An improved, standardised protocol for the isolation, enrichment and targeted neural differentiation of Nestin+ progenitors from adult human dermis

In Vitro Differentiation of Human Skin-Derived Cells into Functional Sensory Neurons-Like

Skin-derived precursor cells (SKPs) are neural crest stem cells that persist in certain adult tissues, particularly in the skin. They can generate a large type of cell in vitro, including neurons. SKPs were induced to differentiate into sensory neurons (SNs) by molecules that were previously shown to be important for the generation of SNs: purmorphamine, CHIR99021, BMP4, GDNF, BDNF, and NGF. We showed that the differentiation of SKPs induced the upregulation of neurogenins. At the end of the differentiation protocol, transcriptional analysis was performed on BRN3A and a marker of pain-sensing nerve cell PRDM12 genes: 1000 times higher for PRDM12 and 2500 times higher for BRN3A in differentiated cells than they were in undifferentiated SKPs. Using immunostaining, we showed that 65% and 80% of cells expressed peripheral neuron markers BRN3A and PERIPHERIN, respectively. Furthermore, differentiated cells expressed TRPV1, PAR2, TRPA1, substance P, CGRP, HR1. Using calcium imaging, we observed that a proportion of cells responded to histamine, SLIGKV (a specific agonist of PAR2), polygodial (a specific agonist of TRPA1), and capsaicin (a specific agonist of TRPV1). In conclusion, SKPs are able to differentiate directly into functional SNs. These differentiated cells will be very useful for further in vitro studies.

Therapeutically engineered induced neural stem cells are tumour-homing and inhibit progression of glioblastoma

Transdifferentiation (TD) is a recent advancement in somatic cell reprogramming. The direct conversion of TD eliminates the pluripotent intermediate state to create cells that are ideal for personalized cell therapy. Here we provide evidence that TD-derived induced neural stem cells (iNSCs) are an efficacious therapeutic strategy for brain cancer. We find that iNSCs genetically engineered with optical reporters and tumouricidal gene products retain the capacity to differentiate and induced apoptosis in co-cultured human glioblastoma cells. Time-lapse imaging shows that iNSCs are tumouritropic, homing rapidly to co-cultured glioblastoma cells and migrating extensively to distant tumour foci in the murine brain. Multimodality imaging reveals that iNSC delivery of the anticancer molecule TRAIL decreases the growth of established solid and diffuse patient-derived orthotopic glioblastoma xenografts 230- and 20-fold, respectively, while significantly prolonging the median mouse survival. These findings establish a strategy for creating autologous cell-based therapies to treat patients with aggressive forms of brain cancer.

Neural stem cells have a tropism for glioblastoma. Here the authors employ fibroblasts directly reprogrammed into induced neural stem cells and loaded with cytotoxic molecules to migrate to xenotransplanted brain tumours in mice, achieving tumour shrinkage and prolonged survival.

Drug-loaded nanoparticle systems and adult stem cells: a potential marriage for the treatment of malignant glioma?

Despite all recent advances in malignant glioma research, only modest progress has been achieved in improving patient prognosis and quality of life. Such a clinical scenario underscores the importance of investing in new therapeutic approaches that, when combined with conventional therapies, are able to effectively eradicate glioma infiltration and target distant tumor foci. Nanoparticle-loaded delivery systems have recently arisen as an exciting alternative to improve targeted anti-glioma drug delivery. As drug carriers, they are able to efficiently protect the therapeutic agent and allow for sustained drug release. In addition, their surface can be easily manipulated with the addition of special ligands, which are responsible for enhancing tumor-specific nanoparticle permeability. However, their inefficient intratumoral distribution and failure to target disseminated tumor burden still pose a big challenge for their implementation as a therapeutic option in the clinical setting. Stem cell-based delivery of drug-loaded nanoparticles offers an interesting option to overcome such issues. Their ability to incorporate nanoparticles and migrate throughout interstitial barriers, together with their inherent tumor-tropic properties and synergistic anti-tumor effects make these stem cell carriers a good fit for such combined therapy. In this review, we will describe the main nanoparticle delivery systems that are presently available in preclinical and clinical studies. We will discuss their mechanisms of targeting, current delivery methods, attractive features and pitfalls. We will also debate the potential applications of stem cell carriers loaded with therapeutic nanoparticles in anticancer therapy and why such an attractive combined approach has not yet reached clinical trials.

Multipotent nestin-positive stem cells reside in the stroma of human eccrine and apocrine sweat glands and can be propagated robustly in vitro

Human skin harbours multiple different stem cell populations. In contrast to the relatively well-characterized niches of epidermal and hair follicle stem cells, the localization and niches of stem cells in other human skin compartments are as yet insufficiently investigated. Previously, we had shown in a pilot study that human sweat gland stroma contains Nestin-positive stem cells. Isolated sweat gland stroma-derived stem cells (SGSCs) proliferated in vitro and expressed Nestin in 80% of the cells. In this study, we were able to determine the precise localization of Nestin-positive cells in both eccrine and apocrine sweat glands of human axillary skin. We established a reproducible isolation procedure and characterized the spontaneous, long-lasting multipotent differentiation capacity of SGSCs. Thereby, a pronounced ectodermal differentiation was observed. Moreover, the secretion of prominent cytokines demonstrated the immunological potential of SGSCs. The comparison to human adult epidermal stem cells (EpiSCs) and bone marrow stem cells (BMSCs) revealed differences in protein expression and differentiation capacity. Furthermore, we found a coexpression of the stem cell markers Nestin and Iα6 within SGSCs and human sweat gland stroma. In conclusion the initial results of the pilot study were confirmed, indicating that human sweat glands are a new source of unique stem cells with multilineage differentiation potential, high proliferation capacity and remarkable self renewal. With regard to the easy accessibility of skin tissue biopsies, an autologous application of SGSCs in clinical therapies appears promising.

Skin-derived mesenchymal stem cells: isolation, culture, and characterization

The increasing interest about stem cell research is linked to the promise of developing such treatments for many life-threatening, debilitating diseases and for cell replacement therapies. Among the various human tissues, skin represents a source characterized by great accessibility and availability with noninvasive procedures and without risks of oncogenesis after their transplantation. In this aim, the identification of suitable protocols for the isolation, characterization, and long-term storage has a pivotal role.

Perivascular localization of dermal stem cells in human scalp

In mammalian skin, the existence of stem cells in the dermis is still poorly understood. Previous studies have indicated that mesenchymal stem cells (MSCs) are situated as pericytes in various mammalian tissues. We speculated that the human adult dermis also contains MSC-like cells positive for CD34 at perivascular sites similar to adipose tissue. At first, stromal cells from adult scalp skin tissues showed colony-forming ability and differentiated into mesenchymal lineages (osteogenic, chondrogenic and adipogenic). Three-dimensional analysis of scalp skin with a confocal microscope clearly demonstrated that perivascular cells were positive for not only NG2, but also CD34, immunoreactivity. Perivascular CD34-positive cells were abundant around follicular portions. Furthermore, CD34-positive cell fractions collected with magnetic cell sorting were capable of differentiating into mesenchymal lineages. This study suggests that dermal perivascular sites act as a niche of MSCs in human scalp skin, which are easily accessible and useful in regenerative medicine.

Basal cell carcinoma: cell of origin, cancer stem cell hypothesis and stem cell markers

Cancer stem cells have recently been described in several high-grade neoplasms. It is still unclear if they also occur in cutaneous malignancies. Cancer stem cells are not identical with somatic stem cells. The presence of tumour stem cells in a neoplasm does not in itself equal that the tumour derives from a somatic stem cell. A cell originally lacking stem cell characteristics could also acquire those features during the course of carcinogenesis and then becomes the clonal founder cell of a tumour. Basal cell carcinoma (BCC) is the most common cutaneous malignancy. A plethora of various stem cell markers has been applied to study its cellular origin. Intriguingly, the anatomical origin of BCC is still uncertain. This review will discuss the various stem cell markers used in BCC and the cellular origin of this tumour, and touches briefly on the possibility of cancer stem cells in BCC. If BCC or other skin cancers harbour tumour stem cells, these cells could be specifically targeted, making use of specific cell surface molecules such as receptor proteins. Novel drugs directed against those receptor proteins could replace currently available shotgun approaches including imiquimod.

p21cip/WAF is a key regulator of long-term radiation damage in mesenchyme-derived tissues

This study aimed to determine the mechanisms responsible for long-term tissue damage following radiation injury. We irradiated p21-knockout (p21(-/-)) and wild-type (WT) mice and determined the long-term deleterious effects of this intervention on mesenchyme-derived tissues. In addition, we explored the mechanisms of radiation-induced mesenchymal stem cell (MSC) dysfunction in isolated bone marrow-derived cells. p21 expression was chronically elevated >200-fold in irradiated tissues. Loss of p21 function resulted in a >4-fold increase in the number of skin MSCs remaining after radiation. p21(-/-) mice had significantly less radiation damage, including 6-fold less scarring, 40% increased growth potential, and 4-fold more hypertrophic chondrocytes in the epiphyseal plate (P<0.01). Irradiated p21(-/-) MSCs had 4-fold increased potential for bone or fat differentiation, 4-fold greater proliferation rate, and nearly 7-fold lower senescence as compared to WT MSCs (P<0.01). Ectopic expression of p21 in knockout cells decreased proliferation and differentiation potential and recapitulated the WT phenotype. Loss of p21 function markedly decreases the deleterious effects of radiation injury in mesenchyme-derived tissues and preserves tissue-derived MSCs. In addition, p21 is a critical regulator of MSC proliferation, differentiation, and senescence both at baseline and in response to radiation.

Endocrine controls of primary adult human stem cell biology: thyroid hormones stimulate keratin 15 expression, apoptosis, and differentiation in human hair follicle epithelial stem cells in situ and in vitro

Here we demonstrate that physiological concentrations of the thyroid hormones T3 and T4 enhance the KERATIN 15 promoter activity and expression in epithelial stem cells of adult human scalp hair follicles in situ and in vitro. Additionally, T3 and T4 stimulate expression of the immuno-inhibitory surface molecule CD200. Subsequently, T3 and T4 induce apoptosis and differentiation and inhibit clonal growth of these progenitor cells in vitro. These data suggest that human hair follicle bulge-derived epithelial stem cells underlie profound, previously unknown hormonal regulation by thyroid hormones, and show that primary human keratin 15-GFP+ progenitor cells can be exploited to further elucidate fundamental endocrine controls of human epithelial stem cells.