Adipose-derived stem cells protect against endoneurial cell death: Cell therapy for nerve autografts

Hydrogen-Generating Silicon-Based Agent Improves Fat Graft Survival in Rats

BACKGROUND

Regulating excessive inflammation and oxidative stress in fat grafting may improve retention rates. Hydrogen effectively combats oxidative stress and inflammation and reportedly inhibits ischemia-reperfusion injury in various organs. However, with conventional methods of hydrogen administration, incorporating hydrogen continuously into the body over a long period of time is difficult. The authors hypothesized that a silicon (Si)-based agent they recently developed would aid in fat grafting, as it can generate large amounts of hydrogen continuously in the body.

METHODS

Fat grafting was performed on the backs of rats fed either a normal or 1.0 wt% Si-based agent-containing diet. To investigate synergistic effects with adipose-derived stromal cells (ASCs), which improve retention rates of fat grafting, fat grafting with ASCs (1.0 × 10 5 /400 mg fat) was also performed in each rat. Postoperative retention rates of grafted fat over time, inflammatory indices, apoptosis, oxidative stress markers, histologic findings, and expression levels of inflammation-related cytokines and growth factors were compared among the 4 groups.

RESULTS

Intake of Si-based agent and addition of ASCs significantly reduced inflammatory indices, oxidative stress, and apoptosis of grafted fat, and improved long-term retention rates, histologic measures, and grafted fat quality. Under the experimental conditions, intake of the Si-based agent and addition of ASCs yielded comparable improvements in fat graft retention. Combining the 2 enhanced these effects.

CONCLUSIONS

Oral administration of a hydrogen-generating Si-based agent may improve grafted fat retention by regulating the inflammatory response and oxidative stress in grafted fat.

CLINICAL RELEVANCE STATEMENT

This study demonstrates improved grafted fat retention rates using a Si-based agent. This Si-based agent has the potential to expand the range of therapeutic indications of hydrogen-based therapy to conditions for which hydrogen has yet to be found effective, such as fat grafting.

Nerve Suture Combined With ADSCs Injection Under Real-Time and Dynamic NIR-II Fluorescence Imaging in Peripheral Nerve Regeneration in vivo

Peripheral nerve injury gives rise to devastating conditions including neural dysfunction, unbearable pain and even paralysis. The therapeutic effect of current treatment for peripheral nerve injury is unsatisfactory, resulting in slow nerve regeneration and incomplete recovery of neural function. In this study, nerve suture combined with ADSCs injection was adopted in rat model of sciatic nerve injury. Under real-time visualization of the injected cells with the guidance of NIR-II fluorescence imaging in vivo, a spatio-temporal map displaying cell migration from the proximal injection site (0 day post-injection) of the nerve to the sutured site (7 days post-injection), and then to the distal section (14 days post-injection) was demonstrated. Furthermore, the results of electromyography and mechanical pain threshold indicated nerve regeneration and functional recovery after the combined therapy. Therefore, in the current study, the observed ADSCs migration in vivo, electrophysiological examination results and pathological changes all provided robust evidence for the efficacy of the applied treatment. Our approach of nerve suture combined with ADSCs injection in treating peripheral nerve injury under real-time NIR-II imaging monitoring in vivo added novel insights into the treatment for peripheral nerve injury, thus further enhancing in-depth understanding of peripheral nerve regeneration and the mechanism behind.

Effect of Systemic Adipose-derived Stem Cell Therapy on Functional Nerve Regeneration in a Rodent Model

Supplemental Digital Content is available in the text.

Regardless of etiology, peripheral nerve injuries (PNI) result in disruption/loss of neuromuscular junctions, target muscle denervation, and poor sensorimotor outcomes with associated pain and disability. Adipose-derived stem cells (ASCs) have shown promise in neuroregeneration. However, there is a paucity of objective assessments reflective of functional neuroregeneration in experimental PNI. Here, we use a multimodal, static, and dynamic approach to evaluate functional outcomes after ASC therapy in a rodent PNI model.

Differentiated adipose-derived stem cells promote peripheral nerve regeneration

INTRODUCTION

Many reports have indicated that adipose-derived stem cells (ADSCs) are effective for nerve regeneration. We investigated nerve regeneration by combining a polyglycolic acid collagen (PGA-c) tube, which is approved for clinical use, and Schwann cell-like differentiated ADSCs (dADSCs).

METHODS

Fifteen-millimeter-long gaps in the sciatic nerve of rats were bridged in each group using tubes (group I), with tubes injected with dADSCs (group II), or by resected nerve (group III).

RESULTS

Axonal outgrowth was greater in group II than in group I. Tibialis anterior muscle weight revealed recovery only in group III. Latency in nerve conduction studies was equivalent in group II and III, but action potential was lower in group II. Transplanted dADSCs maintained Schwann cell marker expression. ATF3 expression level in the dorsal root ganglia was equivalent in groups II and III.

DISCUSSION

dADSCs maintained their differentiated state in the tubes and are believed to have contributed to nerve regeneration.

Hydrogel scaffolds for differentiation of adipose-derived stem cells

Natural extracellular matrices (ECMs) have been widely used as a support for the adhesion, migration, differentiation, and proliferation of adipose-derived stem cells (ADSCs). However, poor mechanical behavior and unpredictable biodegradation properties of natural ECMs considerably limit their potential for bioapplications and raise the need for different, synthetic scaffolds. Hydrogels are regarded as the most promising alternative materials as a consequence of their excellent swelling properties and their resemblance to soft tissues. A variety of strategies have been applied to create synthetic biomimetic hydrogels, and their biophysical and biochemical properties have been modulated to be suitable for cell differentiation. In this review, we first give an overview of common methods for hydrogel preparation with a focus on those strategies that provide potential advantages for ADSC encapsulation, before summarizing the physical properties of hydrogel scaffolds that can act as biological cues. Finally, the challenges in the preparation and application of hydrogels with ADSCs are explored and the perspectives are proposed for the next generation of scaffolds.

MALAT1 in Human Adipose Stem Cells Modulates Survival and Alternative Splicing of PKCδII in HT22 Cells

Brain injury may be caused by trauma or may occur in stroke and neurodegenerative diseases. Because the central nervous system is unable to regenerate efficiently, there is utmost interest in the use of stem cells to promote neuronal survival. Of interest here are human adipose-derived stem cells (hASCs), which secrete factors that enhance regeneration and survival of neurons in sites of injury. We evaluated the effect of hASC secretome on immortalized mouse hippocampal cell line (HT22) after injury. Protein kinase C δ (PKCδ) activates survival and proliferation in neurons and is implicated in memory. We previously showed that alternatively spliced PKCδII enhances neuronal survival via B-cell lymphoma 2 Bcl2 in HT22 neuronal cells. Our results demonstrate that following injury, treatment with exosomes from the hASC secretome increases expression of PKCδII in HT22 cells and increases neuronal survival and proliferation. Specifically, we demonstrate that metastasis-associated lung adenocarcinoma transcript 1 (MALAT1), a long noncoding RNA contained in the hASC exosomes mediates PKCδII splicing, thereby increasing neuronal survival. Using antisense oligonucleotides for MALAT1 and RNA immunoprecipitation assays, we demonstrate that MALAT1 recruits splice factor serine-arginine-rich splice factor 2 (SRSF2) to promote alternative splicing of PKCδII. Finally, we evaluated the role of insulin in enhancing hASC-mediated neuronal survival and demonstrated that insulin treatment dramatically increases the association of MALAT1 and SRSF2 and substantially increases survival and proliferation after injury in HT22 cells. In conclusion, we demonstrate the mechanism of action of hASC exosomes in increasing neuronal survival. This effect of hASC exosomes to promote wound healing can be further enhanced by insulin treatment in HT22 cells.