Building a Partnership Between a University and Local High School to Foster and Grow Interest in Biomedical Sciences and Engineering.

To help foster interest in science, technology, engineering, and math (STEM), it is important to develop opportunities that excite and teach young minds about STEM-related fields. Over the past several years, our university-based research group has sought to help grow excitement around the biomechanics and biomedical engineering fields. The purposes of this technical brief are to (1) discuss the development of a partnership built between a St. Louis area high school and biomechanics research lab and (2) provide practical guidance for other researchers looking to implement a long-term outreach program. The partnership uses three different outreach opportunities. The first opportunity consisted of 12th-grade students visiting university research labs for an up-close perspective of ongoing biomedical research. The second opportunity was a biomedical research showcase where research-active graduate students traveled to the high school to perform demonstrations. The third opportunity consisted of a collaborative capstone project where a high school student was able to carry out research directly in a university lab. To date, we have expanded our reach from 19 students to interacting with over 100 students, which has yielded increased interest in STEM related research. Our postprogram survey showed that outreach programs such as the one described herein can increase interest in STEM within all ages of high school students. Building partnerships between high schools and university researchers increases the interest in STEM amongst high school students, and gives graduate students an outlet to present work to an eager-to-learn audience.

Effect of matrix properties on transmission and reflectance mode division-of-focal-plane Stokes polarimetry.

Significance: Division-of-focal-plane Stokes polarimetry is emerging as a powerful tool for the microstructural characterization of soft tissues. How individual extracellular matrix (ECM) properties influence polarimetric signals in reflectance or transmission modes of quantitative polarized light imaging (QPLI) is not well understood. Aim: We aimed to investigate how ECM properties affect outcomes obtained from division-of-focal-plane polarimetric imaging in reflectance or transmission modes. Approach: Tunable collagen gel phantoms were used to modulate ECM properties of anisotropy, collagen density, crosslinking, and absorber density; the effects of degree of linear polarization (DoLP) and angle of polarization (AoP) on polarimetry outcomes were assessed. A model biological tissue (i.e., bovine tendon) was similarly imaged and evaluated using both reflectance and transmission modes. Results: Reflectance QPLI resulted in decreased DoLP compared with transmission mode. A 90 deg shift in AoP was observed between modes but yielded similar spatial patterns. Collagen density had the largest effect on outcomes besides anisotropy in both imaging modes. Conclusions: Both imaging modes were sufficiently sensitive to detect structural anisotropy differences in gels of varying fiber alignment. Conclusions drawn from phantom experiments should carry over when interpreting data from more complex tissues and can help provide context for interpretation of other Stokes polarimetry data.

The effects of NF-κB suppression on the early healing response following intrasynovial tendon repair in a canine model.

The highly variable clinical outcomes noted after intrasynovial tendon repair have been associated with an early inflammatory response leading to the development of fibrovascular adhesions. Prior efforts to broadly suppress this inflammatory response have been largely unsuccessful. Recent studies have shown that selective inhibition of IkappaB kinase beta (IKK-ß), an upstream activator of nuclear factor kappa-light chain enhancer of activated B cells (NF-κB) signaling, mitigates the early inflammatory response and leads to improved tendon healing outcomes. In the current study, we test the hypothesis that oral treatment with the IKK-ß inhibitor ACHP (2-amino-6-[2-(cyclopropylmethoxy)-6-hydroxyphenyl]-4-piperidin-4-yl nicotinenitrile an inhibitor) will modulate the postoperative inflammatory response and improve intrasynovial flexor tendon healing. To test this hypothesis, the flexor digitorum profundus tendon of 21 canines was transected and repaired within the intrasynovial region and assessed after 3 and 14 days. Histomorphometry, gene expression analyses, immunohistochemistry, and quantitative polarized light imaging were used to examine ACHP-mediated changes. ACHP led to reduction in phosphorylated p-65, indicating that NF-κB activity was suppressed. ACHP enhanced expression of inflammation-related genes at 3 days and suppressed expression of these genes at 14 days. Histomorphometry revealed enhanced cellular proliferation and neovascularization in ACHP-treated tendons compared with time-matched controls. These findings demonstrate that ACHP effectively suppressed NF-κB signaling and modulated early inflammation, leading to increased cellular proliferation and neovascularization without stimulating the formation of fibrovascular adhesions. Together, these data suggest that ACHP treatment accelerated the inflammatory and proliferative phases of tendon healing following intrasynovial flexor tendon repair. Clinical Significance: Using a clinically relevant large-animal model, this study revealed that targeted inhibition of nuclear factor kappa-light chain enhancer of activated B cells signaling with ACHP provides a new therapeutic strategy for enhancing the repair of sutured intrasynovial tendons.

Modulation of TRPV4 protects against degeneration induced by sustained loading and promotes matrix synthesis in the intervertebral disc.

While it is well known that mechanical signals can either promote or disrupt intervertebral disc (IVD) homeostasis, the molecular mechanisms for transducing mechanical stimuli are not fully understood. The transient receptor potential vanilloid 4 (TRPV4) ion channel activated in isolated IVD cells initiates extracellular matrix (ECM) gene expression, while TRPV4 ablation reduces cytokine production in response to circumferential stretching. However, the role of TRPV4 on ECM maintenance during tissue-level mechanical loading remains unknown. Using an organ culture model, we modulated TRPV4 function over both short- (hours) and long-term (days) and evaluated the IVDs' response. Activating TRPV4 with the agonist GSK101 resulted in a Ca2+ flux propagating across the cells within the IVD. Nuclear factor (NF)-κB signaling in the IVD peaked at 6 h following TRPV4 activation that subsequently resulted in higher interleukin (IL)-6 production at 7 days. These cellular responses were concomitant with the accumulation of glycosaminoglycans and increased hydration in the nucleus pulposus that culminated in higher stiffness of the IVD. Sustained compressive loading of the IVD resulted in elevated NF-κB activity, IL-6 and vascular endothelial growth factor A (VEGFA) production, and degenerative changes to the ECM. TRPV4 inhibition using GSK205 during loading mitigated the changes in inflammatory cytokines, protected against IVD degeneration, but could not prevent ECM disorganization due to mechanical damage in the annulus fibrosus. These results indicate TRPV4 plays an important role in both short- and long-term adaptations of the IVD to mechanical loading. The modulation of TRPV4 may be a possible therapeutic for preventing load-induced IVD degeneration.

Biomechanical Effect of Differential Tensioning on Suture-Augmented Ulnar Collateral Ligament Reconstruction of the Elbow.

BACKGROUND: Medial ulnar collateral ligament (mUCL) reconstructions are becoming increasingly prevalent among the overhand throwing population. Suture tape augmentation has the potential to provide biomechanical advantages over standard docking reconstruction. However, the optimal tensioning of the suture augmentation technique has not yet been evaluated. PURPOSE: To compare the subfailure biomechanical performance and graft strain of a standard docking mUCL reconstruction to an mUCL reconstruction using suture tape augmentation tensioned with 1 mm or 3 mm of laxity. STUDY DESIGN: Controlled laboratory study. METHODS: A total of 18 cadaveric elbows were dissected to the mUCL anterior band and biomechanically assessed via a valgus torque protocol to failure. Elbows were randomly assigned to be reconstructed via (1) a standard docking technique, (2) a suture-augmented reconstruction with 1-mm laxity, or (3) a suture-augmented reconstruction with 3-mm laxity. Reconstructed elbows were then subjected to the same loading protocol. Subfailure mechanical properties, failure mode, and mUCL/palmaris strain were assessed. RESULTS: All reconstruction groups had decreased rotational stiffness, torque at 5° of angular rotation, and resilience compared with matched native controls. There were no differences in transition torque between groups. The failure mode of suture-augmented specimens was most often due to bone tunnel failure or reaching the maximum allowable angular displacement. In native controls or docking reconstructions, the primary failure mechanism was in the ligament or graft midsubstance. There were no significant differences in strain on the reconstructed or suture-augmented groups at any laxity compared with native controls. CONCLUSION: Suture augmentation results in similar subfailure joint biomechanical properties as the standard docking reconstruction procedure at both laxity levels in a cadaveric model. There are improvements in the failure mode of suture-augmented specimens compared with standard docking. Graft strain may be modestly reduced in the 1-mm laxity group compared with other reconstruction groups. CLINICAL RELEVANCE: Suture augmentation at both 1-mm and 3-mm laxity appears to offer similar advantages in subfailure biomechanics to standard docking reconstruction of the mUCL, with some improvements associated with failure mode. Strain data suggest a potential avoidance of graft stress shielding when tensioning the suture augmentation to 3-mm laxity, which is not as apparent with 1-mm laxity.

Pleiotropic Effects of Simvastatin and Losartan in Preclinical Models of Post-Traumatic Elbow Contracture.

Elbow trauma can lead to post-traumatic joint contracture (PTJC), which is characterized by loss of motion associated with capsule/ligament fibrosis and cartilage damage. Unfortunately, current therapies are often unsuccessful or cause complications. This study aimed to determine the effects of prophylactically administered simvastatin (SV) and losartan (LS) in two preclinical models of elbow PTJC: an in vivo elbow-specific rat injury model and an in vitro collagen gel contraction assay. The in vivo elbow rat (n = 3-10/group) injury model evaluated the effects of orally administered SV and LS at two dosing strategies [i.e., low dose/high frequency/short duration (D1) vs. high dose/low frequency/long duration (D2)] on post-mortem elbow range of motion (via biomechanical testing) as well as capsule fibrosis and cartilage damage (via histopathology). The in vitro gel contraction assay coupled with live/dead staining (n = 3-19/group) evaluated the effects of SV and LS at various concentrations (i.e., 1, 10, 100 µM) and durations (i.e., continuous, short, or delayed) on the contractibility and viability of fibroblasts/myofibroblasts [i.e., NIH3T3 fibroblasts with endogenous transforming growth factor-beta 1 (TGFß1)]. In vivo, no drug strategy prevented elbow contracture biomechanically. Histologically, only SV-D2 modestly reduced capsule fibrosis but maintained elevated cellularity and tissue hypertrophy, and both SV strategies lessened cartilage damage. SV modest benefits were localized to the anterior region, not the posterior, of the joint. Neither LS strategy had meaningful benefits in capsule nor cartilage. In vitro, irrespective of the presence of TGFß1, SV (≥10 µM) prevented gel contraction partly by decreasing cell viability (100 µM). In contrast, LS did not prevent gel contraction or affect cell viability. This study demonstrates that SV, but not LS, might be suitable prophylactic drug therapy in two preclinical models of elbow PTJC. Results provide initial insight to guide future preclinical studies aimed at preventing or mitigating elbow PTJC.

Increasing Dorsal Tilt in Distal Radius Fractures Does Not Increase Median Nerve Strain.

Although extensive research shows an association between distal radius fractures and the development of median nerve related pathologies such as carpal tunnel syndrome, none directly track how the resulting angular deformity relates to likelihood of development of median nerve pathology. Methods: Median nerve strain was measured with a custom-built system using a camera, optical markers, and a proprietary segmentation algorithm. After initial validation of the system in a cadaver model, our system was used to assess strain in 10 cadaver arms with a simulated distal radius fracture and increasing dorsal angulation. The measured strain at each angle was then analyzed using a linear regression model. Results: The linear regression model in the validation experiment demonstrated a regression coefficient of 1.00067 (P < 0.0001) with r2 = 0.899, thus validating the use of the optical tracking system. The average strain at maximum dorsal angulation (50 degrees) across all specimens was -0.2%. Linear regression analysis of the effect of increasing dorsal angulation on strain in the osteotomy model yielded a regression coefficient of -0.000048 (P = 0.714), r2 = 0.00129, suggesting no significant correlation between increasing dorsal tilt and median nerve strain. Conclusions: Increases in median nerve strain at the wrist are negligible with increasing dorsal tilt in a distal radius fracture model. It is therefore likely that other factors, such as increased pressure within the carpal tunnel, are the primary cause of median neuropathy in distal radius malunions. Therefore, correction of dorsal tilt may not be required to improve neurologic symptoms.

Cellular and Chemical Gradients to Engineer the Meniscus-to-Bone Insertion.

Tissue-engineered menisci hold promise as an alternative to allograft procedures but require a means of robust fixation to the native bone. The insertion of the meniscus into bone is critical for meniscal function and inclusion of a soft tissue-to-bone interface in a tissue engineered implant can aid in the fixation process. The native insertion is characterized by gradients in composition, tissue architecture, and cellular phenotype, which are all difficult to replicate. In this study, a soft tissue-to-bone interface is tissue engineered with a cellular gradient of fibrochondrocytes and mesenchymal stem cells and subjected to a biochemical gradient through a custom media diffusion bioreactor. These constructs, consisting of interpenetrating collagen and boney regions, display improved mechanical performance and collagen organization compared to controls without a cellular or chemical gradient. Media gradient exposure produces morphological features in the constructs that appear similar to the native tissue. Collectively, these data show that cellular and biochemical gradients improve integration between collagen and bone in a tissue engineered soft tissue-to-bone construct.