Peptide amphiphile nanofiber hydrogel delivery of Sonic hedgehog protein to the penis and cavernous nerve suppresses intrinsic and extrinsic apoptotic signaling mechanisms, which are an underlying cause of erectile dysfunction

Sonic hedgehog suppresses penile remodeling after cavernous nerve injury and sustains long-term normal penis morphology

BACKGROUND

Cavernous nerve (CN) injury, which occurs in prostatectomy and diabetic cases, initiates penile remodeling, including smooth muscle apoptosis and increased collagen in the corpora cavernosa, which are underlying causes of erectile dysfunction. Sonic hedgehog (SHH) is a critical regulator of penile smooth muscle, and SHH treatment suppresses corpora cavernosa remodeling that occurs with CN injury.

AIM

We examine if SHH treatment by peptide amphiphile (PA) in the first week after CN injury is sufficient to prevent long-term penis remodeling and if apoptosis inhibitors also suppress penile remodeling.

METHODS

Bilateral CN crush was performed on adult Sprague-Dawley rats (P115-120) that underwent 1 of 3 treatments with novel extended-release nanofiber PA hydrogels for delivery: SHH protein (n = 10), mouse serum albumin protein (control, n = 7), or caspase 3 inhibitor (AC-DEVD-CHO, n = 10). Rats were sacrificed after 18 to 24 days. Additional rats underwent CN injury (n = 6) or CN injury and SHH PA treatment for 2 and 4 days (n = 8) and included sham controls (n = 3) and nonsurgery controls (n = 3).

OUTCOMES

Trichrome stain, hydroxyproline assay, and Western analysis for α-actin (smooth muscle) and GAPDH were performed to examine smooth muscle retention and collagen abundance.

RESULTS

Smooth muscle decreased with CN injury. Corpora cavernosa showed increased smooth muscle at 2, 4, and 24 days after CN injury with SHH PA treatment in comparison with mouse serum albumin treatment among CN-injured controls. Caspase 3-inhibited penis demonstrated little smooth muscle preservation. Collagen was decreased 23% with SHH PA treatment (P < .001) at 18 to 24 days after CN injury. Collagen was unchanged with caspase 3 inhibitor treatment (P > .99).

CLINICAL TRANSLATION

It is important to know that treatments given at the time of CN injury have a sustained effect on preserving penile architecture and thus erectile function, making them valuable for clinical translation.

STRENGTHS AND LIMITATIONS

SHH PA treatment preserves penile smooth muscle after CN injury. Time points past 24 days were not examined, although penile remodeling takes place acutely after CN injury. Measurement of erectile function was not examined.

CONCLUSIONS

SHH treatment by PA in the first week after CN injury is sufficient to suppress penile remodeling and to preserve penile smooth muscle over time, which is critical to prevent development of erectile dysfunction. There is a difference in the corpora cavernosa smooth muscle from proximal to distal in the penis of the Sprague-Dawley rat model. It is critical when examining therapy efficacy to ensure that comparable regions of the penis are analyzed.

STATEMENT OF SIGNIFICANCE

In this study, we examine if suppression of apoptosis in penile smooth muscle in the first week after cavernous nerve injury is sufficient to preserve smooth muscle long-term.

Knockdown of programmed cell death factor 4 restores erectile function by attenuating apoptosis in rats with bilateral cavernous nerve crush injury

BACKGROUND

Apoptosis is an important pathologic mechanism of erectile dysfunction after radical prostatectomy. Studies have shown that programmed cell death factor 4 is connected to the modulation of apoptosis in many cells. However, the programmed cell death factor 4 function in the cavernous nerve injury erectile dysfunction is unclear.

OBJECTIVE

This investigation aimed to explore the programmed cell death factor 4 function in erectile dysfunction in rats with bilateral cavernous nerve crush.

MATERIALS AND METHODS

The experiment used 30 male Sprague Dawley rats (18 months old) that were screened for normal erectile function by the apomorphine test. Ten rats were randomized into Sham and bilateral cavernous nerve crush groups to detect changes in programmed cell death factor 4 expression. The remaining 20 rats were distributed at random to four groups: the Sham group treated by sham surgery, the phosphate-buffered saline group, the lentivirus containing negative control short hairpin RNA group, and the lentivirus containing short hairpin RNA targeting programmed cell death factor 4 group underwent bilateral cavernous nerve crush and were afterward administered intracavernous injections of phosphate-buffered saline, lentivirus containing negative control short hairpin RNA, or lentivirus containing short hairpin RNA targeting programmed cell death factor 4. Electrical stimulation of the cavernous nerve was conducted 2 weeks later for penile erectile function assessment. The cavernous tissue was collected for histological analysis and western blotting.

RESULTS

The apoptosis level in rat corpus cavernosum was elevated, and programmed cell death factor 4 expression was increased after bilateral cavernous nerve crush. Knockdown of programmed cell death factor 4 significantly improved erectile function in bilateral cavernous nerve crush rats. Furthermore, lentivirus containing short hairpin RNA targeting programmed cell death factor 4 treatment raised smooth muscle content and attenuated cavernous fibrosis and apoptotic levels. Additionally, programmed cell death factor 4 was found to mediate the PI3K/AKT pathway.

DISCUSSION AND CONCLUSION

Elevated programmed cell death factor 4 expression may be an important pathogenetic mechanism for erectile dysfunction after bilateral cavernous nerve crush, and the knockdown of programmed cell death factor 4 enhanced erectile function in 18-month-old rats after cavernous nerve damage. The potential mechanism may be the stimulation of the PI3K/AKT pathway to attenuate the cavernous apoptosis level.

Microscopically segregated ligand distribution in co-assembled peptide-amphiphile nanofibers

Peptide amphiphiles (PAs) self-assemble into cylindrical nanofibers with applications in protein purification, tissue engineering, and regenerative medicine. For these applications, functionalized PAs are often co-assembled with oppositely charged filler PAs. Finding the conditions at which these fibers are homogeneously mixed or segregated is crucial for the required application. We co-assemble negative C12VVEE fillers and positive C12VVKK-OEG4-Z33 ligands, which are important for antibody purifications. Our results show that the ligands tend to cluster and locally segregate in the fiber surfaces. The Z33s are overall neutral and form large aggregates in bulk solution due to short range attractions. However, full segregation of the C12VVKK-OEG4-Z33 is not observed in the cylindrical surface due to the electrostatic penalty of forming large domains of similarly charged molecules. This is commensurate with previous theoretical predictions, showing that the competition between short-range attractive interactions and long-range electrostatic repulsions leads to pattern formation in cylindrical surfaces. This work offers valuable insight into the design of functionalized nanofibers for various biomedical and chemical applications.

Recent advances in peptide-based bioactive hydrogels for nerve repair and regeneration: from material design to fabrication, functional tailoring and applications

The injury of both central and peripheral nervous systems can result in neurological disorders and severe nervous diseases, which has been one of the challenges in the medical field. The use of peptide-based hydrogels for nerve repair and regeneration (NRR) provides a promising way for treating these problems, but the effects of the functions of peptide hydrogels on the NRR efficiency have been not understood clearly. In this review, we present recent advances in the material design, matrix fabrication, functional tailoring, and NRR applications of three types of peptide-based hydrogels, including pure peptide hydrogels, other component-functionalized peptide hydrogels, and peptide-modified polymer hydrogels. The case studies on the utilization of various peptide-based hydrogels for NRR are introduced and analyzed, in which the effects and mechanisms of the functions of hydrogels on NRR are illustrated specifically. In addition, the fabrication of medical NRR scaffolds and devices for pre-clinical application is demonstrated. Finally, we provide potential directions on the development of this promising topic. This comprehensive review could be valuable for readers to know the design and synthesis strategies of bioactive peptide hydrogels, as well as their functional tailoring, in order to promote their practical applications in tissue engineering, biomedical engineering, and materials science.

Nanotechnology in sexual medicine

Statement of Significance: There is significant potential for improvement in erectile function and prevention of erectile dysfunction if these diverse and novel nanotherapies can be translated to the clinic.

A Novel Multi-compartment Rotating Bioreactor for Improving ADSC-Spheroid Formation and its Application in Neurogenic Erectile Dysfunction

OBJECTIVE

The aim of this study was to construct a multicompartment synchronous rotating bioreactor (MCSRB) for batch-production of homogenized adipose-derived stem cell (ADSC) microspheres and treat neurogenic erectile dysfunction (ED).

METHODS

Firstly, an MCSRB was constructed using a centrifugal device and hinged trays. Secondly, influence factors (density, rotational speed) on the formation of ADSC-spheroids were explored. Finally, a neurogenic ED model was established to verify the effectiveness and safety of ADSC-spheroids for ED treatment.

RESULTS

An MCSRB promoted ADSCs to gather microspheres, most of which were 90-130 μm in diameter. Supernatant from three-dimensional culture led to a significant increase in cytokine expression in ADSCs and migration rate in human umbilical vein endothelial cells (HUVECs) compared to control groups. The erectile function and pathological changes of the penis were improved in the ADSC-spheroids treatment group compared to the traditional ADSCs treatment group (p < 0.01).

CONCLUSION

Efficient, batch, controlled and homogenized production of ADSC stem cell microspheres, and effective improvement of erectile dysfunction in neurogenic rats can be achieved using the MCSRB device.

Aggregation-Induced Asymmetric Charge States of Amino Acids in Supramolecular Nanofibers

Electrostatic interactions contribute critically to the kinetic pathways and thermodynamic outcomes of peptide self-assembly involving one or more than one charged amino acids. While it is well understood in protein folding that those amino acids with acidic/basic side chains could shift their pKas when placed in a hydrophobic microenvironment, to what extent aggregation of monomeric peptide units from the bulk solution could alter their charged status and how this change in pKa values would reciprocally impact their assembly outcomes. Here, we design and analyze two solution systems containing peptide amphiphiles with hydrocarbon chains of different lengths to determine the factor of deprotonation on assembly. Our results suggest that models of supramolecular nanofibers with uniformly distributed, fully charged amino acids are oversimplified. We demonstrate, with molecular dynamics simulations, and validate with experimental results that asymmetric, different protonation states of the peptides lead to distinct nanostructures after self-assembly. The results give estimates on the electrostatic interactions in peptide amphiphiles required for their self-assembly and shed light on modeling molecular assembly systems containing charged amino acids.

Molecular pathogenesis and treatment of cavernous nerve injury-induced erectile dysfunction: A narrative review

Introduction: Erectile dysfunction (ED) is a common complication after radical prostatectomy (RP), and it seriously affects the quality of life in patients and their partners. The primary trigger of postoperative ED is surgical injury to the cavernous nerves that control penile erection and run along the anterolateral aspect of the prostate. Despite the introduction and ongoing innovation of nerve-sparing techniques, a significant number of patients still suffer from moderate cavernous nerve injury (CNI), which is thought to be transient and reversible. Therefore, early postoperative penile rehabilitation therapy may salvage patients’ erectile function by promoting cavernous nerve regeneration and preventing penile structural alterations.

Aims: To present a comprehensive overview of the current molecular pathogenesis of CNI-induced ED, as well as novel therapeutic strategies and their potential mechanisms.

Methods: A literature search was performed using PubMed. Search terms included erectile dysfunction, cavernous nerve injury, pathogenesis, pathway, and treatment.

Results: The NOS/NO pathway, oxidative stress-related pathway, RhoA/ROCK pathway, transforming growth factor-β (TGF-β), sonic hedgehog (Shh), and hydrogen sulfide (H2S) are involved in the molecular pathogenesis of CNI-induced ED. Multiple neurotrophins, including brain-derived nerve growth factor (BDNF), glial cell line-derived neurotrophic factor (GDNF), and neurturin (NTN), were found to promote cavernous nerve regeneration. Emerging therapeutic approaches can be roughly summarized into four categories, namely small molecule and drug, stem cell-based therapy (SCT), micro-energy therapy and platelet-rich plasma (PRP) therapy.

Conclusion: These pathways collectively lead to the irreversible damage to the penile structure after CNI. The combined early rehabilitation strategies of promoting upstream nerve regeneration and recovering abnormal molecular signals of downstream penis are presumed to save patients’ erectile function after RP. In future studies, the cross-talk between these molecular pathways needs to be further clarified, and the questions of how denervation injury induces the molecular alterations in the penis also need to be addressed.

Repair of Peripheral Nerve Injury Using Hydrogels Based on Self-Assembled Peptides

Peripheral nerve injury often occurs in young adults and is characterized by complex regeneration mechanisms, poor prognosis, and slow recovery, which not only creates psychological obstacles for the patients but also causes a significant burden on society, making it a fundamental problem in clinical medicine. Various steps are needed to promote regeneration of the peripheral nerve. As a bioremediation material, self-assembled peptide (SAP) hydrogels have attracted international attention. They can not only be designed with different characteristics but also be applied in the repair of peripheral nerve injury by promoting cell proliferation or drug-loaded sustained release. SAP hydrogels are widely used in tissue engineering and have become the focus of research. They have extensive application prospects and are of great potential biological value. In this paper, the application of SAP hydrogel in peripheral nerve injury repair is reviewed, and the latest progress in peptide composites and fabrication techniques are discussed.