A proliferative burst during preadolescence establishes the final cardiomyocyte number.

It is widely believed that perinatal cardiomyocyte terminal differentiation blocks cytokinesis, thereby causing binucleation and limiting regenerative repair after injury. This suggests that heart growth should occur entirely by cardiomyocyte hypertrophy during preadolescence when, in mice, cardiac mass increases many-fold over a few weeks. Here, we show that a thyroid hormone surge activates the IGF-1/IGF-1-R/Akt pathway on postnatal day 15 and initiates a brief but intense proliferative burst of predominantly binuclear cardiomyocytes. This proliferation increases cardiomyocyte numbers by ~40%, causing a major disparity between heart and cardiomyocyte growth. Also, the response to cardiac injury at postnatal day 15 is intermediate between that observed at postnatal days 2 and 21, further suggesting persistence of cardiomyocyte proliferative capacity beyond the perinatal period. If replicated in humans, this may allow novel regenerative therapies for heart diseases.

Transglutaminase 2 Facilitates Murine Wound Healing in a Strain-Dependent Manner.

Transglutaminase 2 (TG2) plays a role in cellular processes that are relevant to wound healing, but to date no studies of wound healing in TG2 knockout mice have been reported. Here, using 129T2/SvEmsJ (129)- or C57BL/6 (B6)-backcrossed TG2 knockout mice, we show that TG2 facilitates murine wound healing in a strain-dependent manner. Early healing of in vivo cutaneous wounds and closure of in vitro scratch wounds in murine embryonic fibroblast (MEF) monolayers were delayed in 129, but not B6, TG2 knockouts, relative to their wild-type counterparts, with wound closure in 129 being faster than in B6 wild-types. A single dose of exogenous recombinant wild-type TG2 to 129 TG2-/- mice or MEFs immediately post-wounding accelerated wound closure. Neutrophil and monocyte recruitment to 129 cutaneous wounds was not affected by Tgm2 deletion up to 5 days post-wounding. Tgm2 mRNA and TG2 protein abundance were higher in 129 than in B6 wild-types and increased in abundance following cutaneous and scratch wounding. Tgm1 and factor XIIA (F13A) mRNA abundance increased post-wounding, but there was no compensation by TG family members in TG2-/- relative to TG2+/+ mice in either strain before or after wounding. 129 TG2+/+ MEF adhesion was greater and spreading was faster than that of B6 TG2+/+ MEFs, and was dependent on syndecan binding in the presence, but not absence, of RGD inhibition of integrin binding. Adhesion and spreading of 129, but not B6, TG2-/- MEFs was impaired relative to their wild-type counterparts and was accelerated by exogenous addition or transfection of TG2 protein or cDNA, respectively, and was independent of the transamidase or GTP-binding activity of TG2. Rho-family GTPase activation, central to cytoskeletal organization, was altered in 129 TG2-/- MEFs, with delayed RhoA and earlier Rac1 activation than in TG2+/+ MEFs. These findings indicate that the rate of wound healing is different between 129 and B6 mouse strains, correlating with TG2 abundance, and although not essential for wound healing, TG2 facilitates integrin- and syndecan-mediated RhoA- and Rac1-activation in fibroblasts to promote efficient wound contraction.

Standardised method for cardiomyocyte isolation and purification from individual murine neonatal, infant, and adult hearts.

Primary cardiomyocytes are invaluable for understanding postnatal heart development. However, a universal method to obtain freshly purified cardiomyocytes without using different age-dependent isolation procedures and cell culture, is lacking. Here, we report the development of a standardised method that allows rapid isolation and purification of high-quality cardiomyocytes from individual neonatal through to adult C57BL/6J murine hearts. Langendorff retrograde perfusion, which is currently limited to adult hearts, was adapted for use in neonatal and infant hearts by developing an easier in situ aortic cannulation technique. Tissue digestion conditions were optimised to achieve efficient digestion of hearts of all ages in a comparable timeframe (<14 min). This resulted in a high yield (1.56-2.2 × 106 cells/heart) and viability (~70-100%) of cardiomyocytes post-isolation. An immunomagnetic cell separation step was then applied to yield highly purified cardiomyocytes (~95%) as confirmed by immunocytochemistry, flow cytometry, and qRT-PCR. For cell type-specific studies, cardiomyocyte DNA, RNA, and protein could be extracted in sufficient yields to conduct molecular experiments. We generated transcriptomic datasets for neonatal cardiomyocytes from individual hearts, for the first time, which revealed nine sex-specific genes (FDR < 0.05) encoded on the sex chromosomes. Finally, we also developed an in situ fixation protocol that preserved the native cytoarchitecture of cardiomyocytes (~94% rod-shaped post-isolation), and used it to evaluate cell morphology during cardiomyocyte maturation, as well as capture spindle-shaped neonatal cells undergoing cytokinesis. Together, these procedures allow molecular and morphological profiling of high-quality cardiomyocytes from individual hearts of any postnatal age.

Adaptation to exercise-induced stress is not dependent on cardiomyocyte α1A-adrenergic receptors.

The 'fight or flight' response to physiological stress involves sympathetic nervous system activation, catecholamine release and adrenergic receptor stimulation. In the heart, this induces positive inotropy, previously attributed to the ß1-adrenergic receptor subtype. However, the role of the α1A-adrenergic receptor, which has been suggested to be protective in cardiac pathology, has not been investigated in the setting of physiological stress. To explore this, we developed a tamoxifen-inducible, cardiomyocyte-specific α1A-adrenergic receptor knock-down mouse model, challenged mice to four weeks of endurance swim training and assessed cardiac outcomes. With 4-OH tamoxifen treatment, expression of the α1A-adrenergic receptor was knocked down by 80-89%, without any compensatory changes in the expression of other adrenergic receptors, or changes to baseline cardiac structure and function. Swim training caused eccentric hypertrophy, regardless of genotype, demonstrated by an increase in heart weight/tibia length ratio (30% and 22% in vehicle- and tamoxifen-treated animals, respectively) and an increase in left ventricular end diastolic volume (30% and 24% in vehicle- and tamoxifen-treated animals, respectively) without any change in the wall thickness/chamber radius ratio. Consistent with physiological hypertrophy, there was no increase in fetal gene program (Myh7, Nppa, Nppb or Acta1) expression. In response to exercise-induced volume overload, stroke volume (39% and 30% in vehicle- and tamoxifen-treated animals, respectively), cardiac output/tibia length ratio (41% in vehicle-treated animals) and stroke work (61% and 33% in vehicle- and tamoxifen-treated animals, respectively) increased, regardless of genotype. These findings demonstrate that cardiomyocyte α1A-adrenergic receptors are not necessary for cardiac adaptation to endurance exercise stress and their acute ablation is not deleterious.

Spontaneous Coronary Artery Dissection and Fibromuscular Dysplasia: Vasculopathies With a Predilection for Women.

The burden of cardiovascular disease in women is being increasingly appreciated. Nevertheless, both clinicians and the general public are largely unaware that cardiovascular disease is the leading cause of death worldwide in women in all countries and that outcomes after a heart attack are worse for women than men. Of note, certain types of cardiovascular disease have a predilection for women, including spontaneous coronary artery dissection (SCAD) and fibromuscular dysplasia (FMD). Although uncommon, SCAD is being increasingly recognised as the cause of an acute coronary syndrome (ACS) and can recur. It is a potentially fatal, under-diagnosed condition that affects relatively young women, who often have few traditional risk factors, and is the commonest cause of a myocardial infarction associated with pregnancy. In contrast, FMD often remains silent but when manifested can also cause major sequelae, including renal infarction, stroke, cervical artery dissection and gut infarction. Here we provide an update on the diagnosis, aetiology and management of these important disorders that overwhelmingly affect women.

Transglutaminase diseases: from biochemistry to the bedside.

In humans, 9 members of the transglutaminase (TG) family have been identified, of which 8 [factor XIII (FXIII)A and TG1-TG7] catalyze post-translational protein-modifying reactions, and 1 does not (protein 4.2). The TG enzymatic activities considered in our discussion of human disease include deamidation of glutamine (Gln) residues, amine incorporation into Gln residues, and protein crosslinking. Except for TG7, which remains poorly studied, all individual TG members have been correlated with disparate human diseases that arise from either TG function or lack of function. Loss of TG function is associated with numerous orphan diseases that affect a relatively small number of individuals: loss of FXIIIa (transamidase-activated form) crosslinking leads to defects in blood coagulation in FXIII deficiency; loss of TG1 and TG5 cross linking leads to defects in epidermal cornification in lamellar ichthyosis and acral peeling skin syndrome, respectively; loss of TG3 crosslinking in hair-cuticle formation leads to uncombable hair syndrome; the predicted loss of TG6 crosslinking leads to spinocerebellar ataxia-35; and loss of the structural erythrocyte membrane protein, protein 4.2, leads to hereditary spherocytosis type 5. The enzymatic activity of TG2 is involved in the exacerbation of celiac disease and in at least 1 case of hemoglobinopathy, characterized by shortened erythrocyte lifespan. TGs are also autoantigens in a number of immune diseases, resulting in the production of autoantibodies against FXIIIa in acquired FXIII deficiency, TG2 in celiac disease, TG3 in dermatitis herpetiformis, TG4 in autoimmume polyglandular syndrome type 1, and TG6 in gluten axonal neuropathy and gluten ataxia. Much still remains to be learned and confirmed with respect to disease mechanisms, particularly with respect to TG-related immune diseases, in which development of isozyme-specific inhibitors may be useful for treatment.-Lorand, L., Iismaa, S. E. Transglutaminase diseases: from biochemistry to the bedside.

Molecular mechanism of transglutaminase-2 in corneal epithelial migration and adhesion.

Migration of cells in the ocular surface underpins physiological wound healing as well as many human diseases. Transglutaminase (TG)-2 is a multifunctional cross-linking enzyme involved in the migration of skin fibroblasts and wound healing, however, its functional role in epithelial migration has not been evaluated. This study investigated the importance of TG-2 in a murine corneal wound healing model as well as the mechanistic role of TG-2 in the regulation of related biological processes such as cell adhesion and migration of cultured human corneal epithelial (HCE-T) cells. Corneal wound closure was delayed in homozygous TG-2 deleted mice compared to wild type mice. HCE-T cells that were knocked-down for TG-2 expression through stable expression of a short-hairpin (sh) RNA targeting TG-2, were delayed in closure of scratch wounds (48 compared to 12h in control cells expressing scrambled shRNA). TG-2 knockdown did not influence epithelial cell cycle progression or proliferation, rather, it led to reduced epithelial cell adhesion, spreading and velocity of migration. At the molecular level, TG-2 knockdown reduced phosphorylation of ß-3 integrin at Tyr747, paxillin at Ser178, vinculin at Tyr822 and focal adhesion kinase at Tyr925 simultaneous with reduced activation of Rac and CDC42. Phosphorylation of paxillin at Ser178A has been shown to be indispensable for the migration of corneal epithelial cells (Kimura et al., 2008) [18]. TG-2 dependent ß-3 integrin activation, serine-phosphorylation of paxillin, and Rac and CDC42 activation may thus play a key functional role in enhancing corneal epithelial cell adhesion and migration during wound healing.

Prevalence and correlates of anxiety and depressive symptoms after Spontaneous Coronary Artery Dissection (SCAD): a cross-sectional study.

AIMS: Spontaneous coronary artery dissection (SCAD) is recognised as a particularly stressful cause of heart attack. However few studies have documented the prevalence of post-SCAD anxiety and depressive symptoms, or identified patients most at risk. This study documents the prevalence and correlates of post-SCAD anxiety and depressive symptoms. METHOD AND RESULTS: 310 (95% women) SCAD survivors were recruited by the Victor Chang Cardiac Research Institute from a database of 433 SCAD survivors. Participants completed an online questionnaire to gather demographic, medical and psychosocial information, including the Generalised Anxiety Disorder-7 (GAD-7) and the Patient Health Questionnaire-9 (PHQ-9). Bivariate and multivariate analyses were undertaken to identify the significant demographic, psychosocial and medical correlates of post-SCAD anxiety and depressive symptoms. Time between SCAD and questionnaire completion varied from 2 months to 18 years (mean = 5.5 years; SD = 3.5 years). Rates of anxiety and depressive symptoms were 20.7% (GAD-7 ≥ 10) and 20.9% (PHQ-9 ≥ 10) respectively, and did not vary by time since event. In bivariate analyses, correlates (p < .05) of anxiety and depressive symptoms were absence of a close confidante, financial strain, mental health diagnosis pre-SCAD, comorbid obesity, not being in paid employment (anxiety only), younger age (depression only), and not knowing another SCAD survivor (depression only). Variables retained in multivariate models were absence of a close confidante, financial strain, not being in paid employment, mental health diagnosis pre-SCAD (depression only), and younger age (depression only). CONCLUSION: This study demonstrated that over one in four SCAD survivors experience either anxiety or depressive symptoms after SCAD, and identified those who may need additional support in their psychological recovery.

Correction: Psychosocial and lifestyle impacts of spontaneous coronary artery dissection: A quantitative study.

[This corrects the article DOI: 10.1371/journal.pone.0296224.].

Cognitive and physical fatigue: the experience and consequences of 'brain fog' after Spontaneous Coronary Artery Dissection (SCAD), a qualitative study.

AIMS: Brain fog and fatigue are common issues after acute coronary syndrome. However, little is known about the nature and impact of these experiences in spontaneous coronary artery dissection (SCAD) survivors. The aims of this study were to understand the experiences of brain fog and the coping strategies used after SCAD. METHODS AND RESULTS: Participants were recruited from the Victor Chang Cardiac Research Institute Genetics Study database and were considered eligible if their event occurred within 12-months. Seven semi-structured online focus groups were conducted between December to January 2021-2022, with this study reporting findings related to brain fog and fatigue. Interviews were transcribed and thematically analysed using an iterative approach. Participants (N=30) were a mean age of 52.2 ((9.5) and mostly female (n=27, 90%). The overarching theme of brain fog after SCAD included four main themes: how brain fog is experienced, perceived causes, impacts, and how people cope. Experiences included memory lapses, difficulty concentrating and impaired judgement, and perceived causes included medication, fatigue and tiredness, and menopause and hormonal changes. Impacts of brain fog included rumination, changes in self-perception, disruption to hobbies/pastimes, and limitations at work. Coping mechanisms included setting reminders and expectations, being one's own advocate, lifestyle and self-determined medication adjustments, and support from peers. CONCLUSION: Brain fog is experienced by SCAD survivors and the impacts are varied and numerous, including capacity to work. SCAD survivors reported difficulty understanding causes and found their own path to coping. Recommendations for clinicians are provided.

Psychosocial and lifestyle impacts of spontaneous coronary artery dissection: A quantitative study.

INTRODUCTION: Recent studies suggest that acute myocardial infarction due to spontaneous coronary artery dissection (SCAD) carries significant psychosocial burden. This survey-based quantitative study builds on our earlier qualitative investigation of the psychosocial impacts of SCAD in Australian SCAD survivors. The study aimed to document the prevalence and predictors of a broad range of psychosocial and lifestyle impacts of SCAD. METHOD: Australian SCAD survivors currently enrolled in the Victor Chang Cardiac Research Institute genetics study were invited to participate in an online survey to assess the psychosocial impacts of SCAD. Participants completed a questionnaire, developed using findings from our earlier qualitative research, which assessed 48 psychosocial and five lifestyle impacts of SCAD. Participants also provided demographic and medical data and completed validated measures of anxiety and depression. RESULTS: Of 433 SCAD survivors invited to participate, 310 (72%) completed the questionnaire. The most common psychosocial impacts were 'shock about having a heart attack' (experienced by 87% respondents), 'worry about having another SCAD' (81%), 'concern about triggering another SCAD' (77%), 'uncertainty about exercise and physical activity' (73%) and 'confusion about safe levels of activity and exertion' (73.0%) and 'being overly aware of bodily sensations' (73%). In terms of lifestyle impacts, the SCAD had impacted on work capacity for almost two thirds of participants, while one in ten had sought financial assistance. The key predictors of psychosocial impacts were being under 50, current financial strain, and trade-level education. The key predictors of lifestyle impacts were being over 50, SCAD recurrence, trade-level education, and current financial strain. All psychosocial impacts and some lifestyle impacts were associated with increased risk of anxiety and/or depression. CONCLUSION AND IMPLICATIONS: This quantitative study extends our previous qualitative investigation by documenting the prevalence of each of 48 psychosocial and five lifestyle impacts identified in our earlier focus group research, and by providing risk factors for greater SCAD impacts. The findings suggest the need for supports to address initial experiences of shock, as well as fears and uncertainties regarding the future, including SCAD recurrence and exercise resumption. Support could be targeted to those with identified risk factors. Strategies to enable SCAD survivors to remain in or return to the paid workforce are also indicated.

Polygenic Risk in Families With Spontaneous Coronary Artery Dissection.

Importance: Spontaneous coronary artery dissection (SCAD) is a poorly understood cause of acute coronary syndrome that predominantly affects women. Evidence to date suggests a complex genetic architecture, while a family history is reported for a minority of cases. Objective: To determine the contribution of rare and common genetic variants to SCAD risk in familial cases, the latter via the comparison of a polygenic risk score (PRS) with those with sporadic SCAD and healthy controls. Design, Setting, and Participants: This genetic association study analyzed families with SCAD, individuals with sporadic SCAD, and healthy controls. Genotyping was undertaken for all participants. Participants were recruited between 2017 and 2021. A PRS for SCAD was calculated for all participants. The presence of rare variants in genes associated with connective tissue disorders (CTD) was also assessed. Individuals with SCAD were recruited via social media or from a single medical center. A previously published control database of older healthy individuals was used. Data were analyzed from January 2022 to October 2023. Exposures: PRS for SCAD comprised of 7 single-nucleotide variants. Main Outcomes and Measures: Disease status (familial SCAD, sporadic SCAD, or healthy control) associated with PRS. Results: A total of 13 families with SCAD (27 affected and 12 unaffected individuals), 173 individuals with sporadic SCAD, and 1127 healthy controls were included. A total of 188 individuals with SCAD (94.0%) were female, including 25 of 27 with familial SCAD and 163 of 173 with sporadic SCAD; of 12 unaffected individuals from families with SCAD, 6 (50%) were female; and of 1127 healthy controls, 672 (59.6%) were female. Compared with healthy controls, the odds of being an affected family member or having sporadic SCAD was significantly associated with a SCAD PRS (where the odds ratio [OR] represents an increase in odds per 1-SD increase in PRS) (affected family member: OR, 2.14; 95% CI, 1.78-2.50; adjusted P = 1.96 × 10-4; sporadic SCAD: OR, 1.63; 95% CI, 1.37-1.89; adjusted P = 5.69 × 10-4). This association was not seen for unaffected family members (OR, 1.03; 95% CI, 0.46-1.61; adjusted P = .91) compared with controls. Further, those with familial SCAD were overrepresented in the top quintile of the control PRS distribution (OR, 3.70; 95% CI, 2.93-4.47; adjusted P = .001); those with sporadic SCAD showed a similar pattern (OR, 2.51; 95% CI, 1.98-3.04; adjusted P = .001). Affected individuals within a family did not share any rare deleterious variants in CTD-associated genes. Conclusions and Relevance: Extreme aggregation of common genetic risk appears to play a significant role in familial clustering of SCAD as well as in sporadic case predisposition, although further study is required.

Transglutaminase inhibition protects against oxidative stress-induced neuronal death downstream of pathological ERK activation.

Molecular deletion of transglutaminase 2 (TG2) has been shown to improve function and survival in a host of neurological conditions including stroke, Huntington's disease, and Parkinson's disease. However, unifying schemes by which these cross-linking or polyaminating enzymes participate broadly in neuronal death have yet to be presented. Unexpectedly, we found that in addition to TG2, TG1 gene expression level is significantly induced following stroke in vivo or due to oxidative stress in vitro. Forced expression of TG1 or TG2 proteins is sufficient to induce neuronal death in Rattus norvegicus cortical neurons in vitro. Accordingly, molecular deletion of TG2 alone is insufficient to protect Mus musculus neurons from oxidative death. By contrast, structurally diverse inhibitors used at concentrations that inhibit TG1 and TG2 simultaneously are neuroprotective. These small molecules inhibit increases in neuronal transamidating activity induced by oxidative stress; they also protect neurons downstream of pathological ERK activation when added well after the onset of the death stimulus. Together, these studies suggest that multiple TG isoforms, not only TG2, participate in oxidative stress-induced cell death signaling; and that isoform nonselective inhibitors of TG will be most efficacious in combating oxidative death in neurological disorders.

Generation of induced pluripotent stem cell lines from a sister pair who suffered post-partum or recurrent Spontaneous Coronary Artery Dissections.

Spontaneous Coronary Artery Dissection (SCAD) results from a bleed within a coronary artery wall that impairs blood flow as it expands. It is the most common cause of myocardial infarction in pregnant women. Here, peripheral blood mononuclear cells from two sisters who had suffered SCADs were reprogrammed using Sendai Virus. Expression of pluripotency markers, capability to differentiate to the three germ layers, and cellular integrity were confirmed. This is the first report of a SCAD family induced pluripotent stem cell (iPSC) cohort, including a sister who suffered post-partum SCAD, and one who suffered from multiple recurrences.

Prevalence of Anxiety, Depression, and Distress in SCAD and Non-SCAD AMI Patients: A Comparative Study.

PURPOSE: Spontaneous coronary artery dissection (SCAD) is an increasingly recognized cause of acute myocardial infarction (AMI), particularly in younger women without classic cardiac risk factors. Spontaneous coronary artery dissection is considered to be particularly stressful; however, few studies have quantified SCAD survivor stress levels. This study compared anxiety, depression, and distress levels in SCAD and non-SCAD AMI patients. METHOD: A sample of 162 AMI (35 [22%] SCAD) patients was recruited from hospitals and via social media, in Australia and the United States. All had had their AMI in the past 6 mo. Participants completed an online questionnaire comprising the Generalized Anxiety Disorder-2 (GAD2), Patient Health Questionnaire-2 (PHQ2), Kessler-6 (K6), and Cardiac Distress Inventory (CDI). T-tests, χ 2 tests, Mann-Whitney tests, and analysis of covariance were used to compare SCAD and non-SCAD samples. Logistic regression was used to identify the unique predictors of anxiety, depression, and distress, controlling for relevant confounders. RESULTS: Patients with SCAD were more commonly female and significantly younger than non-SCAD patients. Patients with SCAD scored significantly higher on the GAD2, PHQ2, K6, and CDI and a significantly larger proportion was classified as anxious, depressed, or distressed using these instruments. In logistic regression, together with mental health history, having had a SCAD-AMI predicted anxiety, depression, and distress, after controlling for female sex, younger age, and other confounding variables. CONCLUSION: This study supports the view that anxiety, depression, and distress are more common after SCAD-AMI than after traditional AMI. These findings highlight the psychosocial impacts of SCAD and suggest that psychological support should be an important component of cardiac rehabilitation for these patients.

Fibulin-3 is necessary to prevent cardiac rupture following myocardial infarction.

Despite the high prevalence of heart failure in the western world, there are few effective treatments. Fibulin-3 is a protein involved in extracellular matrix (ECM) structural integrity, however its role in the heart is unknown. We have demonstrated, using single cell RNA-seq, that fibulin-3 was highly expressed in quiescent murine cardiac fibroblasts, with expression highest prior to injury and late post-infarct (from ~ day-28 to week-8). In humans, fibulin-3 was upregulated in left ventricular tissue and plasma of heart failure patients. Fibulin-3 knockout (Efemp1-/-) and wildtype mice were subjected to experimental myocardial infarction. Fibulin-3 deletion resulted in significantly higher rate of cardiac rupture days 3-6 post-infarct, indicating a weak and poorly formed scar, with severe ventricular remodelling in surviving mice at day-28 post-infarct. Fibulin-3 knockout mice demonstrated less collagen deposition at day-3 post-infarct, with abnormal collagen fibre-alignment. RNA-seq on day-3 infarct tissue revealed upregulation of ECM degradation and inflammatory genes, but downregulation of ECM assembly/structure/organisation genes in fibulin-3 knockout mice. GSEA pathway analysis showed enrichment of inflammatory pathways and a depletion of ECM organisation pathways. Fibulin-3 originates from cardiac fibroblasts, is upregulated in human heart failure, and is necessary for correct ECM organisation/structural integrity of fibrotic tissue to prevent cardiac rupture post-infarct.

Genome-wide association meta-analysis of spontaneous coronary artery dissection identifies risk variants and genes related to artery integrity and tissue-mediated coagulation.

Spontaneous coronary artery dissection (SCAD) is an understudied cause of myocardial infarction primarily affecting women. It is not known to what extent SCAD is genetically distinct from other cardiovascular diseases, including atherosclerotic coronary artery disease (CAD). Here we present a genome-wide association meta-analysis (1,917 cases and 9,292 controls) identifying 16 risk loci for SCAD. Integrative functional annotations prioritized genes that are likely to be regulated in vascular smooth muscle cells and artery fibroblasts and implicated in extracellular matrix biology. One locus containing the tissue factor gene F3, which is involved in blood coagulation cascade initiation, appears to be specific for SCAD risk. Several associated variants have diametrically opposite associations with CAD, suggesting that shared biological processes contribute to both diseases, but through different mechanisms. We also infer a causal role for high blood pressure in SCAD. Our findings provide novel pathophysiological insights involving arterial integrity and tissue-mediated coagulation in SCAD and set the stage for future specific therapeutics and preventions.

Transglutaminase 2 and its role in pulmonary fibrosis.

RATIONALE: Idiopathic pulmonary fibrosis (IPF) is a deadly progressive disease with few treatment options. Transglutaminase 2 (TG2) is a multifunctional protein, but its function in pulmonary fibrosis is unknown. OBJECTIVES: To determine the role of TG2 in pulmonary fibrosis. METHODS: The fibrotic response to bleomycin was compared between wild-type and TG2 knockout mice. Transglutaminase and transglutaminase-catalyzed isopeptide bond expression was examined in formalin-fixed human lung biopsy sections by immunohistochemistry from patients with IPF. In addition, primary human lung fibroblasts were used to study TG2 function in vitro. MEASUREMENTS AND MAIN RESULTS: TG2 knockout mice developed significantly reduced fibrosis compared with wild-type mice as determined by hydroxyproline content and histologic fibrosis score (P < 0.05). TG2 expression and activity are increased in lung biopsy sections in humans with IPF compared with normal control subjects. In vitro overexpression of TG2 led to increased fibronectin deposition, whereas transglutaminase knockdown led to defects in contraction and adhesion. The profibrotic cytokine transforming growth factor-ß causes an increase in membrane-localized TG2, increasing its enzymatic activity. CONCLUSIONS: TG2 is involved in pulmonary fibrosis in a mouse model and in human disease and is important in normal fibroblast function. With continued research on TG2, it may offer a new therapeutic target.

Anesthesia and Intubation of Preadolescent Mouse Pups for Cardiothoracic Surgery.

Murine surgical models play an important role in preclinical research. Mechanistic insights into myocardial regeneration after cardiac injury may be gained from cardiothoracic surgery models in 0-14-day-old mice, the cardiomyocytes of which, unlike those of adults, retain proliferative capacity. Mouse pups up to 7 days old are effectively immobilized by hypothermia and do not require intubation for cardiothoracic surgery. Preadolescent (8-14-day-old) mouse pups, however, do require intubation, but this is challenging and there is little information regarding anesthesia to facilitate intubation. Here, we present dosage regimens of ketamine/xylazine/atropine in 10-day-old C57BL/6J mouse pups that allow endotracheal intubation, while minimizing animal mortality. Empirical titration of ketamine/xylazine/atropine dosage regimens to body weight indicated that the response to anesthesia of mouse pups of different weights was non-linear, whereby doses of 20/4/0.12 mg/kg, 30/4/0.12 mg/kg, and 50/6/0.18 mg/kg facilitated intubation of pups weighing between 3.15-4.49 g (n = 22), 4.50-5.49 g (n = 20), and 5.50-8.10 g (n = 20), respectively. Lower-body-weight pups required more intubation attempts than heavier pups (p < 0.001). Survival post-intubation correlated with body weight (59%, 70%, and 80% for low-, mid-, and high-weight groups, respectively, R2 = 0.995). For myocardial infarction surgery after intubation, a surgical plane of anesthesia was induced with 4.5% isoflurane in 100% oxygen and maintained with 2% isoflurane in 100% oxygen. Survival post-surgery was similar for the three weight groups at 92%, 86%, and 88% (p = 0.91). Together with refinements in animal handling practices for intubation and surgery, and minimizing cannibalization by the dam post-surgery, overall survival for the entire procedure (intubation plus surgery) correlated with body weight (55%, 60%, and 70% for low-, mid-, and high-weight groups, respectively, R2 = 0.978). Given the difficulty encountered with intubation of 10-day old pups and the associated high mortality, we recommend cardiothoracic surgery in 10-day-old pups be restricted to pups weighing at least 5.5 g.