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. 2021 Aug 13:2021:1938819.
doi: 10.1155/2021/1938819. eCollection 2021.

SDF-1 α/OPF/BP Composites Enhance the Migrating and Osteogenic Abilities of Mesenchymal Stem Cells

Linli Li  1   2   3 , Xifeng Liu  1   2 , Bipin Gaihre  1   2 , Sungjo Park  4 , Yong Li  1   2 , Andre Terzic  4 , Lichun Lu  1   2
Affiliations

SDF-1 α/OPF/BP Composites Enhance the Migrating and Osteogenic Abilities of Mesenchymal Stem Cells

Linli Li et al. Stem Cells Int. .

Abstract

In situ cell recruitment is a promising regenerative medicine strategy with the purpose of tissue regeneration without stem cell transplantation. This chemotaxis-based strategy is aimed at ensuring a restorative environment through the release of chemokines that promote site-specific migration of healing cell populations. Stromal cell-derived factor-1α (SDF-1α) is a critical chemokine that can regulate the migration of mesenchymal stem cells (MSCs). Accordingly, here, SDF-1α-loaded microporous oligo[poly(ethylene glycol) fumarate]/bis[2-(methacryloyloxy)ethyl] phosphate composites (SDF-1α/OPF/BP) were engineered and probed. SDF-1α/OPF/BP composites were loaded with escalating SDF-1α concentrations, namely, 0 ng/ml, 50 ng/ml, 100 ng/ml, and 200 ng/ml, and were cocultured with MSC. Scratching assay, Transwell assay, and three-dimensional migration model were utilized to assess the migration response of MSCs. Immunofluorescence staining of Runx2 and osteopontin (OPN), ELISA assay of osteocalcin (OCN) and alkaline phosphatase (ALP), and Alizarin Red S staining were conducted to assess the osteogenesis of MSCs. All SDF-1α/OPF/BP composites engendered a release of SDF-1α (>80%) during the first four days. SDF-1α released from the composites significantly promoted migration and osteogenic differentiation of MSCs documented by upregulated expression of osteogenic-related proteins, ALP, Runx2, OCN, and OPN. SDF-1α at 100 ng/ml was optimal for enhanced migration and osteogenic proficiency. Thus, designed SDF-1α/OPF/BP composites were competent in promoting the homing and osteogenesis of MSCs and thus offer a promising bioactive scaffold candidate for on-demand bone tissue regeneration.

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Conflict of interest statement

The authors declared that they have no conflicts of interest to this work.

Figures

Figure 1
Figure 1
Three-dimensional migration assay of MSCs on the four groups of SDF-1α/OPF/BP composites. (a) Schematic illustration of the three-dimensional migration model. (b) 3D spheroid migration assay showed that the migrating distances of the SDF100 and SDF200 groups were higher than those of the SDF50 and control groups. (c) Calcein AM staining of 3D spheroids after 72 hours of culture with SDF-1α/OPF/BP composites. The red line indicates the distance of migrating cells.
Figure 2
Figure 2
(a) Schematic illustration of the construction of SDF-1α/OPF/BP composites for the repair of the bone defect. (b, c) SEM images of OPF/BP hydrogel. (d) AFM image of OPF/BP hydrogel. (e) Photograph of OPF/BP hydrogel discs. (f) Release profiles of SDF-1α/OPF/BP composites showed the concentrations of SDF-1α in the culture medium. The release curve showed all groups reached 80% release percentage on the 4th day.
Figure 3
Figure 3
Two-dimensional migration assay of MSCs on the four groups of SDF-1α/OPF/BP composites. (a) Scratching assay of MSCs (light micrographs) and (b) Transwell assay of MSCs (fluorescent micrographs stained by calcein AM staining). (c) Scratching assay showed that the wound healing rates of the SDF100 and SDF200 groups were significantly higher (∗p < 0.05) than those of the SDF50 and control groups. (d) Transwell assay showed that the migrating rates of the three SDF groups were significantly higher (∗p < 0.05) than those of the control group on the first day, and the migrating rates of the SDF100 and SDF200 groups were significantly higher (∗p < 0.05) than those of the SDF50 and control groups on the second day. The red line indicates areas without migrating cells.
Figure 4
Figure 4
CXCR4 immunofluorescence staining of rat BMSCs. (a) CXCR4 immunofluorescence staining after 96 hours of coculture with SDF-1α/OPF/BP composites. (b) The percentage of CXCR4-positive areas of the SDF200, SDF100, and SDF50 groups was significantly higher (∗p < 0.05) than that of the control group.
Figure 5
Figure 5
Osteogenic differentiation assays of MSCs after 21 days of culture on the four groups of SDF-1α/OPF/BP composites. (a) Runx2 immunofluorescence staining on the 21st day of osteogenic differentiation. (b) Alizarin Red S staining on the 21st day of osteogenic differentiation. (c) The percentage of Runx2-positive areas of the SDF200 and SDF100 groups was significantly higher (∗p < 0.05) than that of the SDF50 and control groups. (d) The percentage of Alizarin Red S stained area of the SDF200 and SDF100 groups was significantly higher (∗p < 0.05) than that of the SDF50 and control groups.
Figure 6
Figure 6
Osteogenic differentiation assays of MSCs after 14 and 21 days of culture on the four groups of SDF-1α/OPF/BP composites. (a) OPN immunofluorescence staining on the 21st day of osteogenic differentiation. (b) The percentage of OPN-positive areas of the SDF200 and SDF100 groups was significantly higher (∗p < 0.05) than that of the SDF50 and control groups. (c) ALP assay showed that ALP expression levels of the four groups were similar at day 14, while the expression levels in the control group were significantly lower (∗p < 0.05) than those of the other three groups on the 21st day. (d) OCN assay showed that the OCN expression levels in the SDF200 and SDF100 groups were significantly higher (∗p < 0.05) than those of the SDF50 and control groups on both days 14 and 21.
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