During aging, senescent cells accumulate in various tissues accompanied by decreased regenerative capacities of quiescent stem cells, resulting in deteriorated organ function and overall degeneration. In this regard, the adult human heart with a generally low regenerative potential is of extreme interest as a target for rejuvenating strategies with blood borne factors that might be able to activate endogenous stem cell populations. Here, we investigated for the first time the effects of human blood plasma and serum on adult human cardiac stem cells (hCSCs) and showed significantly increased proliferation capacities and metabolism accompanied by a significant decrease of senescent cells, demonstrating a beneficial serum-mediated effect that seemed to be independent of age and sex. However, RNA-seq analysis of serum-treated hCSCs revealed profound effects on gene expression depending on the age and sex of the plasma donor. We further successfully identified key pathways that are affected by serum treatment with p38-MAPK playing a regulatory role in protection from senescence and in the promotion of proliferation in a serum-dependent manner. Inhibition of p38-MAPK resulted in a decline of these serum-mediated beneficial effects on hCSCs in terms of decreased proliferation and accelerated senescence. In summary, we provide new insights in the regulatory networks behind serum-mediated protective effects on adult human cardiac stem cells.

Scaffold materials for bone regeneration are crucial for supporting endogenous healing after accidents, infections, or tumor resection. Although beneficial impacts of microtopological or nanotopological cues in scaffold topography are commonly acknowledged, less consideration is given to the interplay between the microscale and nanoscale. Here, micropores with a 60.66 ± 24.48 µm diameter ordered by closely packed collagen fibers are identified in pre-wetted Spongostan, a clinically-approved collagen sponge. On a nanoscale level, a corrugated surface of the collagen sponge is observable, leading to the presence of 32.97 ± 1.41 nm pores. This distinct micro-and nanotopography is shown to be solely sufficient for guiding osteogenic differentiation of human stem cells in vitro. Transplantation of Spongostan into a critical-size calvarial rat bone defect further leads to fast regeneration of the lesion. However, masking the micro-and nanotopographical cues using SiO 2 nanoparticles prevents bone regeneration in vivo. Therefore, we demonstrate that the identified micropores allow migration of stem cells, which are further driven towards osteogenic differentiation by scaffold nanotopography. The present findings emphasize the necessity of considering both microand nanotopographical cues to guide intramembranous ossification, and might provide an optimal cell-and growth-factor-free scaffold for bone regeneration in clinical settings. Cells 2020, 9, 654 2 of 17 Cells 2020, 9, 654 3 of 17 Materials and Methods Study DesignThe study design is depicted in Figure 1. Briefly, micropores and nanopores were identified in Spongostan, followed by assessment of their osteoinductive capacity in vitro. For investigation of bone regeneration in vivo, Spongostan was transplanted into critical-size calvarial defects. Next to an empty control, we applied sole collagen fibers (control lacking the microtopography of Spongostan) and Spongostan masked with nanoparticles (control lacking nano-and microtopography).Cells 2020, 9, x 3 of 18 Study DesignThe study design is depicted in Figure 1. Briefly, micropores and nanopores were identified in Spongostan, followed by assessment of their osteoinductive capacity in vitro. For investigation of bone regeneration in vivo, Spongostan was transplanted into critical-size calvarial defects. Next to an empty control, we applied sole collagen fibers (control lacking the microtopography of Spongostan) and Spongostan masked with nanoparticles (control lacking nano-and microtopography).

Sexual dimorphisms contribute, at least in part, to the severity and occurrence of a broad range of neurodegenerative, cardiovascular, and bone disorders. In addition to hormonal factors, increasing evidence suggests that stem cell‐intrinsic mechanisms account for sex‐specific differences in human physiology and pathology. Here, we discuss sex‐related intrinsic mechanisms in adult stem cell populations, namely mesoderm‐derived stem cells, neural stem cells (NSCs), and neural crest‐derived stem cells (NCSCs), and their implications for stem cell differentiation and regeneration. We particularly focus on sex‐specific differences in stem cell‐mediated bone regeneration, in neuronal development, and in NSC‐mediated neuroprotection. Moreover, we review our own recently published observations regarding the sex‐dependent role of NF‐κB‐p65 in neuroprotection of human NCSC‐derived neurons and sex differences in NCSC‐related disorders, so‐called neurocristopathies. These observations are in accordance with the increasing evidence pointing toward sex‐specific differences in neurocristopathies and degenerative diseases like Parkinson's disease or osteoporosis. All findings discussed here indicate that sex‐specific variability in stem cell biology may become a crucial parameter for the design of future treatment strategies.

Bone substitute materials are becoming increasingly important in oral and maxillofacial surgery. Reconstruction of critical size bone defects is still challenging for surgeons. Here, we compared the clinically applied organic bone substitute materials NanoBone® (nanocrystalline hydroxyapatite and nanostructured silica gel; n = 5) and Actifuse (calcium phosphate with silicate substitution; n = 5) with natural collagen-based Spongostan™ (hardened pork gelatin containing formalin and lauryl alcohol; n = 5) in bilateral rat critical-size defects (5 mm diameter). On topological level, NanoBone is known to harbour nanopores of about 20 nm diameter, while Actifuse comprises micropores of 200–500 µm. Spongostan™, which is clinically applied as a haemostatic agent, combines in its wet form both nano- and microporous topological features by comprising 60.66 ± 24.48 μm micropores accompanied by nanopores of 32.97 ± 1.41 nm diameter. Micro-computed tomography (µCT) used for evaluation 30 days after surgery revealed a significant increase in bone volume by all three bone substitute materials in comparison to the untreated controls. Clearly visual was the closure of trepanation in all treated groups, but granular appearance of NanoBone® and Actifuse with less closure at the margins of the burr holes. In contrast, transplantion of Spongostan™ lead to complete filling of the burr hole with the highest bone volume of 7.98 ccm and the highest bone mineral density compared to all other groups. In summary, transplantation of Spongostan™ resulted in increased regeneration of a rat calvarial critical size defect compared to NanoBone and Actifuse, suggesting the distinct nano- and microtopography of wet Spongostan™ to account for this superior regenerative capacity. Since Spongostan™ is a clinically approved product used primarily for haemostasis, it may represent an interesting alternative in the reconstruction of defects in the maxillary region.

Female sex is increasingly associated with a loss of bone mass during aging and an increased risk of developing nonunion fractures. Hormonal factors and cell-intrinsic mechanisms are suggested to drive these sexual dimorphisms, although underlying molecular mechanisms are still a matter of debate. Here, we observed a decreased capacity of calvarial bone recovery in female rats and a profound sexually dimorphic osteogenic differentiation in human adult neural crest-derived stem cells (NCSCs). Next to an elevated expression of pro-osteogenic regulators, global transcriptomics revealed Lysine Demethylase 5D (KDM5D) to be highly upregulated in differentiating male NCSCs. Loss of function by siRNA or pharmacological inhibition of KDM5D significantly reduced the osteogenic differentiation capacity of male NCSCs. In summary, we demonstrated craniofacial osteogenic differentiation to be sexually dimorphic with the expression of KDM5D as a prerequisite for accelerated male osteogenic differentiation, emphasizing the analysis of sex-specific differences as a crucial parameter for treating bone defects.