Tissue Regeneration and Organ Repair: Science or Science Fiction?

Elena A. Armandola, PhD

Disclosures
In This Article

Skin Substitutes and Bone/Cartilage Replacements

One area in which tissue engineering is already being applied to the clinic with some success is that of skin substitutes and bone/cartilage replacements.[13,14] Dr. E. Tanczos,[15] from BioTissue Technology, Freiburg, Germany, illustrated a few of the applications for which new skin substitutes are already being made available for human use.

Skin replacements are based on autologous keratinocytes cultured in a fibrin glue. Indications for their use may include chronic wounds (eg, ulcers) or burns. As reported by Dr. Tanczos, the clinical evaluation of 84 patients with chronic ulcers (eg, diabetic or venous ulcers) resistant to therapy for more than 1 year showed that 46% of the patients experienced a healing of their wounds, 41% showed an improvement, and 13% did not have any improvement. A multicentric randomized study is now under way in which 240 individuals are enrolled (120 patients and 120 controls) to further evaluate the efficacy of this approach.

Another application of skin substitutes has been found in the management of vitiligo. This disease, although it has only a 1% to 2% incidence, may have a great influence on the patients' well being owing to the negative effects that the vitiligo lesions have on the psychological sphere of the patients. Autologous melanocytes cultured in fibrin glue have been used to correct discolored vitiliginous areas with good success -- up to 80% of the discolored area could be treated with 1 application. Progressive repigmentation was also observed in another study[16] 90 days after transplantation of noncultured keratinocytes and melanocytes or cultured melanocytes.

Mucogingival cells have also been successfully cultured in a collagen matrix and used to treat chronic mucosal damage linked to dental pathologies. In the odontoiatric field, it has also been possible to culture bone tissue for replacement of oral bone material, that might allow to bypass the morbidity and complications associated with autologous bone grafts. A small periosteal biopsy allows isolation of osteoblasts that can then be cultured and used for repairing the oral bone damage.

An important aspect of regenerating bone tissue for odontoiatric applications is the mechanical behavior of the newly generated bone tissue. It is clear that biomechanical stability is an essential feature for a tissue that should be able to carry a great deal of strain such as that given, for example, by dental implants. For this reason, the choice of the structure on which bone regeneration is carried out is essential; it should be highly biocompatible, support an even cell distribution, and not interfere with cell differentiation. According to the results presented by Dr. Tanczos, more than 80 patients have been successfully treated, so far.

Cartilage has also been successfully cultured in a 3-dimensional (3-D) dissolvable matrix, and studies on cartilage repair in animal models of arthrosis suggest that this approach may be applicable to humans.[17,18] Up to now, 70 patients with cartilage damage were treated resulting in defect filling, no cell loss, and improvement of the symptoms. The transplanted tissue needed no condral suture as it spontaneously joined to the endogenous tissue. The in vivo regenerated cartilage achieved pressure resistance and stiffness values comparable to those of native human cartilage. Further investigations will help in determining which patients might benefit from this treatment and the extent of disease amelioration.

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