Carol Podlasek - US grants

DESCRIPTION (provided by applicant): The proposed research will examine the role of Sonic hedgehog (Shh) in penile development and the dysregulation of this pathway in diabetes induced erectile dysfunction. Shh is a secreted glycopeptide that is critically relevant in mesenchymal-epithelial interaction in developing tissues. We will show preliminary evidence that Shh signaling in the corpora is neurally regulated during penile development and in the adult, and propose to determine the impact of diabetic neuropathy on the expression and activity of Shh in corporal bodies. Diabetes mellitus is a common risk factor for erectile dysfunction, which is a devastating pathologic development that effects 10-30 million American men and costs in excess of $150 million for inpatient urologic care alone (1985 dollars). Although angiopathy and neuropathy are frequent complications in the natural history of DM, the precise cause of diabetic impotence remains unknown. We will examine the hypothesis that neural Shh signaling is elemental in establishing and maintaining normal penile morphology and that erectile dysfunction associated with diabetic neuropathy results from disruption of the homeostatic functions of the Shh pathway. The power of this proposal is its potential to provide novel and critically important insight into the mechanism of diabetes induced erectile function. This may provide the basis for new treatments to prevent or treat this complication and may provide collateral insights into other neurovascular complications of diabetes. The proposed experiments are ideally suited to satisfy the goals of this RFA since novel and innovative technology is utilized to advance our current understanding of one aspect of urogenital development, specifically how neural Shh signaling during postnatal morphogenesis of the penis establishes corporal cavernosal integrity required for erection. Re-establishment of this signaling pathway offers great promise for erectile dysfirnction treatment. Knowledge gained in these studies may be applied to investigate the role of neural input in establishing tissue identity and examining the function of neuropathy in disease.

[unreadable] DESCRIPTION (provided by applicant): The proposed research will examine the significance of Sonic hedgehog (Shh) signaling during postnatal development of the penis and will examine the potential regulation of Shh by testosterone. Shh is a secreted glycopeptide that is critically important to mesenchymal-epithelial interactions between tissue layers during embryogenesis. A significant function for Shh in postnatal development has only recently been identified in an organ that undergoes considerable postnatal morphogenesis, the prostate (Podlasek et al., 1999a). Thus Shh function is not restricted to the embryonic period and in organs that undergo extensive postnatal differentiation, Shh activity may be substantial. Like the prostate, development in the penis is primarily a postnatal event, with extensive development taking place after birth. We will present preliminary evidence in the adult that establishes Shh to be absolutely essential for maintaining penile homeostasis. This is significant since diabetic rats exhibit profoundly altered Shh signaling. This same rat model (BB/WOR) has a high incidence of erectile dysfunction (McVary et al., 1997). Thus there is evidence to suggest a potential link between disrupted Shh signaling and the physiological abnormality of erectile dysfunction. Diabetic impotence is a devastating pathologic development that affects 10-30 million American men, and costs in excess of $150 million for inpatient urologic care alone (1985 dollars). As individuals live longer there is a greater concern for quality of life and treatment options for individuals with erectile dysfunction are only partially effective (Vale et al., 2000). A better understanding of how penile morphology is established and maintained in the juvenile would significantly enhance the potential for improved treatment. The proposed experiments are ideally suited to satisfy the goals of this RFA since innovative technology is used to identify novel signaling molecules involved in urologic tissue development and altered regulation of this molecule is prominent in urologic complications of diabetes. The power of this proposal is its potential to provide novel and critically important insight into the mechanism of diabetes induced erectile dysfunction.

DESCRIPTION (provided by applicant): Erectile dysfunction (ED) is a serious medical condition that affects 52% of men between the ages of 40 and 70 and costs in excess of $150 million for inpatient care alone (1985 dollars). Diabetes is a contributing factor in 50% of individuals with ED. Current treatment options for ED are only partially effective (Vale, 2000). Therefore a need exists to develop new therapeutic approaches to treat ED. The process of erection involves critical integration of vascular, neural, hormonal and morphologic* influences. As ED develops the balance between these processes becomes skewed. In both diabetic and cavernous nerve injury induced ED models, profound alterations in smooth muscle and endothelial function and abundance commonly accompany the observed impotence. Current treatments for ED aim to increase the available NO and thus smooth muscle relaxation. However as the smooth muscle morphology of the corpora cavernosa becomes increasingly abnormal, these traditional treatment strategies become less effective and eventually fail. In this application we propose a novel approach, in which we aim to elucidate the underlying mechanisms that cause corpora cavernosa smooth muscle abnormalities and thus ED to occur. Sonic hedgehog (Shh) is a crucial regulator of penile morphology. Shh inhibition alters per morphology such that smooth muscle and endothelium significantly decrease, the sinusoid architecture collapses and ED occurs. The morphological and physiological changes of the Shh inhibited penis parallel observations of smooth muscle loss and decreased Shh protein in diabetic and CN injured rat models of ED and in human diabetic penes, thus implicating a physiological link between decreased Shh protein and ED. Shh protein treatment can induce VEGF and NOS, thus suggesting a potentialmechanism through which decreased Shh protein can cause ED. We propose the hypothesis that Shh inhibition represents an underlying cause of ED rather than a symptom of smooth muscle loss. Increasing our understanding of Shh signaling in the penis will provide valuable insight that may lead to new treatment strategies for impotence.

Erectile dysfunction (ED) affects 52% of men between the ages of 40 and 70. 30-87% of prostate cancer patients treated by prostatectomy experience ED and PDE5 inhibitors are ineffective in 29-86% of prostatectomy patients who experience ED, depending on their nerve injury status. The reduced efficacy of treatments in this population makes novel therapeutic approaches to treat ED essential. Significantly increased apoptosis of penile smooth muscle is common in both animal models and human patients with ED. We propose that abundant apoptosis observed in penile smooth muscle when the CN is cut is a major contributing factor to ED development. If apoptosis could be prevented following prostatectomy while the CN regenerates, then resumption of normal erectile function would occur more quickly, and irreversible morphology changes in the penis that cause ED would be prevented. Understanding the mechanisms that regulate smooth muscle apoptosis in the penis is critical for development of new therapeutic approaches for ED treatment and prevention. Sonic hedgehog (SHH) is an essential regulator of penile smooth muscle. When SHH is inhibited in the penis, there is a 12-fold increase in smooth muscle apoptosis that results in ED. SHH protein treatment is able to suppress CN injury induced apoptosis, indicating that SHH has significant potential to be developed as a treatment to prevent ED by suppressing smooth muscle apoptosis. The Affi-Gel bead technology used in these studies is not applicable to humans, so we propose to develop nanoparticle delivery of SHH protein to the penis and hypothesize that SHH delivery via nanoparticles will be effective in suppressing apoptosis induction caused by CN injury. This novel technology has substantial potential to be developed into a therapy to prevent apoptosis in patients at the time of prostatectomy, so has significant clinical relevance. The mechanism of how SHH itself is regulated in the penis and how decreased SHH protein induces apoptosis is poorly understood. It is likely that neural input/integrity regulates SHH in the penis since SHH protein is significantly decreased in two models of neuropathy, the CN injured rat and in the BB/WOR diabetic rat. Since SHH protein is decreased in diabetic human penes in parallel with observations in the rat, this lends clinical significance to how decreased SHH protein can induce apoptosis in the penis. Our results suggest that HIP out competes PTCH1 for SHH binding after CN injury. Thus we hypothesize that loss of neural input decreases SHH protein in the penis and induces apoptosis in penile smooth muscle through a PTCH1 and HIP dependent mechanism.