C Ibarra

University of Massachusetts Amherst, Amherst Center, Massachusetts, United States

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Publications (9)12.85 Total impact

  • [show abstract] [hide abstract]
    ABSTRACT: In the repair of cartilage defects, autologous tissue offers the advantage of lasting biocompatibility. The ability of bovine chondrocytes isolated from hyaline cartilage to generate tissue-engineered cartilage in a predetermined shape, such as a human ear, has been demonstrated; however, the potential of chondrocytes isolated from human elastic cartilage remains unknown. In this study, the authors examined the multiplication characteristics of human auricular chondrocytes and the ability of these cells to generate new elastic cartilage as a function of the length of time they are maintained in vitro. Human auricular cartilage, harvested from patients 5 to 17 years of age, was digested in collagenase, and the chondrocytes were isolated and cultured in vitro for up to 12 weeks. Cells were trypsinized, counted, and passaged every 2 weeks. Chondrocyte-polymer (polyglycolic acid) constructs were created at each passage and then implanted into athymic mice for 8 weeks. The ability of the cells to multiply in vitro and their ability to generate new cartilage as a function of the time they had been maintained in vitro were studied. A total of 31 experimental constructs from 12 patients were implanted and compared with a control group of constructs without chondrocytes. In parallel, a representative sample of cells was evaluated to determine the presence of collagen. The doubling rate of human auricular chondrocytes in vitro remained constant within the population studied. New tissue developed in 22 of 31 experimental implants. This tissue demonstrated the physical characteristics of auricular cartilage on gross inspection. Histologically, specimens exhibited dense cellularity and lacunae-containing cells embedded in a basophilic matrix. The specimens resembled immature cartilage and were partially devoid of the synthetic material of which the construct had been composed. Analyses for collagen, proteoglycans, and elastin were consistent with elastic cartilage. No cartilage was detected in the control implants. Human auricular chondrocytes multiply well in vitro and possess the ability to form new cartilage when seeded onto a three-dimensional scaffold. These growth characteristics might some day enable chondrocytes isolated from a small auricular biopsy to be expanded in vitro to generate a large, custom-shaped, autologous graft for clinical reconstruction of a cartilage defect, such as for congenital microtia.
    Plastic &amp Reconstructive Surgery 05/1999; 103(4):1111-9. · 3.54 Impact Factor
  • Y L Cao, C Ibarra, C Vacanti
    [show abstract] [hide abstract]
    ABSTRACT: Restoration of organ structure and function, utilizing tissue engineering technologies, often requires the use of a temporary porous scaffold. The function of the scaffold is to direct the growth of cells migrating from the surrounding tissue (tissue conduction), or of cells seeded within the porous structure of the scaffold. The scaffold must therefore provide a suitable substrate for cell attachment, differentiated function, and, in certain cases, cell proliferation (1-3). These critical requirements may be met by the choice of an appropriate material from which to construct the scaffold, although the suitability of the scaffold may also be affected by the processing technique. There are many biocompatible materials that could potentially be used to construct scaffolds, however, a biodegradable material is normally desirable, since the role of the scaffold is usually only a temporary one. Many natural and synthetic biodegradable polymers, such as collagen, poly(α-hydroxyesters), and poly(anhydrides), have been widely and successfully used as scaffolding materials because of their versatility and ease of processing. Many researchers have used poly(α-hydroxyesters) as starting materials from which to fabricate scaffolds, using a wide variety of processing techniques. These polymers have proven successful as temporary substrates for a number of cell types, allowing cell attachment, proliferation, and maintenance of differentiated function (10). Poly(α-hydroxyesters) such as the polyoxamers are a family of more than 30 different nontoxic, nonionic surface active agents. These compounds are made at elevated temperature and pressure by the sequential additi on of propylene oxide and then ethylene oxide to neutralize the salt that is generally retained in the final product.
    Methods in molecular medicine 01/1999; 18:75-83.
  • [show abstract] [hide abstract]
    ABSTRACT: New cartilage formation has been successfully achieved by technology referred to as tissue engineering. Polymers and hydrogels such as poly(glycolic acid), calcium alginate, and poly(ethylene) and poly(propylene) hydrogels have been used as cell carriers to regenerate cartilage in the nude mouse model. The next step toward human applications of engineered cartilage is to demonstrate their potential in immunocompetent animal models. This study compared the suitability of three polymers for generating tissue engineered elastic cartilage using autologous cells in an immuno-competent porcine animal model. Auricular cartilage was obtained from pigs. Chondrocytes were isolated onto fiber based poly(glycolic acid) (PGA) scaffolds or suspended in calcium alginate or pluronic F127 gel at constant concentrations. Chondrocyte-polymer constructs were either implanted (PGA) or injected (calcium alginate and pluronic) as autologous implants subcutaneously into the pigs from which the cells had been isolated. Specimens were harvested and analyzed grossly and historically after 6 weeks in vivo. All explants demonstrated cartilage formation to a variable degree. When using PGA or calcium alginate, the overall histological appearance of the tissue formed is that of fibrocartilage with thick bundles of collagen dispersed in the tissue. When using pluronics as scaffold, histologic features resemble those of native elastic cartilage, showing a more organized arrangement of the cells, which seems to correlate to functional properties as elastin presence in the tissue engineered cartilage. Elastic cartilage engineered in an immunocompetent animal model varies with the type of polymer used. The behavior of the cell-polymer constructs is not fully understood and outcome seems to be related to several factors, including inflammatory reaction. Further studies with similar models are needed to determine the feasibility of engineering tissue generated from different cell-polymer constructs prior to human application.
    Journal of Biomaterials Science Polymer Edition 02/1998; 9(5):475-87. · 1.70 Impact Factor
  • [show abstract] [hide abstract]
    ABSTRACT: Islet transplantation is a potential cure for diabetes mellitus. The major problem for clinical application remains the prevention of transplant rejection without major side effects. Broad application in early disease will make the usage of xenogeneic tissue necessary. Immunoisolation is an experimental strategy to prevent rejection, by separating the transplanted allogeneic or xenogeneic cells from the host immune system using a barrier device. Current methods of immunoisolation use artificial, not completely inert materials as barrier devices and induce an unwanted foreign body reaction. Using recipient own cells for encapsulation the foreign body reaction could be prevented. This study describes a new method of encapsulation of islets of Langerhans within a capsule of chondrocytes, which may serve as an immunoisolation barrier utilizing the immunoprivileged properties of the chondrocyte matrix and demonstrates the functional survival of the encapsulated islets in vivo.
    Zentralblatt für Chirurgie 02/1998; 123(7):830-3. · 0.69 Impact Factor
  • J M Pollok, C Ibarra, J P Vacanti
    Transplantation Proceedings 07/1997; 29(4):2131-3. · 0.95 Impact Factor
  • J M Pollok, C Ibarra, J P Vacanti
    Transplantation Proceedings 01/1997; 29(1-2):909-11. · 0.95 Impact Factor
  • Transplantation Proceedings 01/1997; 29(1-2):986-8. · 0.95 Impact Factor
  • [show abstract] [hide abstract]
    ABSTRACT: Little is known about the survival and function of chondrocytes when stored as a suspension at different temperatures. We compared the functional viability of chondrocytes stored in suspension at room temperature to those stored at 4 degrees C in either tissue culture medium or phosphate-buffered saline. Approximately half (47%) of the cells stored in culture media at 4 degrees C maintained viability after 4 weeks, while the cells stored at 4 degrees C in phosphate-buffered saline or in either suspension at room temperature for the same time demonstrated almost no viability. Viable cells that had been stored in cold culture media demonstrated the ability to multiply at the same rate as they had prior to cold storage, when returned to an incubator at 37 degrees C. These cells also maintained their ability to form new cartilage when seeded onto polymer matrices and implanted subcutaneously in nude mice. This investigation indicates that preservation of bovine chondrocytes at 4 degrees C in an appropriate media yields viable, functional cells that can be subsequently utilized to engineer new cartilage.
    Tissue Engineering 01/1996; 2(1):75-81. · 4.07 Impact Factor
  • [show abstract] [hide abstract]
    ABSTRACT: We studied the feasibility of creating new tissue engineered tendons, using bovine tendon fibroblasts (tenocytes) attached to synthetic biodegradable polymer scaffolds in athymic mice. Calffore- and hind-limbs were obtained from a local slaughterhouse within 6 hours of sacrifice. Tenocytes were isolated from the calf tendons. Cells were seeded onto an array of fibers composed of polymer (PGA) configured either as a random mesh of fibers, or as an array of parallel fibers. Fifty cell-polymer constructs were implanted subcutaneously in athymic mice and harvested at 3, 6, 8, 10 and 12 weeks. Grossly, all excised specimens resembled the tendons from which the cells had been isolated. Histologic sections stained with hematoxylin and eosin (H&E) and Masson's trichrome showed cells arranged longitudinally within parallel collagen fibers in the periphery. Centrally, collagen fibers were more randomly arranged, although they seemed to attain a parallel arrangement of cells and fibers over time. By 10 weeks, specimens showed very similar histologic characteristics to normal tendon. Histologically, 12-week samples were virtually identical to normal tendon. When longitudinal polymer fibers seeded with cell had been implanted, the collagen fibers seen in the neo-tendons became organized at an earlier interval of time. Biomechanical tests demonstrated linear increase in tensile strength of the neo-tendons over time. Eight-week specimens showed 30% the tensile strength of normal tendon samples of similar size. By 12 weeks, tensile strength was already 57% that of normal bovine tendon.
    MRS Proceedings. 12/1994; 394.

Publication Stats

254 Citations
383 Views
12.85 Total Impact Points

Institutions

  • 1999
    • University of Massachusetts Amherst
      Amherst Center, Massachusetts, United States
  • 1998
    • University of Massachusetts Medical School
      • Department of Anesthesiology
      Worcester, Massachusetts, United States
  • 1994–1998
    • Harvard Medical School
      • Department of Surgery
      Boston, MA, United States