ABSTRACT:The anterior cruciate ligament (ACL) fails to heal after suture repair. One hypothesis for this failure is the premature loss of the fibrin clot, or provisional scaffolding, between the two ligament ends in the joint environment. To test this hypothesis, a substitute provisional scaffold of collagen-platelet rich plasma (PRP) hydrogel was used to fill the ACL wound site at the time of suture repair and the structural properties of the healing ACLs evaluated 4 weeks after surgery. Bilateral ACL transections were performed in five 30-kg Yorkshire pigs and treated with suture repair. In each animal, one of the repairs was augmented with placement of a collagen-PRP hydrogel at the ACL transection site, while the contralateral knee had suture repair alone. In addition, six control knees with intact ACLs from three additional animals were used as a control group. No postoperative immobilization was used. After 4 weeks the animals underwent in vivo magnetic resonance imaging to assess the size of the healing ACL, followed by biomechanical testing to determine tensile properties. The supplementation of suture repair with a collagen-PRP hydrogel resulted in significant improvements in load at yield, maximum load, and linear stiffness at 4 weeks. We conclude that use of a stabilized provisional scaffold, such as a collagen-PRP hydrogel, to supplement primary repair of the ACL can result in improved biomechanical properties at an early time point. Further studies to determine the long-term effect of primary repair enhancement are needed. ß

In this study, we hypothesize that supplementation of suture repair of the anterior cruciate ligament (ACL) with platelet-rich plasma (PRP) will improve the biomechanics of the repair. Six 30-kg pigs underwent bilateral suture repair of the ACL. One side was treated with suture repair alone, while the contralateral side was treated with suture repair augmented with PRP. After 14 weeks in vivo, anteriorposterior (AP) knee laxity and the tensile properties of the repaired ligament were measured. The addition of PRP to the suture repairs did not improve AP knee laxity at 308 (p ¼ 0.73) or 608 (p ¼ 0.65). It also did not improve the maximum tensile load (p ¼ 0.64) or linear stiffness (p ¼ 0.42) of the ACL repairs after 14 weeks in vivo. The model had 80% power to detect a 30% improvement of biomechanical properties with PRP; thus, we are confident that a clinically meaningful effect as a result of adding PRP is unlikely. Use of PRP alone to supplement suture repair of the ACL is ineffective in this animal model. ß

Sarcopenia and osteoporosis are important public health problems that occur concurrently. A bivariate genome-wide association study (GWAS) identified METTL21c as a suggestive pleiotropic gene for both bone and muscle. METTL21 family of proteins methylates chaperones involved in the etiology of both Inclusion Body Myositis with Paget's disease. To validate these GWAS results, Mettl21c mRNA expression was reduced with siRNA in a mouse myogenic C2C12 cell line and the mouse osteocyte-like cell line MLO-Y4. At day 3, as C2C12 myoblasts start to differentiate into myotubes, a significant reduction in the number of myocytes aligning/organizing for fusion was observed in the siRNA-treated cells. At day 5, both fewer and smaller myotubes were observed in the siRNA-treated cells as confirmed by histomorphometric analyses and immunostaining with Myosin Heavy Chain (MHC) antibody, which only stains myocytes/myotubes but not myoblasts. Intracellular calcium (Ca2+) measurements of the siRNA-treated myotubes showed a decrease in maximal amplitude peak response to caffeine suggesting that less Ca2+ is available for release due to the partial silencing of Mettl21c, correlating with impaired myogenesis. In siRNA-treated MLO-Y4 cells, 48 hours after treatment with dexamethasone, there was a significant increase in cell death, suggesting a role of Mettl21c in osteocyte survival. To investigate the molecular signaling machinery induced by the partial silencing of Mettl21c, we monitored with a real-time PCR gene array the activity of 10 signaling pathways. We discovered that Mettl21c knockdown modulated only the NFκB signaling pathway (i.e., Birc3, Ccl5 and Tnf). These results suggest that Mettl21c might exert its bone-muscle pleiotropic function via the regulation of the NFκB signaling pathway, which is critical for bone and muscle homeostasis. These studies also provide rationale for cellular and molecular validation of GWAS, and warrant additional in vitro and in vivo studies to advance our understanding of role of METTL21C in musculoskeletal biology.

Introduction: Patients admitted to the hospital with sepsis are 8 times more likely to die than patients with other diagnoses. There is no diagnostic test that clearly identifies the presence of the dysregulated host response that is central to sepsis. Researchers have identified serum albumin as a possible predictor of mortality in a number of critically ill patient populations. However, these studies primarily focus on the levels on admission, neglecting the clinically significant decrease that occurs subsequently. The purpose of this study was to examine the relationship between the trend of serum albumin over time and mortality in adults admitted to the intensive care unit (ICU) with sepsis. Methods: This retrospective, correlational study used existing medical record data. All patients admitted to the ICU at a Midwestern regional medical center with a primary sepsis diagnosis were included in the initial sample. Logistic regression analysis was used to assess the ability of serum albumin to predict mortality. Results: Serum albumin trend, admission serum albumin level, and lowest serum albumin level were significant unique predictors of mortality. The probability of survival decreases by 70.6% when there is a strong negative trend in serum albumin level, by 63.4% when admission serum albumin is ≤2.45 g/dl, and by 76.4% when the lowest serum albumin is ≤1.45 g/dl. Conclusion: Clinicians are encouraged to measure serum albumin levels in patients with sepsis. Low serum albumin levels and a strong negative trend in serial measurements should instigate aggressive monitoring and treatment in this population.

Immobilization of the tendon and ligament has been shown to result in a rapid and significant decrease in material properties. It has been proposed that tissue degradation leading to tendon rupture or pain in humans may also be linked to mechanical unloading following focal tendon injury. Hence, understanding the remodeling mechanism associated with mechanical unloading has relevance for the human conditions of immobilization (e.g., casting), delayed repair of tendon ruptures, and potentially overuse injuries as well. This is the first study to investigate the time course of gene expression changes associated with tissue harvest and mechanical unloading culture in an explant model. Rat tail tendon fascicles were harvested and placed in culture unloaded for up to 48 h and then evaluated using qRT-PCR for changes in two anabolic and four catabolic genes at 12 time points. Our data demonstrates that Type I Collagen, Decorin, Cathepsin K, and MMP2 gene expression are relatively insensitive to unloaded culture conditions. However, changes in both MMP3 and MMP13 gene expression are rapid, dramatic, sustained, and changing during at least the first 48 h of unloaded culture. This data will help to further elucidate the mechanism for the loss of mechanical properties associated with mechanical unloading in tendon. ß