The Evolving Clinical Presentation of Acute Rejection in Facial Transplantation

Continuous oxygen monitoring to enhance ex-vivo organ machine perfusion and reconstructive surgery

Continuous oxygenation monitoring of machine-perfused organs or transposed autologous tissue is not currently implemented in clinical practice. Oxygenation is a critical parameter that could be used to verify tissue viability and guide corrective interventions, such as perfusion machine parameters or surgical revision. This work presents an innovative technology based on oxygen-sensitive, phosphorescent metalloporphyrin allowing continuous and non-invasive oxygen monitoring of ex-vivo perfused vascularized fasciocutaneous flaps. The method comprises a small, low-energy optical transcutaneous oxygen sensor applied on the flap's skin paddle as well as oxygen sensing devices placed into the tubing. An intermittent perfusion setting was designed to study the response time and accuracy of this technology over a total of 54 perfusion cycles. We further evaluated correlation between the continuous oxygen measurements and gold-standard perfusion viability metrics such as vascular resistance, with good agreement suggesting potential to monitor graft viability at high frequency, opening the possibility to employ feedback control algorithms in the future. This proof-of-concept study opens a range of research and clinical applications in reconstructive surgery and transplantation at a time when perfusion machines undergo rapid clinical adoption with potential to improve outcomes across a variety of surgical procedures and dramatically increase access to transplant medicine.

Immunosuppressive strategies in face and hand transplantation: a comprehensive systematic review of current therapy regimens and outcomes

Background

Recipients of Vascularized Composite Allotransplants require effective immunosuppressive therapy to prevent graft rejection. This systematic review summarizes the current body of literature on immunosuppressive regimens used in face and hand transplants while summarizing their outcome in terms of rejection, renal failure, and infections.

Methods

A systematic search of electronic databases was conducted to identify relevant studies from 1998 until July 1st, 2023. We included all studies that discussed immunosuppressive strategies in face and hand transplant recipients according to PRISMA.

Results

The standard triple maintenance therapy was mostly adjusted due to nephrotoxicity or high incidence of rejection. The most common alternative treatments utilized were sirolimus (25/91; 27.5%) or everolimus (9/91; 9.9%) following hand- and photophoresis (7/45; 15.6%), sirolimus (5/45; 11.1%) or belatacept (1/45; 2.2%) following face transplantation. Episodes of rejection were reported in 60 (65.9%) of hand- and 33 (73%) of face transplant patients respectively. Graft loss of 12 (13.2%) hand and 4 (8.9%) face transplants was reported. Clinical CMV infection was observed in 6 (6.6%) hand and 7 (15.5%) face transplant recipients.

Conclusions

Based on the herein presented data, facial grafts exhibited a heightened incidence of rejection episodes and CMV infections. Facial mucosa adds complexity to the immunological graft composition highlighting the need of individualized immunosuppressive regimens and further research.

International consensus recommendations on face transplantation: A 2-step Delphi study

Face transplantation is a viable reconstructive approach for severe craniofacial defects. Despite the evolution witnessed in the field, ethical aspects, clinical and psychosocial implications, public perception, and economic sustainability remain the subject of debate and unanswered questions. Furthermore, poor data reporting and sharing, the absence of standardized metrics for outcome evaluation, and the lack of consensus definitions of success and failure have hampered the development of a "transplantation culture" on a global scale. We completed a 2-round online modified Delphi process with 35 international face transplant stakeholders, including surgeons, clinicians, psychologists, psychiatrists, ethicists, policymakers, and researchers, with a representation of 10 of the 19 face transplant teams that had already performed the procedure and 73% of face transplants. Themes addressed included patient assessment and selection, indications, social support networks, clinical framework, surgical considerations, data on patient progress and outcomes, definitions of success and failure, public image and perception, and financial sustainability. The presented recommendations are the product of a shared commitment of face transplant teams to foster the development of face transplantation and are aimed at providing a gold standard of practice and policy.

Minimally and Non-invasive Approaches to Rejection Identification in Vascularized Composite Allotransplantation

OBJECTIVE

Rejection is common and pernicious following Vascularized Composite Allotransplantation (VCA). Current monitoring and diagnostic modalities include the clinical exam which is subjective and biopsy with dermatohistopathologic Banff grading, which is subjective and invasive. We reviewed literature exploring non- and minimally invasive modalities for diagnosing and monitoring rejection (NIMMs) in VCA.

METHODS

PubMed, Cochrane, and Embase databases were queried, 3125 unique articles were reviewed, yielding 26 included studies exploring 17 distinct NIMMs. Broadly, NIMMs involved Imaging, Liquid Biomarkers, Epidermal Sampling, Clinical Grading Scales, and Introduction of Additional Donor Tissue.

RESULTS

Serum biomarkers including MMP3 and donor-derived microparticles rose with rejection onset. Epidermal sampling non-invasively enabled measurement of cytokine & gene expression profiles implicated in rejection. Both hold promise for monitoring. Clinical grading scales were useful diagnostically as was reflection confocal microscopy. Introducing additional donor tissue showed promise for preemptively identifying rejection but requires additional allograft tissue burden for the recipient.

CONCLUSION

NIMMs have the potential to dramatically improve monitoring and diagnosis in VCA. Many modalities show promise however, additional research is needed and a multimodal algorithmic approach should be explored.

Methods of ex vivo analysis of tissue status in vascularized composite allografts

Vascularized composite allotransplantation can improve quality of life and restore functionality. However, the complex tissue composition of vascularized composite allografts (VCAs) presents unique clinical challenges that increase the likelihood of transplant rejection. Under prolonged static cold storage, highly damage-susceptible tissues such as muscle and nerve undergo irreversible degradation that may render allografts non-functional. Skin-containing VCA elicits an immunogenic response that increases the risk of recipient allograft rejection. The development of quantitative metrics to evaluate VCAs prior to and following transplantation are key to mitigating allograft rejection. Correspondingly, a broad range of bioanalytical methods have emerged to assess the progression of VCA rejection and characterize transplantation outcomes. To consolidate the current range of relevant technologies and expand on potential for development, methods to evaluate ex vivo VCA status are herein reviewed and comparatively assessed. The use of implantable physiological status monitoring biochips, non-invasive bioimpedance monitoring to assess edema, and deep learning algorithms to fuse disparate inputs to stratify VCAs are identified.

Real-Time Monitoring Using Multiplexed Multi-Electrode Bioelectrical Impedance Spectroscopy for the Stratification of Vascularized Composite Allografts: A Perspective on Predictive Analytics

Vascularized composite allotransplantation addresses injuries to complex anatomical structures such as the face, hand, and abdominal wall. Prolonged static cold storage of vascularized composite allografts (VCA) incurs damage and imposes transportation limits to their viability and availability. Tissue ischemia, the major clinical indication, is strongly correlated with negative transplantation outcomes. Machine perfusion and normothermia can extend preservation times. This perspective introduces multiplexed multi-electrode bioimpedance spectroscopy (MMBIS), an established bioanalytical method to quantify the interaction of the electrical current with tissue components, capable of measuring tissue edema, as a quantitative, noninvasive, real-time, continuous monitoring technique to provide crucially needed assessment of graft preservation efficacy and viability. MMBIS must be developed, and appropriate models explored to address the highly complex multi-tissue structures and time-temperature changes of VCA. Combined with artificial intelligence (AI), MMBIS can serve to stratify allografts for improvement in transplantation outcomes.

The Effect of Narrow-Band Ultraviolet B Irradiation on the Vascularized Composite Allotransplantation Rat Model

INTRODUCTION

Vascularized composite allotransplantation (VCA) allows functional and esthetic reconstruction for patients with complex anatomical defects. However, acute and chronic graft rejections are significant obstacles to VCA. Ultraviolet light is an oncogenic environmental hazard. However, ultraviolet B (UVB) has an immunomodulation effect. Therefore, this study aims to elucidate the impact of UVB irradiation on the VCA rat model.

METHODS

The rat vascularized bone marrow allotransplantation model was used. A vascularized bone marrow from a Brown Norway rat (RT1Ac) was transplanted into a Lewis rat (RT1Ab). The allograft and surrounding abdominal skin were exposed to narrow-band ultraviolet B (NB-UVB) (311 nm) radiation with an energy of 1350 mJ/cm2 3 times a week until the end of the study period. There were 5 study groups: syngeneic transplantation (group 1), allogeneic transplantation (group 2), allogenic transplantation-NB-UVB (group 3), allogenic transplantation-antilymphocyte serum (ALS)-tacrolimus (group 4), and allogenic transplantation-antilymphocyte serum-tacrolimus-NB-UVB (group 5).

RESULTS

Group 5 had decreased graft survival compared with group 4. In the donor cell chimerism analysis, donor cell chimerism decreased significantly after UVB irradiation and was unresponsive to the administered immunosuppressants. After UVB irradiation, the CD8 T-cell ratio was increased, and the regulatory T-cell ratio was decreased.

CONCLUSIONS

The preliminary data showed that NB-UVB irradiation of the VCA rat model may decrease graft survival. However, further studies are needed to elucidate the possible mechanisms of this phenomenon.

Software-based Detection of Acute Rejection Changes in Face Transplant

BACKGROUND

 An objective, non-invasive method for redness detection during acute allograft rejection in face transplantation (FT) is lacking.

METHODS

 A retrospective cohort study was performed with 688 images of 7 patients with face transplant (range, 1 to 108 months post-transplant). Healthy controls were matched to donor age, sex, and had no prior facial procedures. Rejection state was confirmed via tissue biopsy. An image-analysis software developed alongside VicarVision (Amsterdam, Netherlands) was used to produce R, a measure of differences between detectable color and absolute red. R is inversely proportional to redness, where lower R values correspond to increased redness. Linear mixed models were used to study fixed effect of rejection state on R values. Estimated marginal means of fitted models were calculated for pairwise comparisons.

RESULTS

 Of 688 images, 175, 170, 202, and 141 images were attributable to Banff Grade 0,1,2, and 3, respectively. Estimated change in R value of facial allografts decreased with increasing Banff Grade (p = 0.0001). The mean R value of clinical rejection (Banff Grade ⅔) (16.67, 95% Confidence Interval [CI] 14.79-18.58) was lower (p = 0.005) than non-rejection (Banff Grade 0/1) (19.38, 95%CI 17.43-21.33). Both clinical and non-rejection mean R values were lower (p = 0.0001) than healthy controls (24.12, 95%CI 20.96-27.28).

CONCLUSION

 This proof-of-concept study demonstrates that software-based analysis can detect and monitor acute rejection changes in FT. Future studies should expand on this tool's potential application in telehealth and as a screening tool for allograft rejection.

Face transplantation: A longitudinal histological study focusing on chronic active and mucosal rejection in a series with long-term follow-up

The 2007 Banff working classification of skin-containing Tissue Allograft Pathology addressed only acute T cell-mediated rejection in skin. We report the longitudinal long-term histological follow-up of six face transplant recipients, focusing on chronic and mucosal rejection. We identified three patterns suggestive of chronic rejection (lichen planus-like, vitiligo-like and scleroderma-like). Four patients presented lichen planus-like and vitiligo-like chronic rejection at 52 ± 17 months posttransplant with severe concomitant acute T cell-mediated rejection. After lichen planus-like rejection, two patients developed scleroderma-like alterations. Graft vasculopathy with C4d deposits and de novo DSA led to subsequent graft loss in one patient. Chronic active rejection was frequent and similar patterns were noted in mucosae. Concordance between 124 paired skin and mucosal biopsies acute rejection grades was low (κ = 0.2, p = .005) but most grade 0/I mucosal rejections were associated with grade 0/I skin rejections. We defined discordant (grade≥II mucosal rejection and grade 0/I skin rejection) (n = 55 [70%]) and concordant (grade≥II rejection in both biopsies) groups. Mucosal biopsies of the discordant group displayed lower intra-epithelial GranzymeB/FoxP3 ratios suggesting a less aggressive phenotype (p = .08). The grading system for acute rejection in mucosa may require phenotyping. Whether discordant infiltrates reflect a latent allo-immune reaction leading to chronic rejection remains an open question.

Speech Characteristics and Oromyofunctional Outcomes in Two Bimaxillary Face Transplantation Patients in Helsinki

OBJECTIVES/HYPOTHESIS

Facial functional restoration is one of the main goals in face transplantation. We report the oromyofacial function outcomes of two bimaxillary face transplantation (FT) patients in Helsinki.

STUDY DESIGN

Outcome Study.

METHODS

Two male patients, aged 34 and 59, had severe functional facial disabilities following self-inflicted gunshot injuries sustained to their mid and lower faces several years earlier. Both underwent tooth-bearing maxillomandibular face transplantation in 2016 and 2018. We collected data regarding speech, swallowing, sensory recovery, motor recovery, and olfaction prior to transplantation. Patient charts were reviewed from the follow-up period of 4 and 2 years, respectively.

RESULTS

Speech intelligibility, acceptability, and articulation continued to improve during follow-up for both patients. Voice quality and resonance were mainly normal at last follow-up. Swallowing improved once lip occlusion was regained, with only minor aspiration evident on videofluorography. Both patients had significant improvement in facial mimic muscle function after FT. The first patient who only had buccal sensory nerves connected has only recovered protective facial sensation, whereas our second patient with buccal, infraorbital, and alveolar nerves connected has almost complete facial two-point discrimination.

CONCLUSION

Both patients have regained satisfactory facial sensory and motor function. Sensory recovery seems to be faster and more precise if multiple sensory nerve coaptations are performed. Swallowing and speech have continued to improve over time although not reaching the level of the normal population. We demonstrate how speech-corrective surgery can safely be performed in a FT patient and can improve speech recovery.

LEVEL OF EVIDENCE

4 Laryngoscope, 2021.

Facial Transplantation

Facial transplantation represents a unique surgical solution for challenging facial injury patterns in which conservative reconstructive techniques fail to provide a satisfactory functional and aesthetic result. With advances in the field of vascularized composite allotransplantation over the past 15 years, more than 40 of these procedures have been performed worldwide with two recent reports of facial re-transplantation. In this article we discuss the multidisciplinary approach that is required for successful transplantation as well as the surgical techniques used and postoperative management. With ongoing research, recent technological innovation, and increased efforts to promote greater generalizability and transparency in this field, patients with these complex injuries will continue to see improvements in their treatment options, and thus quality of life.

Mucosa and Rejection in Facial Vascularized Composite Allotransplantation: A Systematic Review

BACKGROUND

Facial vascularized composite allotransplantation (fVCA) presents an established approach to restore form and function of patients with catastrophic facial defects. Skin is one of the target tissues of the rejection process, and due to its easy accessibility has become the gold standard in the diagnosis of rejection. Mucosal rejection frequently occurs; however, the added value of mucosal rejection assessment for patient management is unknown.

METHODS

We conducted a systematic review of manuscripts listed in the MEDLINE/PubMed and GoogleScholar databases to identify articles that provide data on mucosal rejection following fVCA. For inclusion, papers had to be available as full-text and written in English. Non-VCA studies and animal studies were excluded. We followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.

RESULTS

We included 17 articles that described changes in allotransplanted mucosa of fVCAs. These articles yielded data on 168 BANFF graded biopsies of corresponding skin and mucosa biopsies. Rejection grades were consistently higher in mucosal biopsies. Concordance between allograft skin and mucosa biopsy grades increased with an increasing skin-BANFF grade. Mucosa rejection grades were on average lower in the early stages of the posttransplant period (<postoperative mo 12, time of motor, and sensory recovery) when compared to the later stages (>postoperative mo 12).

CONCLUSIONS

The mucosa of facial allotransplants is one of the primary targets of rejection. The data indicates that higher-grade skin rejection does not occur in absence of mucosal rejection. Further investigations are needed to elucidate the exact role of mucosal biopsies for fVCA patient management.

Pathologies of oral and sinonasal mucosa following facial vascularized composite allotransplantation

BACKGROUND

Cutaneous changes of facial vascularized composite allotransplants (fVCAs) are extensively described in the literature. Parts of the nose, nasal, and oral cavities are included in most fVCAs. Distinctively, the nose and mouth are lined by mucosa. Little is known about the histopathology and complications of the mucosa involved in fVCA patients.

METHODS

The study constitutes a retrospective cohort study of nine fVCA patients. Medical records were reviewed for information about changes of oral and nasal mucous membranes. Types of mucosal lesions were recorded and analyzed. Uni- and multivariate generalized estimating equation (GEE) models were used to assess the odds of developing mucosal inflammation in the presence of clinico-pathologic variables.

RESULTS

A total of 186 clinical encounters with examination of oral and nasal mucous membranes were included. Membranes were devoid of clinical pathology in 101 instances (53% of all clinical assessments). Ulcerations/erosions (27%), edema (18%), and erythema (14%) were the most common lesions. Oral lesions affected the lips (58%), buccal mucosa (38%), and palate (5%). Sinonasal processes predominantly affected nasal vestibules and septae. In univariate analysis, sirolimus, skin rejection, and skin Banff grade were associated with the presence of an acute inflammatory mucosal lesion (p<0.05). In multivariate analysis, skin Banff grade and sirolimus were independent predictors of mucosal inflammation.

CONCLUSION

Pathologies of fVCA mucous membranes are more common than previously reported. Mucosal assessment plays an important role in the pleomorphic allograft rejection process evaluation rather than diagnosis and treatment based on cutaneous pathology.  A closer look at the pathophysiology of fVCA mucosal rejection and inflammation is warranted.

Have We Achieved Optimal Skin Color Matching in Partial Facial Transplantation? A Survey Study of the General Public and Medical Professionals

BACKGROUND

Skin color matching is an essential factor in achieving optimal aesthetic outcome in partial facial transplantation. However, there is no published literature evaluating the success of color matching to date. Furthermore, a medical professional's perception of an optimal color match may not necessarily translate to that of the general public. The purpose of our study was to evaluate skin color matching between the donor allograft and recipient native tissue in partial facial transplantations to determine the level of success perceived by the general public and medical professionals.

METHODS

Published photographs of partial face transplant recipients were used to create a survey where recipient native and donor allograft skin samples were juxtaposed. Thirty-three members of the general public and 30 medical professionals were asked to rate skin color match on a scale from "excellent match" to "not a match."

RESULTS

Overall, 47% of given ratings were positive, indicating an "excellent" or "good match," and 53% of ratings were negative, indicating a "poor match" or "lack of match" between the skin sample pairings shown. Of the 19 partial face transplant patients who were rated, 9 patients received >50% positive ratings, and 10 patients received <50% positive ratings. Medical professionals consistently gave more positive ratings, with statistically significant differences in 7 of the 19 rated patients (P < 0.05).

CONCLUSION

The results suggest that there is need for improvement in color matching in partial facial transplantation, and that the general public is more critical of skin color matching compared to medical professionals.

The past the present and the future of face transplantation

PURPOSE OF REVIEW

Face transplantation represents vascularized composite allotransplantation (VCA) organ and became one of the most rewarding reconstructive options for severely disfigured patients. This review summarizes the past, current and future challenges of face transplantation, based on our experience and literature reports.

RECENT FINDINGS

In 2005, first partial face transplantation was reported by French team. In 2008, we have performed the US first near-total face transplantation. Currently, more than 40 face transplant cases were reported worldwide. Based on the outcomes of our three patients and the literature reports, face transplantation improved aesthetics, function and the quality of life of face transplant patients. However, there are still many challenges encountered including the side effects of immunosuppressive protocols, the psychological and social problems as well as the financial challenges which need to be address in the near future to maintain face transplantation in the armamentarium of reconstructive surgery.

SUMMARY

Currently, feasibility of face transplantation was confirmed; however, the life-long immunosuppressive protocols bearing serious side effects are still required to prevent face rejection. Thus, for the future of face and other VCA, novel approaches of cell-based therapies or engineered scaffolds should be developed to make face transplantation safer.

Recognizing Emotional Expression as an Outcome Measure After Face Transplant

IMPORTANCE

Limited quantitative data exist on the restoration of nonverbal communication via facial emotional expression after face transplant. Objective and noninvasive methods for measuring outcomes and tracking rehabilitation after face transplant are lacking.

OBJECTIVE

To measure emotional expression as an indicator of functional outcomes and rehabilitation after face transplant via objective, noninvasive, and nonobtrusive software-based video analysis.

DESIGN, SETTING, AND PARTICIPANTS

This single-center case-control study analyzed videos with commercially available video analysis software capable of detecting emotional expression. The study participants were 6 patients who underwent face transplant at Brigham and Women's Hospital between April 2009 and March 2014. They were matched by age, race/ethnicity, culture, and sex to 6 healthy controls with no prior facial surgical procedures. Participants were asked to perform either emotional expressions (direct evaluation) or standardized facial movements (indirect evaluation). Videos were obtained in a clinical setting, except for direct evaluation videos of 3 patients that were recorded at the patients' residences. Data analysis was performed from June 2018 to November 2018.

MAIN OUTCOMES AND MEASURES

The possibility of detecting the emotional expressions of happiness, sadness, anger, fear, surprise, and disgust was evaluated using intensity score values between 0 and 1, representing expressions that are absent or fully present, respectively.

RESULTS

Six patients underwent face transplant (4 men; mean [SD] age, 42 [14] years). Four underwent full face transplants, and 2 underwent partial face transplants of the middle and lower two-thirds of the face. In healthy controls, happiness was the only emotion reliably recognized in both indirect (mean [SD] intensity score, 0.92 [0.05]) and direct (mean [SD] intensity score, 0.91 [0.04]) evaluation. Indirect evaluation showed that expression of happiness significantly improved 1 year after transplant (0.04 point per year; 95% CI, 0.02 to 0.06 point per year; P = .002). Expression of happiness was restored to a mean of 43% (range, 14% to 75%) of that of healthy controls after face transplant. The expression of sadness showed a significant change only during the first year after transplant (-0.53 point per year; 95% CI, -0.82 to -0.24 point per year; P = .005). All other emotions were detectable with no significant change after transplant. Nearly all emotions were detectable in long-term direct evaluation of 3 patients, with expression of happiness restored to a mean of 26% (range, 5% to 59%) of that of healthy controls.

CONCLUSIONS AND RELEVANCE

Partial restoration of facial emotional expression is possible after face transplant. Video analysis software may provide useful clinical information and aid rehabilitation after face transplant.

Blood proteome profiling using aptamer-based technology for rejection biomarker discovery in transplantation

Face transplantation is a promising solution for patients with devastating facial injuries who lack other satisfactory treatment options. At the same time, this type of transplantation is accompanied with high risks of acute transplant rejection. The limitations of traditional skin biopsy and the need to frequently monitor the condition of face transplant call for less invasive biomarkers to better diagnose and treat acute rejection. Discovery of peripheral serum proteins accurately reflecting the transplant status would represent a reasonable solution to meet this demand. However, to date, there is no clinical data available to address the feasibility of this approach. In this study, we used the next generation aptamer-based SOMAscan proteomics platform to profile 1305 proteins of peripheral blood serum in twenty-four samples taken from 6 patients during no-rejection, nonsevere rejection, and severe rejection episodes. Also, we provide a detailed description of biosample processing and all steps to generate and analyze the SOMAscan dataset with hope it will assist in performing biomarker discovery in other transplantation centers using this platform.

MMP3 Is a Non-invasive Biomarker of Rejection in Skin-Bearing Vascularized Composite Allotransplantation: A Multicenter Validation Study

Background: There is unmet need for non-invasive immunomonitoring to improve diagnosis and treatment of acute rejection in vascularized composite allotransplantation (VCA). Circulating matrix metalloproteinase 3 (MMP3) was described as a candidate non-invasive biomarker to predict treatment response to acute rejection in clinical VCA. However, larger validation studies are yet to be reported to allow for more definitive conclusions.

Methods: We retrospectively measured MMP3 levels using ELISA in a total of 140 longitudinal serum samples from six internal and three external face transplant recipients, as well as three internal and seven external upper extremity transplant recipients. The control groups comprised serum samples from 36 kidney transplant recipients, 14 healthy controls, and 38 patients with autoimmune skin disease. A linear mixed model was used to study the effect of rejection state (pre-transplant, no-rejection, non-severe rejection (NSR), and severe rejection) on MMP3 levels.

Results: In VCA, MMP3 levels increased significantly (p < 0.001) between pre- and post-transplant no-rejection states. A further increase occurred during severe rejection (p < 0.001), while there was no difference in MMP3 levels between non-severe and no-rejection episodes. A threshold of 5-fold increase from pre-transplant levels could discriminate severe from NSR with 76% sensitivity and 81% specificity (AUC = 0.79, 95% CI = 0.65–0.92, p < 0.001). In kidney transplantation, the MMP3 levels were significantly (p < 0.001) elevated during antibody-mediated rejection but not during T-cell mediated rejection (TCMR) (p = 0.547). MMP3 levels in healthy controls and autoimmune skin disease patients were comparable with either pre-transplant or no-rejection/NSR episodes of VCA patients.

Conclusion: The results of this study suggest that serum MMP3 protein is a promising marker for stratifying patients according to severity of rejection, complementary to biopsy findings.