Chondrogenic priming of human fetal synovium-derived stem cells in an adult stem cell matrix microenvironment

Hypoxia Modulates Regenerative Potential of Fetal Stem Cells

Adult mesenchymal stem cells (MSCs) are prone to senescence, which limits the scope of their use in tissue engineering and regeneration and increases the likelihood of post-implantation failure. As a robust alternative cell source, fetal stem cells can prevent an immune reaction and senescence. However, few studies use this cell type. In this study, we sought to characterize fetal cells' regenerative potential in hypoxic conditions. Specifically, we examined whether hypoxic exposure during the expansion and differentiation phases would affect human fetal nucleus pulposus cell (NPC) and fetal synovium-derived stem cell (SDSC) plasticity and three-lineage differentiation potential. We concluded that fetal NPCs represent the most promising cell source for chondrogenic differentiation, as they are more responsive and display stronger phenotypic stability, particularly when expanded and differentiated in hypoxic conditions. Fetal SDSCs have less potential for chondrogenic differentiation compared to their adult counterpart. This study also indicated that fetal SDSCs exhibit a discrepancy in adipogenic and osteogenic differentiation in response to hypoxia.

Decellularized extracellular matrix mediates tissue construction and regeneration

Contributing to organ formation and tissue regeneration, extracellular matrix (ECM) constituents provide tissue with three-dimensional (3D) structural integrity and cellular-function regulation. Containing the crucial traits of the cellular microenvironment, ECM substitutes mediate cell–matrix interactions to prompt stem-cell proliferation and differentiation for 3D organoid construction in vitro or tissue regeneration in vivo. However, these ECMs are often applied generically and have yet to be extensively developed for specific cell types in 3D cultures. Cultured cells also produce rich ECM, particularly stromal cells. Cellular ECM improves 3D culture development in vitro and tissue remodeling during wound healing after implantation into the host as well. Gaining better insight into ECM derived from either tissue or cells that regulate 3D tissue reconstruction or organ regeneration helps us to select, produce, and implant the most suitable ECM and thus promote 3D organoid culture and tissue remodeling for in vivo regeneration. Overall, the decellularization methodologies and tissue/cell-derived ECM as scaffolds or cellular-growth supplements used in cell propagation and differentiation for 3D tissue culture in vitro are discussed. Moreover, current preclinical applications by which ECM components modulate the wound-healing process are reviewed.

Liver Kinase B1 Fine-Tunes Lineage Commitment of Human Fetal Synovium-Derived Stem Cells

Liver kinase B1 (LKB1), a serine/threonine protein, is a key regulator in stem cell function and energy metabolism. Herein, we describe the role of LKB1 in modulating the differentiation of synovium-derived stem cells (SDSCs) toward chondrogenic, adipogenic, and osteogenic lineages. Human fetal SDSCs were transduced with CRISPR associated protein 9 (Cas9)-single-guide RNA vectors to knockout or lentiviral vectors to overexpress the LKB1 gene. Analyses including ICE (Inference of CRISPR Edits) data from Sanger sequencing and quantitative polymerase chain reaction (qPCR) as well as Western blot demonstrated successful knockout (KO) or overexpression (OE) of LKB1 in human fetal SDSCs without any detectable side effects in morphology, proliferation rate, and cell cycle. LKB1 KO increased CD146 expression; interestingly, LKB1 OE increased SSEA4 level. The qPCR data showed that LKB1 KO upregulated the levels of SOX2 and NANOG while LKB1 OE lowered the expression of POU5F1 and KLF4. Furthermore, LKB1 KO enhanced, and LKB1 OE inhibited, chondrogenic and adipogenic differentiation potential. However, perhaps due to the inherent inability to achieve osteogenesis, LKB1 did not obviously affect osteogenic differentiation. These data demonstrate that LKB1 plays a significant role in determining human SDSCs' adipogenic and chondrogenic differentiation, which might provide an approach for fine-tuning the direction of stem cell differentiation in tissue engineering and regeneration. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:258-268, 2020.