicate that further expansion of the chondrocytes (p = 2) can lead to compromised tissue properties.

Animals↗

PubMed2006

Tissue engineering cartilage with aged articular chondrocytes in vivo.

BACKGROUND: Tissue engineering has the potential to repair cartilage structures in middle-aged and elderly patients using their own "aged" cartilage tissue as a source of reparative chondrocytes. However, most studies on tissue-engineered cartilage have used chondrocytes from postfetal or very young donors. The authors hypothesized that articular chondrocytes isolated from old animals could produce neocartilage in vivo as well as articular chondrocytes from young donors. METHODS: Articular chondrocytes from 8-year-old sheep (old donors) and 3- to 6-month-old sheep (young donors) were isolated. Cells were mixed in fibrin gel polymer at 40 x 10 cells/ml until polymerization. Cell-polymer constructs were implanted into the subcutaneous tissue of nude mice and harvested at 7 and 12 weeks. RESULTS: Samples and native articular cartilage controls were examined histologically and assessed biochemically for total DNA, glycosaminoglycan, and hydroxyproline content. Histological analysis showed that samples made with chondrocytes from old donors accumulated basophilic extracellular matrix and sulfated glycosaminoglycans around the cells in a manner similar to that seen in samples made with chondrocytes from young donors at 7 and 12 weeks. Biochemical analysis revealed that DNA, glycosaminoglycan, and hydroxyproline content increased in chondrocytes from old donors over time in a pattern similar to that seen with chondrocytes from young donors. CONCLUSIONS: This study demonstrates that chondrocytes from old donors can be rejuvenated and can produce neocartilage just as chondrocytes from young donors do when encapsulated in fibrin gel polymer in vivo. This study suggests that middle-aged and elderly patients could benefit from cartilage tissue-engineering repair using their own "aged" articular cartilage as a source of reparative chondrocytes.

Age Factors↗

PubMed2005

Long-term acceptance of renal allografts following prenatal inoculation with adult bone marrow.

BACKGROUND: The aim was to investigate if intravascular in utero injection of adult bone marrow into swine fetuses could lead to macrochimerism and tolerance to the donor. METHODS: Outbred Yorkshire sows and boars screening negative for MHC allele SLA of MGH miniature swine were bred. A laparotomy was performed on the sows at 50 days gestation to expose the uterus. Bone marrow harvested from SLA miniature swine was T-cell depleted and injected intravascularly into seventeen fetuses. Flow cytometry was performed to detect donor cells (chimerism) in the peripheral blood after birth. Mixed lymphocyte reactions (MLR) and cell-mediated lympholysis (CML) assays were used to assess the response to donor MHC. Previously frozen skin grafts from the bone marrow donor were placed on the offspring from the first litter. Donor-matched renal transplant from SLA donors were performed on chimeric swine, with and without a short 12-day course of cyclosporine, and one nonchimeric littermate. RESULTS: Nine inoculated offspring demonstrated donor cell chimerism in the peripheral blood and lymphohematopoietic tissues. All animals with detectable chimerism within the first three weeks were consistently nonreactive to donor MHC in vitro. Animals challenged with donor skin grafts displayed prolonged graft survival without producing antidonor antibodies. All chimeric animals accepted donor-matched kidney allografts, even one without cyclosporine. The kidney in the nonchimeric littermate rejected by day 21. CONCLUSIONS: Transplantation of allogeneic adult bone marrow into immunocompetent fetal recipients resulted in chimerism. In utero inoculation led to operational tolerance to the donor's major histocompatibility antigens and long-term acceptance to organ allografts.

Animals↗

PubMed2005

In utero bone marrow transplantation induces kidney allograft tolerance across a full major histocompatibility complex barrier in Swine.

BACKGROUND: In utero hematopoietic stem-cell transplantation has been shown to induce donor-specific tolerance in small-animal models. However, tolerance has been difficult to achieve in large-animal studies. METHODS: Outbred swine underwent in utero transplantation of fully major histocompatibility complex (MHC)-mismatched CD3-depleted bone marrow mixed with fresh bone marrow to achieve a final CD3 content of 1.5%. Transplantation was performed at 50 to 55 days' gestation and two animals survived long term and demonstrated multilineage peripheral blood hematopoietic chimerism. These two long-term survivors were analyzed for in vitro evidence of donor-specific tolerance by mixed leukocyte reaction (MLR), cell-mediated lysis (CML), and antibody testing and in vivo by kidney transplantation. RESULTS: Both animals demonstrated in vitro donor-specific unresponsiveness by MLR and CML and did not demonstrate anti-donor antibody production. Donor matched kidney transplants were performed without immunosuppression and functioned for more than 100 days, with no evidence for rejection. CONCLUSIONS: The authors demonstrate conclusively that in utero transplantation of fully MHC-mismatched bone marrow in swine can lead to engraftment and stable multilineage hematopoietic chimerism and tolerance to postnatal donor MHC-matched kidney transplantation without the need for immunosuppression.

Animals↗

PubMed2005

Stable multilineage chimerism across full MHC barriers without graft-versus-host disease following in utero bone marrow transplantation in pigs.

Stable engraftment of hematopoietic progenitors and multilineage chimerism following in utero bone marrow transplantation could be a promising modality for treatment of prenatally diagnosed blood dyscrasias. For treatment of these diseases, stable chimerism in the myeloid and erythroid lineages is important because it is anticipated that donor-derived cells will compensate for defects in these host lineages. In the present study, a preparation of bone marrow that includes fresh, unmanipulated marrow mixed with T-cell-depleted marrow to achieve 1.5% T-cell content, was injected into the intrahepatic portion of the umbilical vein of porcine fetuses at mid-gestation. Donor hematopoietic progenitor cell engraftment was assessed in fetal liver and recipient bone marrow postnatally by donor-specific polymerase chain reaction of colony-forming units. Chimerism was assessed in lymphoid tissues and peripheral blood by flow cytometry. Graft-versus-host disease (GVHD) was assessed by histological analysis of biopsies of skin, bone marrow, liver, and intestine. In this report, we demonstrate that stable multilineage chimerism across a full major histocompatibility complex disparity can be achieved without GVHD through in utero bone marrow transplantation.

Animals↗

PubMed2005

Tissue engineering for meniscus repair.

Meniscus injury is common in today's active society. Despite the frequent presentation of meniscus injury, the decision to repair or resect a torn meniscus is not always straightforward. Current repair techniques are effective in the peripheral vascularized meniscus, but their success is not dependable in the avascularized zone. Tissue engineering, a discipline that combines the technologies of cell culture and biodegradable scaffolds to deliver a cellular repair, may be one future answer to this problem. The concept of using cell-based repair for torn menisci could improve healing of lesions in the avascular zone and broadly expand the indication for repair rather than removal, obviating the need for meniscectomy. This article reviews current advances in the relatively new field of tissue engineering toward the development of a tissue-engineered meniscal repair technique.

Chondrocytes↗

PubMed2005

Tissue-engineered flexible ear-shaped cartilage.

BACKGROUND: Previous attempts to engineer human ear-shaped constructs mimicked human shape but lacked the flexibility and size of a human ear. Recently, the authors engineered flexible cartilage by incorporating a perichondrium-like layer into the construct. In this study, they used lyophilized swine perichondrium as a pseudoperichondrium, examined its ability to confer flexibility to tissue-engineered cartilage, and used it to engineer flexible cartilage in the shape and size of a human ear. METHODS: Auricular chondrocytes and perichondrium were isolated from swine. Chondrocytes were mixed with fibrin polymer and gelled to form 5 x 20-mm constructs. Constructs alone (control, n = 6) or constructs sandwiched between two layers of lyophilized swine perichondrium (experimental, n = 6) were implanted into athymic mice. Auricular chondrocytes in fibrin polymer and lyophilized perichondrium were also used to form a tri-layer, ear-shaped construct, which was implanted into an athymic rat and externally stented for 6 weeks (n = 1). At 12 weeks, constructs were analyzed with histology and gross mechanical testing. RESULTS: New cartilaginous tissue was engineered in both the experimental and control groups. In samples laminated with lyophilized swine perichondrium, the intimate integration of the laminate with the neocartilage closely resembled the histoarchitecture of the native swine ear. Experimental constructs had mechanical properties similar to those of the native swine ear, while control constructs fractured with similar testing. The engineered ear could not be fractured with gross mechanical testing, and its size, shape, and flexibility remained stable. CONCLUSIONS: This study demonstrates that it is possible to engineer a cartilage construct that resembles the human ear not only in shape but also in size and flexibility. This study also confirms that lamination is a reliable method to confer elastic-like flexibility to an engineered cartilage construct.

Animals↗

PubMed2005

Producing a flexible tissue-engineered cartilage framework using expanded polytetrafluoroethylene membrane as a pseudoperichondrium.

BACKGROUND: Both native and engineered cartilage is brittle and fractures easily without perichondrium. The aim of this study was to understand the role of the perichondrium and try to enhance the flexible properties of tissue-engineered cartilage using expanded polytetrafluoroethylene (ePTFE) membrane as a pseudoperichondrium. METHODS: The study was conducted in two phases. In phase I, native swine auricular cartilage of different thicknesses was studied by histologic evaluation and failure testing. Next, isolated perichondrium was bonded to native cartilage slices using fibrin glue or Dermabond and tested to failure. In phase II, swine auricular chondrocytes were suspended in fibrin glue. The chondrocyte-fibrin glue composites were then bound to expanded polytetrafluoroethylene membrane in two trilaminar configurations: In group EC-1, the membrane was in the center, whereas it was on the surfaces in group EC-2. Specimens were implanted into nude mice for 4 weeks, 8 weeks, 12 weeks, and 8 months and subjected to histologic evaluation and failure testing. RESULTS: In phase I, the results demonstrated that perichondrium securely bonded to the cartilage plays an important role in maintaining the flexible nature of elastic cartilage. In phase II, failure testing revealed that specimens in group EC-1 (expanded polytetrafluoroethylene core) were fractured during bending and destroyed after torsion, whereas those in group EC-2 (cartilage core) returned to their original shape without fracturing even after rigorous torsion. Histologic analysis demonstrated that transplanted chondrocytes penetrated into the microporous structure of expanded polytetrafluoroethylene and created a bond to it. CONCLUSION: It is possible to engineer flexible cartilage using expanded polytetrafluoroethylene as a pseudoperichondrium.

Animals↗

PubMed2004

Injectable tissue-engineered cartilage with different chondrocyte sources.

Injectable engineered cartilage that maintains a predictable shape and volume would allow recontouring of craniomaxillofacial irregularities with minimally invasive techniques. This study investigated how chondrocytes from different cartilage sources, encapsulated in fibrin polymer, affected construct mass and volume with time. Swine auricular, costal, and articular chondrocytes were isolated and mixed with fibrin polymer (cell concentration of 40 x 10 cells/ml for all groups). Eight samples (1 cm x 1 cm x 0.3 cm) per group were implanted into nude mice for each time period (4, 8, and 12 weeks). The dimensions and mass of each specimen were recorded before implantation and after explantation. Ratios comparing final measurements and original measurements were calculated. Histological, biochemical, and biomechanical analyses were performed. Histological evaluations (n = 3) indicated that new cartilaginous matrix was synthesized by the transplanted chondrocytes in all experimental groups. At 12 weeks, the ratios of dimension and mass (n = 8) for auricular chondrocyte constructs increased by 20 to 30 percent, the ratios for costal chondrocyte constructs were equal to the initial values, and the ratios for articular chondrocyte constructs decreased by 40 to 50 percent. Constructs made with auricular chondrocytes had the highest modulus (n = 3 to 5) and glycosaminoglycan content (n = 4 or 5) and the lowest permeability value (n = 3 to 5) and water content (n = 4 or 5). Constructs made with articular chondrocytes had the lowest modulus and glycosaminoglycan content and the highest permeability value and water content (p < 0.05). The amounts of hydroxyproline (n = 5) and DNA (n = 5) were not significantly different among the experimental groups (p > 0.05). It was possible to engineer injectable cartilage with chondrocytes from different sources, resulting in neocartilage with different properties. Although cartilage made with articular chondrocytes shrank and cartilage made with auricular chondrocytes overgrew, the injectable tissue-engineered cartilage made with costal chondrocytes was stable during the time periods studied. Furthermore, the biomechanical properties of the engineered cartilage made with auricular or costal chondrocytes were superior to those of cartilage made with articular chondrocytes, in this model.

Animals↗

PubMed2004

Analysis of bending behavior of native and engineered auricular and costal cartilage.

A large-deflection elasticity model was used to describe the mechanical behavior of cartilaginous tissues during three-point bending tests. Force-deflection curves were measured for 20-mm long x 4-mm wide x approximately 1-mm thick strips of porcine auricular and costal cartilage. Using a least-squares method with elastic modulus in bending as the only adjustable parameter, data were fit to a model based on the von Karman theory for large deflection of plates. This model described the data well, with an average RMS error of 14.8% and an average R(2) value of 0.98. Using this method, the bending modulus of auricular cartilage (4.6 MPa) was found to be statistically lower (p < 0.05) than that of costal cartilage (7.1 MPa). Material features of the cartilage samples influenced the mechanical behavior, including the orientation of the perichondrium in auricular cartilage. These methods also were used to determine the elastic moduli of engineered cartilage samples produced by seeding chondrocytes into fibrin glue. The modulus of tissue-engineered constructs increased statistically with time (p < 0.05), but still were statistically lower than the moduli of the native tissue samples (p > 0.05), reaching only about a third of the values of native samples.

Animals↗

PubMed2004

Tolerance to composite tissue allografts across a major histocompatibility barrier in miniature swine.

BACKGROUND: Tolerance to composite tissue allografts might allow the widespread clinical use of reconstructive allotransplantation if protocols to achieve this could be rendered sufficiently nontoxic. The authors investigated whether tolerance could be generated in miniature swine to composite tissue allografts across a major histocompatibility (MHC) barrier. A clinically relevant tolerance protocol involving hematopoietic cell transplantation without the need for irradiation or myelosuppressive drugs was tested. METHODS: Seven recipient animals were transiently T-cell depleted and a short course of cyclosporine was initiated. Twenty-four hours later, a donor hematopoietic cell transplant consisting of cytokine-mobilized peripheral blood mononuclear cells or bone marrow cells and a heterotopic limb transplant were performed. In vitro anti-donor responsiveness was assessed by mixed-lymphocyte reaction and cell-mediated lympholysis assays. Acceptance of the limb allografts was determined by gross and histologic appearance. Chimerism in the peripheral blood and lymphohematopoietic organs was assessed by flow cytometry. RESULTS: All seven experimental animals accepted the musculoskeletal elements but rejected the skin of the allografts. All but one of the animals displayed donor-specific unresponsiveness in vitro. The animals that received cytokine mobilized-peripheral blood mononuclear cells showed chimerism but had clinical evidence of graft-versus-host disease (GVHD). None of the animals that received bone marrow cells showed stable chimerism and none developed GVHD. CONCLUSIONS: This protocol can achieve tolerance to the musculoskeletal elements of composite tissue allografts across an MHC barrier in miniature swine. Stable chimerism does not appear to be necessary for tolerance and may not be desirable because of the risk of GVHD.

Animals↗