Tendons have uniquely high tensile strength, critical to their function to transfer force from muscle to bone. When injured, their innate healing response results in aberrant matrix organization and functional properties. Efforts to regenerate tendon are challenged by limited understanding of its normal development. Consequently, there are few known markers to assess tendon formation and parameters to design tissue engineering scaffolds. We profiled mechanical and biological properties of embryonic tendon and demonstrated functional properties of developing tendon are not wholly reflected by protein expression and tissue morphology. Using force volume-atomic force microscopy, we found that nano-and microscale tendon elastic moduli increase nonlinearly and become increasingly spatially heterogeneous during embryonic development. When we analyzed potential biochemical contributors to modulus, we found statistically significant but weak correlation between elastic modulus and collagen content, and no correlation with DNA or glycosaminoglycan content, indicating there are additional contributors to mechanical properties. To investigate collagen cross-linking as a potential contributor, we inhibited lysyl oxidasemediated collagen cross-linking, which significantly reduced tendon elastic modulus without affecting collagen morphology or DNA, glycosaminoglycan, and collagen content. This suggests that lysyl oxidase-mediated cross-linking plays a significant role in the development of embryonic tendon functional properties and demonstrates that changes in cross-links alter mechanical properties without affecting matrix content and organization. Taken together, these data demonstrate the importance of functional markers to assess tendon development and provide a profile of tenogenic mechanical properties that may be implemented in tissue engineering scaffold design to mechanoregulate new tendon regeneration.musculoskeletal | second harmonic generation T endon is a principal tissue involved in movement, functioning primarily to transfer loads from muscle to bone. Acute and chronic tendon injuries are significant clinical problems due to poor innate healing ability and drawbacks associated with surgical repair (1, 2). In 2006, musculoskeletal symptoms were the second most frequent reason for physician visits in the United States, resulting in over 130 million visits at a cost of nearly $850 billion (3). Almost half of these visits involved tendons and ligaments, with incidence expected to rise with an aging population. Thus, efforts have focused on engineering new tissues for replacement, although this has been challenged by a paucity of markers with which to assess functional tendon development and few known cues to direct differentiation and new tissue formation.Characterization of tendon formation in embryonic or engineered tissue has typically relied on molecular markers, as well as matrix composition and organization (4-9). Although useful for assessing cell differentiation and ECM deposition during tissue formation, t...

COVID-19 caused by SARS-CoV-2 has become a global pandemic requiring the development of interventions for the prevention or treatment to curtail mortality and morbidity. No vaccine to boost mucosal immunity, or as a therapeutic, has yet been developed to SARS-CoV-2. In this study, we discover and characterize a cross-reactive human IgA monoclonal antibody, MAb362. MAb362 binds to both SARS-CoV and SARS-CoV-2 spike proteins and competitively blocks ACE2 receptor binding, by overlapping the ACE2 structural binding epitope. Furthermore, MAb362 IgA neutralizes both pseudotyped SARS-CoV and SARS-CoV-2 in 293 cells expressing ACE2. When converted to secretory IgA, MAb326 also neutralizes authentic SARS-CoV-2 virus while the IgG isotype shows no neutralization. Our results suggest that SARS-CoV-2 specific IgA antibodies, such as MAb362, may provide effective immunity against SARS-CoV-2 by inducing mucosal immunity within the respiratory system, a potentially critical feature of an effective vaccine.

Background. Tick transmission of Borrelia spirochetes to humans results in significant morbidity from Lyme disease worldwide. Serum concentrations of antibodies against outer surface protein A (OspA) were shown to correlate with protection from infection with Borrelia burgdorferi, the primary cause of Lyme disease in the United States.Methods. Mice transgenic for human immunoglobulin genes were immunized with OspA from B. burgdorferi to generate human monoclonal antibodies (HuMabs) against OspA. HuMabs were generated and tested in in vitro borreliacidal assays and animal protection assays.Results. Nearly 100 unique OspA-specific HuMabs were generated, and 4 HuMabs (221-7, 857-2, 319-44, and 212-55) were selected as lead candidates on the basis of borreliacidal activity. HuMabs 319-44, 857-2, and 212-55 were borreliacidal against 1 or 2 Borrelia genospecies, whereas 221-7 was borreliacidal (half maximal inhibitory concentration, < 1 nM) against B. burgdorferi, Borrelia afzelii, and Borrelia garinii, the 3 main genospecies endemic in the United States, Europe, and Asia. All 4 HuMabs completely protected mice from infection at 10 mg/kg in a murine model of tick-mediated transmission of B. burgdorferi.Conclusions. Our study indicates that OspA-specific HuMabs can prevent the transmission of Borrelia and that administration of these antibodies could be employed as preexposure prophylaxis for Lyme disease.

Tendon injuries heal as scar tissue with significant dysfunction and propensity to re-injure, motivating efforts to develop stem cell-based therapies for tendon regeneration. For these therapies to succeed, effective cues to guide tenogenesis are needed. Our aim is to identify these cues within the embryonic tendon microenvironment. We recently demonstrated embryonic tendon elastic modulus increases during development and is substantially lower than in adult. Here, we examined how these embryonic mechanical properties influence tenogenically differentiating cells, by culturing embryonic tendon progenitor cells (TPCs) within alginate gel scaffolds fabricated with embryonic tendon mechanical properties. We showed that nano- and microscale moduli of RGD-functionalized alginate gels can be tailored to that of embryonic tendons by adjusting polymer concentration and crosslink density. These gels differentially regulated morphology of encapsulated TPCs as a function of initial elastic modulus. Additionally, higher initial elastic moduli elicited higher mRNA levels of scleraxis and collagen type XII but lower levels of collagen type I, whereas late tendon markers tenomodulin and collagen type III were unaffected. Our results demonstrate the potential to engineer scaffolds with embryonic mechanical properties and to use these scaffolds to regulate the behavior of tenogenically differentiating cells.