The majority of preclinical studies addressing the potential of cell-based regenerative medicine therapies to treat kidney disease have focussed on mesenchymal stem/stromal cells (MSCs) derived from the bone marrow (BM-MSCs). BM-MSCs have been used in numerous clinical trials, but although their safety and feasibility have been demonstrated, the extent of therapeutic efficacy has been inconsistent1. Currently it is not clear if BM-MSCs are the most effective for promoting the regeneration and/or repair of host renal tissue. Other types of MSCs, such as umbilical cord-derived MSCs (UC-MSCs), adipose-derived MSCs (A-MSCs) and skin-derived MSCs (S-MSCs) could present attractive alternatives because they are much easier to source.
The RenalToolBox team has been working establishing methods for the isolation and production of clinical grade MSCs from different sources. In particular:
● The National University of Ireland Galway have found that an antibody against the surface marker CD362 (syndecan 2) can be used to isolate a pure population of BM-MSCs using magnetic-ativated cell sorting (MACS). These CD362+ cells are being used as an ‘advanced therapy medicinal product (ATMP)’ in the ‘Nephstrom’ H2020 project to test their safety in patients with diabetic nephropathy.
● NHSBT has developed protocols for isolating and propagating UC-MSCs under GMP conditions. A previous study showed that UC-MSCs could ameliorate injury in a mouse model of kidney damage2. The advantage of UC-MSCs is that their supply is unlimited, their procurement is non-invasive, and they appear to be less immunogenic than BM-MSCs3. UC-MSCs have also been reported to be potent immunomodulators and have a high proliferative capacity3.
● The University of Heidelberg has established protocols for GMP-manufacturing of A-MSC using human blood-derived supplements and, through a collaboration with Rheacell, is studying the properties of S-MSCs. These MSCs are derived from the reticular dermis of the skin, but unlike other MSCs, they express the surface marker ABCB5, enabling them to be specifically isolated from skin biopsies.
In this project, we will characterise BM-MSCs, UC-MSCs, A-MSCs and S-MSCs in regard to immunophenotype, proliferation and differentiation potential. To establish a matrix of reliable potency assays, we will build on our current techniques4, and develop and validate additional in vitro assays for assessing the immunomodulatory capacity of the MSCs and their extracellular vesicles (EVs). MSC safety and efficacy will be evaluated using the novel biomarkers and in vivo and ex vivo imaging technologies. To assess whether apoptosis of the MSCs shortly following their administration is responsible for their therapeutic effects, following identification of the MSC subtype that is most therapeutic in the preclinical models of kidney injury, we will compare the efficacy of the viable cells with their apoptotic counterparts.
Mechanisms of Action
The majority of studies do not explore whether the therapeutic effects of MSCs are mediated by the cells themselves, or instead, by their derived factors. Of particular interest is the therapeutic potential of cell-derived EVs, which in many studies have been shown to be as efficacious as the cells themselves.
The University of Turin demonstrated that that for some cell types, such as rodent BM-MSCs, most of the beneficial effects are likely to be mediated by MSC-derived EVs5. EVs could be more attractive as a potential therapy than the MSCs due to the fact that the cells could cause microemboli, mal-differentiate or give rise to tumours. However, whether the therapeutic effects of other MSC sub-types are mediated by EVs remains to be established. We will address this by comparing the properties (e.g., miRNA content), of EVs derived from the different types of MSCs and will evaluate their therapeutic efficacy using the in vitro model of ischaemic injury. Depending on in vitro results, regenerative capacity will then be tested in preclinical models. If we find that apoptotic MSCs are comparable to viable MSCs in regard to their therapeutic potential, we will compare the miRNA content of EVs with that of apoptotic bodies derived from the most efficacious MSC sub-type. Knowledge of the therapeutic mechanisms could lead to improved efficacy in the clinic.
1. Ikebe et al (2014) BioMed Res Int: 951512
2. Večerić-Haler et al (2016) Stem Cells Int. Article 3585362
3. Bárcia et al (2015) Stem Cells Int. Article 583984
4. Ketterl N et al (2015) Stem Cell Res Ther 6:236
5. Ranghino et al (2017) Stem Cell Res Ther 8:24