Tissue engineering by cocultivating human elastic chondrocytes and keratinocytes

Application of decellularized tissues in ear regeneration

More than 5 % of people worldwide suffer from hearing disorders. Ototoxic drugs, aging, exposure to loud sounds, rupture, subperichondrial hematoma, perichondritis, burns and frostbite and infections are the main causes of hearing loss, some of which can destroy the cartilage and lead to deformation. On the other hand, disorders of the external ear are diverse and can range from dangerous neoplasms to defects that are not acceptable from a cosmetic standpoint. These issues include injuries, blockages, dermatoses, and infections, and any or all of them may be bothersome to the busy doctor. Using an implant or hearing aid is one of the treatment strategies for deafness. However, these medical devices are not useful for every eligible patient. With the right therapy, many of these issues are not life-threatening and can be treated with confidence in a positive outcome. As medical research and treatment have advanced dramatically in the past ten years, tissue engineering (TE) has emerged as a promising method to regenerate damaged tissue, raising the prospect of a permanent cure for deafness. Decellularization is now seen as a promising development for regenerative medicine, and an increasing number of applications are being found for acellular matrices. Studies on decellularization show that natural scaffolds made from decellularized tissues can serve as a suitable platform while preserving the main components, and the preparation of such scaffolds will be an important part of future bioscience research. It can have wide applications in regenerative medicine and TE. This review intends to give an overview of the status of research and alternative scaffolds in inner and outer ear regenerative medicine from both a preclinical and clinical perspective for ear disorders in order to show how ongoing TE research has the potential to advance and enhance novel disease treatments.

Xiphoid process-derived chondrocytes: a novel cell source for elastic cartilage regeneration

Reconstruction of elastic cartilage requires a source of chondrocytes that display a reliable differentiation tendency. Predetermined tissue progenitor cells are ideal candidates for meeting this need; however, it is difficult to obtain donor elastic cartilage tissue because most elastic cartilage serves important functions or forms external structures, making these tissues indispensable. We found vestigial cartilage tissue in xiphoid processes and characterized it as hyaline cartilage in the proximal region and elastic cartilage in the distal region. Xiphoid process-derived chondrocytes (XCs) showed superb in vitro expansion ability based on colony-forming unit fibroblast assays, cell yield, and cumulative cell growth. On induction of differentiation into mesenchymal lineages, XCs showed a strong tendency toward chondrogenic differentiation. An examination of the tissue-specific regeneration capacity of XCs in a subcutaneous-transplantation model and autologous chondrocyte implantation model confirmed reliable regeneration of elastic cartilage regardless of the implantation environment. On the basis of these observations, we conclude that xiphoid process cartilage, the only elastic cartilage tissue source that can be obtained without destroying external shape or function, is a source of elastic chondrocytes that show superb in vitro expansion and reliable differentiation capacity. These findings indicate that XCs could be a valuable cell source for reconstruction of elastic cartilage.

Formation of tissue engineered composite construct of cartilage and skin using high density polyethylene as inner scaffold in the shape of human helix

BACKGROUND

Formation of external ear via tissue engineering has created interest amongst surgeons as an alternative for ear reconstruction in congenital microtia.

OBJECTIVE

To reconstruct a composite human construct of cartilage and skin in the shape of human ear helix in athymic mice.

METHODS

Six human nasal cartilages were used and digested with Collagenase II. Chondrocytes were passaged in 175 cm(2) culture flasks at a density of 10,000 cells/cm(2). Frozen human plasma was then mixed with human chondrocytes. Six human skin samples were cut into small pieces trypsinized and resuspended. The keratinocytes were plated in six-well plate culture dishes at a density of 2×105 cells per well. Dermis tissues were digested and the fibroblast cells resuspended in six-well plate at the density of 10,000 cells per well. Fibrin-fibroblast layer and fibrin-keratinocytes were formed by mixing with human plasma to create 6 bilayered human skin equivalent (BSE) constructs. The admixture of fibrin chondrocytes layers was wrapped around high density polyethylene (HDP), and implanted at the dorsum of the athymic mice. The construct was left for 4 weeks and after maturation the mice skin above the implanted construct was removed and replaced by BSE for another 4 weeks.

RESULTS

Haematoxylin and Eosin showed that the construct consists of fine arrangement and organized tissue structure starting with HDP followed by cartilage, dermis and epidermis. Safranin-O staining was positive for proteoglycan matrix production. Monoclonal mouse antihuman cytokeratin, 34βE12 staining displayed positive result for human keratin protein.

CONCLUSIONS

The study has shown the possibility to reconstruct ear helix with HDP and tissue engineered human cartilage and skin. This is another step to form a human ear and hopefully will be an alternative in reconstructive ear surgery.

Paracrine factors from fibroblast aggregates in a fibrin-matrix carrier enhance keratinocyte viability and migration

Efficient re-epithelialization of skin lesions is dependent on paracrine support from connective tissue fibroblasts. In deep skin defects, the supporting growth factor incentive is lacking. Current methods of keratinocyte transplantation with compromised attachment, spread, and cell proliferation warrant improvement and refinement. We describe here how human keratinocytes can be stimulated by matrix-embedded factors from a novel process of fibroblast activation: nemosis. Interestingly, the unique set of mediators released in this process also plays a key role in normal wound healing. To develop a system for targeted delivery of nemosis-derived paracrine effectors, herein designated as Finectra, we combined them with fibrin to establish a controlled-release gel. Keratinocytes seeded to cover this active matrix showed better adherence, outgrowth, and viability than did cells on control matrix. The matrix incorporating Finectra supported viability of both primary keratinocytes and green fluorescent protein (GFP)-labeled HaCaT cells, as evaluated by MTT assay and persistence of GFP-fluorescence. The fibrin-Finectra matrix promoted migration of keratinocytes to cover a larger area on the matrix, suggesting better wound coverage on transplantation. An inhibitor of EGFR/c-Met receptor tyrosine kinases abolished keratinocyte responses to fibrin-Finectra matrix. This matrix can thus deliver biologically relevant synergistic stimuli to keratinocytes and hasten re-epithelialization.

Tissue engineering of composite grafts: Cocultivation of human oral keratinocytes and human osteoblast-like cells on laminin-coated polycarbonate membranes and equine collagen membranes under different culture conditions

In complex craniomaxillofacial defects, the simultaneous reconstruction of hard and soft tissue is often necessary. Until now, oral keratinocytes and osteoblast-like cells have not been cocultivated on the same carrier. For the first time, the cocultivation of human oral keratinocytes and human osteoblast-like cells has been investigated in this study. Different carriers (laminin-coated polycarbonate and equine collagen membranes) and various culture conditions were examined. Human oral keratinocytes and human osteoblast-like cells from five patients were isolated from tissue samples, seeded on the opposite sides of the carriers and cultivated for 1 and 2 weeks under static conditions in an incubator and in a perfusion chamber. Proliferation and morphology of the cells were analyzed by EZ4U-tests, light microscopy, and scanning electron microscopy. Cocultivation of both cell-types seeded on one carrier was possible. Quantitative and qualitative growth was significantly better on collagen membranes when compared with laminin-coated polycarbonate membranes independent of the culture conditions. Using perfusion culture in comparison to static culture, the increase of cell proliferation after 2 weeks of cultivation when compared with the proliferation after 1 week was significantly lower, independent of the carriers used. In conclusion, the contemporaneous cultivation of human oral keratinocytes and human osteoblast-like cells on the same carrier is possible, a prerequisite for planned in vivo studies. As carrier collagen is superior to laminin-coated polycarbonate membranes. Regarding the development over time, the increase of proliferation rate is lower in perfusion culture. Examinations of cellular differentiation over time under various culture conditions will be subject of further investigations.

Fibrin: a versatile scaffold for tissue engineering applications

Tissue engineering combines cell and molecular biology with materials and mechanical engineering to replace damaged or diseased organs and tissues. Fibrin is a critical blood component responsible for hemostasis, which has been used extensively as a biopolymer scaffold in tissue engineering. In this review we summarize the latest developments in organ and tissue regeneration using fibrin as the scaffold material. Commercially available fibrinogen and thrombin are combined to form a fibrin hydrogel. The incorporation of bioactive peptides and growth factors via a heparin-binding delivery system improves the functionality of fibrin as a scaffold. New technologies such as inkjet printing and magnetically influenced self-assembly can alter the geometry of the fibrin structure into appropriate and predictable forms. Fibrin can be prepared from autologous plasma, and is available as glue or as engineered microbeads. Fibrin alone or in combination with other materials has been used as a biological scaffold for stem or primary cells to regenerate adipose tissue, bone, cardiac tissue, cartilage, liver, nervous tissue, ocular tissue, skin, tendons, and ligaments. Thus, fibrin is a versatile biopolymer, which shows a great potential in tissue regeneration and wound healing.

Comparativein vitro study of the proliferation and growth of human osteoblast-like cells on various biomaterials

In vitro studies about the growth behavior of osteoblasts onto biomaterials is a basic knowledge and a screening method for the development and application of scaffolds in vivo. In this in vitro study human osteoblast-like (HOB) cells were cultured on seven different biomaterials used in dental and craniomaxillofacial surgery, respectively. The tested biomaterials were synthetic biodegradable (MacroPore, Ethisorb, PDS, Beriplast P) and nonbiodegradable polymers (Palacos) as well as calcium phosphate cement (BoneSource) and titanium. The cell proliferation and cell colonization were analyzed by scanning electron microscopy and EZ4U-test. Statistical analysis were performed. HOB-like cells cultivated on Ethisorb showed the highest proliferation rate. The proliferation rate was statistically significant compared with Palacos, MacroPore, and BoneSource. Whereas, Beriplast, PDS, and titanium yielded lower proliferation rates. However, there was no statistically significant difference compared with Palacos, MacroPore, and BoneSource. SEM analysis showed no significant difference in individual cell features and cell colonization. But an infiltration and a growth of HOB-like cells throughout the porous structure of Ethisorb, which is formed by crossing fibers, is a striking different feature (macrotopography). This feature can explain the highest proliferation rate of Ethisorb. The results showed that HOB-like cells appear to be sensitive to substrate composition and topography. Moreover, the basis for further studies with such biomaterial/osteoblast constructs in vivo are provided. Further focusing points are developing techniques to fabricate three-dimensional porous biomaterial/cell constructs, studying the tissue reaction and the bone regeneration of such constructs compared with the use of autologous bone.

Proliferation rate of human osteoblast-like cells on alloplastic biomaterials and their clinical application for the transnasal duraplasty procedure

The possibility of transmission of slow virus infection (HIV) and Creutzfeld-Jakob disease by cadaveric dura implants makes it necessary to find synthetic, absorbable materials for the reconstruction of the dura mater. Various procedures with autologous or alloplastic material are described. Four commerically available biomaterials were choosen to study the proliferation rate and the biocompatibility of human osteoblast-like cells (HOB-like cells) on 2-dimensional material by biochemical analysis. With a proliferation assay, the viability and the proliferation capacity of osteoblast-like cells were evaluated. A clinical trial was added to study resorbable fleece as one of the previously tested biomaterial in a small patient group (8 patients) to close anterior cranial fossa dura defects. The results of the proliferation assay showed the highest proliferation rate of HOB-like cells on resorbable fleece. All patients in our clinical trial with anterior cranial fossa dura defects were successfully treated with resorbable fleece. There was no evidence for persisting cerebrospinal fluid rhinorrhea or foreign body reaction after the period of wound healing. The present study demonstrated an excellent biocompatibility of resorbable fleece. The vicryl fleece is an alternative alloplastic material for endonasal closure of defined substantial defects of the dura with cerebrospinal fluid.

The effect of cell-based therapy with autologous synovial fibroblasts activated by exogenous TGF-beta1 on the in situ frozen-thawed anterior cruciate ligament

The present study was conducted to clarify the effect of cell therapy with autologous synovial tissue-derived fibroblasts activated by transforming growth factor (TGF)-beta1 on the necrotized anterior cruciate ligament (ACL). Thirty-six mature female Japanese white rabbits were used in this study. In Group I, fibrin glue with autologous synovial tissue-derived fibroblasts after TGF-beta stimulation was wrapped around the necrotized ACL after freeze-thaw treatment. In Group II, the glue without TGF-beta stimulation was wrapped around the frozen-thawed ACL. In Group III, the fibrin glue without fibroblasts was applied in the same manner on the frozen-thawed ACL. Histological observation found that implantation of fibroblasts after TGF-beta stimulation accelerated cellular infiltration into the ACL following fibroblast necrosis. Biomechanically, the transplantation of synovial tissue-derived autologous fibroblasts activated by TGF-beta inhibited mechanical deterioration of the ACL after the freeze-thaw treatment. The present study has shown that cell-based therapy using synovial tissue-derived fibroblasts activated by TGF-beta1 is a possible solution to mechanical deterioration of the graft after ACL reconstruction.

Tissue engineering--body parts from the Petri dish

The development of methods to regenerate human tissues and organs by tissue engineering (TE), will have a dramatic influence on many medical specialities in the future. The essence of plastic surgery is to reconstruct disrupted and damaged tissues by the use of a plethora of techniques spanning from small local skin flaps to highly advanced microsurgery and free composite grafts. However, these methods only focus on moving tissue from one part of the patient to another without actual regeneration. To be able to take the next step in development of the speciality it is of necessity to address this issue. Hence it follows naturally that plastic surgeons lead and represent the driving force of the development within the research of tissue engineering. In this paper we would like to present active research and also give an overview of areas in tissue engineering that are of special interest to the plastic surgeon.