Stem cell therapy is being intensely investigated within the last years. Expectations are high regarding mesenchymal stem cell (MSC) treatment in translational medicine. However, many aspects concerning MSC therapy should be profoundly defined. Due to a variety of approaches that are investigated, potential effects of stem cell therapy are not transparent. On the other hand, most results of MSC administration in vivo have confirmed their safety and showed promising beneficial outcomes. However, the therapeutic effects of MSC-based treatment are still not spectacular and there is a potential risk related to MSC applications into specific cell niche that should be considered in long-term observations and follow-up outcomes. In this review, we intend to address some problems and critically discuss the complex nature of MSCs in the context of their effective and safe applications in regenerative medicine in different diseases including graft versus host disease (GvHD) and cardiac, neurological, and orthopedic disorders.

Mesenchymal stem cells (MSCs) are attractive candidates for cell-based tissue repair approaches. Hundreds of clinical trials using MSCs have been completed and many others are still being investigated. For most therapeutic applications, MSC propagation in vitro is often required. However, ex vivo culture condition is not fully physiological and may affect biological properties of MSCs including their regenerative potential. Moreover, both cell cryopreservation and labelling procedure prior to infusion may have the negative impact on their expected effect in vivo. The incidence of MSC transformation during in vitro culture should be also taken into consideration before using cells in stem cell therapy. In our review, we focused on different aspects of MSC propagation that might influence their regenerative properties of MSC. We also discussed the influence of different factors that might abolish MSC proliferation and differentiation as well as potential impact of stem cell senescence and aging. Despite of many positive therapeutic effects of MSC therapy, one has to be conscious about potential cell changes that could appear during manufacturing of MSCs.

Summary: Heterotopic ossification (HO) is an abnormal formation of mature lamellar bone within extraskeletal soft tissues, such as muscles, tendons, and ligaments. This process is thought to be induced by inflammation associated with tissue injuries. HO is classified using two subtypes: resulting from injury or genetically inherited. HO formation is associated with polytrauma patients with traumatic brain injuries and spinal cord injuries. Moreover, HO is also considered to be a post‐operative risk factor in some orthopaedic procedures. In this review, we summarize our current understanding of the pathology of different types of HO and discuss its current and future therapies. Thus far, research has revealed cellular and molecular pathways leading to HO formation and proposed several possible mechanisms leading to HO and conserved signalling pathways common in the different HO subtypes. Non‐steroidal anti‐inflammatory drug treatment and localized low‐dose irradiation are currently the only available prophylactic treatments for HO. However, they are not always effective and do not target the osteogenic processes directly. New therapeutic strategies targeting the pathological processes of HO, such as bone morphogenetic protein (BMP) inhibitors like noggin, BMP type 1 receptor inhibitor, and nuclear retinoid acid receptor‐gamma (RARγ) agonists, are currently being investigated. In‐depth understanding of the HO pathological process could help to develop effective therapeutic strategies.

Background: Mesenchymal stem/stromal cells (MSC) are commonly used in regenerative medicine. Among different tissues, iliac crest bone marrow (BM) represents the most exploited source, but its disadvantages are a painful aspiration procedure and low cell number. An alternative, readily available source of MSC for research would be beneficial for regenerative medicine development. This work aimed to propose a new source of bone marrow isolation in which the femoral shaft is taken during total hip arthroplasty (THA). Methods: In preliminary experiments, three different gradient methods for cell separation (Ficoll-Paque 1.078 g/mL, 17% sucrose gradient, BM seeding fraction) were tested with regard to the time of primary culture, initial cell number, the phenotype, and morphology of MSC. Then human bone marrow MSC derived from two different sources, iliac crest aspirate (BM-MSCi) or femoral shaft (BM-MSCt), were analyzed in terms of cell number and colony-forming ability followed by differentiation potential of MSC into osteo-, chondro-, and adipogenic lineages as well as mRNA expression of a variety of cytokines and growth factors. Results: Our studies showed that MSC isolated from the bone marrow of two different sources and cultured under appropriate conditions had similar characteristics and comparable propensity to differentiate into mesodermal cells. MSC derived from BM-MSCi or BM-MSCt expressed various growth factors. Interestingly, the expression of EGF, FGF, IGF, and PDGF-A was much higher in BM-MSCt than BM-MSCi. Conclusions: The results of our study demonstrate that human MSC isolated from the BM of the femoral shaft have similar biological characteristics as MSC derived from the iliac crest, suggesting the femoral shaft as a possible alternative source for mesenchymal stem/stromal cells.

Cell-based therapies delivered via intrathecal injection are considered as one of the most promising solutions for the treatment of amyotrophic lateral sclerosis (ALS). Herein, injectable manganese-based biocompatible hydrogel blends were developed, that can allow image-guided cell delivery. The hydrogels can also provide physical support for cells during injection, and at the intrathecal space after transplantation, while assuring cell survival. In this regard, different formulations of methacrylated gellan gum/hyaluronic acid hydrogel blends (GG-MA/HA) were considered as a vehicle for cell delivery. The hydrogels blends were supplemented with paramagnetic Mn²⁺ to allow a real-time monitorization of hydrogel deposition via T₁-weighted magnetic resonance imaging (MRI). The developed hydrogels were easily extruded and formed a stable fiber upon injection into the cerebrospinal fluid. Hydrogels prepared with a 75 : 25 GG-MA to HA ratio supplemented with MnCl₂ at 0.1 mM showed controlled hydrogel degradation, suitable permeability, and a distinct MRI signal in vitro and in vivo. Additionally, human-derived adipose stem cells encapsulated in 75 : 25 GG-MA/HA hydrogels remained viable for up to 14 days of culture in vitro. Therefore, the engineered hydrogels can be an excellent tool for injectable image-guided cell delivery approaches.

The most recent research concerning amyotrophic lateral sclerosis (ALS) emphasizes the role of glia in disease development. Thus, one can suspect that the effective therapeutic strategy in treatment of ALS would be replacement of defective glia. One of the basic problems with human glial progenitors (hGRPs) replacement strategies is the time needed for the cells to become fully functionalin vivo. The lifespan of most popular high copy number SOD1 mutant mice might be too short to acknowledge benefits of transplanted cells. We focused on developing immunodeficient rag2⁻/⁻model of ALS with lower number of transgene copies and longer lifespan. The obtained hSOD1/rag2 double mutant mice have been characterized. QPCR analysis revealed that copy number of hSOD1 transgene varied in our colony (4–8 copies). The difference in transgene copy number may be translated to significant impact on the lifespan. The death of long- and short-living hSOD1/rag2 mice is preceded by muscular weakness as early as one month before death. Importantly, based on magnetic resonance imaging we identified that mutant mice demonstrated abnormalities within the medullar motor nuclei. To conclude, we developed long-living double mutant hSOD1/rag2 mice, which could be a promising model for testing therapeutic utility of human stem cells.