Integrated spatial multiomics reveals fibroblast fate during tissue repair.

In the skin, tissue injury results in fibrosis in the form of scars composed of dense extracellular matrix deposited by fibroblasts. The therapeutic goal of regenerative wound healing has remained elusive, in part because principles of fibroblast programming and adaptive response to injury remain incompletely understood. Here, we present a multimodal -omics platform for the comprehensive study of cell populations in complex tissue, which has allowed us to characterize the cells involved in wound healing across both time and space. We employ a stented wound model that recapitulates human tissue repair kinetics and multiple Rainbow transgenic lines to precisely track fibroblast fate during the physiologic response to skin injury. Through integrated analysis of single cell chromatin landscapes and gene expression states, coupled with spatial transcriptomic profiling, we are able to impute fibroblast epigenomes with temporospatial resolution. This has allowed us to reveal potential mechanisms controlling fibroblast fate during migration, proliferation, and differentiation following skin injury, and thereby reexamine the canonical phases of wound healing. These findings have broad implications for the study of tissue repair in complex organ systems.

The Choice Between Total Hip Arthroplasty and Arthrodesis in Adolescent Patients: A Survey of Orthopedic Surgeons.

For adolescent patients with end-stage hip disease, the choice between total hip arthroplasty (THA) and arthrodesis is complex; the clinical evidence is not definitive, and there are difficult trade-offs between clear short-term benefits from THA and uncertain long-term risks. We surveyed nearly 700 members of the Pediatric Orthopedic Society of North America and the American Association of Hip and Knee Surgeons. Respondents chose between a recommendation of THA or arthrodesis in four clinical vignettes. A clear majority of surgeons recommended THA in two of the vignettes, however opinion was somewhat divided in one vignette (overweight adolescent) and deeply divided in another (adolescent destined for manual labor job). Across all vignettes, recommendations varied systematically according to surgeons' age and their attitudes regarding tradeoffs between life stages.

Long-Term Results of Suture-Button Suspensionplasty in the Treatment of Thumb Carpometacarpal Arthritis: A Minimum 10-Year Follow-Up.

Purpose: Combined trapeziectomy and suture-button suspensionplasty (SBS) is a common and well-established surgical treatment for thumb carpometacarpal (CMC) osteoarthritis. Although short and mid-term follow-up studies have shown promising outcomes with patients retaining excellent range of motion and strength, long-term data are lacking. The aim of our study was to assess the long-term outcomes of patients who underwent SBS surgery for thumb CMC arthritis, with a minimum follow-up period of 10 years. Methods: We evaluated 17 patients, at least 10 years after undergoing SBS surgery for thumb CMC arthritis. We measured grip and pinch strength, range of motion, and trapezial space height and compared it with the respective values measured on the routine postoperative 3-month follow-up visit. All patients have additionally completed the Quick Disabilities of the Arm, Shoulder, and Hand questionnaire. Results: The study included 11 women and 6 men with an average age of 60.3 ± 6.4 years and a mean follow-up of 137.4 ± 11.4 months after surgery. The mean Quick Disabilities of the Arm, Shoulder, and Hand score was 9 (range: 0-40.9) at the long-term follow-up, compared with 26.2 (range: 4.5-75) recorded 3 months after the surgery. Grip and pinch strengths were 116% and 111% of the 3-month postoperative value, respectively. Radial abduction and palmar abduction were 98% and 94% of the 3-month postoperative value, respectively. Kapandji scores were either equal or higher than the previously documented scores. Average height of the trapezial space was 69% of the previous postoperative measurement. Conclusions: Our findings demonstrate that patients who underwent SBS surgery for thumb CMC osteoarthritis achieve excellent long-term outcomes by maintaining favorable subjective and objective results, despite some radiographic subsidence over time. These results indicate SBS to be an effective and durable technique for the long-term management of thumb CMC osteoarthritis. Type of study/level of evidence: Therapeutic IV.

State of the art review: The management of chronic vascular disorders in the hand and upper limb.

This review article summarizes the basic principles of vascular anatomy, physiology, diagnostic work-up and treatment for patients with nontraumatic upper extremity vascular disorders. Vascular disorders can be considered vasospastic or occlusive. The most commonly encountered vasospastic condition is Raynaud's Phenomenon secondary to scleroderma. While historically this has been managed medically with vasodilators, more advanced cases can benefit from surgical treatment to improve blood flow and minimize tissue loss, with compelling evidence that earlier surgical intervention can modify disease process and should be considered. Occlusive disease can present as aneurysm or thrombosis and often requires surgical treatment with resection of the occluded segment with or without vascular reconstruction. In advanced atherosclerotic disease or end stage ischemia, arterialization of the venous system can be considered to avoid more proximal amputations.

Reduction of Tendon Fibrosis Using Galectin-3 Inhibitors.

BACKGROUND: Fibrosis is a complication of both tendon injuries and repairs. We aim to develop a mouse model to assess tendon fibrosis and to identify an antifibrotic agent capable of overcoming tendon fibrosis. METHODS: Adult C57Bl/6 mice underwent a skin incision to expose the Achilles tendon, followed by 50% tendon injury and abrasion with sandpaper. Sham surgeries were conducted on contralateral hindlimbs. Histology and immunofluorescent staining for fibrotic markers (Col1, α-SMA) were used to confirm that the model induced tendon fibrosis. A second experiment was conducted to further examine the role of α-SMA in adhesion formation using α-SMA.mTmG mice (6-8 weeks old) (n=3) with the same injury model. The control group (tendon injury) was compared to the sham group, using the contralateral limb with skin incision only. A second experiment was conducted to further examine the role of α-SMA in adhesion formation using α-SMA.mTmG mice (6-8 weeks old) (n=3) with the same injury model. The control group (tendon injury) was compared to the sham group, using the contralateral limb with skin incision only. Lastly, α-SMA.mTmG mice were randomized to either condition 1. Tendon injury (control group) or 2. Tendon injury with Galectin-3 inhibitor (Gal3i) treatment at time of injury (treatment group). RESULTS: Histological analyses confirmed tendon thickening and collagen deposition after tendon injury and abrasion compared to control. Immunofluorescence showed higher levels of Col1 and α-SMA protein expression after injury compared to sham (*p<0.05). RT-qPCR also demonstrated increased gene expression of Col1 and α-SMA after injury compared to sham (*p<0.05). Gal3 protein expression also increased after injury and co-localized with α-SMA positive fibroblasts surrounding the fibrotic tendon. Gal3i treatment decreased collagen deposition and scarring observed in the treatment group (*p<0.05). Flow cytometry analysis further showed reduced numbers of profibrotic fibroblasts (CD26+) in the treatment compared to the control group (*p<0.05). CONCLUSIONS: Our study provides a reproducible and reliable model to investigate tendon fibrosis. Findings suggest the potential of Gal3i to overcome fibrosis resulting from tendon injuries.

Partial Tendon Injury at the Tendon-to-Bone Enthesis Activates Skeletal Stem Cells.

The tendon enthesis plays a critical role in facilitating movement and reducing stress within joints. Partial enthesis injuries heal in a mechanically inferior manner and never achieve healthy tissue function. The cells responsible for tendon-to-bone healing remain incompletely characterized and their origin is unknown. Here, we evaluated the putative role of mouse skeletal stem cells (mSSCs) in the enthesis after partial-injury. We found that mSSCs were present at elevated levels within the enthesis following injury and that these cells downregulated TGFß signaling pathway elements at both the RNA and protein levels. Exogenous application of TGFß post-injury led to a reduced mSSC response and impaired healing, whereas treatment with a TGFß inhibitor (SB43154) resulted in a more robust mSSC response. Collectively, these data suggest that mSSCs may augment tendon-to-bone healing by dampening the effects of TGFß signaling within the mSSC niche.

Multiomic analysis reveals conservation of cancer-associated fibroblast phenotypes across species and tissue of origin.

Cancer-associated fibroblasts (CAFs) are integral to the solid tumor microenvironment. CAFs were once thought to be a relatively uniform population of matrix-producing cells, but single-cell RNA sequencing has revealed diverse CAF phenotypes. Here, we further probed CAF heterogeneity with a comprehensive multiomics approach. Using paired, same-cell chromatin accessibility and transcriptome analysis, we provided an integrated analysis of CAF subpopulations over a complex spatial transcriptomic and proteomic landscape to identify three superclusters: steady state-like (SSL), mechanoresponsive (MR), and immunomodulatory (IM) CAFs. These superclusters are recapitulated across multiple tissue types and species. Selective disruption of underlying mechanical force or immune checkpoint inhibition therapy results in shifts in CAF subpopulation distributions and affected tumor growth. As such, the balance among CAF superclusters may have considerable translational implications. Collectively, this research expands our understanding of CAF biology, identifying regulatory pathways in CAF differentiation and elucidating therapeutic targets in a species- and tumor-agnostic manner.

The role of gender in non-small cell lung cancer: a narrative review.

The role of gender in the development, treatment and prognosis of thoracic malignancies has been underappreciated and understudied. While most research has been grounded in tobacco-related malignancies, the incidence of non-smoking related lung cancer is on the rise and disproportionately affecting women. Recent research studies have unveiled critical differences between men and women with regard to risk factors, timeliness of diagnosis, incongruent screening practices, molecular and genetic mechanisms, as well as response to treatment and survival. These studies also highlight the increasingly recognized need for targeted therapies that account for variations in the response and complications as a function of gender. Similarly, screening recommendations continue to evolve as the role of gender is starting to be ellucidated. As women have been underrepresented in clinical trials until recently, the data regarding optimal care and outcomes is still lagging behind. Understanding the underlying similarities and differences between men and women is paramount to providing adequate care and prognostication to patients of either gender. This review provides an overview of the critical role that gender plays in the care of patients with non-small cell lung cancer and other thoracic malignancies, with an emphasis on the need for increased awareness and further research to continue elucidating these disparities.

Navigating the Infinite Number of Educational Resources: The Development of a Publicly Available Surgical Educational Digital Resource Library.

OBJECTIVE: There has been an explosion of digital resources available for general surgical education and board preparation. This makes it difficult for a new learner, regardless of their training level, to determine which resources best fit their needs. The uncertainty surrounding resource selection due to the large number of options causes stress, anxiety, and inefficiency for surgical learners. Our objective was to develop a digital surgical educational resource library to assist with selection. DESIGN: A needs assessment via multi-center focus groups encompassing all levels of learners from various subspecialties and training levels (medical students, trainees, junior surgeons, and senior surgeons) was performed to determine what information is desired in a surgical resource library. We conducted follow-up interviews and surveys to learn which resources were most commonly used for studying throughout training. SETTING: Multi-institutional RESULTS: The initial needs assessment detailed requests for an expansive array of surgical resources characterized by media type and price. We identified 104 resources that met these criteria. There were 33 resources used by medical students, 37 by residents, 16 used specifically for surgical boards preparation, and 25 by attending surgeons. These resources were composed of textbooks, review books, question banks, audio resources, video resources, and review courses. The prices of the resources ranged from free to greater than 400 dollars. CONCLUSIONS: A digital resource library should be broad and must address needs that change along a learner's career. Changes and improvements are required not only to meet the changing needs of the learners, but also to ensure the library remains current with the ever-growing number of resources. We plan to incorporate reviews of the resources from those surveyed to help visitors of the online library determine which resources may best suit their needs. Development of a digital resource library may assist learners by helping them easily identify what is available and has been peer reviewed allowing them to determine what best meets their educational needs.

Proceed with Caution: Mouse Deep Digit Flexor Tendon Injury Model.

The purpose of this study was to determine the feasibility of using mouse models for translational study of flexor tendon repair and reconstruction. METHODS: Quantitative data detailing the gross anatomy, biomechanical characteristics, and microscopic structure of the deep digit flexor tendon (DDF) of the mouse hindpaw were obtained. Histological characterization of the DDF and the anatomy of the digit in the mouse hindpaw are detailed. Biomechanical testing determined the load-to-failure, stress, elastic modulus, and the site of tendon failure. RESULTS: In gross anatomy, the origins and insertions of the mouse deep digit flexor tendon are similar to those of the human digit, surrounded by a synovial sheath that is only 1- to 2-cells thick. A neurovascular network runs on each side of the digit outside the synovial sheath, but does not clearly penetrate it. The thickness of the DDF is 0.14 ± 0.03 mm and the width is 0.3 ± 0.03 mm. The thickness of the DDF is less than that of 9-0 nylon needle. The mean failure force of the deep flexor tendon was 2.79 ± 0.53N. CONCLUSIONS: The gross anatomy of the mouse hindpaw digit is similar to that of the human digit except for key differences seen in the synovial sheath and vascular supply. The dimensions of the mouse DDF make it challenging to create a clinically translatable repair model using currently available surgical techniques. Despite the similarities between the human and mouse anatomy, and the powerful basic science tools available in murine models, mice are an unreliable model for assessing flexor tendon injury and repair.

Impact of COVID-19 on presentation, management, and outcomes of acute care surgery for gallbladder disease and acute appendicitis.

BACKGROUND: The ongoing coronavirus disease 2019 (COVID-19) pandemic has significantly disrupted both elective and acute medical care. Data from the early months suggest that acute care patient populations deferred presenting to the emergency department (ED), portending more severe disease at the time of presentation. Additionally, care for this patient population trended towards initial non-operative management. AIM: To examine the presentation, management, and outcomes of patients who developed gallbladder disease or appendicitis during the pandemic. METHODS: A retrospective chart review of patients diagnosed with acute cholecystitis, symptomatic cholelithiasis, or appendicitis in two EDs affiliated with a single tertiary academic medical center in Northern California between March and June, 2020 and in the same months of 2019. Patients were selected through a research repository using international classification of diseases (ICD)-9 and ICD-10 codes. Across both years, 313 patients were identified with either type of gallbladder disease, while 361 patients were identified with acute appendicitis. The primary outcome was overall incidence of disease. Secondary outcomes included presentation, management, complications, and 30-d re-presentation rates. Relationships between different variables were explored using Pearson's r correlation coefficient. Variables were compared using the Welch's t-Test, Chi-squared tests, and Fisher's exact test as appropriate. RESULTS: Patients with gallbladder disease and appendicitis both had more severe presentations in 2020. With respect to gallbladder disease, more patients in the COVID-19 cohort presented with acute cholecystitis compared to the control cohort [50% (80) vs 35% (53); P = 0.01]. Patients also presented with more severe cholecystitis in 2020 as indicated by higher mean Tokyo Criteria Scores [mean (SD) 1.39 (0.56) vs 1.16 (0.44); P = 0.02]. With respect to appendicitis, more patients were diagnosed with a perforated appendix at presentation in 2020 [20% (36) vs 16% (29); P = 0.02] and a greater percentage were classified as emergent cases using the emergency severity index [63% (112) vs 13% (23); P < 0.001]. While a greater percentage of patients were admitted to the hospital for gallbladder disease in 2020 [65% (104) vs 50% (76); P = 0.02], no significant differences were observed in hospital admissions for patients with appendicitis. No significant differences were observed in length of hospital stay or operative rate for either group. However, for patients with appendicitis, 30-d re-presentation rates were significantly higher in 2020 [13% (23) vs 4% (8); P = 0.01]. CONCLUSION: During the COVID-19 pandemic, patients presented with more severe gallbladder disease and appendicitis. These findings suggest that the pandemic has affected patients with acute surgical conditions.

Perioperative opioid use and pain-related outcomes in the Veterans Health Administration.

Understanding variation in perioperative opioid exposure and its effect on patients' outcomes is critical for pain management. This study characterized perioperative exposure to morphine and its association with postoperative pain and 30-day readmissions. We utilized nationwide Veterans Healthcare Administration (VHA) data on four high-volume surgical procedures, 2007-2014. We identified 235,239 Veterans undergoing orthopedic, general, or vascular surgery; 5.4% high trajectories (116.1 OME/Day), 53.2% medium trajectories (39.7 OME/Day), and 41.4% low trajectories (19.1 OME/Day). Modeled estimates suggest that patients in the high OME group had higher risk of a pain-related readmission (OR: 1.59; CI: 1.39, 1.83) compared to the low OME trajectory. Yet when stratified by pain trajectory, patients with high pain and high OME had lower risk of a pain-related readmission compared to patients in the high pain low OME group (OR: 0.76, CI: 0.62, 0.94). In conclusion, patients receiving high perioperative OME are more likely to return to care for pain-related problems. This study highlights opportunities to reduce the amount of prescriptions opioids in the communities.

The Effect of Surgical Trainee Education on Opioid Prescribing: An International Evaluation.

INTRODUCTION: Up to 6% of opioid naive patients who undergo surgery become chronic opioid users. The aim of this study was to determine if formal opioid prescribing education of general surgery residents is associated with decreased opioid prescribing postoperatively. METHODS: We surveyed surgery residents at 3 general surgery programs in the United States and 1 in Israel. Residents were divided into 2 groups based on whether or not they received formal opioid prescribing education. RESULTS: Of those surveyed, 107 (50%) responded. 45% of residents had formal opioid prescribing education, which included instructional videos, current literature, and hospital guidelines. For the 4 operations analyzed, residents who received no formal teaching prescribed a higher number of opioids (lumpectomy p = 0.001, open inguinal hernia repair p = 0.004, laparoscopic appendectomy p = 0.007, thyroidectomy p = 0.002). The largest difference in opioid prescribing was seen in "high prescribers," defined as residents prescribing 15 or more opioid pills. For thyroidectomy, 24.4% of residents without formal education prescribed 20 or more oxycodone 5mg pills compared to 0% of residents with formal education. The Israeli cohort was less likely to receive a pain focused education and was also less likely to prescribe opioids to their patients for all 4 procedures evaluated. CONCLUSIONS: Although a minority of general surgery residents are receiving an opioid prescribing education, a formal educational program was associated with significantly decreased opioid prescribing. There is a need for a generalizable educational opioid program for surgery residents.

The influence of hormone replacement therapy on lung cancer incidence and mortality.

OBJECTIVE: Data regarding the effects of hormone replacement therapy (HRT) on non-small cell lung cancer (NSCLC) are mixed. We hypothesized HRT would have a protective benefit with reduced NSCLC incidence among women in a large, prospective cohort. METHODS: We used data from the multicenter randomized Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (1993-2001). Participants were women aged 50 to 74 years followed prospectively for up to 13 years for cancer screening. The influence of HRT on the primary outcome of NSCLC incidence and secondary outcomes of all-cause and disease-specific mortality were assessed with Kaplan-Meier analysis and Cox proportional hazard models adjusting for covariates. RESULTS: In the overall cohort of 75,587 women, 1147 women developed NSCLC after a median follow-up of 11.5 years. HRT use was characterized as 49.4% current users, 17.0% former users, and 33.6% never users. Increased age, smoking, comorbidities, and family history were associated with increased risk of NSCLC. On multivariable analysis, current HRT use was associated with reduced risk of NSCLC compared with never users (hazard ratio, 0.80; 95% confidence interval, 0.70-0.93; P = .009). HRT or oral contraception use was not associated with significant differences in all-cause mortality or disease-specific mortality. CONCLUSIONS: These data represent among the largest prospective cohorts suggesting HRT use may have a protective effect on the development of NSCLC among women; the physiological basis of this effect merits further study; however, the results may influence discussion surrounding HRT use in women.

Management of Ileal Neuroendocrine Tumors with Liver Metastases.

PURPOSE: Assessment of treating metastatic ileal neuroendocrine tumors (NETs) with complete resection of primary tumor, nodal and liver metastases, plus administration of long-acting somatostatin analogues (SSAs). METHODS: A prospective database was queried for patients with ileal or pancreatic NETs with pathology-confirmed liver metastases and tumor somatostatin receptors. Patients did not have MEN-1 and had no previous treatment. The impacts of SSA treatment on the primary outcome of survival and secondary outcome of progression-free survival were assessed with Kaplan-Meier analysis. Log rank test was used to compare overall and progression-free survival among groups. RESULTS: Seventeen ileal NET patients and 36 pancreatic NET patients who underwent surgical resection between 2001 and 2018, who had pathology-confirmed liver metastases and confirmed tumor somatostatin receptors, did not have MEN-1, and had no previous treatment were identified. Median follow-up for patients with ileal NETs was 80 months (range 0-197 months) and 32 months (range 1-182 months) for pancreatic NETs. Five-year survival was 93% and 72% for ileal and pancreatic NET, respectively. Progression-free 5-year survival was 70% and 36% for ileal and pancreatic NET, respectively. Overall 5-year survival for pNETs was greater in those patients treated with SSA (79%) compared to those who underwent surgery alone (34%, p < 0.01). The average ECOG score was low for surviving patients with ileal (0.15) and pancreatic NET (0.73) indicating a good quality of life. CONCLUSIONS: Resection of primary lymph node and liver metastatic ileal or pancreatic NETs followed with continued SSAs is associated with an excellent progression-free and overall survival and minimal side effects.

Evaluation of Outcomes Following Surgery for Locally Advanced Pancreatic Neuroendocrine Tumors.

Importance: Although outcome of surgical resection of liver metastases from pancreatic neuroendocrine tumors (PNETs) has been extensively studied, little is known about surgery for locally advanced PNETs; it was listed recently by the European neuroendocrine tumor society as a major unmet need. Objective: To evaluate the outcome of patients who underwent surgery for locally aggressive PNETs. Design, Setting, and Participants: This retrospective single-center case series reviewed consecutive patients who underwent resection of T3/T4 PNETs at a single academic institution. Data collection occurred from 2003 to 2018. Data analysis was performed in August 2019. Main Outcomes and Measures: Disease-free survival (primary outcome) and overall mortality (secondary outcome) were assessed with Kaplan-Meier analysis. Recurrence risk (secondary outcome, defined as identification of tumor recurrence on imaging) was assessed with Cox proportional hazard models adjusting for covariates. Results: In this case series, 99 patients with locally advanced nondistant metastatic PNET (56 men [57%]) with a mean (SEM) age of 57.0 (1.4) years and a mean (SEM) follow-up of 5.3 (0.1) years underwent surgically aggressive resections. Of those, 4 patients (4%) underwent preoperative neoadjuvant treatment (including peptide receptor radionuclide therapy and chemotherapy); 18 patients (18%) underwent pancreaticoduodenectomy, 68 patients (69%) had distal or subtotal pancreatic resection, 10 patients (10%) had total resection, and 3 patients (3%) had other pancreatic procedures. Additional organ resection was required in 86 patients (87%): spleen (71 patients [71%]), major blood vessel (17 patients [17%]), bowel (2 patients [2%]), stomach (4 patients [4%]), and kidney (2 patients [2%]). Five-year disease-free survival was 61% (61 patients) and 5-year overall survival was 91% (91 patients). Of those living, 75 patients (76%) had an Eastern Cooperative Oncology Group score of less than or equal to 1 at last followup. Lymph node involvement (HR, 7.66; 95% CI, 2.78-21.12; P < .001), additional organ resected (HR, 6.15; 95% CI, 1.61-23.55; P = .008), and male sex (HR, 3.77; 95% CI, 1.68-8.97; P = .003) were associated with increased risk of recurrence. Functional tumors had a lower risk of recurrence (HR, 0.23; CI, 0.06-0.89; P = .03). Required resection of blood vessels was not associated with a significant increase recurrence risk. Conclusions and Relevance: In this case series, positive lymph node involvement and resection of organs with tumor involvement were associated with an increased recurrence risk. These subgroups may require adjuvant systemic treatment. These findings suggest that patients with locally advanced PNETs who undergo surgical resection have excellent disease-free and overall survival.

Elucidating the fundamental fibrotic processes driving abdominal adhesion formation.

Adhesions are fibrotic scars that form between abdominal organs following surgery or infection, and may cause bowel obstruction, chronic pain, or infertility. Our understanding of adhesion biology is limited, which explains the paucity of anti-adhesion treatments. Here we present a systematic analysis of mouse and human adhesion tissues. First, we show that adhesions derive primarily from the visceral peritoneum, consistent with our clinical experience that adhesions form primarily following laparotomy rather than laparoscopy. Second, adhesions are formed by poly-clonal proliferating tissue-resident fibroblasts. Third, using single cell RNA-sequencing, we identify heterogeneity among adhesion fibroblasts, which is more pronounced at early timepoints. Fourth, JUN promotes adhesion formation and results in upregulation of PDGFRA expression. With JUN suppression, adhesion formation is diminished. Our findings support JUN as a therapeutic target to prevent adhesions. An anti-JUN therapy that could be applied intra-operatively to prevent adhesion formation could dramatically improve the lives of surgical patients.

Flexor Tendon: Development, Healing, Adhesion Formation, and Contributing Growth Factors.

Management of flexor tendon injuries of the hand remains a major clinical problem. Even with intricate repair, adhesion formation remains a common complication. Significant progress has been made to better understand the mechanisms of healing and adhesion formation. However, there has been slow progress in the clinical prevention and reversal of flexor tendon adhesions. The goal of this article is to discuss recent literature relating to tendon development, tendon healing, and adhesion formation to identify areas in need of further research. Additional research is needed to understand and compare the molecular, cellular, and genetic mechanisms involved in flexor tendon morphogenesis, postoperative healing, and mechanical loading. Such knowledge is critical to determine how to improve repair outcomes and identify new therapeutic strategies to promote tissue regeneration and prevent adhesion formation.

A Clearing Technique to Enhance Endogenous Fluorophores in Skin and Soft Tissue.

Fluorescent proteins are used extensively in transgenic animal models to label and study specific cell and tissue types. Expression of these proteins can be imaged and analyzed using fluorescent and confocal microscopy. Conventional confocal microscopes cannot penetrate through tissue more than 4-6 µm thick. Tissue clearing procedures overcome this challenge by rendering thick specimens into translucent tissue. However, most tissue clearing techniques do not satisfactorily preserve expression of endogenous fluorophores. Using simple adjustments to the BABB (Benzoic Acid Benzyl Benzoate) clearing methodology, preservation of fluorophore expression can be maintained. Modified BABB tissue clearing is a reliable technique to clear skin and soft tissue specimens for the study of dermal biology, wound healing and fibrotic pathologies.