GDNF-Transduced Schwann Cell Grafts Enhance Regeneration of Erectile Nerves

Nerve graft for erectile dysfunction after radical prostatectomy: animal study and clinical data-a narrative review

Introduced in the late 1990s, nerve grafting, particularly with sural and genitofemoral nerves, aims to enhance erectile function recovery when neurovascular bundles cannot be preserved following radical prostatectomy. Over the past three decades, researchers have conducted numerous animal and clinical studies to explore the application and clinical effectiveness of this method, with the hope of benefiting patients suffering from erectile dysfunction after radical prostatectomy. Animal studies have demonstrated the potential of various grafting materials, including autologous nerve and vein grafts, and bioengineered grafts, in promoting nerve regeneration and erectile function recovery. Clinical studies, especially those focusing on sural and genitofemoral nerve grafts, have shown mixed results with varied success rates due to methodological weaknesses and small sample sizes. This review thoroughly incorporates current data, explores emerging nerve grafting methods, demonstrates the complexity of nerve grafting outcomes, and emphasizes the necessity for continuous research, including multi-institutional randomized controlled trials, to establish standardized protocols and optimize patient selection for nerve grafting in the management of erectile dysfunction after radical prostatectomy.

Advances in Genetic Reprogramming: Prospects from Developmental Biology to Regenerative Medicine

The foundations of cell reprogramming were laid by Yamanaka and co-workers, who showed that somatic cells can be reprogrammed into pluripotent cells (induced pluripotency). Since this discovery, the field of regenerative medicine has seen advancements. For example, because they can differentiate into multiple cell types, pluripotent stem cells are considered vital components in regenerative medicine aimed at the functional restoration of damaged tissue. Despite years of research, both replacement and restoration of failed organs/ tissues have remained elusive scientific feats. However, with the inception of cell engineering and nuclear reprogramming, useful solutions have been identified to counter the need for compatible and sustainable organs. By combining the science underlying genetic engineering and nuclear reprogramming with regenerative medicine, scientists have engineered cells to make gene and stem cell therapies applicable and effective. These approaches have enabled the targeting of various pathways to reprogramme cells, i.e., make them behave in beneficial ways in a patient-specific manner. Technological advancements have clearly supported the concept and realization of regenerative medicine. Genetic engineering is used for tissue engineering and nuclear reprogramming and has led to advances in regenerative medicine. Targeted therapies and replacement of traumatized , damaged, or aged organs can be realized through genetic engineering. Furthermore, the success of these therapies has been validated through thousands of clinical trials. Scientists are currently evaluating induced tissue-specific stem cells (iTSCs), which may lead to tumour-free applications of pluripotency induction. In this review, we present state-of-the-art genetic engineering that has been used in regenerative medicine. We also focus on ways that genetic engineering and nuclear reprogramming have transformed regenerative medicine and have become unique therapeutic niches.

Comparison of the therapeutic effects of human umbilical cord blood-derived mesenchymal stem cells and adipose-derived stem cells on erectile dysfunction in a rat model of bilateral cavernous nerve injury

Background: Cavernous nerve injury (CNI) is the leading cause of erectile dysfunction (ED) after radical prostatectomy and pelvic fracture. Transplantation of human adipose-derived stem cells (ASCs) has been widely used to restore erectile function in CNI-ED rats and patients. Umbilical cord blood-derived MSCs (CBMSCs) are similarly low immunogenic but much primitive compared to ASCs and more promising in large-scale commercial applications due to the extensive establishment of cord blood banks. However, whether CBMSCs and ASCs have differential therapeutic efficacy on CNI-ED and the underlying mechanisms are still not clear.

Materials and methods: A bilateral cavernous nerve injury (BCNI) rat model was established by crushing the bilateral cavernous nerves. After crushing, ASCs and CBMSCs were intracavernously injected immediately. Erectile function, Masson staining, and immunofluorescence analyses of penile tissues were assessed at 4 and 12 weeks. PKH-26-labeled ASCs or CBMSCs were intracavernously injected to determine the presence and differentiation of ASCs or CBMSCs in the penis 3 days after injection. In vitro experiments including intracellular ROS detection, mitochondrial membrane potential assay, EdU cell proliferation staining, cell apoptosis assay, and protein chip assay were conducted to explore the underlying mechanism of CBMSC treatment compared with ASC treatment.

Results: CBMSC injection significantly restored erectile function, rescued the loss of cavernous corporal smooth muscles, and increased the ratio of smooth muscle to collagen. PKH-26-labeled CBMSCs or ASCs did not colocalize with endothelial cells or smooth muscle cells in the corpus cavernosum. Moreover, the conditioned medium (CM) of CBMSCs could significantly inhibit the oxidative stress and elevate the mitochondria membrane potential and proliferation of Schwann cells. Better therapeutic effects were observed in the CBMSC group than the ASC group both in vivo and in vitro. In addition, the content of neurotrophic factors and matrix metalloproteinases in CBMSC-CM, especially NT4, VEGF, MMP1, and MMP3 was significantly higher than that of ASC-CM.

Conclusion: Intracavernous injection of CBMSCs exhibited a better erectile function restoration than that of ASCs in CNI-ED rats owing to richer secretory factors, which can promote nerve regeneration and reduce extracellular matrix deposition. CBMSC transplantation would be a promising therapeutic strategy for CNI-ED regeneration in the future.

Icariside II facilitates the differentiation of ADSCs to schwann cells and restores erectile dysfunction through regulation of miR-33/GDNF axis

BACKGROUND

Adipose derived stem cells (ADSCs) have the property to differentiate into neuron-like cells, which may provide a novel insight for the restoration of erectile dysfunction (ED) mainly induced by cavernous nerve injury. Icariside II (ICA II) has been reported to play a key role in the regulation of erectile function via stimulating the differentiation of ADSCs to Schwann Cells (SCs). However, the function and molecular mechanisms of ICA II in ED remains to be further clarified.

METHODS

The expression of S100, P75, GDNF and miR-33 was detected by qRT-PCR. And the relative proteins expression was determined by western blot. Cell viability was measured by Cell Counting Kit-8 (CCK-8) assay. Bioinformatics, luciferase reporter and RNA immunoprecipitation (RIP) assays were performed to verify the interaction between miR-33 and GDNF. Intracavernosal pressure (ICP), the ratio of ICP and mean arterial pressure (MAP), as well as nNOS expression were examined to evaluate the erectile function of SD rats with bilateral cavernous nerve injury (BCNI).

RESULTS

ICA II and miR-33 respectively promoted and inhibited the differentiation of ADSCs to SCs. MiR-33 could negatively regulate P75 and GDNF expression. ICA II exerted promotion effects on differentiation of ADSCs to SCs via regulating miR-33. GDNF was identified to be a target of miR-33. MiR-33 overexpression abrogated the stimulatory effect of ICA II on ADSCs' differentiation, which was blocked by GDNF overexpression. treated with ICA II recovered the erectile function of BCNI model rats through regulation of miR-33.

CONCLUSION

ICA II contributed to the differentiation of ADSCs to SCs viamiR-33/GDNF axis, contributing to the recovery of erectile function in BCNI rats.

Biodelivery of nerve growth factor and gold nanoparticles encapsulated in chitosan nanoparticles for schwann-like cells differentiation of human adipose-derived stem cells

The constant release of neurotrophic factors through a nanomaterial-based delivery system can be an important strategy in medical and pharmaceutical fields for nerve tissue engineering. The present study was aimed at encapsulating NGF and AuNPs in chitosan nanoparticles (NGF-CNPs and AuNPs-CSNPs) and its evaluation on the differentiation potential of human adipose-derived stem cells (h-ADSCs) to Schwann-like cells. The NGF-CNPs were prepared by ionotropic gelation method with tripolyphosphate (TPP) as a crosslinker. After synthesis and characterization of nanoparticles, NGF encapsulation efficiency and release profile were observed by Bradford assay. Next, the effects of NGF-CSNPs and AuNPs-CSNPs on h-ADSCs survival were assessed through MTT assay. Also, the efficacy of Schwann-like cells differentiation was assessed by immunocytochemistry and real-time RT-PCR for S100β and MBP markers. NGF encapsulation efficiency was found about 85% and controlled and sustained release of NGF was observed during 7 days in vitro (74.63 ± 2.07%). The findings revealed that these nanoparticles are cytocompatible. The immunocytochemical analysis indicated that NGF-CSNPs and AuNPs-CSNPs could significantly increase the differentiated rate and myelinogenic potential of Schwann-like cells (p < 0.05). Besides, the expression level of GFAP, S100β, and MBP demonstrated significant upregulation in NGF-CSNPs and AuNPs-CSNPs groups compared to the control group (p < 0.05). Hence, it can be proposed that NGF-CNPs and AuNPs-CSNPs are capable of controlled release with improving the ability of h-ADSCs differentiation to Schwann-like cells. Also, the results show the potential future application of this differentiation in nerve tissue regeneration.

Low-Intensity Extracorporeal Shock Wave Therapy Enhances Brain-Derived Neurotrophic Factor Expression through PERK/ATF4 Signaling Pathway

Low-intensity extracorporeal shock wave therapy (Li-ESWT) is used in the treatment of erectile dysfunction, but its mechanisms are not well understood. Previously, we found that Li-ESWT increased the expression of brain-derived neurotrophic factor (BDNF). Here we assessed the underlying signaling pathways in Schwann cells in vitro and in penis tissue in vivo after nerve injury. The result indicated that BDNF were significantly increased by the Li-ESWT after nerve injury, as well as the expression of BDNF in Schwann cells (SCs, RT4-D6P2T) in vitro. Li-ESWT activated the protein kinase RNA-like endoplasmic reticulum (ER) kinase (PERK) pathway by increasing the phosphorylation levels of PERK and eukaryotic initiation factor 2a (eIF2α), and enhanced activating transcription factor 4 (ATF4) in an energy-dependent manner. In addition, GSK2656157—an inhibitor of PERK—effectively inhibited the effect of Li-ESWT on the phosphorylation of PERK, eIF2α, and the expression of ATF4. Furthermore, silencing ATF4 dramatically attenuated the effect of Li-ESWT on the expression of BDNF, but had no effect on hypoxia-inducible factor (HIF)1α or glial cell-derived neurotrophic factor (GDNF) in Schwann cells. In conclusion, our findings shed new light on the underlying mechanisms by which Li-ESWT may stimulate the expression of BDNF through activation of PERK/ATF4 signaling pathway. This information may help to refine the use of Li-ESWT to further improve its clinical efficacy.

Recovery of erectile function comparing autologous nerve grafts, unseeded conduits, Schwann-cell-seeded guidance tubes and GDNF-overexpressing Schwann cell grafts

Dissection of the cavernous nerves during radical prostatectomy for prostate cancer eliminates spontaneous erections. Using the rat as an experimental model, we compared the regenerative capacity of autologous nerve grafts and Schwann-cell-seeded nerve guides. After bilateral excision of cavernous nerve segments, cavernous nerves were reconstructed using unseeded silicon tubes, nerve autografts and silicon tubes seeded with either Glial-cell-line-derived (GDNF)-overexpressing or green fluorescent protein (GFP)-expressing Schwann cells (SCs) (16 study nerves per group). Control groups underwent either a sham operation or bilateral excision of cavernous nerve segments without repair. After 12 weeks erectile function was assessed by neurostimulation and intracavernous pressure (ICP) measurement. The reconstructed nerve segments were excised and histologically analyzed. We demonstrated an intact erectile response upon neurostimulation in 25% (4/16) of autologous nerve grafts, in 50% (8/16) of unseeded tubes, in 75% (12/16) of the Schwann-cell-GFP group and in 93.75% (15/16) of the GDNF group. ICP was significantly increased when comparing the Schwann-cell-GFP group with nerve autografts, unseeded conduits and negative controls (P<0.005). In conclusion, Schwann-cell-seeded scaffolds combined with neurotrophic factors are superior to unseeded tubes and autologous nerve grafts. They present a promising therapeutic approach for the repair of erectile nerve gaps.

Gene delivery in tissue engineering and regenerative medicine

As a promising strategy to aid or replace tissue/organ transplantation, gene delivery has been used for regenerative medicine applications to create or restore normal function at the cell and tissue levels. Gene delivery has been successfully performed ex vivo and in vivo in these applications. Excellent proliferation capabilities and differentiation potentials render certain cells as excellent candidates for ex vivo gene delivery for regenerative medicine applications, which is why multipotent and pluripotent cells have been intensely studied in this vein. In this review, gene delivery is discussed in detail, along with its applications to tissue engineering and regenerative medicine. A definition of a stem cell is compared to a definition of a stem property, and both provide the foundation for an in-depth look at gene delivery investigations from a germ lineage angle.

Construction and identification of human glial cell-derived neurotrophic factor gene-modified Schwann cells from rhesus monkeys

The objective of this study was to construct stable rhesus monkey Schwann cells (SCs) modified with the human glial cell-derived neurotrophic factor (hGDNF) gene. hGDNF gene amplification was performed with pUC19-hGDNF as templates, and then the coding sequence of hGDNF was inserted into the eukaryotic expression vector pBABE-puro to obtain the recombinant vector pBABE-puro-hGDNF. The recombinant vector pBABE-puro-hGDNF was identified with restriction enzyme, and then underwent DNA sequencing. SCs from rhesus monkeys were transfected with the recombinant vector pBABE-puro-hGDNF, and then the expression levels of mRNA and protein of the hGDNF gene were determined with real-time fluorescence quantitative PCR and Western blot, respectively, in the transfected SCs. The biological activity of GDNF gene-modified SCs (GDNF-SCs) was assessed by MTT assay. The length of the hGDNF coding sequence of PCR products was 569 bp. After the recombinant eukaryotic expression vectors were digested with restriction enzyme, there was a specific segment of 596 bp. The results of DNA sequencing of the specific segment of 596 bp were the same as that of hGDNF in GenBank, suggesting that the hGDNF gene was successfully inserted into the recombinant retrovirus vectors. The expression levels of mRNA and protein were significantly higher in transfected SCs as compared to nontransfected SCs (p<0.05). MTT assay indicated that the OD value was significantly higher in GDNF-SCs group than in SCs and DMEM groups (p<0.05). hGDNF-SCs can steadily and efficiently release hGDNF. This study provides a basis for cell therapy of nerve injury.

Neural tissue engineering options for peripheral nerve regeneration

Tissue engineered nerve grafts (TENGs) have emerged as a potential alternative to autologous nerve grafts, the gold standard for peripheral nerve repair. Typically, TENGs are composed of a biomaterial-based template that incorporates biochemical cues. A number of TENGs have been used experimentally to bridge long peripheral nerve gaps in various animal models, where the desired outcome is nerve tissue regeneration and functional recovery. So far, the translation of TENGs to the clinic for use in humans has met with a certain degree of success. In order to optimize the TENG design and further approach the matching of TENGs with autologous nerve grafts, many new cues, beyond the traditional ones, will have to be integrated into TENGs. Furthermore, there is a strong requirement for monitoring the real-time dynamic information related to the construction of TENGs. The aim of this opinion paper is to specifically and critically describe the latest advances in the field of neural tissue engineering for peripheral nerve regeneration. Here we delineate new attempts in the design of template (or scaffold) materials, especially in the context of biocompatibility, the choice and handling of support cells, and growth factor release systems. We further discuss the significance of RNAi for peripheral nerve regeneration, anticipate the potential application of RNAi reagents for TENGs, and speculate on the possible contributions of additional elements, including angiogenesis, electrical stimulation, molecular inflammatory mediators, bioactive peptides, antioxidant reagents, and cultured biological constructs, to TENGs. Finally, we consider that a diverse array of physicochemical and biological cues must be orchestrated within a TENG to create a self-consistent coordinated system with a close proximity to the regenerative microenvironment of the peripheral nervous system.

Erectile function restoration after repair of resected cavernous nerves by adipose-derived stem cells combined with autologous vein graft in rats

Cavernous nerve (CN) injury is the main cause of erectile dysfunction (ED) following radical prostatectomy. The recovery of erectile function following this procedure remains challenging. Here, we investigated the ability of adipose-derived stem cells (ADSCs) combined with autologous vein graft to improve erectile function in a rat model of bilateral long CN resection. Sprague-Dawley rats (n = 36) were randomized into four groups. Group A underwent sham operation. In Groups B, C, and D, an 8-mm segment of CN was excised bilaterally. In Group B and C, a 10-mm segment of autologous saphenous vein was interposed bilaterally at the site of injury, and the two nerve stumps were inserted into the vein lumen. 50 μL ADSCs were injected into each vein in Group B, and 50 μL of phosphate-buffered saline was injected in Group C. Group D underwent no repair. Erectile function assessed after 3 months by measuring intracavernosal pressure demonstrated significant recovery in erectile function in Group B with minimal recovery in Group C or D. Immunohistochemical staining showed that the nNOS-positive area was significantly larger in Group B than in Group D. ADSCs combined with autologous vein graft treatment had beneficial effects on the smooth muscle/collagen ratio in the corpus cavernosum. This procedure, therefore, provided a means of regenerating CN tissue and restoring autonomic erectile function after long bilateral CN resection (0.8 cm) in rats.

Rat cavernous nerve reconstruction with CD133+ cells derived from human bone marrow

INTRODUCTION

Erectile dysfunction remains a major complication after surgery of pelvic organs, especially after radical prostatectomy.

AIM

The aim of this study was to assess the effect of endothelial progenitor cells on the regeneration of cavernous nerves in a rat injury model.

METHODS

A 2 mm length of the right and left cavernous nerves of 8-week-old male nude rats were excised. Alginate gel sponge sheets supplemented with 1 × 10(4) CD133+ cells derived from human bone marrow were then placed over the gaps on both sides (CD group). The same experiments were performed on sham-operated rats (SH group), rats with only the nerve excision (EX group), and rats with alginate gel sheets placed on the injured nerves (AL group).

MAIN OUTCOME MEASURES

Immunofluorescence staining and molecular evaluation were performed 4 days later. Functional and histological evaluations were performed 12 weeks later.

RESULTS

The intracavernous pressure elicited by electrical stimulation and the neuronal nitric oxide synthase-positive area in surrounding tissues of the prostate was significantly greater in the CD group. Immunofluorescence microscopy showed that CD133+ cells were assimilated as vascular endothelial cells, and the real-time polymerase chain reaction showed upregulation of nerve growth factor and vascular endothelial growth factor in the alginate gel sponge sheets of the CD group.

CONCLUSIONS

Transplantation of CD133+ cells accelerated the functional and histological recovery in this cavernous nerve injury model, and the recovery mechanism is thought to be angiogenesis and upregulation of growth factors. CD133+ cells could be an optional treatment for cavernous nerve injury after prostatectomy in clinical settings.

Treatment of erectile dysfunction: new targets and strategies from recent research

In recent years, research on penile erection has increasingly been centered on the molecular mechanisms involved. Major progress has been made in the field and at present a whole number of neurotransmitters, chemical effectors, growth factors, second-messenger molecules, ions, intercellular proteins, and hormones have been characterized as components of the complex process of erection. This knowledge has led to the discovery of several new therapeutic targets and multiple medical approaches for the treatment of erectile dysfunction (ED). This review focuses on the progress made in this field within the last few years.

Sympathetic innervation induced in engrafted engineered cardiomyocyte sheets by glial cell line derived neurotrophic factor in vivo

The aim of myocardial tissue engineering is to repair or regenerate damaged myocardium with engineered cardiac tissue. However, this strategy has been hampered by lack of functional integration of grafts with native myocardium. Autonomic innervation may be crucial for grafts to function properly with host myocardium. In this study, we explored the feasibility of in vivo induction of autonomic innervation to engineered myocardial tissue using genetic modulation by adenovirus encoding glial cell line derived neurotrophic factor (GDNF). GFP-transgene (control group) or GDNF overexpressing (GDNF group) engineered cardiomyocyte sheets were transplanted on cryoinjured hearts in rats. Nerve fibers in the grafts were examined by immunohistochemistry at 1, 2, and 4 weeks postoperatively. Growth associated protein-43 positive growing nerves and tyrosine hydroxylase positive sympathetic nerves were first detected in the grafts at 2 weeks postoperatively in control group and 1 week in GDNF group. The densities of growing nerve and sympathetic nerve in grafts were significantly increased in GDNF group. No choline acetyltransferase immunopositive parasympathetic nerves were observed in grafts. In conclusion, sympathetic innervation could be effectively induced into engrafted engineered cardiomyocyte sheets using GDNF.

Schwann cell-mediated delivery of glial cell line-derived neurotrophic factor restores erectile function after cavernous nerve injury

OBJECTIVES

To evaluate the time-course of functional recovery after cavernous nerve injury using glial cell line-derived neurotrophic factor-transduced Schwann cell-seeded silicon tubes.

METHODS

Sections of the cavernous nerves were excised bilaterally (5 mm), followed by immediate bilateral surgical repair. A total of 20 study nerves per group were reconstructed by interposition of empty silicon tubes and silicon tubes seeded with either glial cell line-derived neurotrophic factor-overexpressing or green fluorescent protein-expressing Schwann cells. Control groups were either sham-operated or received bilateral nerve transection without nerve reconstruction. Erectile function was evaluated by relaparotomy, electrical nerve stimulation and intracavernous pressure recording after 2, 4, 6, 8 and 10 weeks. The animals underwent re-exploration only once, and were killed afterwards. The nerve grafts were investigated for the maturation state of regenerating nerve fibers and the fascular composition.

RESULTS

Recovery of erectile function took at least 4 weeks in the current model. Glial cell line-derived neurotrophic factor-transduced Schwann cell grafts restored erectile function better than green fluorescent protein-transduced controls and unseeded conduits. Glial cell line-derived neurotrophic factor-transduced grafts promoted an intact erectile response (4/4) at 4, 6, 8 and 10 weeks that was overall significantly superior to negative controls (P < 0.001). Maximum intracavernous pressure on electrostimulation was significantly elevated using glial cell line-derived neurotrophic factor-transduced grafts compared with negative controls (P = 0.018) and unseeded tubes (P = 0.034). Return of function was associated with the electron microscopic evidence of preganglionic myelinated nerve fibers and postganglionic unmyelinated axons.

CONCLUSIONS

Schwann cell-mediated delivery of glial cell line-derived neurotrophic factor presents a viable approach for the treatment of erectile dysfunction after cavernous nerve injury.

Stem cell therapy for voiding and erectile dysfunction

Voiding dysfunction comprises a variety of disorders, including stress urinary incontinence and overactive bladder, and affects millions of men and women worldwide. Erectile dysfunction (ED) also decreases quality of life for millions of men, as well as for their partners. Advanced age and diabetes are common comorbidities that can exacerbate and negatively impact upon the development of these disorders. Therapies that target the pathophysiology of these conditions to halt progression are not currently available. However, stem cell therapy could fill this therapeutic void. Stem cells can reduce inflammation, prevent fibrosis, promote angiogenesis, recruit endogenous progenitor cells, and differentiate to replace damaged cells. Adult multipotent stem cell therapy, in particular, has shown promise in case reports and preclinical animal studies. Stem cells also have a role in urological tissue engineering for ex vivo construction of bladder wall and urethral tissue (using a patient's own cells) prior to transplantation. More recent studies have focused on bioactive factor secretion and homing of stem cells. In the future, clinicians are likely to utilize allogeneic stem cell sources, intravenous systemic delivery, and ex vivo cell enhancement to treat voiding dysfunction and ED.

Emerging tools for erectile dysfunction: a role for regenerative medicine

Erectile dysfunction (ED) is the most common sexual disorder reported by men to their health-care providers and the most investigated male sexual dysfunction. Currently, the treatment of ED focuses on 'symptomatic relief' of ED and, therefore, tends to provide temporary relief rather than providing a cure or reversing the cause. The identification of a large population of "difficult-to-treat" patients has triggered researchers to identify novel treatment approaches, which focus on cure and restoration of the underlying cause of ED. Regenerative medicine has developed extensively in the past few decades and preclinical trials have emphasized the benefit of growth factor therapy, gene transfer, stem cells and tissue engineering for the restoration of erectile function. Development of clinical trials involving immunomodulation in postprostatectomy ED patients and the use of maxi-K channels for gene therapy are illustrative of the advances in the field. However, the search for novel treatment targets and a wealth of preclinical studies represent a dynamic and continuing field of enquiry.

Peripheral nerve repair with cultured schwann cells: getting closer to the clinics

Peripheral nerve injuries are a frequent and disabling condition, which affects 13 to 23 per 100.000 persons each year. Severe cases, with structural disruption of the nerve, are associated with poor functional recovery. The experimental treatment using nerve grafts to replace damaged or shortened axons is limited by technical difficulties, invasiveness, and mediocre results. Other therapeutic choices include the adjunctive application of cultured Schwann cells and nerve conduits to guide axonal growth. The bone marrow is a rich source of mesenchymal cells, which can be differentiated in vitro into Schwann cells and subsequently engrafted into the damaged nerve. Alternatively, undifferentiated bone marrow mesenchymal cells can be associated with nerve conduits and afterward transplanted. Experimental studies provide evidence of functional, histological, and electromyographical improvement following transplantation of bone-marrow-derived cells in animal models of peripheral nerve injury. This paper focuses on this new therapeutic approach highlighting its direct translational and clinical utility in promoting regeneration of not only acute but perhaps also chronic cases of peripheral nerve damage.

Regeneration of the cavernous nerve by Sonic hedgehog using aligned peptide amphiphile nanofibers

SHH plays a significant role in peripheral nerve regeneration and has clinical potential to be used as a regenerative therapy for the CN in prostatectomy patients and in other patients with neuropathy of peripheral nerves. Efforts to regenerate the cavernous nerve (CN), which provides innervation to the penis, have been minimally successful, with little translation into improved clinical outcomes. We propose that, Sonic hedgehog (SHH), is critical to maintain CN integrity, and that SHH delivered to the CN by novel peptide amphiphile (PA) nanofibers, will promote CN regeneration, restore physiological function, and prevent penile morphology changes that result in erectile dysfunction (ED). We performed localization studies, inhibition of SHH signaling in the CN, and treatment of crushed CNs with SHH protein via linear PA gels, which are an innovative extended release method of delivery. Morphological, functional and molecular analysis revealed that SHH protein is essential to maintain CN architecture, and that SHH treatment promoted CN regeneration, suppressed penile apoptosis and caused a 58% improvement in erectile function in less than half the time reported in the literature. These studies show that SHH has substantial clinical application to regenerate the CN in prostatectomy and diabetic patients, that this methodology has broad application to regenerate any peripheral nerve that SHH is necessary for maintenance of its structure, and that this nanotechnology method of protein delivery may have wide spread application as an in vivo delivery tool in many organs.

Enhancement of regeneration with glia cell line-derived neurotrophic factor-transduced human amniotic fluid mesenchymal stem cells after sciatic nerve crush injury

OBJECT

Human amniotic fluid-derived mesenchymal stem cells (AFMSCs) have been shown to promote peripheral nerve regeneration, and the local delivery of neurotrophic factors may additionally enhance nerve regeneration capacity. The present study evaluates whether the transplantation of glia cell line-derived neurotrophic factor (GDNF)-modified human AFMSCs may enhance regeneration of sciatic nerve after a crush injury.

METHODS

Peripheral nerve injury was produced in Sprague-Dawley rats by crushing the left sciatic nerve using a vessel clamp. Either GDNF-modified human AFMSCs or human AFMSCs were embedded in Matrigel and delivered to the injured nerve. Motor function and electrophysiological studies were conducted after 1 and 4 weeks. Early or later nerve regeneration markers were used to evaluate nerve regeneration. The expression of GDNF in the transplanted human AFMSCs and GDNF-modified human AFMSCs was monitored at 7-day intervals.

RESULTS

Human AFMSCs were successfully transfected with adenovirus, and a significant amount of GDNF was detected in human AFMSCs or the culture medium supernatant. Increases in the sciatic nerve function index, the compound muscle action potential ratio, conduction latency, and muscle weight were found in the groups treated with human AFMSCs or GDNF-modified human AFMSCs. Importantly, the GDNF-modified human AFMSCs induced the greatest improvement. Expression of markers of early nerve regeneration, such as increased expression of neurofilament and BrdU and reduced Schwann cell apoptosis, as well as late regeneration markers, consisting of reduced vacuole counts, increased expression of Luxol fast blue and S100 protein, paralleled the results of motor function. The expression of GDNF in GDNF-modified human AFMSCs was demonstrated up to 4 weeks; however, the expression decreased over time.

CONCLUSIONS

The GDNF-modified human AFMSCs appeared to promote nerve regeneration. The consecutive expression of GDNF was demonstrated in GDNF-modified human AFMSCs up to 4 weeks. These findings support a nerve regeneration scenario involving cell transplantation with additional neurotrophic factor secretion.

Biocompatibility of Different Nerve Tubes

Bridging nerve gaps with suitable grafts is a major clinical problem. The autologous nerve graft is considered to be the gold standard, providing the best functional results; however, donor site morbidity is still a major disadvantage. Various attempts have been made to overcome the problems of autologous nerve grafts with artificial nerve tubes, which are “ready-to-use” in almost every situation. A wide range of materials have been used in animal models but only few have been applied to date clinically, where biocompatibility is an inevitable prerequisite. This review gives an idea about artificial nerve tubes with special focus on their biocompatibility in animals and humans.

Interposition nerve grafting during radical prostatectomy: cumulative review and critical appraisal of literature

In 1997, the first report of sural nerve interposition grafting during radical prostatectomy was published in Urology. The favorable findings in this initial pilot study generated numerous follow-up reports that have demonstrated conflicting and contradictory outcomes. Certainly, controversy exists regarding the true benefit of nerve grafting. This review will objectively and critically summarize the salient literature, discuss evolving techniques, and offer insight into the future of interposition grafting in the current era of clinically localized prostate cancer and robotic prostatectomy.

Preclinical evidence for the benefits of penile rehabilitation therapy following nerve-sparing radical prostatectomy

Erectile dysfunction following radical prostatectomy remains a frequent problem despite the development of nerve-sparing techniques. This erectile dysfunction is believed to be neurogenic, enhanced by hypoxia-induced structural changes which result in additional veno-occlusive dysfunction. Recently, daily use of intracavernous vasoactive substances and oral use of PDE5-inhibitors have been clinically studied for treatment of postprostatectomy erectile dysfunction. Since these studies showed benefits of “penile rehabilitation therapy,” these effects have been studied in a preclinical setting. We reviewed experimental literature on erectile tissue preserving and neuroregenerative treatment strategies, and found that preservation of the erectile tissue by the use of intracavernous nitric oxide donors or vasoactive substances, oral PDE5-inhibitors, and hyperbaric oxygen therapy improved erectile function by antifibrotic effects and preservation of smooth muscle. Furthermore, neuroregenerative strategies using neuroimmunophilin ligands, neurotrophins, growth factors, and stem cell therapy show improved erectile function by preservation of NOS-containing nerve fibers.