Expression of TNF-related apoptosis-inducing ligand (TRAIL) in keratinocytes mediates apoptotic cell death in allogenic T cells.

The objective of the present study was to evaluate the aptitude of TRAIL gene expression for inducing apoptosis in co-cultivated T-cells. This should allow preparing a strategy for the development of a durable, allogenic skin substitute based on the induction of an immune-privileged transplant. In order to counteract the significant potential of rejection in transplanted allogenic keratinocytes, we created a murine keratinocyte cell line which expressed TRAIL through stable gene transfer. The exogenic protein was localized on the cellular surface and was not found in soluble condition as sTRAIL. Contact to TRAIL expressing cells in co-culture induced cell death in sensitive Jurkat-cells, which was further intensified by lymphocyte activation. This cytotoxic effect is due to the induction of apoptosis. We therefore assume that the de-novo expression of TRAIL in keratinocytes can trigger apoptosis in activated lymphocytes and thus prevent the rejection of keratinocytes in allogenic, immune-privileged transplants.

Posttraumatic lipoma: fact or fiction?

BACKGROUND: Both trauma and lipomas are a common occurrence in surgical practice. Lipomas are usually benign adipose tumors with as-yet unexplained pathogenesis and etiology. A link between soft tissue trauma and the formation of lipomas has been described, with the latter being named posttraumatic lipomas. METHODS: Twenty-three cases of posttraumatic lipomas in 19 patients treated at our institution between August 2001 and January 2005 were reviewed with regard to medical history, magnetic resonance imaging findings, intraoperative findings, clinical chemistry, and histology. RESULTS: The mean age of the patients was 50.0 years (+/-15.5). The average time between soft tissue trauma and lipoma formation was 2.6 years (range, 0.5-6.0 years). Sixteen of the 19 patients reported extensive and slowly resolving hematoma formation after the traumatic event. Nine of 23 lipomas were found on the upper extremities, 3 on the lower extremities, 9 on the trunk, and 2 on the face. All tumors were located epifascially. Twenty-two lipomas were removed by simple excision and, in one case, aspiration lipectomy was performed. Pathology demonstrated capsulated and noncapsulated benign adipose tumors in 23 cases. The average body mass index, amounted to 30 kg/m(2) (+/-7.6 kg/m(2)). Seven patients without known bleeding disorders presented with an elevated partial thromboplastin time. CONCLUSIONS: The pathogenetic link between soft tissue trauma and the formation of posttraumatic lipomas is still controversially discussed. There are 2 potential explanations to correlate soft tissue trauma and adipose tissue tumor growth. The first is the formation of so-called posttraumatic pseudolipomas by prolapsing adipose tissue through fascia resulting from direct impact. A second possibility points toward lipoma formation as a result of preadipocyte differentiation and proliferation mediated by cytokine release following soft tissue trauma and hematoma formation.

Outcome of simultaneous and staged microvascular free tissue transfer connected to arteriovenous loops in areas lacking recipient vessels.

BACKGROUND: Arteriovenous loops are an indispensable tool in free flap surgery when appropriate recipient vessels are missing. In this study, the authors analyzed whether the outcome differs when flaps were transferred simultaneously or subsequently after construction of arteriovenous loops. METHODS: Twenty-seven patients requiring free tissue transfer received arteriovenous loops by pedicled or free vein grafts because of inadequate local recipient vessels. In head and neck reconstruction, pedicled brachiocephalic or free saphenous vein grafts were anastomosed to cervical or axillary vessels. Pedicled major saphenous vein grafts were used in the pelvic area whereas, in lower leg and foot reconstruction, free saphenous or brachiocephalic veins were used. Flaps were transferred simultaneously (n = 10) or 4 to 17 days later (n = 17). RESULTS: Thrombosis required revision in staged transfer (n = 3 patients) or in simultaneous flap transfer (n = 2). No free flap was lost. Fisher's exact test did not indicate a significant difference between a simultaneous or staged flap transfer. CONCLUSIONS: Temporary arteriovenous loops provide adequate recipient vessels and flow to supply microvascular free flap tissue transfer in areas lacking recipient vessels and in which no other reconstructive options exists. No statistical differences in complications and overall outcome were found between immediate or secondary free tissue transfer. Meticulous monitoring of microvascular perfusion, however, is mandatory in both approaches and early intervention is necessary to ensure successful tissue transfer.

Inhibition of apoptosis by expression of antiapoptotic proteins in recombinant human keratinocytes.

The Fas ligand/Fas interaction plays an important role in the regulation of immune responses. Allografted cells undergo Fas-mediated apoptosis induced by CD8+ T cells. Our objective was to prevent human keratinocytes from immunologically induced apoptosis. We focused on three proteins with inhibitory function on Fas-mediated apoptosis. Human keratinocytes were transfected with either Flip, Faim, or Lifeguard (LFG). The treatment proved to be practicable and efficient. The recombinant keratinocytes with expression of our target proteins were cocultured with CD8+ T cells and the apoptotic activity was then evaluated. Activation of caspase-8 was detectable in control but not in the recombinant cells. Quantitative analysis revealed significant induction of T-cell-induced apoptosis in nontransfected keratinocytes (p = 0.04, n = 12) but not in Flip (p = 0.66), Faim (p = 0.42), or LFG (p = 0.44) expressing cells. Our results suggest that heterotopic expression of antiapoptotic proteins can induce the resistance of keratinocytes to a major mechanism of rejection.

Inhibition of Apoptosis by Expression of Antiapoptotic Proteins in Recombinant Human Keratinocytes.

The Fas ligand/Fas interaction plays an important role in the regulation of immune responses. Allografted cells undergo Fas-mediated apoptosis induced by CD8+ T cells. Our objective was to prevent human keratinocytes from immunologically induced apoptosis. We focused on three proteins with inhibitory function on Fas-mediated apoptosis. Human keratinocytes were transfected with either Flip, Faim, or Lifeguard (LFG). The treatment proved to be practicable and efficient. The recombinant keratinocytes with expression of our target proteins were cocultured with CD8+ T cells and the apoptotic activity was then evaluated. Activation of caspase-8 was detectable in control but not in the recombinant cells. Quantitative analysis revealed significant induction of T-cell-induced apoptosis in nontransfected keratinocytes (p = 0.04, n = 12) but not in Flip (p = 0.66), Faim (p = 0.42), or LFG (p = 0.44) expressing cells. Our results suggest that heterotopic expression of antiapoptotic proteins can induce the resistance of keratinocytes to a major mechanism of rejection.

Use of spider silk fibres as an innovative material in a biocompatible artificial nerve conduit.

Defects of peripheral nerves still represent a challenge for surgical nerve reconstruction. Recent studies concentrated on replacement by artificial nerve conduits from different synthetic or biological materials. In our study, we describe for the first time the use of spider silk fibres as a new material in nerve tissue engineering. Schwann cells (SC) were cultivated on spider silk fibres. Cells adhered quickly on the fibres compared to polydioxanone monofilaments (PDS). SC survival and proliferation was normal in Live/Dead assays. The silk fibres were ensheathed completely with cells. We developed composite nerve grafts of acellularized veins, spider silk fibres and SC diluted in matrigel. These artificial nerve grafts could be cultivated in vitro for one week. Histological analysis showed that the cells were vital and formed distinct columns along the silk fibres. In conclusion, our results show that artificial nerve grafts can be constructed successfully from spider silk, acellularized veins and SC mixed with matrigel.