Myocardin restores erectile function in diabetic rats: phenotypic modulation of corpus cavernosum smooth muscle cells

ROUX-en-Y gastric bypass surgery improves metabolic syndrome-related erectile dysfunction in mice via the IRS-1/PI3K/AKT/eNOS pathway

Objective

Although many clinical studies have shown that ROUX-en-Y gastric bypass (RYGB) surgery significantly improves metabolic syndrome-related erectile dysfunction (MED), the role and mechanism are unclear.

Aim

In this study we used a mouse model to explore how RYGB improves MED induced by a high-fat diet (HFD).

Methods

We established a mouse model of metabolic syndrome by feeding an HFD for 16 weeks. The mice were randomly assigned to the standard chow diet (SCD), HFD, or RYGB groups. Body weight, fasting blood glucose, plasma insulin, and total plasma cholesterol were analyzed. Erectile responses were evaluated by determining the mean systolic blood pressure and the intracavernosal pressure (ICP). Penile histologic examination (Masson's trichrome and immunohistochemical stain) and Western blot were performed.

Result

Compared with the SCD group, the ICP in the sham group was significantly lower, and the ICP of the RYGB was significantly increased. Masson's trichrome and immunohistochemical staining showed that the content of endothelium and smooth muscle in the corpus cavernosum of mice with MED was significantly reduced. Western blot analysis showed a significant decrease in α-smooth muscle actin and a significant increase in osteopontin in penile tissue in the sham group, which was improved by RYGB surgery. Furthermore, RYGB significantly increased IRS-1/PI3K/Akt/eNOS phosphorylation.

Clinical Translation

In this study we explored the mechanism of bariatric surgery to improve erectile dysfunction associated with metabolic syndrome and provided a theoretical basis for clinical research.

Strengths and Limitations

First, we did not investigate the mechanism by which RYGB affects the IRS-1/PI3K/Akt/eNOS signaling pathway. Second, the effect of the IRS-1/PI3K/Akt/eNOS signaling pathway on the function of corpus cavernosum endothelial cells and smooth muscle cells remains to be investigated in cellular studies.

Conclusion

This study demonstrated that RYGB may not only improve metabolic parameters but also restore erectile function in MED patients. The mechanism of the therapeutic effect of RYGB may be reactivation of the IRS-1/PI3K/Akt/eNOS pathway.

Effects of endoplasmic reticulum stress on erectile function in rats with cavernous nerve injury

Background

Erectile dysfunction (ED) occurs in an increasing number of patients after radical prostatectomy and cystectomy, and the phenotypic modulation of corpus cavernosum smooth muscle cells is closely related to ED.

Aim

To determine whether endoplasmic reticulum stress (ERS) is implicated in the phenotypic modulation of ED induced by bilateral cavernous nerve injury (BCNI).

Methods

In total, 36 Sprague-Dawley rats were randomly divided into 3 groups: sham, in which rats received sham surgery with bilateral cavernous nerve exposure plus phosphate-buffered saline; control, in which rats received BCNI plus phosphate-buffered saline; and experimental, in which rats received BCNI plus 4-phenylbutyric acid. Analysis of variance and a Bonferroni multiple-comparison test were utilized to evaluate differences among groups.

Outcomes

Erectile function, smooth muscle/collagen ratios, and the expression levels of phenotypic modulation and ERS were measured.

Results

Two ratios-maximum intracavernosal pressure/mean arterial pressure and smooth muscle/collagen-were decreased in the control group as compared with the sham group. In penile tissue, there was increased expression of GRP78 (78-kDa glucose-regulated protein), p-PERK/PERK (phosphorylated protein kinase R-like endoplasmic reticulum kinase/protein kinase R-like endoplasmic reticulum kinase), caspase 3, CHOP (C/EBP homologous protein), and OPN (osteopontin) but decreased expression of nNOS (neuronal nitric oxide synthase) and α-SMA (α-smooth muscle actin). As compared with the control group, erectile function was improved and pathologic changes were partially recovered in the experimental group.

Clinical Translation

The present study demonstrated that ERS is involved in ED caused by cavernous nerve injury, thereby providing a new target and theoretical basis for clinical treatment.

Strengths and Limitations

The present study demonstrated for the first time that ERS is related to ED caused by cavernous nerve injury. Inhibition of ERS reverses phenotypic modulation and improves erectile function in rats with BCNI. Additional in vitro studies should be performed to verify these conclusions and explore the specific mechanism of phenotypic modulation.

Conclusion

The present study demonstrated that inhibiting ERS reverses phenotypic modulation and enhances erectile function in rats with BCNI.

An atypical erectile dysfunction patient with infertility treated with penile prosthesis implantation and testicular epididymal sperm aspiration (TESA)-intracytoplasmic sperm injection (ICSI): A case report

RATIONALE

Erectile dysfunction (ED) is common in middle-aged and elderly men, affecting more than 100 million males worldwide. Most ED cases can be attributed to organic and/or psychological factors. Here we report an atypical ED case with no clear manifestation fitting the diagnosis for recognized types of ED.

PATIENT CONCERNS

The 35-year-old male is unable to have normal erection since puberty, and unable to complete intercourse with his wife. He had no history of trauma, surgery or psychiatric/psychological disease. The patient has a normal male karyotype. There is no significant finding in physical examination, nocturnal penile tumescence test, and ultrasound measurement of penis vascular functions. The serum levels of major hormones are all in normal ranges.

DIAGNOSES

Atypical ED, psychogenic ED not excluded; infertility.

INTERVENTIONS

Oral phosphodiesterase inhibitors Tadalafil (20 mg, BIW) or Sildenafil (50 mg, BIW) had no effect in this patient. Penile prosthesis implantation helped the patient to acquire normal sexual life, but did solve the ejaculation failure and infertility. Motile sperms were obtained by testicular epididymal sperm aspiration under the guidance of ultrasound, and intracytoplasmic sperm injection was performed with occytes retrieved from his wife.

OUTCOMES

The patient sexual life was significantly improved after penile prosthesis implantation; the patient wife is currently in the first trimester of pregnancy as the result of in vitro fertilization.

CONCLUSIONS

The no response to phosphodiesterase type 5 inhibitors (PDE5) treatment may suggest an impediment of PDE5-related pharmacological pathways or the presence of defect/injury in the neural system. This special case raises a question if some patients with persistent ED may have similar manifestations and can be treated with the same procedures.

Myocardin Reverses Hypoxia-Inducible Factor-1α Mediated Phenotypic Modulation of Corpus Cavernosum Smooth Muscle Cells in Hypoxia Induced by Cobalt Chloride

PURPOSE

We aimed to investigate the mechanism of phenotypic transformation of corporal cavernosum smooth muscle cells (CCSMCs) under hypoxic conditions in vitro.

MATERIALS AND METHODS

In this study, a hypoxia model was established using cobalt chloride (CoCl₂). CCSMCs were treated with different concentrations of CoCl₂ for varying time periods, and cell viability was assessed. Hypoxia-inducible factor-1α (HIF-1α), myocardin (Myocd) and phenotypic markers were detected in the CCSMCs. We also transfected the CCSMCs with si-HIF-1α and Ad-Myocd and evaluated the effects on phenotypic modulation of CCSMCs and the relationship between HIF-1α and Myocd was evaluated.

RESULTS

CoCl₂ inhibited the viability of CCSMCs in a dose- and time-dependent manner, and treatment with 300 µM CoCl₂ for 48 hours were the optimal conditions for establishing the hypoxia model. The results showed increased expression levels of HIF-1α and osteopontin and decreased Myocd, alpha-smooth muscle actin, and calponin levels in CCSMCs under hypoxia. HIF-1α knockdown reversed hypoxia-induced phenotypic transformation with elevated Myocd expression. Overexpression of Myocd also reversed the effect of hypoxia on the phenotypic switch, but did not affect HIF-1α expression.

CONCLUSIONS

Our findings showed that HIF-1α was involved in the effect of hypoxia induced by CoCl₂ on CCSMC phenotypic modulation, and Myocd overexpression could inhibit this process. Thus, Myocd might be a potential therapeutic target for erectile dysfunction under hypoxia or HIF-1α activation.

[CRISPR/Cas9-mediated TEAD1 knockout induces phenotypic modulation of corpus cavernosum smooth muscle cells in diabetic rats with erectile dysfunction]

OBJECTIVE

To construct a corpus cavemosum smooth muscle cell (CCSMCs) line with TEAD1 knockout from diabetic rats with erectile dysfunction (ED) using CRISPR/Cas9 technology and explore the role of TEAD1 in phenotypic modulation of CCSMCs in diabetic rats with ED.

OBJECTIVE

Models of diabetic ED were established in male Sprague-Dawley rats by intraperitoneal injection of streptozotocin. CCSMCs from the rat models were primarily cultured and identified with immunofluorescence assay. Three sgRNAs (sgRNA-1, sgRNA-2 and sgRNA-3) were transfected via lentiviral vectors into 293T cells to prepare the sgRNA-Cas9 lentivirus. CCSMCs from diabetic rats with ED were infected by the lentivirus, and the cellular expression of TEAD1 protein was detected using Western blotting. In CCSMCs infected with the sgRNA-Cas9 lentivirus (CCSMCs-sgRNA-2), or the empty lentiviral vector (CCSMCs-sgRNA-NC) and the blank control cells (CCSMCs-CK), the expressions of cellular phenotypic markers SMMHC, calponin and PCNA at the mRNA and protein levels were detected using real-time fluorescence quantitative RT-PCR (qRT-PCR) and Western blotting, respectively.

OBJECTIVE

The primarily cultured CCSMCs from diabetic rats with ED showed a high α-SMA-positive rate of over 95%. The recombinant lentivirus of TEAD1-sgRNA was successfully packaged, and stable TEAD1-deficient CCSMC lines derived from diabetic rat with ED were obtained. Western blotting confirmed that the protein expression of TEAD1 in TEAD1-sgRNA-2 group was the lowest (P < 0.05), and this cell line was used in subsequent experiment. The results of qRT-PCR and Western blotting showed significantly up-regulated expressions of SMMHC and calponin (all P < 0.05) and down-regulated expression of PCNA (all P < 0.05) at both the mRNA and protein levels in TEAD1-deficient CCSMCs from diabetic rats with ED.

OBJECTIVE

We successfully constructed a stable CCSMCs line with CRISPR/Cas9-mediated TEAD1 knockout from diabetic rats with ED. TEAD1 gene knockout can induce phenotype transformation of the CCSMCs from diabetic rats with ED from the synthetic to the contractile type.

The near-infrared dye IR-61 restores erectile function in a streptozotocin-induced diabetes model via mitochondrial protection

This study aimed to evaluate the therapeutic effect of IR-61, a novel mitochondrial heptamethine cyanine dye with antioxidant effects, on diabetes mellitus-induced erectile dysfunction (DMED). Eight-week-old male Sprague-Dawley rats were intraperitoneally injected with streptozotocin (STZ) to induce type 1 diabetes. Eight weeks after STZ injection, all rats were divided into three groups: the control group, DM group, and DM + IR-61 group. In the DM + IR-61 group, the rats were administered IR-61 (1.6 mg kg^-1) twice a week by intravenous injection. At week 13, erectile function was evaluated by determining the ratio of the maximal intracavernous pressure to mean arterial pressure, and the penises were then harvested for fluorescent imaging, transmission electron microscopy, histological examinations, and Western blot analysis. Whole-body imaging suggested that IR-61 was highly accumulated in the penis after intravenous injection. IR-61 treatment significantly improved the maximal ICP of diabetic rats. Additionally, IR-61 ameliorated diabetes-induced inflammation, apoptosis, and phenotypic transition of corpus cavernosum smooth muscle cells (CCSMCs) in penile tissue. IR-61 also attenuated mitochondrial damage, reduced reactive oxygen species production in the corpus cavernosum and upregulated sirtuin1 (SIRT1), sirtuin3 (SIRT3), nuclear factor (erythroid-derived 2)-like 2 (Nrf2), and heme oxygenase expression in penile tissue. In conclusion, IR-61 represents a potential therapeutic option for DMED by protecting the mitochondria of CCSMCs, which may be mediated by activation of the SIRT1, SIRT3, and Nrf2 pathways.

Exosomes derived from smooth muscle cells ameliorate diabetes-induced erectile dysfunction by inhibiting fibrosis and modulating the NO/cGMP pathway

Erectile dysfunction (ED) is a major health issue among men with diabetes, and ED induced by diabetes mellitus (DMED) is particularly difficult to treat. Therefore, novel therapeutic approaches for the treatment of DMED are urgently needed. Exosomes, nanosized particles involved in many physiological and pathological processes, may become a promising tool for DMED treatment. In this study, we investigated the therapeutic effect of exosomes derived from corpus cavernosum smooth muscle cells (CCSMC‐EXOs) on erectile function in a rat model of diabetes and compared their effect with that of exosomes derived from mesenchymal stem cells (MSC‐EXOs). We incubated labelled CCSMC‐EXOs and MSC‐EXOs with CCSMCs and then observed uptake of the exosomes at different time points using laser confocal microscopy. CCSMC‐EXOs were more easily taken up by CCSMCs. The peak concentration and retention time of labelled CCSMC‐EXOs and MSC‐EXOs in the corpus cavernosum of DMED rats after intracavernous injection were compared by in vivo imaging techniques. Intracavernous injection of CCSMC‐EXOs was associated with a relatively high peak concentration and long retention time. Our data showed that CCSMC‐EXOs could improve erectile function in DMED rats. Meanwhile, CCSMC‐EXOs could exert antifibrotic effects by increasing the smooth muscle content and reducing collagen deposition. CCSMC‐EXOs also increased the expression of eNOS and nNOS, followed by increased levels of NO and cGMP. These findings initially identify the possible role of CCSMC‐EXOs in ameliorating DMED through inhibiting corporal fibrosis and modulating the NO/cGMP signalling pathway, providing a theoretical basis for a breakthrough in the treatment of DMED.

Mitochondrial ATP synthase regulates corpus cavernosum smooth muscle cell function in vivo and in vitro

Adenosine triphosphate (ATP) levels are closely associated with diabetes-related erectile dysfunction (DMED). Mitochondrial ATP synthase serves a key role in ATP production. The present study aimed to investigate the relationship between F₁-ATP synthase and DMED in vivo and in vitro. The F₁-ATP synthase expression levels in corpus cavernosum tissues from rats with DMED were examined. F₁-ATP synthase expression was found to be lower in corpus cavernosum tissues from rats with DMED compared with healthy controls, suggesting a role for ATP synthase under high glucose conditions. In addition, the present study also demonstrated that hyperglycemia could downregulate F₁-ATP synthase expression in rat corpus cavernosum smooth muscle cells (CCSMCs) in vitro. The overexpression of F₁-ATP synthase in CCSMCs influenced the phenotypic CCSMC transformation, upregulated eNOS expression, increased cGMP levels and reduced CCSMC apoptosis under high glucose in vitro. In conclusion, the present study indicates that the upregulation of mitochondrial ATP synthase expression may improve CCSMC function, suggesting that mitochondrial ATP synthase could serve as a potential therapeutic target for the treatment of DMED.

Hypoxia-Induced Phenotypic Transformation of Corpus Cavernosum Smooth Muscle Cells After Cavernous Nerve Crush Injury by Down-Regulating P38 Mitogen-Activated Protein Kinase Expression

INTRODUCTION

Cavernosal nerve (CN) injury is commonly caused by radical prostatectomy surgery, and it might directly lead to erectile dysfunction (ED). Currently, the role of mitogen-activated protein kinase (MAPK) family proteins in phenotypic transformation of corpus cavernosum smooth muscle cell (CCSMC) after CNs injury is poorly understood.

AIM

To investigate the role of p38 MAPK in hypoxia-induced phenotypic transformation of CCSMCs after CN injury.

METHODS

In total, 20 Sprague-Dawley rats (male and 8 weeks of age) were randomly divided into 2 groups, including a sham group and CNCI group. In the sham group, rats were sham-operated by identifying 2 CNs without causing direct damage to the CNs. In the CNCI group, rats were subjected to bilateral CN crush injury. CCSMCs were isolated from the normal corpus cavernosum tissues of the Sprague-Dawley rat and then cultured in 21% or 1% O₂ concentration context for 48 hours.

MAIN OUTCOME MEASURES

Intracavernous pressure/mean arterial pressure were analyzed to measure erectile response. The impact of hypoxia on penile pathology, as well as the expression of extracellular signal-regulated kinases, the c-Jun NH2-terminal kinase, and p38 MAPK, were analyzed.

RESULTS

Compared with the sham group, the intracavernous pressure/mean arterial pressure rate and α-smooth muscle actin expression of CNCI group were decreased significantly (P = .0001; P = .016, respectively), but vimentin expression was significantly increased (P = .023). Phosphorylated p38 level in CNCI group was decreased significantly (P = .017; sham: 0.17 ± 0.005; CNCI: 0.14 ± 0.02). The CCSMCs in the normoxia group were long fusiform, whereas the morphology of CCSMCs in the hypoxia group became hypertrophic. After hypoxia for 48 hours, the expression of α-smooth muscle actin and phosphorylated p38 MAPK was decreased significantly (P = .01; P = .024, normoxia: 0.66 ± 0.18, hypoxia: 0.26 ± 0.08, respectively), and the expression of hypoxia-inducible factor-1α and collagen I was increased significantly in hypoxia group (P = .04; P = .012, respectively).

CONCLUSIONS

Hypoxia induced the phenotypic transformation of CCSMCs after CNCI might be associated with the downregulation of phosphorylated p38 MAPK. Chen S, Huang X, Kong X, et al. Hypoxia-Induced Phenotypic Transformation of Corpus Cavernosum Smooth Muscle Cells After Cavernous Nerve Crush Injury by Down-Regulating p38 Mitogen-Activated Protein Kinase Expression. Sex Med 2019;7:433-440.

In vivo tracking on longer retention of transplanted myocardin gene-modified adipose-derived stem cells to improve erectile dysfunction in diabetic rats

BACKGROUND

Stem cell therapy has revealed a promising future for treating erectile dysfunction (ED), but the fate and curative mechanism of intracavernosal transplanted stem cells are under further exploration. This study aimed to demonstrate the effects of myocardin gene modification on improving erectile function and prolonging the retention of implanted adipose-derived stem cells (ASCs) using in vivo small animal imaging.

METHODS

ASCs were isolated, cultured, and identified by flow cytometry and osteogenic and adipogenic induction. The effects of gene modification on cell proliferation, apoptosis, and contraction were determined by CCK-8, EdU, flow cytometry, and collagen gel lattice contraction assays as well as confocal microscopy. A total of 20 normal and 60 diabetes mellitus ED to (DMED) Sprague-Dawley rats were recruited to the 7 day and 21 day groups. Each group contained subgroups of 10 rats each: the negative control (NC), DMED + ASCs plus Ad-Luc-Myocardin, DMED + ASCs plus Ad-Luc, and DMED + phosphate buffer solution (PBS) groups. Erectile function was evaluated with the intracavernosal pressure/mean arterial pressure (△ICP/MAP) ratio. In vivo small animal imaging and an EdU cell tracking strategy were introduced to detect the transplanted ASCs, and IHC and WB were performed to assess smooth muscle cell protein levels.

RESULTS

The ASCs expressed high CD29 and CD90 and scant CD45, while the multi-induction potential was verified by oil red O and alizarin red staining. Gene transfection of myocardin had no significant influence on ASC apoptosis but inhibited cell proliferation and promoted cell contraction. Myocardin combined with ASCs enhanced the therapeutic potential of ASCs for improving the △ICP/MAP ratio as well as α-SMA and calponin expression. In vivo imaging confirmed that ASCs resided within the cavernous body in 21 days, while only a few red EdU dots were detected.

CONCLUSIONS

Myocardin induced ASC differentiation towards smooth muscle-like cells and enhanced the therapeutic potential of ASCs for ameliorating ED in STZ-induced diabetic rats. Notably, in vivo small animal tracking was an effective strategy for monitoring the implanted stem cells, and this strategy might have advantages over traditional EdU assays.

Identification and Functional Verification of MicroRNAs in the Obese Rat With Erectile Dysfunction

INTRODUCTION

Obesity is a potential risk factor for erectile dysfunction (ED). MicroRNAs (miRNAs) regulate the expression of genes involved in various pathophysiologic processes.

AIM

To identify the miRNA profile in the corpus cavernosum (CC) of obese rats with ED and elucidate the potential function of miRNA in the pathogenesis of ED.

METHODS

Obesity was induced in rats by a high-fat diet. After the erectile function test, experimental animals were divided into two groups: obese rats with ED and obese rats with normal erectile function. The CCs from these rats were collected for miRNA microarray analysis. The results were verified by real-time polymerase chain reaction analysis. Subsequently, the targets of differentially expressed miRNAs were predicted. Bioinformatics analysis was applied to predict the functions of differentially expressed miRNAs in ED. Apomorphine-induced penile erection and intracavernous pressure measurements were used to evaluate the effects of miRNA on the erectile function of rats.

MAIN OUTCOME MEASURES

MiRNA expression in the CC of obese rats with ED and those with normal erectile function was detected by miRNA microarray analysis. Candidate miRNAs were validated by real-time polymerase chain reaction. Bioinformatics analysis was used to predict the functions of miRNAs. Apomorphine-induced penile erection and intracavernous pressure measurements were used to reflect the erectile function of rats.

RESULTS

Sixty-eight miRNAs were differentially expressed in the CC of obese rats with ED (≥1.5-fold change). The real-time polymerase chain reaction results were consistent with the miRNA microarray analysis results. Specifically, miR-328a was significantly upregulated in rats with ED compared with control rats and was chosen for functional evaluation in the pathogenesis of ED. Overexpression of miR-328a noticeably decreased the erectile response to apomorphine and the expression of heme oxygenase-1.

CONCLUSION

MiRNAs are involved in the pathogenesis of obesity-related ED. MiR-328a might facilitate the induction of ED. Bai Y, Zhang L, Jiang Y, et al. Identification and Functional Verification of MicroRNAs in the Obese Rat With Erectile Dysfunction. Sex Med 2017;5:e261-e271.

The effects of miRNA-145 on the phenotypic modulation of rat corpus cavernosum smooth muscle cells

To investigate the effect of miR-145 on the phenotypic modulation in rat corpus cavernosum smooth muscle cells. Corpus cavernosum smooth muscle cells were treated with either miR-145 mimics or miR-145 negative control. Cell proliferation were analyzed by the MTS assay and colony formation assay. Wound healing assay were performed to detect the effect of miR-145 on cell migration. The mRNA and protein levels of phenotype marker proteins were assessed by quantitative real-time polymerase chain reaction and western blotting. The intracavernosal pressure and mean arterial pressure were measured to assess erectile function at one month after the injection of platelet-derived growth factor-BB and miR-145. Our results showed that miR-145 inhibited the proliferation and migration of cavernosal smooth muscle cells. Smooth muscle cell phenotypic markers were also affected by overexpression of miR-145, as indicated by the increase in α-smooth muscle actin, calponin and smooth muscle myosin heavy chain expression. Moreover, significantly attenuated erectile function was observed in the platelet-derived growth factor-BB group as compared with the platelet-derived growth factor-BB+miR-145 group. These findings indicated that miR-145 regulate phenotypic modulation of corpus cavernosum smooth muscle cells.

Effect of Testosterone on the Phenotypic Modulation of Corpus Cavernosum Smooth Muscle Cells in a Castrated Rat Model

OBJECTIVE

To investigate the effect of testosterone (T) on the phenotypic modulation of corpus cavernosum smooth muscle (CCSM) cells in a castrated rat model.

MATERIALS AND METHODS

Thirty male Sprague-Dawley rats were randomly divided into 3 groups: control, castration, and castration with T supplementation (castration + T). Erectile function, histologic change, and biochemical markers were assessed for phenotypic modulation of CCSM cells in corporal tissue. Moreover, the primary rat CCSM cells were isolated and examined by Western blot analysis.

RESULTS

Our data showed that serum T level, mean weight of the body, erectile function, and smooth muscle-to-collagen ratio were significantly decreased in the castration group compared with those in the control and castration + T groups. The expressions of CCSM cells' phenotypic markers, such as α-smooth muscle actin, calponin, and smooth muscle myosin heavy chain 11, were markedly lower, whereas osteopontin protein expression was significantly higher in castrated rats than in control and castrated + T rats. In addition, the immunofluorescence staining of α-smooth muscle actin and calponin markedly decreased in the primary CCSM cells of the castrated rats compared with the intensity of the control and the castration + T rats.

CONCLUSION

CCSM cells undergo phenotype modulation in castrated rats, whereas T reversed the alterations. T may play a key role in the phenotype modulation of CCSM cells.

Myocardin in biology and disease

Myocardin (MYOCD) is a potent transcriptional coactivator that functions primarily in cardiac muscle and smooth muscle through direct contacts with serum response factor (SRF) over cis elements known as CArG boxes found near a number of genes encoding for contractile, ion channel, cytoskeletal, and calcium handling proteins. Since its discovery more than 10 years ago, new insights have been obtained regarding the diverse isoforms of MYOCD expressed in cells as well as the regulation of MYOCD expression and activity through transcriptional, post-transcriptional, and post-translational processes. Curiously, there are a number of functions associated with MYOCD that appear to be independent of contractile gene expression and the CArG-SRF nucleoprotein complex. Further, perturbations in MYOCD gene expression are associated with an increasing number of diseases including heart failure, cancer, acute vessel disease, and diabetes. This review summarizes the various biological and pathological processes associated with MYOCD and offers perspectives to several challenges and future directions for further study of this formidable transcriptional coactivator.