Natural history of undifferentiated pleomorphic sarcoma: Experience from the US Sarcoma Collaborative.

BACKGROUND: Undifferentiated pleomorphic sarcoma (UPS) is a relatively rare but aggressive neoplasm. We sought to utilize a multi-institutional US cohort of sarcoma patients to examine predictors of survival and recurrence patterns after resection of UPS. METHODS: From 2000 to 2016, patients with primary UPS undergoing curative-intent surgical resection at seven academic institutions were retrospectively reviewed. Epidemiologic and clinicopathologic factors were reviewed by site of origin. Overall survival (OS), recurrence-free survival (RFS), time-to-locoregional (TTLR), time-to-distant recurrence (TTDR), and patterns of recurrence were analyzed. RESULTS: Of the 534 UPS patients identified, 53% were female, with a median age of 60 and median tumor size of 8.5 cm. The median OS, RFS, TTLR, and TTDR for the entire cohort were 109, 49, 86, and 46 months, respectively. There were no differences in these survival outcomes between extremity and truncal UPS. Compared with truncal, extremity UPS were more commonly amenable to R0 resection (87% vs. 75%, p = 0.017) and less commonly associated with lymph node metastasis (1% vs. 6%, p = 0.031). R0 resection and radiation treatment, but not site of origin (extremity vs. trunk) were independent predictors of OS and RFS. TTLR recurrence was shorter for UPS resected with a positive margin and for tumors not treated with radiation. CONCLUSION: For patients with resected extremity and truncal UPS, tumor size >5 cm and positive resection margin are associated with worse survival OS and RFS, irrespectively the site of origin. R0 surgical resection and radiation treatment may help improve these survival outcomes.

Calcifications and Cystic Morphology on Preoperative Imaging Predict Survival After Resection of Pancreatic Neuroendocrine Tumors.

BACKGROUND: Radiographic calcifications and cystic morphology are associated with higher and lower tumor grade, respectively, in pancreatic neuroendocrine tumors (PNETs). Whether calcifications and/or cystic morphology could be used preoperatively to predict post-resection survival in patients with PNETs remains elusive. METHODS: Patients undergoing curative-intent resection of well-differentiated PNETs from 2000 to 2017 at eight academic institutions participating in the US Neuroendocrine Tumor Study Group were identified. Preoperative cross-sectional imaging reports were reviewed to identify the presence of calcifications and of a cystic component occupying >50% of the total tumor area. Clinicopathologic characteristics and recurrence-free survival (RFS) were compared. RESULTS: Of 981 patients studied, 18% had calcifications and 17% had cystic tumors. Tumors with calcifications were more commonly associated with Ki-67 ≥3% (47% vs. 33%; p = 0.029), lymph node metastasis (36% vs. 24%; p = 0.011), and distant metastasis (13% vs. 4%; p < 0.001). In contrast, cystic tumors were less commonly associated with lymph node metastasis (12% vs. 30%; p < 0.001). Five-year RFS after resection was most favorable for cystic tumors without calcifications (91%), intermediate for solid tumors without calcifications (77%), and least favorable for any calcified PNET (solid 69%, cystic 67%; p = 0.043). Calcifications remained an independent predictor of RFS on multivariable analysis (p = 0.043) controlling for nodal (p < 0.001) and distant metastasis (p = 0.001). CONCLUSIONS: Easily detectable radiographic features, such as calcifications and cystic morphology, can be used preoperatively to stratify prognosis in patients with PNETs and possibly inform the decision to operate or not, as well as guide the extent of resection and potential use of neoadjuvant therapy.

A Novel Machine-Learning Approach to Predict Recurrence After Resection of Colorectal Liver Metastases.

BACKGROUND: Surgical resection of hepatic metastases remains the only potentially curative treatment option for patients with colorectal liver metastases (CRLM). Widely adopted prognostic tools may oversimplify the impact of model parameters relative to long-term outcomes. METHODS: Patients with CRLM who underwent a hepatectomy between 2001 and 2018 were identified in an international, multi-institutional database. Bootstrap resampling methodology used in tandem with multivariable mixed-effects logistic regression analysis was applied to construct a prediction model that was validated and compared with scores proposed by Fong and Vauthey. RESULTS: Among 1406 patients who underwent hepatic resection of CRLM, 842 (59.9%) had recurrence. The full model (based on age, sex, primary tumor location, T stage, receipt of chemotherapy before hepatectomy, lymph node metastases, number of metastatic lesions in the liver, size of the largest hepatic metastases, carcinoembryonic antigen [CEA] level and KRAS status) had good discriminative ability to predict 1-year (area under the receiver operating curve [AUC], 0.693; 95% confidence interval [CI], 0.684-0.704), 3-year (AUC, 0.669; 95% CI, 0.661-0.677), and 5-year (AUC, 0.669; 95% CI, 0.661-0.679) risk of recurrence. Studies analyzing validation cohorts demonstrated similar model performance, with excellent model accuracy. In contrast, the AUCs for the Fong and Vauthey scores to predict 1-year recurrence were only 0.527 (95% CI, 0.514-0.538) and 0.525 (95% CI, 0.514-0.533), respectively. Similar trends were noted for 3- and 5-year recurrence. CONCLUSION: The proposed clinical score, derived via machine learning, which included clinical characteristics and morphologic data, as well as information on KRAS status, accurately predicted recurrence after CRLM resection with good discrimination and prognostic ability.

Minimally Invasive Versus Open Liver Resection for Hepatocellular Carcinoma in the Setting of Portal Vein Hypertension: Results of an International Multi-institutional Analysis.

BACKGROUND: Patients with hepatocellular carcinoma (HCC) and portal vein hypertension assessed with platelet count (PVH-PLT; platelet count < 100,000/mL) are often denied surgery even when the disease is technically resectable. Short- and long-term outcomes of patients undergoing minimally invasive surgery (MIS) versus open resection for HCC and PVH-PLT were compared. METHODS: Propensity score matching (PSM) was used to balance the clinicopathological differences between MIS and non-MIS patents. Univariate comparison and standard survival analyses were utilized. RESULTS: Among 1974 patients who underwent surgery for HCC, 13% had a PVH-PLT and 33% underwent MIS. After 1:1 PSM, 407 MIS and 407 non-MIS patients were analyzed. Incidence of complications and length-of-stay (LoS) were higher among non-MIS versus MIS patients (both p ≤ 0.002). After PSM, among 178 PVH-PLT patients (89 MIS and 89 non-MIS), patients who underwent a non-MIS approach had longer LoS (> 7 days; non-MIS: 55% vs. MIS: 29%), as well as higher morbidity (non-MIS: 42% vs. MIS: 29%) [p <0.001]. In contrast, long-term oncological outcomes were comparable, including 3-year overall survival (non-MIS: 66.2% vs. MIS: 72.9%) and disease-free survival (non-MIS: 47.3% vs. MIS: 50.2%) [both p ≥ 0.08]. CONCLUSION: An MIS approach was associated with improved short-term outcomes, but similar long-term outcomes, compared with open liver resection for patients with HCC and PVH-PLT. An MIS approach for liver resection should be considered for patients with HCC, even those individuals with PVH-PLT.

Response to preoperative chemotherapy: impact of change in total burden score and mutational tumor status on prognosis of patients undergoing resection for colorectal liver metastases.

BACKGROUND: Progression of colorectal liver metastasis (CRLM) on preoperative chemotherapy has been associated with a worse prognosis compared with patients who have responsive disease. Defining response can be challenging as traditional criteria largely assess only tumor size. METHODS: Patients who underwent hepatectomy between 2010 and 2017 were identified using a multi-centric database. This study aimed to define the impact of preoperative chemotherapy response relative to initial tumor burden score (TBS) and determine impact of clinico-pathological variables on overall survival (OS). RESULTS: Among 784 patients who received preoperative chemotherapy, the regimen was oxaliplatin- (66%) or irinotecan-based (34%). Among patients with a TBS<6 at diagnosis, genetic status was the most important prognostic variable. Patients with a TBS<6, 5-year OS was 55%, 35%, and 0% for patients with KRAS/NRAS/BRAF wild-type, KRAS/NRAS, and BRAF mutations, respectively. Among patients who presented with CRLM with a TBS≥6, only Δ-TBS was prognostically important and patients with a Δ-TBS ≥ -10% had a 5-year OS of 27% compared with 49% for patients with a Δ-TBS < -10%. CONCLUSIONS: Prognostic stratification of patients with CRLM receiving preoperative chemotherapy should be multi-faceted and include consideration of initial tumor burden, change in tumor burden due to chemotherapy, and tumor genetic status.

Predictive Value of Chromogranin A and a Pre-Operative Risk Score to Predict Recurrence After Resection of Pancreatic Neuroendocrine Tumors.

INTRO: Chromogranin A (CgA) may be prognostic for patients with neuroendocrine tumors; however, the clinical utility of this test is unclear. METHODS: Patients undergoing resection for pancreatic neuroendocrine tumors (pNET) were selected from the eight institutions of the US Neuroendocrine Tumor Study Group database. Cox regression was used to identify pre-operative variables that predicted recurrence-free survival (RFS), and those with p < 0.1 were included in a risk score. The risk score was tested in a unique subset of the overall cohort. RESULTS: In the entire cohort of 287 patients, median follow-up time was 37 months, and 5-year RFS was 73%. Cox regression analysis identified four variables for inclusion in the risk score: CgA > 5x ULN (HR 4.3, p = 0.01), tumor grade 2/3 (HR 3.7, p = 0.01), resection for recurrent disease (HR 6.2, p < 0.01), and tumor size > 4 cm (HR 4.5, p = 0.1). Each variable was assigned 1 point. Risk-score testing in the unique validation cohort of 63 patients revealed a 95% negative predictive value for recurrence in patients with zero points. DISCUSSION: This simple pre-operative risk scoring system resulted in a high degree of specificity for identifying patients at low-risk for tumor recurrence. This test can be utilized pre-operatively to aid informed decision-making.

Surrogate End Points for Overall Survival in Metastatic, Locally Advanced, or Unresectable Pancreatic Cancer: A Systematic Review and Meta-Analysis of 24 Randomized Controlled Trials.

BACKGROUND: Overall survival (OS) has traditionally been the primary end point in studies evaluating the clinical benefit of first-line chemotherapy in metastatic, locally advanced, or unresectable pancreatic cancer (MLAUPC). Given the prolonged follow-up assessment required to obtain OS and its potential to be confounded by second-line treatments, this study sought to determine whether progression-free survival (PFS), response rate (RR), or disease control rate (DCR) can serve as a reliable surrogate for OS. METHODS: A systematic review and meta-analysis was performed including all phase 3 clinical trials for MLAUPC, with gemcitabine as the control arm of the trial. The hazard ratios (HRs) for OS and PFS and odds ratios (ORs) for RR and DCR were recorded. A weighted Pearson correlation coefficient was estimated for the association between OS and the other outcomes. The primary analysis used a random effects weighting model, whereas the secondary analyses used a fixed effects- or sample size-weighted approach. RESULTS: For the study, 24 randomized controlled trials were identified. The Pearson correlation coefficient between OS and PFS was 0.86 (95% confidence interval [CI] 0.67-0.94; p < 0.001). Sensitivity analysis of the studies with little to no crossover further showed a correlation coefficient of 0.91 (95% CI 0.76-0.97; p < 0.001). The correlation coefficient between OS and RR was 0.45 (95% CI 0.07-0.72; p = 0.02) and between OS and DCR was 0.74 (95% CI 0.38-0.90; p < 0.001). CONCLUSIONS: First-line chemotherapy trials for MLAUPC show a robust correlation between OS and PFS, affirming its role as a surrogate of OS.

Surgical Considerations in the Management of Gastric Adenocarcinoma.

Since Theodor Billroth and César Roux perfected the methods of postgastrectomy reconstruction in as early as the late nineteenth century, surgical management of gastric cancer has made incremental progress. The longstanding and contentious debate on the optimal extent of lymph node dissection for gastric cancer seems to have settled in favor of D2 dissection. Pylorus-preserving distal (central) gastrectomy has emerged as a less invasive, function-preserving option for T1N0 middle-third gastric cancers. Frozen section analysis of margins seems partially helpful in this direction. Last, the role of palliative gastrectomy in patients with metastatic seems less important than initially thought.

Repair and tissue engineering techniques for articular cartilage.

Chondral and osteochondral lesions due to injury or other pathology commonly result in the development of osteoarthritis, eventually leading to progressive total joint destruction. Although current progress suggests that biologic agents can delay the advancement of deterioration, such drugs are incapable of promoting tissue restoration. The limited ability of articular cartilage to regenerate renders joint arthroplasty an unavoidable surgical intervention. This Review describes current, widely used clinical repair techniques for resurfacing articular cartilage defects; short-term and long-term clinical outcomes of these techniques are discussed. Also reviewed is a developmental pipeline of acellular and cellular regenerative products and techniques that could revolutionize joint care over the next decade by promoting the development of functional articular cartilage. Acellular products typically consist of collagen or hyaluronic-acid-based materials, whereas cellular techniques use either primary cells or stem cells, with or without scaffolds. Central to these efforts is the prominent role that tissue engineering has in translating biological technology into clinical products; therefore, concomitant regulatory processes are also discussed.

Digoxin and adenosine triphosphate enhance the functional properties of tissue-engineered cartilage.

Toward developing engineered cartilage for the treatment of cartilage defects, achieving relevant functional properties before implantation remains a significant challenge. Various chemical and mechanical stimuli have been used to enhance the functional properties of engineered musculoskeletal tissues. Recently, Ca(2+)-modulating agents have been used to enhance matrix synthesis and biomechanical properties of engineered cartilage. The objective of this study was to determine whether other known Ca(2+) modulators, digoxin and adenosine triphosphate (ATP), can be employed as novel stimuli to increase collagen synthesis and functional properties of engineered cartilage. Neocartilage constructs were formed by scaffold-free self-assembling of primary bovine articular chondrocytes. Digoxin, ATP, or both agents were added to the culture medium for 1 h/day on days 10-14. After 4 weeks of culture, neocartilage properties were assessed for gross morphology, biochemical composition, and biomechanical properties. Digoxin and ATP were found to increase neocartilage collagen content by 52-110% over untreated controls, while maintaining proteoglycan content near native tissue values. Furthermore, digoxin and ATP increased the tensile modulus by 280% and 180%, respectively, while the application of both agents increased the modulus by 380%. The trends in tensile properties were found to correlate with the amount of collagen cross-linking. Live Ca(2+) imaging experiments revealed that both digoxin and ATP were able to increase Ca(2+) oscillations in monolayer-cultured chondrocytes. This study provides a novel approach toward directing neocartilage maturation and enhancing its functional properties using novel Ca(2+) modulators.

Developing functional musculoskeletal tissues through hypoxia and lysyl oxidase-induced collagen cross-linking.

The inability to recapitulate native tissue biomechanics, especially tensile properties, hinders progress in regenerative medicine. To address this problem, strategies have focused on enhancing collagen production. However, manipulating collagen cross-links, ubiquitous throughout all tissues and conferring mechanical integrity, has been underinvestigated. A series of studies examined the effects of lysyl oxidase (LOX), the enzyme responsible for the formation of collagen cross-links. Hypoxia-induced endogenous LOX was applied in multiple musculoskeletal tissues (i.e., cartilage, meniscus, tendons, ligaments). Results of these studies showed that both native and engineered tissues are enhanced by invoking a mechanism of hypoxia-induced pyridinoline (PYR) cross-links via intermediaries like LOX. Hypoxia was shown to enhance PYR cross-linking 1.4- to 6.4-fold and, concomitantly, to increase the tensile properties of collagen-rich tissues 1.3- to 2.2-fold. Direct administration of exogenous LOX was applied in native cartilage and neocartilage generated using a scaffold-free, self-assembling process of primary chondrocytes. Exogenous LOX was found to enhance native tissue tensile properties 1.9-fold. LOX concentration- and time-dependent increases in PYR content (∼ 16-fold compared with controls) and tensile properties (approximately fivefold compared with controls) of neocartilage were also detected, resulting in properties on par with native tissue. Finally, in vivo subcutaneous implantation of LOX-treated neocartilage in nude mice promoted further maturation of the neotissue, enhancing tensile and PYR content approximately threefold and 14-fold, respectively, compared with in vitro controls. Collectively, these results provide the first report, to our knowledge, of endogenous (hypoxia-induced) and exogenous LOX applications for promoting collagen cross-linking and improving the tensile properties of a spectrum of native and engineered tissues both in vitro and in vivo.

Topographic variations in biomechanical and biochemical properties in the ankle joint: an in vitro bovine study evaluating native and engineered cartilage.

PURPOSE: The purposes of this study were to identify differences in the biomechanical and biochemical properties among the articulating surfaces of the ankle joint and to evaluate the functional and biological properties of engineered neocartilage generated using chondrocytes from different locations in the ankle joint. METHODS: The properties of the different topographies within the ankle joint (tibial plafond, talar dome, and distal fibula) were evaluated in 28 specimens using 7 bovine ankles; the femoral condyle was used as a control. Chondrocytes from the same locations were used to form 28 neocartilage constructs by tissue engineering using an additional 7 bovine ankles. The functional properties of neocartilage were compared with native tissue values. RESULTS: Articular cartilage from the tibial plafond, distal fibula, talar dome, and femoral condyle exhibited Young modulus values of 4.8 ± 0.5 MPa, 3.9 ± 0.1 MPa, 1.7 ± 0.2 MPa, and 4.0 ± 0.5 MPa, respectively. The compressive properties of the corresponding tissues were 370 ± 22 kPa, 242 ± 18 kPa, 255 ± 26 kPa, and 274 ± 18 kPa, respectively. The tibial plafond exhibited 3-fold higher tensile properties and 2-fold higher compressive and shear moduli compared with its articulating talar dome; the same disparity was observed in neocartilage. Similar trends were detected in biochemical data for both native and engineered tissues. CONCLUSIONS: The cartilage properties of the various topographic locations within the ankle are significantly different. In particular, the opposing articulating surfaces of the ankle have significantly different biomechanical and biochemical properties. The disparity between tibial plafond and talar dome cartilage and chondrocytes warrants further evaluation in clinical studies to evaluate their exact role in the pathogenesis of ankle lesions. CLINICAL RELEVANCE: Therapeutic modalities for cartilage lesions need to consider the exact topographic source of the cells or cartilage grafts used. Furthermore, the capacity of generating neocartilage implants from location-specific chondrocytes of the ankle joint may be used in the future as a tool for the treatment of chondral lesions.

Passive strain-induced matrix synthesis and organization in shape-specific, cartilaginous neotissues.

Tissue-engineered musculoskeletal soft tissues typically lack the appropriate mechanical robustness of their native counterparts, hindering their clinical applicability. With structure and function being intimately linked, efforts to capture the anatomical shape and matrix organization of native tissues are imperative to engineer functionally robust and anisotropic tissues capable of withstanding the biomechanically complex in vivo joint environment. The present study sought to tailor the use of passive axial compressive loading to drive matrix synthesis and reorganization within self-assembled, shape-specific fibrocartilaginous constructs, with the goal of developing functionally anisotropic neotissues. Specifically, shape-specific fibrocartilaginous neotissues were subjected to 0, 0.01, 0.05, or 0.1 N axial loads early during tissue culture. Results found the 0.1-N load to significantly increase both collagen and glycosaminoglycan synthesis by 27% and 67%, respectively, and to concurrently reorganize the matrix by promoting greater matrix alignment, compaction, and collagen crosslinking compared with all other loading levels. These structural enhancements translated into improved functional properties, with the 0.1-N load significantly increasing both the relaxation modulus and Young's modulus by 96% and 255%, respectively, over controls. Finite element analysis further revealed the 0.1-N uniaxial load to induce multiaxial tensile and compressive strain gradients within the shape-specific neotissues, with maxima of 10.1%, 18.3%, and -21.8% in the XX-, YY-, and ZZ-directions, respectively. This indicates that strains created in different directions in response to a single axis load drove the observed anisotropic functional properties. Together, results of this study suggest that strain thresholds exist within each axis to promote matrix synthesis, alignment, and compaction within the shape-specific neotissues. Tailoring of passive axial loading, thus, presents as a simple, yet effective way to drive in vitro matrix development in shape-specific neotissues toward more closely achieving native structural and functional properties.

Combined use of chondroitinase-ABC, TGF-ß1, and collagen crosslinking agent lysyl oxidase to engineer functional neotissues for fibrocartilage repair.

Patients suffering from damaged or diseased fibrocartilages currently have no effective long-term treatment options. Despite their potential, engineered tissues suffer from inferior biomechanical integrity and an inability to integrate in vivo. The present study identifies a treatment regimen (including the biophysical agent chondroitinase-ABC, the biochemical agent TGF-ß1, and the collagen crosslinking agent lysyl oxidase) to prime highly cellularized, scaffold-free neofibrocartilage implants, effecting continued improvement in vivo. We show these agents drive in vitro neofibrocartilage matrix maturation toward synergistically enhanced Young's modulus and ultimate tensile strength values, which were increased 245% and 186%, respectively, over controls. Furthermore, an in vitro fibrocartilage defect model found this treatment regimen to significantly increase the integration tensile properties between treated neofibrocartilage and native tissue. Through translating this technology to an in vivo fibrocartilage defect model, our results indicate, for the first time, that a pre-treatment can prime neofibrocartilage for significantly enhanced integration potential in vivo, with interfacial tensile stiffness and strength increasing by 730% and 745%, respectively, compared to integration values achieved in vitro. Our results suggest that specifically targeting collagen assembly and organization is a powerful means to augment overall neotissue mechanics and integration potential toward improved clinical feasibility.

Primary closure versus non-closure of dog bite wounds. a randomised controlled trial.

INTRODUCTION: Dog bite wounds represent a major health problem. Despite their importance, their management and especially the role of primary closure remain controversial. In this randomised controlled trial, the outcome between primary suturing and non-closure was compared. METHODS: 168 consecutive patients with dog bite injuries were included in this study. The wounds were allocated randomly in two treatment approaches: Group 1, consisting of eighty-two patients, had their wound sutured, whilst Group 2, consisting of eighty-six patients, did not have their wounds sutured. All wounds were cleansed using high-pressure irrigation and povidone iodine. All patients received the same type of antibiotic treatment. Our measured outcomes included presence of infection and cosmetic appearance. Cosmetic outcome was evaluated using the Vancouver Scar Scale (VSS). Wound and patient characteristics, such as time of management, wound location and size, and patient age, were recorded and analysed for their potential role in the resulting outcome. RESULTS: The overall infection rate was 8.3%. No difference in the infection rate between primary suturing and non-suturing group was detected in the present study. The cosmetic appearance of the sutured wounds was significantly better (mean score 1.74) compared to the wounds that were left open (mean score 3.05) (p=0.0001). The infection rate was comparable among all age groups. Wounds treated within 8h of injury demonstrated an infection rate of 4.5%, which is lower compared to the 22.2% rate observed in wounds treated later than 8h. The wounds located at the head and neck exhibited better results in both infection rate and cosmetic outcome. Additionally, wounds >3 cm negatively affected the cosmetic appearance of the outcome. CONCLUSIONS: Primary suturing of wounds caused by dog bites resulted in similar infection rate compared to non-suturing. However, primary suturing exhibited improved cosmetic appearance. Time of management appeared to be critical, as early treatment resulted in lower infection rate and improved cosmetic appearance regardless suturing or not. Furthermore, wounds located at the head and face demonstrated better results.

Induced collagen cross-links enhance cartilage integration.

Articular cartilage does not integrate due primarily to a scarcity of cross-links and viable cells at the interface. The objective of this study was to test the hypothesis that lysyl-oxidase, a metalloenzyme that forms collagen cross-links, would be effective in improving integration between native-to-native, as well as tissue engineered-to-native cartilage surfaces. To examine these hypotheses, engineered cartilage constructs, synthesized via the self-assembling process, as well as native cartilage, were implanted into native cartilage rings and treated with lysyl-oxidase for varying amounts of time. For both groups, lysyl-oxidase application resulted in greater apparent stiffness across the cartilage interface 2-2.2 times greater than control. The construct-to-native lysyl-oxidase group also exhibited a statistically significant increase in the apparent strength, here defined as the highest observed peak stress during tensile testing. Histology indicated a narrowing gap at the cartilage interface in lysyl-oxidase treated groups, though this alone is not sufficient to indicate annealing. However, when the morphological and mechanical data are taken together, the longer the duration of lysyl-oxidase treatment, the more integrated the interface appeared. Though further data are needed to confirm the mechanism of action, the enhancement of integration may be due to lysyl-oxidase-induced pyridinoline cross-links. This study demonstrates that lysyl-oxidase is a potent agent for enhancing integration between both native-to-native and native-to-engineered cartilages. The fact that interfacial strength increased manifold suggests that cross-linking agents should play a significant role in solving the difficult problem of cartilage integration. Future studies must examine dose, dosing regimen, and cellular responses to lysyl-oxidase to optimize its application.

A copper sulfate and hydroxylysine treatment regimen for enhancing collagen cross-linking and biomechanical properties in engineered neocartilage.

The objective of this study was to improve the biomechanical properties of engineered neotissues through promoting the development of collagen cross-links. It was hypothesized that supplementing medium with copper sulfate and the amino acid hydroxylysine would enhance the activity of lysyl oxidase enzyme to form collagen cross-links, increasing the strength and integrity of the neotissue. Neocartilage constructs were generated using a scaffoldless, self-assembling process and treated with copper sulfate and hydroxylysine, either alone or in combination, following a 2-factor, full-factorial study design. Following a 6-wk culture period, the biomechanical and biochemical properties of the constructs were measured. Results found copper sulfate to significantly increase pyridinoline (PYR) cross-links in all copper sulfate-containing groups over controls. When copper sulfate and hydroxylysine were combined, the result was synergistic, with a 10-fold increase in PYR content over controls. This increase in PYR cross-links manifested in a 3.3-fold significant increase in the tensile properties of the copper sulfate + hydroxylysine group. In addition, an 123% increase over control values was detected in the copper sulfate group in terms of the aggregate modulus. These data elucidate the role of copper sulfate and hydroxylysine toward improving the biomechanical properties of neotissues through collagen cross-linking enhancement.