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

The GDNF-gel/HA-Mg conduit promotes the repair of peripheral nerve defects by regulating PPAR-γ/RhoA/ROCK signaling pathway

Magnesium (Mg)-based conduits have gained more attention in repairing peripheral nerve defects. However, they are limited due to poor corrosion resistance and rapid degradation rate. To tackle this issue, glial cell line-derived neurotrophic factor (GDNF)- Gelatin methacryloyl (Gel)/hydroxylapatite (HA)-Mg nerve conduit was developed and implanted in sciatic nerve defect model in Sprague-Dawley (SD) rats. The sciatic functional index measurement showed that the GDNF-Gel/HA-Mg nerve conduit effectively promoted the recovery of sciatic nerve function. The pathological examination results showed that there were more regenerated nerve tissues in GDNF-Gel/HA-Mg group, with a higher number of regenerating axons, and the thickness of the myelin sheath was significantly larger than that of control group (NC group). Immunofluorescence results revealed that the GDNF-Gel/HA-Mg conduit significantly promoted the expression of genes associated with nerve repair. RNA-seq and molecular test results indicated that GDNF-Gel/HA-Mg might be involved in the repair of peripheral nerve defects by regulating PPAR-γ/RhoA/ROCK signaling pathway. Biological sciences; Neuroscience; Molecular neuroscience; Techniques in neuroscience.

Regulation of Schwann Cell and DRG Neurite Behaviors within Decellularized Peripheral Nerve Matrix

Decellularized nerve hydrogels (dNHs) containing bioactive molecules are promising biomaterials for peripheral nerve injury (PNI) treatment and have been extensively applied in clinical and preclinical practice. However, most previous research projects studied their influences on nerve-related cellular behaviors in two dimensions (2D) without taking hydrogel biomechanics into consideration. The molecular mechanisms underlying the beneficial microenvironment provided by dNHs also remain unclear. In this study, dNHs from rat sciatic nerves were prepared, and their effects on Schwann cell (SC) and dorsal root ganglion (DRG) neurite behaviors were evaluated and compared to commercial rat tail type I collagen (Col) hydrogels in three-dimensional (3D) environments. We found that dNHs could promote SC proliferation and neurite outgrowth, and both the hydrogel mechanics and components contributed to the dNH functionalization. Through proteomics analysis, we found that laminin (LAM) and type V collagen (COLV) exclusively and abundantly existed in dNHs. By adding exogenous LAM and COLV into Col hydrogels, we demonstrated that they regulated SC gene expression and that LAM could promote SC spreading and neurite outgrowth, while COLV improved SC proliferation. Lastly, dNHs were fabricated into paper-like, aligned nerve scaffolds through unidirectional freezing to expand the dNH applications in PNI treatment.

Anisotropic scaffolds for peripheral nerve and spinal cord regeneration

The treatment of long-gap (>10 mm) peripheral nerve injury (PNI) and spinal cord injury (SCI) remains a continuous challenge due to limited native tissue regeneration capabilities. The current clinical strategy of using autografts for PNI suffers from a source shortage, while the pharmacological treatment for SCI presents dissatisfactory results. Tissue engineering, as an alternative, is a promising approach for regenerating peripheral nerves and spinal cords. Through providing a beneficial environment, a scaffold is the primary element in tissue engineering. In particular, scaffolds with anisotropic structures resembling the native extracellular matrix (ECM) can effectively guide neural outgrowth and reconnection. In this review, the anatomy of peripheral nerves and spinal cords, as well as current clinical treatments for PNI and SCI, is first summarized. An overview of the critical components in peripheral nerve and spinal cord tissue engineering and the current status of regeneration approaches are also discussed. Recent advances in the fabrication of anisotropic surface patterns, aligned fibrous substrates, and 3D hydrogel scaffolds, as well as their in vitro and in vivo effects are highlighted. Finally, we summarize potential mechanisms underlying the anisotropic architectures in orienting axonal and glial cell growth, along with their challenges and prospects.

Revisiting the Regenerative Therapeutic Advances Towards Erectile Dysfunction

Erectile dysfunction (ED) is an inability to attain or maintain adequate penile erection for successful vaginal intercourse, leading to sexual and relationship dissatisfaction. To combat ED, various surgical and non-surgical approaches have been developed in the past to restore erectile functions. These therapeutic interventions exhibit significant impact in providing relief to patients; however, due to their associated adverse effects and lack of long-term efficacy, newer modalities such as regenerative therapeutics have gained attention due to their safe and prolonged efficacy. Stem cells and platelet-derived biomaterials contained in platelet-rich plasma (PRP) are thriving as some of the major therapeutic regenerative agents. In recent years, various preclinical and clinical studies have evaluated the individual, as well as combined of stem cells and PRP to restore erectile function. Being rich in growth factors, chemokines, and angiogenic factors, both stem cells and PRP play a crucial role in regenerating nerve cells, myelination of axons, homing and migration of progenitor cells, and anti-fibrosis and anti-apoptosis of damaged cavernous nerve in corporal tissues. Further, platelet-derived biomaterials have been proven to be a biological supplement for enhancing the proliferative and differentiation potential of stem cells towards neurogenic fate. Therefore, this article comprehensively analyzes the progresses of these regenerative therapies for ED.

Modern Trends for Peripheral Nerve Repair and Regeneration: Beyond the Hollow Nerve Guidance Conduit

Peripheral nerve repair and regeneration remains among the greatest challenges in tissue engineering and regenerative medicine. Even though peripheral nerve injuries (PNIs) are capable of some degree of regeneration, frail recovery is seen even when the best microsurgical technique is applied. PNIs are known to be very incapacitating for the patient, due to the deprivation of motor and sensory abilities. Since there is no optimal solution for tackling this problem up to this day, the evolution in the field is constant, with innovative designs of advanced nerve guidance conduits (NGCs) being reported every day. As a basic concept, a NGC should act as a physical barrier from the external environment, concomitantly acting as physical guidance for the regenerative axons across the gap lesion. NGCs should also be able to retain the naturally released nerve growth factors secreted by the damaged nerve stumps, as well as reducing the invasion of scar tissue-forming fibroblasts to the injury site. Based on the neurobiological knowledge related to the events that succeed after a nerve injury, neuronal subsistence is subjected to the existence of an ideal environment of growth factors, hormones, cytokines, and extracellular matrix (ECM) factors. Therefore, it is known that multifunctional NGCs fabricated through combinatorial approaches are needed to improve the functional and clinical outcomes after PNIs. The present work overviews the current reports dealing with the several features that can be used to improve peripheral nerve regeneration (PNR), ranging from the simple use of hollow NGCs to tissue engineered intraluminal fillers, or to even more advanced strategies, comprising the molecular and gene therapies as well as cell-based therapies.