The promise of cell therapy for repair and restoration of damaged tissues or organs relies on administration of large dose of cells whose healing benefits are still limited and sometimes irreproducible due to uncontrollable cell loss and death at lesion sites. Using a large amount of therapeutic cells increases the costs for cell processing and the risks of side effects. Optimal cell delivery strategies are therefore in urgent need to enhance the specificity, efficacy, and reproducibility of cell therapy leading to minimized cell dosage and side effects. Here, we addressed this unmet need by developing injectable 3D microscale cellular niches (microniches) based on biodegradable gelatin microcryogels (GMs). The microniches are constituted by in vitro priming human adipose-derived mesenchymal stem cells (hMSCs) seeded within GMs resulting in tissue-like ensembles with enriched extracellular matrices and enhanced cell-cell interactions. The primed 3D microniches facilitated cell protection from mechanical insults during injection and in vivo cell retention, survival, and ultimate therapeutic functions in treatment of critical limb ischemia (CLI) in mouse models compared with free cell-based therapy. In particular, 3D microniche-based therapy with 10 5 hMSCs realized better ischemic limb salvage than treatment with 10 6 freeinjected hMSCs, the minimum dosage with therapeutic effects for treating CLI in literature. To the best of our knowledge, this is the first convincing demonstration of injectable and primed cell delivery strategy realizing superior therapeutic efficacy for treating CLI with the lowest cell dosage in mouse models. This study offers a widely applicable cell delivery platform technology to boost the healing power of cell regenerative therapy.C ell-based regenerative therapy holds great promise for repair and restoration of damaged tissues or organs with numerous clinical trials and preclinical animal testing reported for treating complex diseases (1). Common route of cell administration for clinical cell therapy is based on either systematic administration (e.g., i.v. infusion), relying on cells homing to the lesion sites (2), or direct injection of cells into the damaged tissues (3). However, therapeutic benefits of the administered cells are still limited and sometimes irreproducible due to cell loss and cell death (4). Taking cell therapy for ischemic heart diseases as an example, only ∼5% of mesenchymal stem cells (MSCs) survived after being transplanted into an infarcted porcine heart (5). Mechanical damage during injection, high rate of cell loss and leakage to surrounding tissues, cell death due to lack of appropriate cell-cell and cell-matrix interactions in the ischemic and inflammatory lesion tissues could all contribute to poor cell retention, survival, functionality, and reproducibility of the treatment (6, 7).A rational solution to enhance the therapeutic efficacy and reproducibility of cell therapy is to administer a large dose of cells to ensure sufficient number of functional cells ...

Mesenchmal stem cells (MSCs) can be differentiated into either adipocytes or osteoblasts, and a reciprocal relationship exists between adipogenesis and osteogenesis. Multiple transcription factors and signaling pathways have been reported to regulate adipogenic or osteogenic differentiation, respectively, yet the molecular mechanism underlying the cell fate alteration between adipogenesis and osteogenesis still remains to be illustrated. MicroRNAs are important regulators in diverse biological processes by repressing protein expression of their targets. Here, miR-22 was found to regulate adipogenic and osteogenic differentiation of human adipose tissue-derived mesenchymal stem cells (hADMSCs) in opposite directions. Our data showed that miR-22 decreased during the process of adipogenic differentiation but increased during osteogenic differentiation. On one hand, overexpression of miR-22 in hADMSCs could inhibit lipid droplets accumulation and repress the expression of adipogenic transcription factors and adipogenic-specific genes. On the other hand, enhanced alkaline phosphatase activity and matrix mineralization, as well as increased expression of osteo-specific genes, indicated a positive role of miR-22 in regulating osteogenic differentiation. Target databases prediction and validation by Dual Luciferase Reporter Assay, western blot, and real-time polymerase chain reaction identified histone deacetylase 6 (HDAC6) as a direct downstream target of miR-22 in hADMSCs. Inhibition of endogenous HDAC6 by small-interfering RNAs suppressed adipogenesis and stimulated osteogenesis, consistent with the effect of miR-22 overexpression in hADMSCs. Together, our results suggested that miR-22 acted as a critical regulator of balance between adipogenic and osteogenic differentiation of hADMSCs by repressing its target HDAC6.

The success of treatment for sclerodermatous chronic graft-versus-host disease (ScGVHD) remains disappointing. The immunomodulatory ability of bone marrow (BM)-derived mesenchymal stem cells (MSCs) shows promise in treating GVHD, especially given its previous success in treating patients with acute GVHD (aGVHD). The potential efficacy and safety issues for treating cGVHD, particularly ScGVHD, remain to be clarified, however. Here, we report 4 patients with ScGVHD who received MSCs expanded ex vivo from unrelated donors by intra-BM injection. After MSC infusion, the ratio of helper T lymphocyte (Th) 1 cells to Th2 cells was dramatically reversed, with an increase in Th1 and a decrease in Th2 achieving a new balance. Correspondingly, symptoms gradually improved in all 4 patients. During the course of MSC treatment, the patients' vital signs and laboratory results remained normal. At the time of this report, none of the 4 patients had experienced recurrence of leukemia. Although this study alone cannot guarantee the application of MSCs in ScGVHD, our findings strongly suggest that this treatment is therapeutically practicable, with no detectable side effects. This approach may provide new insight into the clinical treatment of ScGVHD, with the aim of greatly increasing the survival rate in patients with leukemia who undergo allogeneic BM transplantation (BMT).

a b s t r a c tElucidation of the molecular mechanisms governing human adipose-derived mesenchymal stem cells (hASCs) osteogenic differentiation is of great importance for improving the treatment of bone-related diseases. In this study, we examined the role of microRNA (miR)-100 on the osteogenesis of hASCs. Overexpression of miR-100 inhibited osteogenic differentiation of hASCs in vitro, whereas downregulation of miR-100 enhanced the process. Target prediction analysis and dual luciferase report assay confirmed that bone morphogenetic protein receptor type II (BMPR2) was a direct target of miR-100. Furthermore, knockdown of BMPR2 by RNA interference inhibited osteogenic differentiation of hASCs, similar as the effect of upregulation miR-100. Taken together, our findings imply that miR-100 plays a negative role in osteogenic differentiation and might act through targeting BMPR2.