Histomorphometric analysis of irradiated recipient vessels and transplant vessels of free flaps in patients undergoing reconstruction after ablative surgery

Risk Factors for Flap Loss: Analysis of Donor and Recipient Vessel Morphology in Patients Undergoing Microvascular Head and Neck Reconstructions

In microvascular head and neck reconstruction, various factors such as diabetes, alcohol consumption, and preoperative radiation hold a risk for flap loss. The primary objective of this study was to examine the vessel morphology of both recipient and donor vessels and to identify predictors for changes in the diameters of H.E.-stained specimens associated with flap loss in a prospective setting. Artery and vein samples (N = 191) were collected from patients (N = 100), with sampling from the recipient vessels in the neck area and the donor vessels prior to anastomosis. External vessel diameter transverse (ED), inner vessel diameter transverse (ID), thickness vessel intima (TI), thickness vessel media (TM), thickness vessel wall (TVW), and intima-media ratio (IMR) for the recipient (R) and transplant site (T) in arteries (A) and veins (V) were evaluated using H.E. staining. Flap loss (3%) was associated with increased ARED (p = 0.004) and ARID (p = 0.004). Preoperative radiotherapy led to a significant reduction in the outer diameter of the recipient vein in the neck (p = 0.018). Alcohol consumption (p = 0.05), previous thrombosis (p = 0.007), and diabetes (p = 0.002) were associated with an increase in the total thickness of venous recipient veins in the neck. Diabetes was also found to be associated with dilation of the venous media in the neck vessels (p = 0.007). The presence of cardiovascular disease (CVD) was associated with reduced intimal thickness (p = 0.016) and increased total venous vessel wall thickness (p = 0.017) at the transplant site. Revision surgeries were linked to increased internal and external diameters of the graft artery (p = 0.04 and p = 0.003, respectively), while patients with flap loss showed significantly increased artery diameters (p = 0.004). At the transplant site, alcohol influenced the enlargement of arm artery diameters (p = 0.03) and the intima-media ratio in the radial forearm flap (p = 0.013). In the anterolateral thigh, CVD significantly increased the intimal thickness and the intima-media ratio of the graft artery (p = 0.01 and p = 0.02, respectively). Patients with myocardial infarction displayed increased thickness in the A. thyroidea and artery media (p = 0.003). Facial arteries exhibited larger total vessel diameters in patients with CVD (p = 0.03), while facial arteries in patients with previous thrombosis had larger diameters and thicker media (p = 0.01). The presence of diabetes was associated with a reduced intima-media ratio (p < 0.001). Although the presence of diabetes, irradiation, and cardiovascular disease causes changes in vessel thickness in connecting vessels, these alterations did not adversely affect the overall success of the flap.

Common Carotid-to-Internal Jugular Arteriovenous Loop for Single-Stage Microsurgical Reconstruction in the Radiated Vessel-Depleted Neck

ABSTRACT

Management of head and neck defects in a radiated field can be quite challenging owing to the dearth of vasculature and significant degree of post-radiation fibrosis. In this setting, arteriovenous (AV) loop vascular grafts can bypass nonviable local vessels to provide viable and reliable inflow and outflow vessels for free tissue transfer in an otherwise hostile environment. Prior reports of the Corlett loop utilizing a cephalic vein transposition has been described however a common carotid-to-internal jugular AV loop has not been recently reported. Three patients underwent carotid artery to internal jugular vein AV loop creation to facilitate free-flap reconstruction secondary to radiation-induced vessel depletion. The specific technique described utilizes the saphenous vein as a donor and spares the cephalic vein for the possibility of flap complication. All three cases resulted in successful reconstruction, maintaining healthy tissue, vascular flow, and flap viability at all follow-up intervals. In our experience, vascular augmentation via AV loop formation provides reliable vascular inflow and outflow in the vessel-depleted neck to facilitate microvascular reconstruction. Sparing the cephalic vein yields an additional salvage mechanism in the event of venous congestion.

Surgical Techniques for Head and Neck Reconstruction in the Vessel-Depleted Neck

The vessel-depleted neck presents a unique and challenging scenario for reconstructive surgery of the head and neck. Prior surgery and radiation often result in significant scarring and damage to the neck vasculature, making identification of suitable recipient vessels for microvascular free tissue transfer exceedingly difficult. Therefore, alternative reconstructive techniques and/or vessel options must be considered to obtain a successful reconstructive outcome for a patient. In this article, we discuss our experience and approach to the management of the vessel-depleted neck, emphasizing the importance of preoperative planning and having multiple backup options prior to surgery. The various preoperative imaging modalities and available options for recipient arteries and veins are presented in detail. Additionally, we discuss modifications of select free flaps to maximize their utility in successful reconstruction. Together with thoughtful preoperative planning, these techniques can help aid the reconstructive surgeon in addressing the complex decisions associated with the vessel-depleted neck.

Altered Organelle Calcium Transport in Ovarian Physiology and Cancer

Calcium levels have a huge impact on the physiology of the female reproductive system, in particular, of the ovaries. Cytosolic calcium levels are influenced by regulatory proteins (i.e., ion channels and pumps) localized in the plasmalemma and/or in the endomembranes of membrane-bound organelles. Imbalances between plasma membrane and organelle-based mechanisms for calcium regulation in different ovarian cell subtypes are contributing to ovarian pathologies, including ovarian cancer. In this review, we focused our attention on altered calcium transport and its role as a contributor to tumor progression in ovarian cancer. The most important proteins described as contributing to ovarian cancer progression are inositol trisphosphate receptors, ryanodine receptors, transient receptor potential channels, calcium ATPases, hormone receptors, G-protein-coupled receptors, and/or mitochondrial calcium uniporters. The involvement of mitochondrial and/or endoplasmic reticulum calcium imbalance in the development of resistance to chemotherapeutic drugs in ovarian cancer is also discussed, since Ca²⁺ channels and/or pumps are nowadays regarded as potential therapeutic targets and are even correlated with prognosis.

Microsurgery in musculoskeletal oncology

Sarcomas are rare mesenchymal bone and soft tissue tumors of the musculoskeletal system. In the past, the primary treatment modality was amputation of the involved limb and the 5-year survival was very low for high-grade tumors. During the last three decades, limb salvage has become the rule rather than the exception and the use of neoadjuvant and adjuvant therapies (radiation and chemotherapy) has dramatically increased disease-free survival. Reconstruction of large bone and soft tissue defects, though, still remains a significant challenge in sarcoma patients. In particular, vascularized tissue transfer has proved extremely helpful in dealing with complex bone and soft tissue or functional defects that are frequently encountered as a result of the tumor or as a complication of surgery and adjuvant therapies. The principles, indications and results of microsurgical reconstruction differ from trauma patients and are directly related not only to the underlying disease process, but also to the local and systemic therapeutic modalities applied to the individual patient. Although plastic reconstruction in the oncological patients is not free of complications, usually these complications are manageable and do not jeopardize oncological outcome. The overall treatment strategy should be tailored to the patient's and sarcoma profile.

An expression analysis of markers of radiation-induced skin fibrosis and angiogenesis in wound healing disorders of the head and neck

BACKGROUND

Radiation-induced fibrosis (RIF) is one of the severe long-term side effects of radiation therapy (RT) with a crucial impact on the development of postoperative wound healing disorders (WHD). The grades of fibrosis vary between mild to severe depending on individual radiosensitivity. In this study, we have investigated the molecular pathways that influence RIF and have correlated data from immunohistochemistry (IHC) for von -Willebrand Factor (vWF) and from Real-Time Polymerase Chain Reaction (RT-PCR) concerning markers such as Transforming Growth Factor (TGF)-β 1, and vWF, with clinical data concerning the occurrence of WHD during follow-up.

METHODS

Expression profiles of the genes encoding TGF-β 1, vWF, and α-procollagen (PC) were analyzed, by RT-PCR, in specimens from patients with (n = 20; 25.6 %) and without (n = 58; 74.4 %) a history of previous RT to the head and neck. Moreover, IHC against vWF was performed. Clinical data on the occurrence of cervical WHDs were analyzed and correlated.

RESULTS

A statistically significant increase in the expression profiles of α-PC and TGF-β 1 was observed in previously irradiated skin samples (occurrence of RT >91 days preoperatively). vWF showed a statistically significant increase in non-irradiated tissue. Moreover, analysis of expression profiles in patients with and without WHDs during follow-up was performed. IHC showed a reduced amount of vessels and structural changes in epidermal tissue post-RT.

CONCLUSIONS

The expression of markers of fibrosis and angiogenesis was analyzed in order to gain insight into molecular pathways that account for structural changes in irradiated skin and that eventually lead to WHDs. The results are congruent with reports from the literature and are a possible starting point for further research, as anti-TGF-β 1 treatment, for example, could represent new therapeutic opportunities in the management of previously irradiated patients.

Expression of transforming growth factor beta 1-related signaling proteins in irradiated vessels

AIM

Microvascular free tissue transfer is a standard method in head and neck reconstructive surgery. However, previous radiotherapy of the operative region is associated with an increased incidence in postoperative flap-related complications and complete flap loss. As transforming growth factor beta (TGF-β) 1 and galectin-3 are well known markers in the context of fibrosis and lectin-like oxidized low-density lipoprotein 1 (LOX-1) supports vascular atherosclerosis, the aim of this study was to evaluate the expression of TGF-β1 and related markers as well as LOX-1 in irradiated vessels.

MATERIALS AND METHODS

To evaluate the expression of galectin-3, Smad 2/3, TGF-β1, and LOX-1, 20 irradiated and 20 nonirradiated arterial vessels were used for immunohistochemical staining. We semiquantitatively assessed the ratio of stained cells/total number of cells (labeling index).

RESULTS

Expression of galectin-3, Smad 2/3, and TGF-β1 was significantly increased in previously irradiated vessels compared with nonirradiated controls. Furthermore, LOX-1 was expressed significantly higher in irradiated compared with nonirradiated vessels.

CONCLUSION

Fibrosis-related proteins like galectin-3, Smad 2/3, and TGF-β1 are upregulated after radiotherapy and support histopathological changes leading to vasculopathy of the irradiated vessels. Furthermore, postoperative complications in irradiated patients can be explained by increased endothelial dysfunction caused by LOX-1 in previously irradiated patients. Consequently, not only TGF-β1 but also galectin-3 inhibitors may decrease complications after microsurgical tissue transfer.

Effect of neoadjuvant chemoradiation and postoperative radiotherapy on expression of heat shock protein 70 (HSP70) in head and neck vessels

Background

Preoperative radiotherapy and chemotherapy in patients with head and neck cancer result in changes to the vessels that are used to construct microsurgical anastomoses. The aim of the study was to investigate quantitative changes and HSP70 expression of irradiated neck recipient vessels and transplant vessels used for microsurgical anastomoses.

Methods

Of 20 patients included in this study five patients received neoadjuvant chemoradiation, another five received conventional radiotherapy and 10 patients where treated without previous radiotherapy. During surgical procedure, vessel specimens where obtained by the surgeon. Immunhistochemical staining of HSP70 was performed and quantitative measurement and evaluation of HSP70 was carried out.

Results

Conventional radiation and neoadjuvant chemoradiation revealed in a thickening of the intima layer of recipient vessels. A increased expression of HSP70 could be detected in the media layer of the recipient veins as well as in the transplant veins of patients treated with neoadjuvant chemoradiation. Radiation and chemoradiation decreased the HSP70 expression of the intima layer in recipient arteries. Conventional radiation led to a decrease of HSP70 expression in the media layer of recipient arteries.

Conclusion

Our results showed that anticancer drugs can lead to a thickening of the intima layer of transplant and recipient veins and also increase the HSP70 expression in the media layer of the recipient vessels. In contrast, conventional radiation decreased the HSP70 expression in the intima layer of arteries and the media layer of recipient arteries and veins. Comparing these results with wall thickness, it was concluded, that high levels of HSP70 may prevent the intima layer of arteries and the media layer of vein from thickening.

Reconstruction of irradiated bone segmental defects with a biomaterial associating MBCP+(R), microstructured collagen membrane and total bone marrow grafting: an experimental study in rabbits

The bone tissue engineering models used today are still a long way from any oncologic application as immediate postimplantation irradiation would decrease their osteoinductive potential. The aim of this study was to reconstruct a segmental critical size defect in a weight-bearing bone irradiated after implantation. Six white New Zealand rabbits were immediately implanted with a biomaterial associating resorbable collagen membrane EZ(R) filled and micro-macroporous biphasic calcium phosphate granules (MBCP+(R)). After a daily schedule of radiation delivery, and within 4 weeks, a total autologous bone marrow (BM) graft was injected percutaneously into the center of the implant. All the animals were sacrificed at 16 weeks. Successful osseous colonization was found to have bridged the entire length of the defects. Identical distribution of bone ingrowth and residual ceramics at the different levels of the implant suggests that the BM graft plays an osteoinductive role in the center of the defect. Periosteum-like formation was observed at the periphery, with the collagen membrane most likely playing a role. This model succeeded in bridging a large segmental defect in weight-bearing bone with immediate postimplantation fractionated radiation delivery. This has significant implications for the bone tissue engineering approach to patients with cancer-related bone defects.

Free flap transfer in cranio-maxillofacial surgery: a review of the current data

BACKGROUND

The advances of cranio-maxillofacilal surgery are considerably driven by the evolution of microsurgical techniques. At present, these methods continue to provide new therapeutic options to the field. Especially, free flap transfer has evolved to become an integral part of current treatment protocols for head and neck malignancies. It ensures uneventful wound healing even after previous radiotherapy and can often preserve form and function. For many patients, this may lead to a significant improvement in their quality of life.

OBJECTIVES

This review summarizes aspects of tumor therapy, the impact of radiation, and discusses different techniques of microvascular tissue transfer.

DISCUSSION

Specific advantages in different anatomical sites of the head and neck region are highlighted in contrast to existing alternatives. Selected cases exemplify the use of popular transplants.

SUMMARY

While planning reconstructions, it is important to consider both the functional and aesthetic aspects. The best individual outcome is based on a thoughtful match of available methods to a given defect and the patient's condition.

Influence of Previous Radiotherapy on Free Tissue Transfer in the Head and Neck Region: Evaluation of 455 Cases

OBJECTIVE/HYPOTHESIS

The aim of this retrospective cohort study was to investigate the effect of prior radiotherapy (XRT) on the outcome of microvascular free tissue transfer in the head and neck region.

METHODS

Four hundred fifty-five patients, subdivided into three groups, were analyzed. Groups I (no previous XRT, n=110), II (previous radiochemotherapy with 50 Gy focus dosage in the primary treatment regime for oral cancer, n=322), and III (secondary reconstruction after XRT-induced complications, n=23) were compared regarding flap success rate, postoperative complications, postoperative mortality, duration of intensive care (DOIC), and hospitalization (DOH).

RESULTS

Flap success did not differ significantly across groups (I: 95.5%, II: 93.2%, III: 91.3%. Risk of postoperative complications was significantly lower for group I (12.7%) compared with groups II (23.9%) and III (39.1%). DOIC and DOH were significantly shorter for patients in group I than for those in groups II and III.

CONCLUSIONS

XRT before free tissue transfer does not significantly increase flap loss or postoperative mortality but does increase postoperative complications and length of hospitalization.

Adequate Venous Drainage

Reconstruction of the cervical esophagus with free jejunum can yield excellent functional results. Flap survival alone, however, does not guarantee satisfying functional outcomes. Critical factors that determine the level of function of the flap include the duration of ischemia and degree of venous congestion. An attempt is made in this study to evaluate the degree that these 2 factors influence outcome and to establish safe methods for avoiding suboptimal functional results. Out of 71 patients that underwent free jejunal transfer for the reconstruction of the cervical esophagus between January 1995 and December 1999, 60 patients with available chart records were included into this study. A retrospective chart review was performed on all 60 patients to evaluate the degree of venous congestion in those patients and the choice of recipient veins and method of anastomosis of those veins (end-to-end versus end-to-side). A more detailed review was performed on the 8 patients that underwent reexploration and detailed history, operative method, ischemia time, choice of recipient vessels, technique of anastomosis, immediate postoperative course, and outcome were determined. Following exploration of the flaps, all flaps survived. Two developed partial necrosis. When smaller veins were used as recipient vessels, the chances of venous congestion were found to be higher than when larger recipient veins were used (chi2 analysis, P <0.02). Method of anastomosis and previous radiotherapy were both found to be significant determinants of venous congestion (chi2 P <0.05 for both). Venous problems accounted for 87.5% (7/8) of all reexplorations. In 75% (6/8) of the reexplored patients, pharyngocutaneous fistula formation or stricture formation was noted.The degree of venous congestion and previous radiotherapy are factors that influence the functional outcome of free jejunal flaps. Proper selection of the recipient veins is a critical factor in providing adequate venous outflow and minimizing venous congestion. End-to-side anastomosis to large vessels is a more reliable method that was found to have a significant influence on minimizing venous congestion and is a useful method for the salvage of venous congested flaps.

Micro-lightguide spectrophotometry as an intraoral monitoring method in free vascular soft tissue flaps

PURPOSE

The aim of this prospective study was to measure the hemoglobin oxygen saturation (HbO(2)%) and relative Hb concentration of free vascular soft tissue flaps using micro-lightguide spectrophotometry. The objective was to measure the normal range and topographic differences in HbO(2)% and rel. Hb conc. in tissue transfers before establishing this as a clinical method for monitoring perfusion and vitality.

PATIENTS AND METHODS

In 39 patients who had received free vascular soft tissue flaps (34 radial forearm flaps; 8 latissimus flaps) to cover defects after tumor surgery, the capillary HbO(2)% in transferred tissue was measured spectrophotometrically preoperatively at the donor site and postoperatively up to the third postoperative day. On average about 500 hemoglobin spectra (200 to 800 spectra) were measured over each 24-hour period. Additionally, the relative Hb concentration was determined for the individual measuring times. The measurements were carried out topographically on the flap base, flap center, and flap periphery.

RESULTS

The preoperative HbO(2) values at the donor site of free soft tissue flaps were between 20% and 40% in all topographic regions. In the case of clinically successful flaps, a normal distribution of the HbO(2) values of 20% to 80% was obtained in the immediate postoperative period, and from the second day on, a normal distribution of 45% to 60%. In the case of 2 flaps with partial necrosis, HbO(2) values of less than 10% to 15% were measured from the second postoperative day on. The relative Hb concentration had no influence on the amount of HbO(2)% measured in the transferred capillaries. In the postoperative phase, here was no topographic difference between the individual flap regions.

CONCLUSIONS

As a noninvasive method, micro-lightguide spectrophotometry permits quantitative determination of HbO(2)% and relative Hb concentration over the entire surface of soft tissue flaps. In the case of partially unsuccessful flaps, HbO(2) values of less than 10% to 15% were measured beforehand, thus indicating that these HbO(2) values are not sufficient to support the vitality of the free tissue transfer. When combined with clinical observation, application can be recommended for the vitality measurement of free soft tissue flaps and permits more information to be obtained on topographic capillary perfusion conditions.

Histopathologic damage to vessels in head and neck microsurgery

PURPOSE

This study assessed the incidence of pre-existing damage in recipient arteries excised before the vessels were used for microvascular anastomoses between 1988 and 1999.

PATIENTS AND METHODS

Recipient arteries of the head and neck region from 100 patients who had undergone ablative surgery requiring microvascular tissue reconstruction were examined histologically. Past illnesses believed to be risk factors included hypertension, myocardial disease, and diabetes. Blood vessels chosen for microsurgical anastomoses were examined using histological staining, scanning electron microscopy, and immunofluorescence.

RESULTS

Of the patients undergoing microvascular surgery, 51% showed histologic vessel abnormalities. Marked thickening of the blood vessel wall and severe exfoliation of the endothelial cells were observed in most arteries. Thickening of the intima was evaluated using scanning electron microscopy (Friedman's method; Microvasc Res 3:416, 1971). Values higher than twice the ratio of wall thickness-to-lumen diameter were observed in 9 recipient arteries. Six graft failures were correlated with both technical errors and pre-existing vessel lesions.

CONCLUSIONS

This study revealed that most patients undergoing microsurgery in the head and neck region had pre-existing damage to vessels that hindered anastomoses. Pre-existing changes in the recipient arteries may cause technical difficulties and must be regarded as additional factors contributing to graft failure.

Influence of radiation therapy on reconstructive flaps after radical resection of head and neck cancer

This study was undertaken to evaluate the influence of radiotherapy (RT) on reconstructive flaps after radical excision of head and neck cancer. Eighty-eight reconstructive flaps were used in 82 patients who received RT either before (PREOP group, 14 flaps) or after (POSTOP group, 74 flaps) surgery. The success and healing rates of the flaps were evaluated. The success and healing rates were lower in the PREOP group than in the POSTOP group (86% vs 99%, P=0.026 for success; and 64% vs 95%, P=0.003 for healing). The rate of acute radiation reaction in flaps in the POSTOP group was significantly lower than in the surrounding normal tissues (35% vs 84%, P=0.003). Late side effects of RT were rare. Our results suggest good radiation tolerance of reconstructive flaps after radical tumour excision in the head and neck region. Success and healing of the flap are likely to be better if RT is administered after surgery.

Vascularization of the area between free grafts and irradiated graft beds in the neck in rats

Inflammatory lesions of the vascular endothelium after preoperative radiotherapy often cause healing-delayed healing of free flaps in the irradiated graft bed. We investigated changes in neovascularization in the transition area between grafted tissues and irradiated tissues of the graft bed. We irradiated the neck(30 and 50 Gy total dose) in 102 Wistar rats and then grafted a free myocutaneous gracilis flap to the irradiated region of the neck 4 weeks later. We examined histologically the tissues of the graft, the transition area between the graft and the irradiated graft bed, and the graft bed. In contrast to control rats, the tissues in the irradiated animals showed a qualitatively reduced and a more irregular capillary distribution, with substantial fibrosis in the irradiated graft bed. We also found significant differences in vascularization and mean capillary lumen in the transitional zone between graft and graft bed in the irradiated rats compared with controls (P = 0.004 and P < 0.001, respectively). Both number and diameter of capillaries were reduced in the irradiated graft bed tissue. The graft failed to improve vascularization in the transitional zone between graft and irradiated tissue, so we conclude that it is the vascularization status of the bed tissue rather than that of the transplant tissue that is the limiting factor for graft healing.

Vascularization in the transition area between free grafted soft tissues and pre-irradiated graft bed tissues following preoperative radiotherapy in the head and neck region

BACKGROUND

The healing of free vascular grafts in a pre-irradiated graft bed is characterized by an increased risk of wound healing disorders. For that reason, the aim of this study was to examine quantitative vascularization pattern between free vascular grafts and the pre-irradiated graft bed as a function of the preoperative irradiation dose.

METHODS

A total of 217 free microvascular hard and soft tissue grafts were used within 199 patients in the head and neck region to cover defects after ablative tumor surgery. Seventy-six patients (group 1) had no prior radiation (RT), 50 patients (group 2) were treated with preoperative radiochemotherapy using 40 to 50 Gy and 5-FU/cisplatin, and 73 patients (group 3) had prior RT (60-70 Gy) between 1 and 7 years before surgery. After healing of the grafts, samples were taken from 42 patients from the graft, the irradiated graft bed, and the transition area between graft and irradiated graft bed. Samples were analyzed as follows: capillary sprouting, structural changes, and distribution patterns were analyzed by immunohistochemical staining (CD34 labeling of capillary endothelium). Three histological sections (2-4 microm) per sample were examined histomorphometrically (ratio capillary area/total area, capillary lumen, and the number of capillaries) by (National Institute of Health) NIH-image-digitized measurements. A statistical analysis was performed using the Kruskal-Wallis and Mann-Whitney test (two-tailed p <.05).

RESULTS

The success rate of vascular grafts in group 1 (0 Gy) was 94%, in group 2 (40-50 Gy/5-FU/cisplatin) 90%, in group 3 (60-70 Gy) 84%. In contrast to groups 1 and 2, group 3 showed qualitatively reduced and more irregular capillary distribution with more marked pericapillary fibrosis in the irradiated tissue. Quantitatively, the ratio capillary area/total area, as a marker of improved capillarization, was significantly reduced in group 3 (median 0.01; IQR 0.02) compared with group 1 (median 0.53; IQR 0.32) and group 2 (median 0.44; IQR 1.40) (p <.001).

CONCLUSION

After preoperative RT, vascularization of the graft bed decreased continuously as a function of the total dose and time after RT. The results strongly advocate the use of a primary reconstruction after a time interval between 4 and 6 weeks following preoperative RT and suggest the use of a total radiation dose of 40 to 50 Gy.

Transforming growth factor beta1 and beta2 (TGFbeta2 / TGFbeta2) profile changes in previously irradiated free flap beds

BACKGROUND

Following preoperative radiotherapy prior to ablative surgery of squamous epithelial carcinomas of the head and neck region, inflammatory changes and the expression of cytokines involved in wound healing could be observed. These processes lead to a delayed healing of free flaps in the graft bed. The aim of the present experimental study was to analyze the expression profiles of transforming growth factor (activated TGFbeta(1), TGFbeta(2)) and latency-associated peptide (LAP) in the irradiated graft beds and the transition area between grafts and irradiated graft beds.

METHODS

In Wistar rats (male, weight 300-500 g) undergoing preoperative irradiation of the neck region with 30 Gy (30 animals) and non-irradiated rats (42 animals), a free myocutaneous gracilis flap taken from the groin was transplanted to the irradiated region of the neck. The interval between irradiation and transplantation was 4 weeks. In each group on postoperative days 3, 7, 14, and 28, cytoplasmatic expression of activated TGFbeta(1), LAP, and TGFbeta(2) was analyzed by immunohistochemistry to determine labeling indices (positive stained cells/total cells).

RESULTS

The success rate in graft beds irradiated with 30 Gy was 76% and in non-irradiated graft beds was 86% (p =.02). In the graft beds irradiated with 30 Gy, there was an increased expression of activated TGFbeta(1) (range, 19.0-33.0), LAP (14.0-21.0), and TGFbeta(2) (3.0-19.5) together with obvious fibrosis. The expression was located in perivascular fibroblasts and endothelial cells. In contrast, a lower expression of activated TGFbeta(1) (11.0-21.0), LAP (1.0-8.0), and TGFbeta(2) (0.0-0.9) (p =.006) was observed in non-irradiated graft beds. In the transition area between graft and irradiated graft bed, high expression of activated TGFbeta(1) (37.0), LAP (19.0), and TGFbeta(2) (16.7-33.4) was observed on the 3rd postoperative day in contrast to the transition area in non-irradiated graft beds (activated TGFbeta(1) 26.0, LAP 7.0, and TGFbeta(2) 0.l).

CONCLUSION

The radiation induced, increased de novo synthesis of LAP, activation of TGFbeta(1), and increased expression of TGFbeta(2) may represent at least one mechanism for the increased fibrosis and wound healing disorders seen in irradiated tissues and in the transition area to graft tissue. The expression of TGFbeta(1,) LAP, and TGFbeta(2) might possess prognostic value with regard to wound healing and fibrosis in previously irradiated graft beds.

Experimental model for transplantation of a modified free myocutaneous gracilis flap to an irradiated neck region in rats

In 102 Wistar rats (male, weight 300-500 g), a modified free myocutaneous gracilis flap was obtained from the groin and transplanted to the neck. To create a pre-irradiated transplant bed, a local area of the neck was irradiated preoperatively with 30 Gy (fractionation: 3 x 10 Gy) in 30 animals, and with 50 Gy (fractionation: 5 x 10 Gy) in a further 30 animals. The interval between preoperative irradiation and transplantation was 4 weeks. Forty-two animals received no such preoperative radiation. The evaluation of healing and the success of the transplanted flap was based on a clinical assessment, carried out on postoperative days 1 7. Testing for significant differences was done nonparametrically using the Kruskal-Wallis test. The survival rate in the nonirradiated animals was 86%. In contrast, the healing of the free flaps in the pre-irradiated transplant bed was significantly lower (P=0.003) 76%, after irradiation with 30 Gy and 50% after 50 Gy. The significant difference (P=0.020) in survival rates after irradiation with 30 and 50 Gy was evidence for the dependence of successful healing on the preoperative radiation dose. Transplantation of the free myocutaneous gracilis flap to a previously irradiated transplant bed in the region of the neck is a suitable model for investigating the healing of free transplants to irradiated tissue. The success rate observed in non-irradiated transplant beds is comparable to that seen with other flap models in rats.