Potential of mesenchymal stem cell in stabilization of abdominal aortic aneurysm sac

Pathophisiology of abdominal aortic aneurysm: biomarkers and novel therapeutic targets

Abdominal aortic aneurysm (AAA) is a vascular pathology with a high rate of morbidity and mortality and a prevalence that, in men over 65 years, can reach around 8%. In this disease, usually asymptomatic, there is a progressive dilatation of the vascular wall that can lead to its rupture, a fatal phenomenon in more than 80% of cases. The treatment of patients with asymptomatic aneurysms is limited to periodic monitoring with imaging tests, control of cardiovascular risk factors and treatment with statins and antiplatelet therapy. There is no effective pharmacological treatment capable of limiting AAA progression or avoiding their rupture. At present, the aortic diameter is the only marker of risk of rupture and determines the need for surgical repair when it reaches values greater than 5.5cm. This review addresses the main aspects related to epidemiology, risk factors, diagnosis and clinical management of AAA, exposes the difficulties to have good biomarkers of this pathology and describes the strategies for the identification of new therapeutic targets and biomarkers in AAA.

Stem cell therapy for faecal incontinence: Current state and future perspectives

Faecal continence is a complex function involving different organs and systems. Faecal incontinence is a common disorder with different pathogeneses, disabling consequences and high repercussions for quality of life. Current management modalities are not ideal, and the development of new treatments is needed. Since 2008, stem cell therapies have been validated, 36 publications have appeared (29 in preclinical models and seven in clinical settings), and six registered clinical trials are currently ongoing. Some publications have combined stem cells with bioengineering technologies. The aim of this review is to identify and summarise the existing published knowledge of stem cell utilization as a treatment for faecal incontinence. A narrative or descriptive review is presented. Preclinical studies have demonstrated that cellular therapy, mainly in the form of local injections of muscle-derived (muscle derived stem cells or myoblasts derived from them) or mesenchymal (bone-marrow- or adipose-derived) stem cells, is safe. Cellular therapy has also been shown to stimulate the repair of both acute and subacute anal sphincter injuries, and some encouraging functional results have been obtained. Stem cells combined with normal cells on bioengineered scaffolds have achieved the successful creation and implantation of intrinsically-innervated anal sphincter constructs. The clinical evidence, based on adipose-derived stem cells and myoblasts, is extremely limited yet has yielded some promising results, and appears to be safe. Further investigation in both animal models and clinical settings is necessary to drawing conclusions. Nevertheless, if the preliminary results are confirmed, stem cell therapy for faecal incontinence may well become a clinical reality in the near future.

Gingival fibroblasts protect against experimental abdominal aortic aneurysm development and rupture through tissue inhibitor of metalloproteinase-1 production

Aims

Abdominal aortic aneurysm (AAA), frequently diagnosed in old patients, is characterized by chronic inflammation, vascular cell apoptosis and metalloproteinase-mediated extracellular matrix destruction. Despite improvement in the understanding of the pathophysiology of aortic aneurysm, no pharmacological treatment is yet available to limit dilatation and/or rupture. We previously reported that human gingival fibroblasts (GFs) can reduce carotid artery dilatation in a rabbit model of elastase-induced aneurysm. Here, we sought to investigate the mechanisms of GF-mediated vascular protection in two different models of aortic aneurysm growth and rupture in mice.

Methods and results

In vitro, mouse GFs proliferated and produced large amounts of anti-inflammatory cytokines and tissue inhibitor of metalloproteinase-1 (Timp-1). GFs deposited on the adventitia of abdominal aorta survived, proliferated, and organized as a layer structure. Furthermore, GFs locally produced Il-10, TGF-β, and Timp-1. In a mouse elastase-induced AAA model, GFs prevented both macrophage and lymphocyte accumulations, matrix degradation, and aneurysm growth. In an Angiotensin II/anti-TGF-β model of aneurysm rupture, GF cell-based treatment limited the extent of aortic dissection, prevented abdominal aortic rupture, and increased survival. Specific deletion of Timp-1 in GFs abolished the beneficial effect of cell therapy in both AAA mouse models.

Conclusions

GF cell-based therapy is a promising approach to inhibit aneurysm progression and rupture through local production of Timp-1.

Rat model of anal sphincter injury and two approaches for stem cell administration

AIM

To establish a rat model of anal sphincter injury and test different systems to provide stem cells to injured area.

METHODS

Adipose-derived stem cells (ASCs) were isolated from BDIX rats and were transfected with green fluorescent protein (GFP) for cell tracking. Biosutures (sutures covered with ASCs) were prepared with 1.5 x 10⁶ GFP-ASCs, and solutions of 10⁶ GFP-ASCs in normal saline were prepared for injection. Anorectal normal anatomy was studied on Wistar and BDIX female rats. Then, we designed an anal sphincter injury model consisting of a 1-cm extra-mucosal miotomy beginning at the anal verge in the anterior middle line. The sphincter lesion was confirmed with conventional histology (hematoxylin and eosin) and immunofluorescence with 4', 6-diamidino-2-phenylindole (commonly known as DAPI), GFP and α-actin. Functional effect was assessed with basal anal manometry, prior to and after injury. After sphincter damage, 36 BDIX rats were randomized to three groups for: (1) Cell injection without repair; (2) biosuture repair; and (3) conventional suture repair and cell injection. Functional and safety studies were conducted on all the animals. Rats were sacrificed after 1, 4 or 7 d. Then, histological and immunofluorescence studies were performed on the surgical area.

RESULTS

With the described protocol, biosutures had been covered with at least 820000-860000 ASCs, with 100% viability. Our studies demonstrated that some ASCs remained adhered after suture passage through the muscle. Morphological assessment showed that the rat anal anatomy is comparable with human anatomy; two sphincters are present, but the external sphincter is poorly developed. Anal sphincter pressure data showed spontaneous, consistent, rhythmic anal contractions, taking the form of “plateaus” with multiple twitches (peaks) in each pressure wave. These basal contractions were very heterogeneous; their frequency was 0.91-4.17 per min (mean 1.6980, SD 0.57698), their mean duration was 26.67 s and mean number of peaks was 12.53. Our morphological assessment revealed that with the aforementioned surgical procedure, both sphincters were completely sectioned. In manometry, the described activity disappeared and was replaced by a gentle oscillation of basal line, without a recognizable pattern. Surprisingly, these findings appeared irrespective of injury repair or not. ASCs survived in this potentially septic area for 7 d, at least. We were able to identify them in 84% of animals, mainly in the muscular section area or in the tissue between the muscular endings. ASCs formed a kind of “conglomerate” in rats treated with injections, while in the biosuture group, they wrapped the suture. ASCs were also able to migrate to the damaged zone. No relevant adverse events or mortality could be related to the stem cells in our study. We also did not find unexpected tissue growths.

CONCLUSION

The proposed procedure produces a consistent sphincter lesion. Biosutures and injections are suitable for cell delivery. ASCs survive and are completely safe in this clinical setting.

The Role of Perivascular Adipose Tissue in Non-atherosclerotic Vascular Disease

Perivascular adipose tissue (PVAT) surrounds most large blood vessels and plays an important role in vascular homeostasis. PVAT releases various chemokines and adipocytokines, functioning in an endocrine and paracrine manner to regulate vascular signaling and inflammation. Mounting evidence suggests that PVAT plays an important role in atherosclerosis and hypertension; however, the role of PVAT in non-atherosclerotic vascular diseases, including neointimal formation, aortic aneurysm, arterial stiffness and vasculitis, has received far less attention. Increasing evidence suggests that PVAT responds to mechanical endovascular injury and regulates the subsequent formation of neointima via factors that promote smooth muscle cell growth, adventitial inflammation and neovascularization. Circumstantial evidence also links PVAT to the pathogenesis of aortic aneurysms and vasculitic syndromes, such as Takayasu's arteritis, where infiltration and migration of inflammatory cells from PVAT into the vascular wall may play a contributory role. Moreover, in obesity, PVAT has been implicated to promote stiffness of elastic arteries via the production of reactive oxygen species. This review will discuss the growing body of data and mechanisms linking PVAT to the pathogenesis of non-atherosclerotic vascular diseases in experimental animal models and in humans.

Transcriptome sequencing revealed candidate genes relevant to mesenchymal stem cells' role in aortic dissection patients

Aortic dissection (AD) results from the imbalance between synthesis and degradation of extracellular matrices in aortic wall, which is characterized by chronic inflammation. Mesenchymal stem cells (MSCs) are known for anti-inflammatory and repairing effects and have therefore been studied for treatment for numerous diseases, including AD. However, it is unclear which genes or signaling pathways contribute to MSCs' role in AD. In the present study, RNA sequencing (RNA-seq) was conducted between MSCs from patients with AS (AD-MSCs) and those from age-matched healthy donors (HD-MSCs). RNA-seq revealed 201 differentially expressed genes (DEGs) under the filter of fold change>2 and P-value <0.05, in which 93 genes were upregulated and 108 downregulated. We selectively verified 9 out of 201 DEGs via reverse transcription-quantitative polymerase chain reaction (RT-qPCR) with an enlarged sample size. The trends of RT-qPCR results were consistent with RNA-seq data. Unsupervised hierarchical clustering of the 9-gene expression profiles enables the division of clinical samples into AD and HD groups. Kyoto Encyclopedia of Genes and Genomes analysis displayed a significant change in adhesion-related signaling pathways in AD-MSCs compared with HD-MSCs, whereas gene ontology analysis demonstrated DEGs were enriched in functions associated with development and morphogenesis, from a functional perspective. The present results indicate that gene expression profiles of AD-MSCs were significantly changed compared with HD-MSCs. These changes are probably associated with MSCs' adhesion capacity and development. These results may provide important insights into the role of MSCs in AD pathogenesis.

Are They Really Stem Cells? Scrutinizing the Identity of Cells and the Quality of Reporting in the Use of Adipose Tissue-Derived Stem Cells

There is an increasing concern that the term adipose tissue-derived stem cell (ASC) is inappropriately used to refer to the adipose stromal vascular fraction (SVF). To evaluate the accuracy and quality of reporting, 116 manuscripts on the application of ASC in humans and animals were examined based on the 2013 published International Federation for Adipose Therapeutics and Science (IFATS)/ International Society for Cellular Therapy (ISCT) joint statement and in reference to current guidelines for clinical trials and preclinical studies. It is disconcerting that 4 among the 47 papers or 8.51% (CI 2.37-20.38) surveyed after publication of IFATS/ISCT statement reported using ASCs but in fact they used unexpanded cells. 28/47 or 59.57% (CI 44.27-73.63) explicitly reported that adherent cells were used, 35/47 or 74.47% (CI 59.65-86.06) identified expression of surface markers, and 25/47 or 53.19% (CI 14.72-30.65) verified the multilineage potential of the cells. While there are a number of papers examined in this survey that were not able to provide adequate information on the characteristics of ASCs used with some erroneously referring to the SVF as stem cells, there are more room for improvement in the quality of reporting in the application of ASCs in humans and animals.