IMPACT SHOULDER ANGLES CORRELATE WITH IMPACT WRIST ANGLES IN STANDING BACK HANDSPRINGS IN PREADOLESCENT AND ADOLESCENT FEMALE GYMNASTS

BACKGROUND AND PURPOSE

In gymnastics, the wrist is exposed to many different stresses including increased extension, especially during back handsprings. Currently a wrist extension angle during impact that places the wrist in danger has not been established. The purpose of this study was to: (1) determine the mean impact wrist angle during a standing back handspring in female preadolescent and adolescent gymnasts and (2) determine which factors predict impact wrist angles.

METHODS

Fifty female gymnasts from six facilities, ages 8-15 were included in this study. Each gymnast completed a questionnaire about gymnastics participation and history of wrist pain. Active range of motion of the shoulder, elbow, wrist, hip, and ankle was measured. Each gymnast was asked to perform a standard back handspring, which was videotaped. The wrist and shoulder flexion angles, at maximum impact, were recorded and measured using motion analysis software. Two-sample t-test was used to assess the relationship between impact wrist angle and wrist pain. Multiple linear regression was used to determine the association between related variables and impact wrist angle.

RESULTS

The mean back handspring impact wrist angle was 95°. Fifteen subjects (30%) reported wrist pain. Years of participation (p=0.02) and impact shoulder angle (p=0.04) were predictive of impact wrist angles.

CONCLUSION

Shoulder angles and years of participation correlate with impact wrist angles during the performance of a standing back handspring. Future studies are necessary to determine if addressing these factors can affect the impact wrist angles.

LEVEL OF EVIDENCE

3.

Pediatric sports specific return to play guidelines following concussion

PURPOSE/BACKGROUND

In 2010, the American Academy of Pediatrics officially adopted the recommended return to play guidelines proposed by the International Conference on Concussion in Sport. The guidelines include a six-step process that provides structure to guide an athlete who is recovering from a concussion in a gradual return to play (RTP) by allowing participation in increasingly difficult physical activities. Unfortunately, the guidelines fail to take into account the variability that occurs within different sports and the resulting challenges medical professionals face in making sure each athlete is able to withstand the rigors of their specific sport, without return of symptoms. Therefore, the purpose of this clinical commentary is to expand upon the current general consensus guidelines for treatment of concussed pediatric athletes and provide sport specific RTP guidelines.

DESCRIPTION OF TOPIC

The intention of the sport specific guidelines is to maintain the integrity of the current six-step model, add a moderate activity phase highlighted by resistance training, and to provide contact and limited contact drills specific to the athlete's sport and/or position. The drills and activities in the proposed seven-step programs are designed to simulate sport specific movements; the sports include: football, gymnastics, cheerleading, wrestling, soccer, basketball, lacrosse, baseball, softball, and ice hockey. These activities will provide sports specific challenges to each athlete while simultaneously accomplishing the objectives of each stage of the RTP progression. The final RTP determination should occur with documented medical clearance from a licensed healthcare provider who has been trained in the evaluation and management of concussions.

DISCUSSION/RELATION TO CLINICAL PRACTICE

There have been significant strides in the management and care of concussed athletes. However, there continues to be a lot of confusion among, athletes, parents, and coaches regarding the proper management of an athlete with a concussion, particularly in the pediatric population. In an effort to eliminate ambiguity and help further promote adherence to the RTP guidelines, the authors developed several sports-specific RTP guidelines.

LEVEL OF EVIDENCE

5.

Where do we go from here? An inside look into the development of Georgia's Youth Concussion Law

Currently, all 50 states and the District of Columbia have youth concussion laws based on the core principals of the 2009 Lystedt Law of Washington State. On April 23, 2013, the state of Georgia signed into law House Bill 284, "The Return to Play Act of 2013" and became one of the last states to pass youth concussion legislation. This Act became effective on January 1, 2014. The purpose of this report is to highlight the legislative process of enacting Georgia House Bill 284 and compare it to the legislation of other states.

Failure analysis of knee arthrodesis with the WichitaFusion Nail

Arthrodesis is a salvage procedure for failed total knee arthroplasty with the intent to create a stable, pain-free limb on which to ambulate or transfer. For many patients, the alternative to arthrodesis may be an above-knee amputation. Available techniques for knee arthrodesis include compression plating, external fixators, and intramedullary fixation. The purpose of this study was to report the knee fusion rate of consecutive patients at 1 institution using an intramedullary fusion nail and to identify patient risk factors for fusion failure. Between November 1998 and November 2008, twenty-eight patients undergoing knee arthrodesis with an average follow-up of 18 months (range, 3-64 months) were retrospectively studied. Demographic information, presence of fusion, clinical function, pain level, and bone defect data were collected and analyzed. Eighty-two percent (23/28) of patients had radiographic evidence of successful fusion with an average time to fusion of 21 weeks (range, 10-58 weeks). When examining patient variables that could correlate with fusion rates, patients with an Anderson Orthopaedic Research Institute type 3 femoral or type 3 tibial defect had a statistically significant lower fusion rate. The intramedullary fusion nail is an effective device for knee arthrodesis that offers ease of insertion through the knee wound with the advantages of initial bone compression and rigid fixation. Although the use of intramedullary fusion nails leads to a high fusion rate, significant bone deficiency limits successful fusion.

Five- to ten-year outcomes for modular metal-on-metal total hip arthroplasty

In recent years, metal-on-metal (MOM) arthroplasty has come under fire with reported adverse outcomes of metal hypersensitivity, adverse local tissue reaction (ALTR), and the carcinogenicity concern from systemic metal ions. We present a retrospective analysis of 354 primary total hip arthroplasties from 2 independent centers. Revision data, predicted survival and Harris Hip Scores (HHS) are reported. Nine hips (2.5%) underwent component revision, and 9 year predicted survival was 95.8%. One revision had elevated metal ions but no histological evidence of ALTR. Average HHS at a minimum 5 year follow up (range 5-10 years) improved significantly from 52 pre-operatively to 93 post-operatively. While a 2.5% revision rate and improved clinical outcomes are reported in this study, longer term follow-up is warranted to monitor for late complications.

Sensory neuropathy associated with aggressive cauterization using a bipolar radiofrequency device in primary TKA

Because significant postoperative blood loss can result in many complications, hemostasis remains a critical part of successful joint replacement outcomes. Advanced techniques, such as electrocautery use after optimally timed tourniquet release, focus on desired patient blood loss outcomes. The purposes of this study were to report the incidence of nerve injury, identify associated risk factors following the use of bipolar electrocautery for hemostasis in the posterior knee during primary total knee arthroplasty, and compare that rate with the rate seen using a standard electrocautery device. Clinical and operative data were retrospectively reviewed for an association with postoperative nerve injury in 241 consecutive patients when using bipolar electrocautery between July 2007 and October 2008. A comparison group of 192 demographically similar consecutive patients between November 2008 and October 2009 was also evaluated to establish a surgeon-specific benchmark when using standard electrocautery. Seven (2.9%) of 241 patients in the bipolar electrocautery group reported documented neuropathies compared with 1 (0.52%) of 192 patients using standard electrocautery. In addition, female sex and rheumatoid arthritis were associated with postoperative nerve injury following bipolar electrocautery. Although the bipolar radiofrequency device is effective in achieving hemostasis, the authors recommend judicious use of this procedure in women or patients with rheumatoid arthritis and cautious, nonaggressive use of posterior compartment bipolar radiofrequency ablation in the remaining patient populations.

Articulating spacers for the treatment of infected total knee arthroplasty: effect of antibiotic combinations and concentrations

Performing 2-stage procedures using articulating antibiotic cement spacers to eradicate infection while providing pain relief and maintaining function has become common among many surgeons. Despite the efficacy of antibiotic cement spacers in the treatment of infected total knee arthroplasty, questions remain regarding the dosing of the antibiotic cement. The authors assessed their experience with different antibiotic regimens and concentrations for the eradication of infection. Sixty-nine infected total knee arthroplasties with an average follow up of 31 months (range, 6-70 months) treated with articulating antibiotic spacers were retrospectively reviewed. Treatment groups were divided according to spacer antibiotic agents used and the amount of antibiotics added to the cement. Low-dose spacers were defined as those incorporating less than 4 g of antibiotic per 40-g bag of cement, and high-dose spacers were defined as those incorporating 4 g or more of antibiotic per 40-g bag of cement. High- vs low-dose spacers using a single or multiple antibiotic agents were compared. The overall rate of infection eradication was 88%. Dose dependency was not detected for spacers that incorporated single or multiple antibiotic agents, and multiple-agent spacers produced comparable success rates despite more frequent use in patients with impaired immune function. Further study of optimal combinations and concentrations of antibiotic agents incorporated into these spacers is needed to help minimize treatment failures while maximizing treatment efficacy.

Complications following distal biceps repair

PURPOSE

Distal biceps rupture is a relatively uncommon injury. Surgical repair is performed in patients who seek increased flexion and supination strength over that which results from nonoperative treatment. The purpose of this study was to evaluate complications associated with surgical repair of the distal biceps tendon in a large series of patients.

METHODS

We retrospectively reviewed 198 consecutive patients with distal biceps ruptures treated with surgical repair, and evaluated time from injury to repair, surgical technique, and complications.

RESULTS

A total of 72 patients (36%) developed complications; 6 patients underwent additional surgery. Minor complications included lateral antebrachial cutaneous nerve paresthesia (26%), radial sensory nerve paresthesia (6%), and superficial infection (2%). Major complications included posterior interosseous nerve injury (4%), symptomatic heterotropic ossification (3%), and re-rupture (2%).

CONCLUSIONS

Minor complications were common after distal biceps tendon repair; however, most were sensory nerve injuries that resolved with time. Major complications were infrequent, and few patients required revision surgery. Complications were more common after distal biceps tendon repair performed more than 28 days after rupture.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Effect on blood loss and cost-effectiveness of pain cocktails, platelet-rich plasma, or fibrin sealant after total knee arthroplasty

This study evaluated the effect of periarticular pain cocktail, platelet-rich plasma, or fibrin sealant injections on blood loss, transfusion rate, and hospital costs after total knee arthroplasty. A retrospective review of 400 patients undergoing primary total knee arthroplasty with one of the different periarticular treatments as stated above was performed. Postoperative blood loss, hemoglobin levels, allogenic blood transfusion rates, and per-case hospital injection cost were reported. Although platelet-rich plasma and fibrin sealant decreased blood loss compared with the control group (P < .001), there was no significant difference in blood loss in the pain-cocktail group or in postoperative hemoglobin levels or transfusion rates between all groups. Significant efficacy and cost-effectiveness for these modalities could not be identified and have, therefore, been discontinued at our practice.

LEVEL OF EVIDENCE

level III.

Clinical outcomes of total wrist arthroplasty

PURPOSE

Current indications for total wrist arthroplasty include patients with symptomatic end stage posttraumatic wrist arthritis, rheumatoid arthritis, and Kienböck disease, as an alternative to wrist arthrodesis. Arthroplasty may have advantage over arthrodesis because of the ability to retain motion. The purpose of this study was to evaluate the short-term clinical outcomes and complications of the Maestro Total Wrist System.

METHODS

We report the results of a retrospective review of 23 total wrist prostheses implanted in 22 patients. We administered the visual analog pain scale and Mayo wrist and Disabilities of the Arm, Shoulder, and Hand questionnaires. We reviewed wrist motion, grip strength, radiographs, and complications.

RESULTS

At a mean follow-up of 28 months (range, 4-55 mo), the Disabilities of the Arm, Shoulder, and Hand score and Mayo wrist score were 31 and 54, respectively. Mean pain scores improved from 8.0 to 2.2. The mean wrist flexion-extension arc was 90°. Radiographs revealed no evidence of prosthetic loosening. Grip strength averaged 60% of the strength of the opposite hand. Complications occurred in 7 of 23 patients. One failure occurred as a result of deep infection in a patient with prior intercarpal fusion, and was successfully converted to a wrist fusion.

CONCLUSIONS

Total wrist arthroplasty performed for pancarpal arthritis as an alternative to wrist arthrodesis can yield successful outcomes with low short-term failure rates.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Proximal row carpectomy with capitate osteochondral autograft transplantation

Proximal row carpectomy (PRC) is an effective treatment option for degenerative or posttraumatic osteoarthritis of the wrist in conditions such as scapholunate advanced collapse, scaphoid nonunion advanced collapse, Kienbock disease, and chronic fracture dislocations of the carpus. PRC involves excision of the scaphoid, lunate, and triquetrum, and relies on the articulation of the remaining capitate from the distal row to articulate with the lunate fossa. PRC offers the potential advantage of greater range of motion, technical ease, and decreased immobilization, and eliminates specific complications found with other motion-preserving procedures such as nonunion, hardware irritation, and impingement. An established relative contraindication for PRC is the presence of advanced capitolunate arthritis. Many authors have offered modifications of the traditional PRC procedure to account for the presence of capitate arthritis. A PRC technique utilizing an osteochondral autograft, from the carpal bank of excised bones, for transfer to the capitate defect is described.

Chronic ethanol ingestion increases aortic endothelial nitric oxide synthase expression and nitric oxide production in the rat

BACKGROUND

Chronic alcohol consumption perturbs cellular function in a variety of organ systems. Previous studies have suggested that moderate alcohol consumption reduces vascular disease, whereas heavier alcohol consumption may worsen it. The mechanisms for these vascular effects of chronic alcohol ingestion continue to be defined and constitute the focus of this study.

METHODS

Male Sprague Dawley rats were fed an isocaloric, Lieber-Decarli liquid diet containing either ethanol (36% calories) or Maltose-Dextrin (substituted for ethanol) for 6 weeks. Telemetric blood pressure measurements were taken before and after ethanol feeding. After the rats were killed, the aortas were analyzed for endothelial nitric oxide (NO) synthase expression and NO production.

RESULTS

Chronic ethanol ingestion decreased mean arterial pressure and increased aortic NO production as demonstrated by direct ex vivo measurements using iron diethyldithio-carbamic acid as well as analysis of nitrosyl-hemoglobin (NO-Hb) levels. Consistent with these assays of vascular NO production, endothelium-dependent relaxation responses to acetycholine (Ach) were enhanced in ethanol-fed animals. Aortic endothelial nitric oxide synthase expression was also increased by chronic ethanol ingestion.

CONCLUSIONS

These findings demonstrate that a regimen of chronic alcohol ingestion in the rat produced generally salutary effects in the systemic vasculature following a 6-week treatment regimen. These findings extend previous in vitro studies to demonstrate that alcohol has potent effects on vascular endothelial nitric oxide synthase expression, NO production, and vascular function. Consistent with previous reports, these findings confirm that alcohol-induced alterations in the production of reactive nitrogen species play an important role in the pathogenesis of alcohol-mediated tissue effects.

Chronic ethanol ingestion increases nitric oxide production in the lung

Chronic ethanol (EtOH) ingestion increases the incidence of acute respiratory distress syndrome. The mechanisms underlying EtOH-induced susceptibility to lung injury continue to be defined. This study examines the hypothesis that EtOH increases endothelial nitric oxide synthase (eNOS) expression and activity in the lungs of a rat model of chronic EtOH ingestion. Male Sprague-Dawley rats were fed liquid diets containing EtOH (36% of calories) or maltose-dextrin as an isocaloric substitution for EtOH (control) for 6 weeks. Selected animals were also treated with the angiotensin-converting enzyme (ACE) inhibitor lisinopril (3 mg/l in diet) for 6 weeks. At study completion, animals were sacrificed, and lung tissue was collected for assays of nitric oxide (NO) metabolism or pulmonary microvascular endothelial cells (MVEC) were isolated for analysis of NO release. Compared to the control diet, chronic EtOH ingestion increased lung H2O2 production, eNOS expression and activity, lung cyclic guanosine monophosphate (cGMP) content, and levels of protein nitration and oxidation. MVEC from animals with chronic EtOH ingestion released greater amounts of NO. EtOH-induced increases in lung H2O2 production, eNOS expression and activity, cGMP content, protein nitration and oxidation, and MVEC NO production were all attenuated by treatment with lisinopril. Chronic EtOH ingestion stimulates ACE-dependent increases in NO production in the lung. These novel findings indicate that chronic EtOH ingestion increases reactive species production in the lung parenchyma and provide new insights into mechanisms by which EtOH causes phenotypic alterations in the lung and alters the lung's response to inflammatory stimuli.

Chronic ethanol exposure stimulates endothelial cell nitric oxide production through PI-3 kinase-and hsp90-dependent mechanisms

BACKGROUND

Chronic ethanol (EtOH) ingestion increases the incidence of the Acute Respiratory Distress Syndrome (ARDS), a severe form of acute lung injury characterized by endothelial and epithelial barrier dysfunction. The regulated production of nitric oxide (NO) by the endothelium plays a central role in normal vascular function, and alterations in NO production have been implicated in barrier dysfunction. Although previous reports examined the impact of acute EtOH stimulation on endothelial NO production, this study extends those observations to clarify mechanisms of chronic EtOH-mediated alterations in endothelial nitric oxide synthase (eNOS) expression and NO production.

METHODS

Porcine pulmonary artery endothelial cells (PAEC) were treated with EtOH (0.04-0.16%, w/v) for 72 hr in sealed chambers to prevent evaporation. NO release and eNOS expression were determined to examine the effect of chronic EtOH stimulation on endothelial NO metabolism.

RESULTS

While there was no change in the extent of phosphorylated eNOS at ser, chronic EtOH stimulation caused dose-dependent increases in NO production and increased eNOS expression, effects that were attenuated by the transcriptional inhibitor, alpha-amanitin (AA), and wortmannin, a specific phosphatidylinositol 3 kinase (PI3 K) inhibitor. EtOH stimulation also increased eNOS interaction with heat shock protein (hsp90), a molecular chaperone known to enhance eNOS activity. Geldanamycin, an hsp90 inhibitor, attenuated chronic EtOH-mediated increases in NO production.

CONCLUSIONS

These results indicate that chronic EtOH exposure increases endothelial NO production by increasing eNOS protein levels through PI3 K-dependent up regulation of eNOS gene transcription and by increasing interactions between eNOS and hsp90. These findings clarify mechanisms by which chronic EtOH stimulation modulates vascular endothelial function and suggest new targets for investigation and intervention in EtOH-induced alterations in susceptibility to lung injury.

Chronic ethanol ingestion increases superoxide production and NADPH oxidase expression in the lung

Alcohol abuse increases the incidence of acute respiratory distress syndrome and causes oxidative stress and cellular dysfunction in the lung. The mechanisms of ethanol (EtOH)-induced oxidative stress in the lung remain to be defined. Chronic alcohol ingestion has been associated with increased renin-angiotensin system (RAS) activity. Therefore, the current study investigated the ability of lisinopril, an angiotensin-converting enzyme (ACE) inhibitor, to modulate oxidative stress in the lung after chronic EtOH ingestion in a well-established rat model. Male Sprague-Dawley rats were fed liquid diets containing EtOH (36% of calories) or maltose-dextrin as an isocaloric substitution for EtOH (Control) for 6 wk. Selected animals were also treated with lisinopril (3 mg/liter) for 6 wk. Chronic EtOH ingestion increased bronchoalveolar lavage fluid glutathione disulfide levels and superoxide formation in lung parenchyma. These effects of EtOH were attenuated by lisinopril treatment. Chronic EtOH ingestion failed to increase ACE expression or angiotensin II levels in lung homogenates, but increased angiotensinogen, angiotensin II type 1 and type 2 receptor levels, and ACE activity. Chronic EtOH ingestion also increased the levels of the NADPH oxidase subunit, gp91phox, an effect that was attenuated by lisinopril, but had no effect on lung p22phox or p47phox levels. These findings suggest that EtOH-mediated RAS activation plays an important role in pulmonary oxidative stress and provide new insights into mechanisms by which EtOH causes oxidative stress in the lung and potential strategies of lung protection through ACE inhibition.

Peroxisome Proliferator-Activated Receptor γ Ligands Stimulate Endothelial Nitric Oxide Production Through Distinct Peroxisome Proliferator-Activated Receptor γ–Dependent Mechanisms

OBJECTIVE

We recently reported that the peroxisome proliferator-activated receptor gamma (PPARgamma) ligands 15-deoxy-Delta(12,14)-prostaglandin J2 (15d-PGJ2) and ciglitazone increased cultured endothelial cell nitric oxide (NO) release without increasing the expression of endothelial nitric oxide synthase (eNOS). The current study was designed to characterize further the molecular mechanisms underlying PPARgamma-ligand-stimulated increases in endothelial cell NO production.

METHODS AND RESULTS

Treating human umbilical vein endothelial cells (HUVEC) with PPARgamma ligands (10 micromol/L 15d-PGJ2, ciglitazone, or rosiglitazone) for 24 hours increased NOS activity and NO release. In selected studies, HUVEC were treated with PPARgamma ligands and with the PPARgamma antagonist GW9662 (2 micromol/L), which fully inhibited stimulation of a luciferase reporter gene, or with small interfering RNA to PPARgamma, which reduced HUVEC PPARgamma expression. Treatment with either small interfering RNA to PPARgamma or GW9662 inhibited 15d-PGJ2-, ciglitazone-, and rosiglitazone-induced increases in endothelial cell NO release. Rosiglitazone and 15d-PGJ2, but not ciglitazone, increased heat shock protein 90-eNOS interaction and eNOS ser1177 phosphorylation. The heat shock protein 90 inhibitor geldanamycin attenuated 15d-PGJ2- and rosiglitazone-stimulated NOS activity and NO production.

CONCLUSIONS

These findings further clarify mechanisms involved in PPARgamma-stimulated endothelial cell NO release and emphasize that individual ligands exert their effects through distinct PPARgamma-dependent mechanisms.

YB-1 coordinates vascular smooth muscle alpha-actin gene activation by transforming growth factor beta1 and thrombin during differentiation of human pulmonary myofibroblasts

Profibrotic regulatory mechanisms for tissue repair after traumatic injury have developed under strong evolutionary pressure to rapidly stanch blood loss and close open wounds. We have examined the roles played by two profibrotic mediators, transforming growth factor beta1 (TGFbeta1) and thrombin, in directing expression of the vascular smooth muscle alpha-actin (SMalphaA) gene, an important determinant of myofibroblast differentiation and early protein marker for stromal cell response to tissue injury. TGFbeta1 is a well known transcriptional activator of the SMalphaA gene in myofibroblasts. In contrast, thrombin independently elevates SMalphaA expression in human pulmonary myofibroblasts at the posttranscriptional level. A common feature of SMalphaA up-regulation mediated by thrombin and TGFbeta1 is the involvement of the cold shock domain protein YB-1, a potent repressor of SMalphaA gene transcription in human fibroblasts that also binds mRNA and regulates translational efficiency. YB-1 dissociates from SMalphaA enhancer DNA in the presence of TGFbeta1 or its Smad 2, 3, and 4 coregulatory mediators. Thrombin does not effect SMalphaA gene transcription but rather displaces YB-1 from SMalphaA exon 3 coding sequences previously shown to be required for mRNA translational silencing. The release of YB-1 from promoter DNA coupled with its ability to bind RNA and shuttle between the nucleus and cytoplasm is suggestive of a regulatory loop for coordinating SMalphaA gene output in human pulmonary myofibroblasts at both the transcriptional and translational levels. This loop may help restrict organ-destructive remodeling due to excessive myofibroblast differentiation.

Induction of vascular smooth muscle alpha-actin gene transcription in transforming growth factor beta1-activated myofibroblasts mediated by dynamic interplay between the Pur repressor proteins and Sp1/Smad coactivators

The mouse vascular smooth muscle alpha-actin (SMA) gene enhancer is activated in fibroblasts by transforming growth factor beta1 (TGFbeta1), a potent mediator of myofibroblast differentiation and wound healing. The SMA enhancer contains tandem sites for the Sp1 transcriptional activator protein and Puralpha and beta repressor proteins. We have examined dynamic interplay between these divergent proteins to identify checkpoints for possible control of myofibroblast differentiation during chronic inflammatory disease. A novel element in the SMA enhancer named SPUR was responsible for both basal and TGFbeta1-dependent transcriptional activation in fibroblasts and capable of binding Sp1 and Pur proteins. A novel Sp1:Pur:SPUR complex was dissociated when SMA enhancer activity was increased by TGFbeta1 or Smad protein overexpression. Physical association of Pur proteins with Smad2/3 was observed as was binding of Smads to an upstream enhancer region that undergoes DNA duplex unwinding in TGFbeta1-activated myofibroblasts. Purbeta repression of the SMA enhancer could not be relieved by TGFbeta1, whereas repression mediated by Puralpha was partially rescued by TGFbeta1 or overexpression of Smad proteins. Interplay between Pur repressor isoforms and Sp1 and Smad coactivators may regulate SMA enhancer output in TGFbeta1-activated myofibroblasts during episodes of wound repair and tissue remodeling.

Structure/function analysis of mouse Purbeta, a single-stranded DNA-binding repressor of vascular smooth muscle alpha-actin gene transcription

Plasticity of smooth muscle alpha-actin gene expression in fibroblasts and vascular smooth muscle cells is mediated by opposing effects of transcriptional activators and repressors. Among these factors, three single-stranded DNA-binding proteins, Puralpha, Purbeta, and MSY1, have been implicated as coregulators of a cryptic 5'-enhancer module. In this study, a molecular analysis of Purbeta, the least well characterized member of this group, was conducted. Southwestern and Northwestern blotting of purified Purbeta deletion mutants using smooth muscle alpha-actin-derived probes mapped the minimal single-stranded DNA/RNA-binding domain to a conserved region spanning amino acids 37-263. Quantitative binding assays indicated that the relative affinity and specificity of Purbeta for single-stranded DNA were influenced by purine/pyrimidine content; by non-conserved regions outside amino acids 37-263; and by cell-derived proteins, specifically MSY1. When overexpressed in A7r5 vascular smooth muscle cells, Purbeta (but not Puralpha) inhibited transcription of a smooth muscle-specific mouse alpha-actin promoter transgene. Structural domains required for Purbeta repressor activity included the minimal DNA-binding region and a C-terminal domain required for stabilizing high affinity protein and nucleic acid interactions. Purbeta inhibitory activity in transfected A7r5 cells was potentiated by MSY1, but antagonized by serum response factor, reinforcing the idea that interplay among activators and repressors may account for phenotypic changes in smooth muscle alpha-actin-expressing cell types.

Vascular smooth muscle alpha-actin gene transcription during myofibroblast differentiation requires Sp1/3 protein binding proximal to the MCAT enhancer

The conversion of stromal fibroblasts into contractile myofibroblasts is an essential feature of the wound-healing response that is mediated by transforming growth factor beta1 (TGF-beta1) and accompanied by transient activation of the vascular smooth muscle alpha-actin (SmalphaA) gene. Multiple positive-regulatory elements were identified as essential mediators of basal SmalphaA enhancer activity in mouse AKR-2B stromal fibroblasts. Three of these elements bind transcriptional activating proteins of known identity in fibroblasts. A fourth site, shown previously to be susceptible to single-strand modifying agents in myofibroblasts, was additionally required for enhancer response to TGF-beta1. However, TGF-beta1 activation was not accompanied by a stoichiometric increase in protein binding to any known positive element in the SmalphaA enhancer. By using oligonucleotide affinity isolation, DNA-binding site competition, gel mobility shift assays, and protein overexpression in SL2 and COS7 cells, we demonstrate that the transcription factors Sp1 and Sp3 can stimulate SmalphaA enhancer activity. One of the sites that bind Sp1/3 corresponds to the region of the SmalphaA enhancer required for TGF-beta1 amplification. Additionally, the TGF-beta1 receptor-regulated Smad proteins, in particular Smad3, are rate-limiting for SmalphaA enhancer activation. Whereas Smad proteins collaborate with Sp1 in activating several stromal cell-associated promoters, they appear to operate independently from the Sp1/3 proteins in activating the SmalphaA enhancer. The identification of Sp and Smad proteins as essential, independent activators of the SmalphaA enhancer provides new insight into the poorly understood process of myofibroblast differentiation.

Reprogramming of vascular smooth muscle alpha-actin gene expression as an early indicator of dysfunctional remodeling following heart transplant

OBJECTIVE

Chronic rejection in cardiac allografts depletes vascular smooth muscle (VSM) alpha-actin from the coronary arterial smooth muscle bed while promoting its abnormal accumulation in cardiomyocytes and myofibroblasts. The objective was to determine if the newly discovered TEF1, MSY1, Puralpha and Purbeta VSM alpha-actin transcriptional reprogramming proteins (TRPs) were associated with development of chronic rejection histopathology in accepted murine cardiac allografts.

METHODS

A mouse heterotopic cardiac transplant model was employed using H2 locus-mismatched mouse strains (DBA/2 or FVB/N to C57BL/6). Recipients were immunosuppressed to promote long-term allograft acceptance and emergence of chronic rejection. Explanted grafts and isolated heart cells were evaluated for changes in the DNA-binding activity and subcellular distribution of VSM alpha-actin transcriptional regulatory proteins.

RESULTS

The DNA-binding activity of all four TRPs was high in the developing mouse ventricle, minimal in adult donor hearts and increased substantially within 30 days after transplantation. Immunohistologic analysis revealed nuclear localization of Purbeta and MSY1 particularly in fibrotic areas of the allograft myocardium demonstrating extravascular accumulation of VSM alpha-actin. Cardiomyocytes isolated from adult, non-transplanted mouse hearts not only exhibited less VSM alpha-actin expression and lower levels of TRPs compared to isolated cardiac fibroblasts or neonatal cardiomyocytes, but also contained a novel size variant of the MSY1 protein.

CONCLUSION

Accumulation of TRPs in cardiac allografts, particularly within the fibroblast-enriched myocardial interstitium, was consistent with their potential role in VSM alpha-actin gene reprogramming, fibrosis and dysfunctional remodeling following transplant. These nuclear protein markers could help stage peri-transplant cellular events that precede formation of graft-destructive fibrosis and coronary vasculopathy during chronic rejection.