Harnessing the Potential of Enzymes as Inhaled Therapeutics in Respiratory Tract Diseases: A Review of the Literature.

Respiratory tract diseases (RTDs) are a global cause of mortality and affect patient well-being and quality of life. Specifically, there is a high unmet need concerning respiratory tract infections (RTIs) due to limitations of vaccines and increased antibiotic resistance. Enzyme therapeutics, and in particular plant-based enzymes, represent an underutilised resource in drug development warranting further attention. This literature review aims to summarise the current state of enzyme therapeutics in medical applications, with a focus on their potential to improve outcomes in RTDs, including RTIs. We used a narrative review approach, searching PubMed and clinicaltrials.gov with search terms including: enzyme therapeutics, enzyme therapy, inhaled therapeutics, botanical enzyme therapeutics, plant enzymes, and herbal extracts. Here, we discuss the advantages and challenges of enzyme therapeutics in the setting of RTDs and identify and describe several enzyme therapeutics currently used in the respiratory field. In addition, the review includes recent developments concerning enzyme therapies and plant enzymes in (pre-)clinical stages. The global coronavirus disease 2019 (COVID-19) pandemic has sparked development of several promising new enzyme therapeutics for use in the respiratory setting, and therefore, it is timely to provide a summary of recent developments, particularly as these therapeutics may also prove beneficial in other RTDs.

The Tissue-Engineered Tendon-Bone Interface: In Vitro and In Vivo Synergistic Effects of Adipose-Derived Stem Cells, Platelet-Rich Plasma, and Extracellular Matrix Hydrogel.

BACKGROUND: Suboptimal healing of the tendon-bone interface remains an unsolved problem. The authors hypothesized that (1) platelet-rich plasma and prolonged in vitro incubation will produce interface scaffolds with greater reseeding of viable adipose-derived stem cells; and (2) when implanted with extracellular matrix hydrogel, constructs will display superior in vivo strength repair and biocompatibility. METHODS: Achilles-calcaneal composite tendon-bone interface scaffold grafts were harvested from 30 Wistar rats. After physicochemical decellularization and lyophilization, scaffolds were revitalized in rat plasma or 100% activated rat platelet-rich plasma and reseeded with viable adipose-derived stem cells. For part 2 of the study, 90 Sprague-Dawley rats underwent reconstruction with one of five decellularized, lyophilized scaffold revitalization/reseeding conditions: (1) phosphate-buffered saline; (2) lyophilized, 100% activated platelet-rich plasma; (3) platelet-rich plasma and extracellular matrix hydrogel; (4) platelet-rich plasma and 14-day reseeding with ASC-luc2-eGFP cells; and (5) plasma, reseeding, and hydrogel. RESULTS: In part 1, platelet-rich plasma-revitalized grafts demonstrated greater live viable adipose-derived stem cell loads at 3, 7, and 14 days and total adipose-derived stem cell loads at 7 and 14 days with visibly greater live surface cellularity, layering, migration, and penetration. In part 2, bioluminescence imaging confirmed cell viability to day 22 after implantation. Biomechanical strength testing demonstrated a significant increase in ultimate failure load for reseeded groups compared with all other groups at week 2, whereas only reseeded grafts with hydrogel remained significantly stronger at weeks 4 and 8. Histologic examination demonstrated most increased tendinous cellular invasion and fibrocartilage repopulation at 8 weeks in the reseeded group with hydrogel. Masson trichrome staining demonstrated persistence of the scaffold structure at week 8 and blinded ImageJ analysis demonstrated significantly more type III collagen in the reseeded/hydrogel group at 2, 4, and 8 weeks. CONCLUSIONS: Decellularized lyophilized allogeneic tendon-bone interface scaffolds can be optimized by revitalization in platelet-rich plasma, reseeding with viable adipose-derived stem cells, and supplemented by an extracellular matrix tendon hydrogel at the time of implantation. When this is done, they display greater repair strength and biocompatibility.

The Effects of Music on Microsurgical Technique and Performance: A Motion Analysis Study.

BACKGROUND: Music is commonly played in operating rooms (ORs) throughout the country. If a preferred genre of music is played, surgeons have been shown to perform surgical tasks quicker and with greater accuracy. However, there are currently no studies investigating the effects of music on microsurgical technique. Motion analysis technology has recently been validated in the objective assessment of plastic surgery trainees' performance of microanastomoses. Here, we aimed to examine the effects of music on microsurgical skills using motion analysis technology as a primary objective assessment tool. METHODS: Residents and fellows in the Plastic and Reconstructive Surgery program were recruited to complete a demographic survey and participate in microsurgical tasks. Each participant completed 2 arterial microanastomoses on a chicken foot model, one with music playing, and the other without music playing. Participants were blinded to the study objectives and encouraged to perform their best. The order of music and no music was randomized. Microanastomoses were video recorded using a digitalized S-video system and deidentified. Video segments were analyzed using ProAnalyst motion analysis software for automatic noncontact markerless video tracking of the needle driver tip. RESULTS: Nine residents and 3 plastic surgery fellows were tested. Reported microsurgical experience ranged from 1 to 10 arterial anastomoses performed (n = 2), 11 to 100 anastomoses (n = 9), and 101 to 500 anastomoses (n = 1). Mean age was 33 years (range, 29-36 years), with 11 participants right-handed and 1 ambidextrous. Of the 12 subjects tested, 11 (92%) preferred music in the OR. Composite instrument motion analysis scores significantly improved with playing preferred music during testing versus no music (paired t test, P <0.001). Improvement with music was significant even after stratifying scores by order in which variables were tested (music first vs no music first), postgraduate year, and number of anastomoses (analysis of variance, P < 0.01). CONCLUSIONS: Preferred music in the OR may have a positive effect on trainees' microsurgical performance; as such, trainees should be encouraged to participate in setting the conditions of the OR to optimize their comfort and, possibly, performance. Moreover, motion analysis technology is a useful tool with a wide range of applications for surgical education and outcomes optimization.

Lasers and ancillary treatments for scar management Part 2: Keloid, hypertrophic, pigmented and acne scars.

The formation of a wide range of excessive scars following various skin injuries is a natural consequence of healing. Scars resulting from surgery or trauma affect approximately 100 million people per annum in the developed world and can have profound physical, aesthetic, psychological and social consequences. Thus, scar treatment is a priority for patient and physician alike. Laser treatment plays an important role in scar management with additional support from ancillary modalities. Subsequent to part 1: Burns scars, part 2 focuses on our strategies and literature review of treatment of keloid, hypertrophic, pigmented and acne scars where lasers are used in conjunction with other measures, and illustrated with case studies.

An Inexpensive Bismuth-Petrolatum Dressing for Treatment of Burns.

BACKGROUND: Xeroform remains the current standard for treating superficial partial-thickness burns but can be prohibitively expensive in developing countries with prevalent burn injuries. This study (1) describes the production of an alternative low-cost dressing and (2) compares the alternative dressing and Xeroform using the metrics of cost-effectiveness, antimicrobial activity, and biocompatibility in vitro, and wound healing in vivo. METHODS: To produce the alternative dressing, 3% bismuth tribromophenate powder was combined with petroleum jelly by hand and applied to Kerlix gauze. To assess cost-effectiveness, the unit costs of Xeroform and components of the alternative dressing were compared. To assess antimicrobial properties, the dressings were placed on agar plated with Escherichia coli and the Kirby-Bauer assay performed. To assess biocompatibility, the dressings were incubated with human dermal fibroblasts and cells stained with methylene blue. To assess in vivo wound healing, dressings were applied to excisional wounds on rats and the rate of re-epithelialization calculated. RESULTS: The alternative dressing costs 34% of the least expensive brand of Xeroform. Antimicrobial assays showed that both dressings had similar bacteriostatic effects. Biocompatibility assays showed that there was no statistical difference (P < 0.05) in the cytotoxicity of Xeroform, alternative dressing, and Kerlix gauze. Finally, the in vivo healing model showed no statistical difference (P < 0.05) in mean re-epithelialization time between Xeroform (13.0 ± 1.6 days) and alternative dressing (13.5 ± 1.0 days). CONCLUSIONS: Xeroform is biocompatible, reduces infection, and enhances healing of burn wounds by preventing desiccation and mechanical trauma. Handmade petrolatum gauze may be a low-cost replacement for Xeroform. Future studies will focus on clinical trials in burn units.

How to train plastic surgeons of the future.

INTRODUCTION: Plastic surgery is a competitive and over-subscribed career choice despite minimal medical school exposure. We quantify factors influencing career interest in plastic surgery, speciality appeal and workforce planning. These findings optimise and refine evidence-based plastic surgery training and postgraduate selection criteria. METHODS: Medical students from two national plastic surgery courses complete a post-course questionnaire. Data categories included past experience and career interest in plastic surgery, sources of exposure, motivational factors, and sub-speciality interest. Data were recorded on modified Likert scales, with linear regression and t-test analyses performed. RESULTS: 175 students completed the questionnaire (81% response). Duration of medical student exposure to plastic surgery was significantly associated with career interest (Linear coefficient 0.12, 95% CI 0.08-0.17, P < 0.0001; r(2) = 0.15). 75 h experience is a significant cut-off to categorise students. Mean (95% CI) career interest is 31 percentage points higher in students with >75 h experience (89.2%, 83.2-95.2) compared to students with ≤75 h experience (58.1%, 52.9-63.3) (P < 0.0001). Influential sources included: (1) Operating Room (2) Consultant/Attending interaction (3) Resident interaction. Motivational factors towards a career in plastic surgery included operative satisfaction (91%), improving patient quality of life (89%), and reconstructive surgery (88%). Sub-speciality interests included: (1) Hand and Upper Limb (28%); (2) Cleft Lip and Palate (26%); (3) Burns (15%). CONCLUSION: This study identified influential and motivational factors upon a career in plastic surgery. Medical student exposure can be tailored to maximise positive educational exposure to optimise evidence-based plastic surgery training and workforce planning.

Tendon Regeneration with Tendon Hydrogel-Based Cell Delivery: A Comparison of Fibroblasts and Adipose-Derived Stem Cells.

BACKGROUND: Tendon hydrogel is a promising biomaterial for improving repair strength after tendon injury. This study compares the capacity of fibroblasts and adipose-derived stem cells to proliferate, survive, and acquire tenogenic properties when seeded into tendon hydrogel in vitro and in vivo. METHODS: The effect of cell density on hydrogel contraction was measured macroscopically. To assess tenogenic properties, RNA was isolated from cells seeded in vitro in hydrogel, and tenocyte markers were quantified. To assess in vitro proliferation and survival, MTS and live-dead assays were performed. Finally, to assess the in vivo survival of cells in hydrogel, subcutaneous injections were performed on rats and in vivo imaging was performed. RESULTS: At 0.5 million cells/ml, both the fibroblasts and adipose-derived stem cells induced minimal hydrogel contraction compared with higher cellular concentrations. Fibroblasts and adipose-derived stem cells seeded at 0.5 million cells/ml in tendon hydrogel up-regulated several tenocyte markers after 1 week. On MTS assay, fibroblasts and adipose-derived stem cells proliferated in hydrogel at similar rates. On live-dead assay, fibroblasts survived longer than adipose-derived stem cells. With use of the in vivo imaging system and histologic evaluation, fibroblasts survived longer than adipose-derived stem cells in hydrogel in vivo. CONCLUSIONS: Tendon healing is mediated by the proliferation, survival, and tenogenic differentiation of cells at the site of injury. Tendon hydrogel delivering dermal fibroblasts may improve and stimulate this process compared with adipose-derived stem cells. Future studies will be needed to evaluate the effects of this hydrogel-based cell delivery on chronic tendon injuries.

Characteristics of Reconstituted Lyophilized Tendon Hydrogel: An Injectable Scaffold for Tendon Regeneration.

BACKGROUND: The authors have developed a tendon hydrogel that may be injected into the site of tendon injury to improve speed and strength of repair. The aim of this study was to compare the biological and physical properties of fresh, hydrated tendon hydrogel with its reconstituted lyophilized counterpart with the goal of increasing clinical feasibility. MATERIALS: Hydrogel was prepared from fresh human cadaveric flexor tendon. Fresh gel was compared to gel aliquots that were lyophilized and reconstituted with sterile deionized water. Scanning electron microscopy was used to examine the microarchitecture of gelated samples. Rat adipose-derived stem cells were seeded in hydrogel, and cell viability was assessed after 7 days. MTS colorimetric assay was used to evaluate both the effect of prolonged storage on gel and the ability of reconstituted lyophilized hydrogel to activate platelet-rich plasma. The viability and proliferation of luciferase-transfected adipose-derived stem cells embedded within hydrogel in vivo was assessed by a bioluminescence in vivo imaging system. RESULTS: Reconstituted lyophilized hydrogel demonstrated similar handling properties compared to fresh gel. Adipose-derived stem cells remained viable 7 days after reseeding in both conditions. Lyophilized hydrogel retained its ability to activate platelet-rich plasma and retained 95 percent of its maximal proliferative capacity at 30 days. The in vivo imaging system demonstrated similar cell proliferation, with signal persisting through day 13. CONCLUSIONS: Reconstitution of lyophilized hydrogel stimulated cell proliferation and platelet-rich plasma activation to a greater degree than did fresh hydrogel. Efficacy after prolonged storage was also shown to be superior. Therefore, this lyophilized formulation of tendon hydrogel may have wider clinical applicability.

Sutureless Microsurgical Anastomosis Using an Optimized Thermoreversible Intravascular Poloxamer Stent.

BACKGROUND: Sutureless microvascular anastomosis has great translational potential to simplify microvascular surgery, shorten operative times, and improve clinical outcomes. The authors developed a transient thermoreversible microvascular stent using a poloxamer to maintain vessel lumen patency before application of commercially available adhesives to seal the anastomosis instead of sutures. Despite technical success, human application necessitates bovine serum albumin removal from existing formulations; rapid poloxamer transition between states; and increased stiffness for reliable, reproducible, and precise microvascular approximation. METHODS: Two commercially available poloxamers were used in this study (P407 and P188). After removing bovine serum albumin, each poloxamer was tested at varying concentrations either alone or in combination to determine the optimal preparation for sutureless microvascular anastomosis. Transition temperature and formulation stiffness were tested in vitro by rheometry, with the most promising combinations tested in an established in vivo model. RESULTS: Increasing poloxamer concentration resulted in an increase in stiffness and decrease in transition temperature. Pure P188 without bovine serum albumin, dissolved in phosphate-buffered saline to a 45% concentration, demonstrated desirable rheologic behavior, with precise gel transition and increased gel stiffness compared with our previous formulation of 17% P407 (96 kPa versus 10 kPa). These characteristics were optimal for microsurgical intravascular use, offering surgical precision and control between liquid and solid states, depending on the surgically controlled local temperature. CONCLUSIONS: Use of 45% P188 without bovine serum albumin demonstrated optimal rheologic and translational properties as a microvascular stent for sutureless anastomosis. Rapid transition, increased stiffness, and safety profile demonstrate safe translational application for human clinical trials.

In Vitro Characteristics of Porcine Tendon Hydrogel for Tendon Regeneration.

PURPOSE: Previous work has characterized the development of a human tendon hydrogel capable of improving mechanical strength after tendon injury. Animal tendon hydrogel has not yet been described, but would prove beneficial due to the cost and ethical concerns associated with the use of human cadaveric tendon. This study details the manufacture and assesses the biocompatibility of porcine tendon hydrogel seeded with human adipoderived stem cells (ASCs). MATERIALS AND METHODS: Porcine tendon was dissected from surrounding connective and muscle tissue and decellularized via 0.2% sodium dodecyl sulfate and 0.2% sodium dodecyl sulfate/ethylenediaminetetraacetic acid wash solutions before lyophilization. Tendon was milled and reconstituted by previously described methods. Decellularization was confirmed by hematoxylin-eosin staining, SYTO Green 11 nucleic acid dye, and DNeasy assay. The protein composition of milled tendon matrix before and after digestion was identified by mass spectrometry. Rheological properties were determined using an ARG2 rheometer. Biocompatibility was assessed by live/dead assay. The proliferation of human ASCs seeded in porcine and human hydrogel was measured by MTS assay. All experimental conditions were performed in triplicate. RESULTS: Decellularization of porcine tendon was successful. Mass spectrometry showed that collagen composes one third of milled porcine tendon before and after pepsin digestion. Rheology demonstrated that porcine hydrogel maintains a fluid consistency over a range of temperatures, unlike human hydrogel, which tends to solidify. Live/dead staining revealed that human ASCs survive in hydrogel 7 days after seeding and retain spindle-like morphology. MTS assay at day 3 and day 5 showed that human ASC proliferation was marginally greater in human hydrogel. CONCLUSIONS: After reconstitution and digestion, porcine hydrogel was capable of supporting growth of human ASCs. The minimal difference in proliferative capacity suggests that porcine tendon hydrogel may be an effective and viable alternative to human hydrogel for the enhancement of tendon healing.

Lasers and ancillary treatments for scar management: personal experience over two decades and contextual review of the literature. Part I: Burn scars.

The formation of a wide range of excessive scars following various skin injuries is a natural consequence of healing. Scars resulting from surgery or trauma affect approximately 100 million people per annum in the developed world and can have profound physical, aesthetic, psychological and social consequences. Thus, scar treatment is a priority for the plastic surgeon. We aim to explore new approaches to the management of such scarring. The senior authors current use of laser technology, chemotherapeutic agents, pharmacotherapy and cryosurgery will be reviewed. This is placed in the context of the current literature and evidence base and is illustrated with case studies, starting with burns scars in part I, and focusing on keloid and hypertrophic scars in part II, acne scars in part III and finally pigmented scars in part IV. In Part I we focus on burns scar treatment with fractional ablative 10,600 nm wavelength carbon dioxide (CO2) laser therapy.

Motion Analysis for Microsurgical Training: Objective Measures of Dexterity, Economy of Movement, and Ability.

BACKGROUND: Evaluation of skill acquisition in microsurgery has traditionally relied on subjective opinions of senior faculty, but is shifting toward early competency-based training using validated models. No objective measures of dexterity, economy of movement, and ability exist. The authors propose a novel video instrument motion analysis scoring system to objectively measure motion. METHODS: Video of expert microsurgeons was analyzed and used to develop a resident motion analysis scoring system based on a mathematical model. Motion analysis scores were compared to blinded, global rating scores of the same videos using the Stanford Microsurgery and Resident Training scale. RESULTS: Eighty-five microsurgical anastomoses from 16 residents ranging from postgraduate years 1 through 6 were analyzed. Composite motion analysis scores for each segmented video correlated positively to arterial anastomotic experience (rho, +0.77; p < 0.001). Stanford Microsurgery and Resident Training scale interrater reliability was consistent between expert assessors, and mean composite motion analysis overall performance and Stanford scores were well matched for each level of experience. Composite motion analysis scores correlated significantly with combined Stanford Microsurgery and Resident Training [instrument handling (rho, +0.66; p < 0.01), efficiency (rho, +0.59; p < 0.01), suture handling (rho, +0.83; p < 0.001), operative flow (rho, +0.67; p < 0.001), and overall performance (rho, +89; p < 0.001)] motion components of the scale. CONCLUSIONS: Instrument motion analysis provides a novel, reliable, and consistent objective assessment for microsurgical trainees. It has an associated cost, but is timely, repeatable, and senior physician independent, and exposes patients to zero risk.

Tendon regeneration with a novel tendon hydrogel: in vitro effects of platelet-rich plasma on rat adipose-derived stem cells.

BACKGROUND: Tendon hydrogel is a promising new injectable substance that has been shown to improve repair strength after tendon injury. This study assesses the capacity of platelet-rich plasma to stimulate proliferation and migration of rat adipose-derived stem cells in tendon hydrogel in vitro. METHODS: To assess proliferation, adipose-derived stem cells were exposed to plasma, plasma supplemented with growth factors, or platelet-rich plasma in culture medium and tendon hydrogel. To assess migration, adipose-derived stem cells were plated onto tendon hydrogel -coated wells and covered with medium containing plasma, plasma supplemented with growth factors, platelet-rich plasma, or bovine serum albumin. Migration from cell-seeded to cell-free zones was assessed at 12-hour intervals. RESULTS: Platelet-rich plasma augmented proliferation to a greater extent compared with plasma and plasma supplemented with growth factors (10%: optical density, 1.18 versus 0.75 versus 0.98, respectively). Platelet-rich plasma was superior to plasma in tendon hydrogel (10%: optical density, 1.19 versus 0.85) but did not augment proliferation to the extent that plasma supplemented with growth factors did (10%: optical density, 1.19 versus 1.56). Platelet-rich plasma enhanced the migration of adipose-derived stem cells compared with serum-free medium (bovine serum albumin) (36 hours: platelet-rich plasma, 1.88; plasma, 1.51; plasma plus growth factor, 1.80; bovine serum albumin, 1.43). CONCLUSIONS: Tendon healing is mediated by migration of cells to the injured area and cellular proliferation at that site. Tendon hydrogel supplemented with platelet-rich plasma stimulates these processes. Future studies will evaluate this combination's ability to stimulate healing in chronic tendon injuries in vivo.

Principles of tendon reconstruction following complex trauma of the upper limb.

Reconstruction of tendons following complex trauma to the upper limb presents unique clinical and research challenges. In this article, the authors review the principles guiding preoperative assessment, surgical reconstruction, and postoperative rehabilitation and management of the upper extremity. Tissue engineering approaches to address tissue shortages for tendon reconstruction are also discussed.

Optimization of an injectable tendon hydrogel: the effects of platelet-rich plasma and adipose-derived stem cells on tendon healing in vivo.

INTRODUCTION: Acute and chronic tendon injuries would benefit from stronger and more expeditious healing. We hypothesize that supplementation of a biocompatible tendon hydrogel with platelet-rich plasma (PRP) and adipose-derived stem cells (ASCs) would augment the tendon healing process. MATERIALS AND METHODS: Using 55 Wistar rats, a full-thickness defect was created within the midsubstance of each Achilles tendon with the addition of one of five experimental conditions: (i) saline control (50-µL), (ii) tendon hydrogel (50-µL), (iii) tendon hydrogel (45-µL)+PRP (5-µL), (iv) tendon hydrogel (45-µL)+2×10(6)-ASCs/mL in phosphate buffered saline (5-µL), and (v) tendon hydrogel (45-µL)+2×10(6)-ASCs/mL in PRP (5-µL). Hydrogel was developed from decellularized, human cadaveric tendons. Fresh rat PRP was obtained per Amable et al.'s technique, and green fluorescent protein/luciferase-positive rat ASCs were utilized. Rats were sacrificed at weeks 1, 2, 4, and 8 after injury. Real-time in vivo bioluminescence imaging of groups with ASCs was performed. Upon sacrifice, Achilles tendons underwent biomechanical and histological evaluation. Comparisons across groups were analyzed using the two-sample Z-test for proportions and the Student's t-test for independent samples. Significance was set at p<0.05. RESULTS: (i) Bioluminescence imaging demonstrated that total photon flux was significantly increased for hydrogel+PRP+ASCs, versus hydrogel+ASCs for each postoperative day imaged (p<0.03). (ii) Mean ultimate failure load (UFL) was increased for hydrogel augmented with PRP and/or ASCs versus hydrogel alone at week 2 (p<0.03). By week 4, hydrogel alone reached a similar mean UFL to hydrogel augmented with PRP and/or ASCs (p>0.3). However, at week 8, hydrogel with PRP and ASCs demonstrated increased strength over other groups (p<0.05), except for hydrogel with PRP (p=0.25). (iii) Upon histological analysis, Hematoxylin and Eosin staining showed increased extracellular matrix formation in groups containing PRP and increased cellularity in groups containing ASCs. Groups containing both PRP and ASCs demonstrated both of these characteristics. CONCLUSION: PRP and ASCs are easily accessible bioactive products that have potentiating effects on tendon hydrogel. Augmentation with these two factors encourages earlier mechanical strength and functional restoration. Thus, biochemically, tendon hydrogel augmented with PRP and/or ASCs, serves as a promising therapeutic modality for augmenting the tendon healing process after injury.

Bench to bedside: integrating advances in basic science into daily clinical practice.

This article focuses on the initial steps of commercial development of a patentable scientific discovery from an academic center through to marketing a clinical product. The basics of partnering with a technology transfer office (TTO) and the complex process of patenting are addressed, followed by a discussion on marketing and licensing the patent to a company in addition to starting a company. Finally, the authors address the basic principles of obtaining clearance from the Food and Drugs Administration, production in a good manufacturing practice (GMP) facility, and bringing the product to clinical trial.

Left ventricular hypertrophy induced by aortic banding impairs relaxation of isolated coronary arteries.

LVH (left ventricular hypertrophy) is associated with impaired coronary vascular reserve. In the present study, we examined the effect of pressure-overload hypertrophy on vasorelaxant responses of guinea-pig isolated coronary small arteries and compared them with mesenteric small arteries. Pressure-overload was induced by banding the ascending aorta of guinea-pigs. Haemodynamics, and ventricular, atrial and lung weights were measured 168 days after banding. Isolated coronary and mesenteric small arteries were contracted with a thromboxane mimetic (U46619) and relaxation to ACH (acetylcholine), ISO (isoprenaline), FSK (forskolin) and SNP (sodium nitroprusside) was examined. Arterial wall morphology was examined by light microscopy. Aortic banding reduced cardiac output and increased systemic vascular resistance; atrial, ventricular and lung weights were increased. Coronary artery adventitial and medial thickness were increased, but mesenteric arterial wall morphology was unaffected. Coronary artery relaxation to ACH, ISO, FSK and SNP were reduced in banded animals. In contrast, relaxation of mesenteric arteries to ACH, FSK and SNP were unaffected by banding, although ISO-induced relaxation was reduced. A COX (cyclo-oxygenase) inhibitor, indomethacin, had no effect on coronary artery responses to ACH in banded or sham animals, but the differences in relaxation of coronary arteries between banded and sham animals were no longer significant following pre-incubation with the NO inhibitors L-NMMA (N(G)-monomethyl-L-arginine) and oxyhaemoglobin. In conclusion, pressure-overload-induced LVH causes impaired relaxation of small coronary arteries to endothelium-dependent and -independent relaxants. These findings are indicative of alterations in vascular smooth muscle responsiveness to vasodilators. Impairment of coronary arterial vasodilation may contribute to the reduced coronary vascular reserve seen in LVH.