Comparison between open reduction and internal fixation and minimally invasive surgery in management of Sanders type II calcaneal fracture: A randomized controlled trial protocol

Background:The minimally invasive surgery possesses an essential and growing function in treating the calcaneal fractures, but the related literature on this topic is limited. For our study, the main purpose was to compare the early prognosis of a group of the patients with Sanders type II fracture of calcaneus treated via minimally invasive surgery and open reduction and internal fixation (ORIF).Methods:This is a prospective randomized controlled trial in the patients who suffer from displaced intra-articular calcaneal fractures. This current study was carried out in accordance with the guidelines of “CONSORT statement” for the randomized controlled studies. All patients were randomly assigned into 2 groups on the basis of a random number table, namely the minimally invasive treatment group and the ORIF group using conventional methods. Inclusion criteria included the followings: aged between 18 to 59 years old; closed and unilateral fracture; patients with displaced intra-articular calcaneal fracture (>2 mm) involving Sanders Type IIC and Type IIB; and patients have enough mental capacity to understand and answer questions in the evaluation scale. In the process of outpatient follow-up, the radiographs were taken at 1, 3, 6, and 12 months. The functional results involved the American Orthopaedic Foot and Ankle Score, Foot Function Index, and the pain score.Conclusions:This protocol will give us research directions in future work.Trial registration:This study protocol was registered in Research Registry (researchregistry6261).     

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.Regenerative medicine and tissue engineering are providing new avenues to treat a multitude of conditions and diseases through restoring, maintaining, or enhancing the function of a wide range of tissues (e.g., muscle, bone, skin) and organs (e.g., heart, lungs, kidneys). Despite recent advancements, the clinical utility of many engineered tissues remains dependent upon the development of methods that promote mechanically robust tissues capable of withstanding the in vivo environment. This problem presents a critical hurdle for efforts geared toward developing de novo musculoskeletal tissues, such as cartilage, meniscus, tendons, and ligaments, for reparative and regenerative strategies. Tissue engineering has the potential to provide alternative treatment options for musculoskeletal injury and disease by generating neotissue that mimics the complex structure of native tissue (1, 2). The objective is to improve the properties of the engineered tissues to achieve native tissue biomechanical properties, maturation, and long-term functionality. For example, in articular cartilage tissue engineering, a variety of methods, including combinations of hydrostatic pressure and growth factor treatment (3), fluid flow (4), and matrix-modulating enzymes (5), have resulted in improved neotissues with tensile moduli ranging from 1.3 to 2.3 MPa; however, native tissue values range from 5 to 25 MPa (6). Similarly, in neofibrocartilage, tensile properties have been reported to be 2.5–3.5 MPa (7, 8), with native fibrocartilage values ranging from 7 to 295 MPa (9, 10). These low properties likely result from the immaturity of the ECM of the neotissues, which is mainly due to lack of collagen cross-links (11). Therefore, it is important that additional treatment modalities be evaluated toward enhancing neotissue tensile properties.Collagen, the most prevalent fibrous protein in the body, supports the mechanical integrity of tissues and organs. In musculoskeletal tissues, collagen comprises the major fraction of the ECM and accounts for ∼65–80% of these tissues’ dry weights (12). After collagen biosynthesis and triple-helix formation, the copper-dependent enzyme lysyl oxidase (LOX) catalyzes extracellular modification of lysine and hydroxylysine amino acids of the collagen fibers into their aldehyde forms (Fig. 1A). Sequentially, this modification induces the formation of covalent pyridinoline (PYR) cross-links between individual collagen fibers (13) (Fig. 1B) and stabilizes the formation of heterotypic fibrils (Fig. 1C) and, subsequently, the tissue ECM. These intermolecular collagen cross-links, present in all native musculoskeletal tissues, signify the maturity of the tissue’s ECM (14). In particular, cartilaginous tissues, ligaments, and tendons feature two forms of collagen cross-links, the difunctional (initial/immature) cross-link dehydrodihydroxylysinonorleucine and the trifunctional (mature) cross-link hydroxylysyl-PYR (15) (Fig. 1B). Several studies have highlighted the pivotal role of these cross-links in native tissues’ biomechanical or functional properties (11, 16, 17). For example, in cartilage, the cross-linked collagen fibrils noncovalently stabilize the highly hydrated, negatively charged proteoglycans (18). These findings suggest the need for recapitulating cross-linking in engineered collagen-rich tissues.Open in a separate windowFig. 1.This illustration represents a hierarchical depiction of a heterotypic collagen fibril that is commonly found in most musculoskeletal tissues, such as cartilage, tendons, and ligaments. The figure emphasizes the internal axial relationships required for the formation of mature cross-links. (A) Detailed view of the axial stagger of individual collagen molecules required for PYR cross-linking. (B) Illustration of relationships among neighboring axial fibers of trifunctional (mature) hydroxylysyl-PYR collagen cross-links. (C) Illustration of a 3D concept of a heterotypic fibril, commonly found in musculoskeletal tissues, consisting of collagen types II (yellow), IX (red), and XI (blue). Figure adapted from ref. 68.Only a few studies to date have evaluated the extent of collagen cross-links (19, 20) and, more importantly, their influence on the tensile and compressive properties of engineered musculoskeletal tissues. In contrast, many studies have investigated how other ECM components, such as glycosaminoglycan (GAG), collagen, and mineralization, contribute to biomechanical properties (19, 21–23). Such work has yielded variable results. Specifically, although it has been suggested that the compressive properties of native articular cartilage are best correlated with the proteoglycan component of the ECM (24), more recent studies have shown a better correlation of the compressive modulus with a combination of both GAG and collagen content (25–27). For engineered tissues, tensile stiffness has been strongly associated with total collagen content (22) as well as PYR content (28). Nevertheless, a significant correlation with compressive properties has also been reported with respect to the PYR content of engineered tissues (28). These findings might suggest that the various tissue biomechanical properties are dependent on more than just the quantity of specific biochemical components (29). Therefore, the unique structural organization, cross-linking, and architecture of the collagen network also likely play equally important roles, along with collagen and GAG quantities, in determining the biomechanical functionality of the tissue.To the best of our knowledge, there are no validated and optimized methods for promoting collagen cross-linking and concomitant improvement in biomechanical properties in a spectrum of native and engineered tissues. Low oxygen tension, however, has been shown to have various molecular effects in different tissues (30, 31) through a hypoxia-dependent mechanism. This molecular mechanism is based on the critical involvement of hypoxia-inducible factor-1 (HIF-1) (32), which is present in many cells (33–35), including articular chondrocytes (36). In diarthrodial joints as well as developmental growth plates, chondrocytes experience hypoxic conditions (37). Low oxygen tension has been shown to affect the metabolism of articular chondrocytes, targeting the production of tissue-specific cartilage ECM proteins (38–42). Deletion of HIF-1α results in chondrocyte death, along with diminished expression of the cyclin-dependent kinase inhibitor p57, highlighting the importance of HIF-1 regulation for cell survival and growth arrest in this hypoxic environment (43). The critical role of HIF-1 in the chondrogenic differentiation of rat mesenchymal stem cells as well as human ES cells has been also identified (42, 44–46). Hypoxia-induced HIF-1 stabilization has been shown to control LOX regulation (47, 48), suggesting that hypoxia could affect ECM stabilization and tissue maturation through LOX-induced PYR cross-link formation. The manifold role of HIF-1 raises the intriguing idea that the ECM of native and engineered tissues and, concomitantly, their functional properties could be manipulated through hypoxia-mediated stimulation of HIF-1–regulated pathways, LOX gene expression, and sequential collagen cross-link formation.Although studies have elucidated the pathway underlying the effects of hypoxia on cartilage growth, function, and synthesis, the ability of endogenous (hypoxia-induced) and exogenous LOX application to enhance collagen cross-linking and concomitant mechanical properties in both native and engineered tissues remains unexplored and is the central hypothesis of the present study. In the series of studies presented here, a variety of musculoskeletal tissues widely used in clinical practice as grafts to replace degenerative tissues as well as neocartilage constructs were investigated to assess hypoxia- and LOX-mediated collagen cross-linking manipulation. The overall goal was to preserve and promote the functional properties of the native explants and neotissues, respectively. Strategically targeting collagen cross-links may be useful for engineering tissues de novo, for elucidating disease processes, and for the development of potential novel therapeutic modalities.     

In Vitro and In Vivo Correlation of Hepatic Fraction of Metabolism by P450 in Dogs

1-Aminobenzotriazole (ABT) has been widely used as a nonspecific mechanism-based inhibitor of cytochrome P450 (P450) enzymes. It is extensively used in preclinical studies to determine the relative contribution of oxidative metabolism mediated by P450 in vitro and in vivo. The aim of present study was to understand the translation of fraction metabolized by P450 in dog hepatocytes to in vivo using ABT, for canagliflozin, known to be cleared by P450-mediated oxidation and UDP-glucuronosyltransferases–mediated glucuronidation, and 3 drug discovery project compounds mainly cleared by hepatic metabolism. In a dog hepatocyte, intrinsic clearance assay with and without preincubation of ABT, 3 Lilly compounds exhibited a wide range of fraction metabolized by P450. Subsequent metabolite profiling in dog hepatocytes demonstrated a combination of metabolism by P450 and UDP-glucuronosyltransferases. In vivo, dogs were pretreated with 50 mg/kg ABT or vehicle at 2 h before intravenous administration of canagliflozin and Lilly compounds. The areas under the concentration-time curve (AUC) were compared for the ABT-pretreated and vehicle-pretreated groups. The measured AUC_ABT/AUC_veh ratios were correlated to fraction of metabolism by P450 in dog hepatocytes, suggesting that in vitro ABT inhibition in hepatocytes is useful to rank order compounds for in vivo fraction of metabolism assessment.     

Low serum bilirubin concentration is a novel risk factor for the development of albuminuria in patients with type 2 diabetes

Objective

Bilirubin has been recognized as an important endogeneous antioxidant. Previous studies reported that bilirubin could prevent atherosclerosis. The aim of this study was to investigate if serum bilirubin concentration could be a predictor for the development of albuminuria in patients with type 2 diabetes.

Materials and Methods

We measured serum bilirubin in 320 consecutive patients with normoalbuminuria. We performed follow-up study to assess the development of albuminuria, mean interval of which was 3.2 ± 0.9 years. Cox proportional hazards regression was used to examine the relationship between serum bilirubin concentration and the development of albuminuria.

Results

During follow-up duration, 43 patients have developed albuminuria. In multivariate analysis, after adjusting for comprehensive risk factors, the risk of developing albuminuria was higher in the lowest quartile of serum bilirubin concentrations than that in the highest quartile of serum bilirubin concentrations (Hazard ratio, 5.76; 95% CI, 1.65 to 24.93).

Conclusions

Low serum bilirubin concentration could be a novel risk factor for the development of albuminuria in patients with type 2 diabetes.