Single-cell transcriptome reveals cellular heterogeneity and lineage-specific regulatory changes of fibroblasts in post-traumatic urethral stricture.

Fibroblast is the critical repair cell for urethral wound healing. The dysfunction of fibroblasts can lead to excessive fibrosis and hypertrophic scar, which eventually leads to post-traumatic urethral stricture. However, the fibroblast subpopulation and intercellular communication in urethral stricture remains poorly understood. Therefore, a comprehensive single-cell resolution transcript landscape of human PTUS needs to be reported. We performed single-cell RNA-sequencing of 13,411 cells from post-urethral stricture tissue and adjacent normal tissue. Unsupervised clustering, function enrichment analysis, cell trajectory construction and intercellular communication analysis were applied to explore the cellular microenvironment and intercellular communication at single-cell level. We found that there is highly cell heterogeneity in urethral stricture tissue, which includes 11 cell lineages based on the cell markers. We identified the molecular typing of fibroblasts and indicated the key fibroblast subpopulations in the process of fibrogenesis during urethral stricture. The intercellular communication between fibroblasts and vascular endothelial cells was identified. As an important bridge in the communication, integrins may be a potential therapeutic target for post-traumatic urethral stricture. In conclusion, this study reveals the cellular heterogeneity and lineage-specific regulatory changes of fibroblasts in post-traumatic urethral stricture, thereby providing new insights and potential genes for post-traumatic urethral stricture treatment.

Physicochemical properties and cytotoxicities of Sr-containing biphasic calcium phosphate bone scaffolds.

This study demonstrates a new biomaterial system composed of Sr-containing hydroxyapatite (Sr-HA) and Sr-containing tricalcium phosphate (Sr-TCP), termed herein Sr-containing biphasic calcium phosphate (Sr-BCP). Furthermore, a series of new Sr-BCP porous scaffolds with tunable structure and properties has also been developed. These Sr-BCP scaffolds were obtained by in situ sintering of a series of composites formed by casting various Sr-containing calcium phosphate cement (Sr-CPC) into different rapid prototyping (RP) porous phenol formaldehyde resins, which acted as the negative moulds for controlling pore structures of the final scaffolds. Results show that the porous Sr-BCP scaffolds are composed of Sr-HA and Sr-TCP. The phase composition and the macro-structure of the Sr-BCP scaffold could be adjusted by controlling the processing parameters of the Sr-CPC pastes and the structure parameters of the RP negative mould, respectively. It is also found that both the compressive strength (CS) and the dissolving rate of the Sr-BCP scaffold significantly vary with their phase composition and macropore percentage. In particular, the compressive strength achieves a maximum CS level of 9.20 +/- 1.30 MPa for the Sr-BCP scaffold with a Sr-HA/Sr-TCP weight ratio of 78:22, a macropore percentage of 30% (400-550 microm in size) and a total-porosity of 63.70%, significantly higher than that of the Sr-free BCP scaffold with similar porosity. All the extracts of the Sr-BCP scaffold exhibit no cytotoxicity. The current study shows that the incorporation of Sr plays an important role in positively improving the physicochemical properties of the BCP scaffold without introducing obvious cytotoxicity. It also reveals a potential clinical application for this material system as bone tissue engineering (BTE) scaffold.

Long-term variations in mechanical properties and in vivo degradability of CPC/PLGA composite.

A new type of bone cement composite was successfully achieved by mixing degradable biosecure polylactic-co-glycolic acid (PLGA) fibers with high initial strength calcium phosphate cement (CPC). Its higher initial strength was mainly responsible for the in situ reinforcing effect of residual tetra-calcium phosphate monoxide (r-TTCP) particles reported in our previous work. So this bone cement composite containing fibers and the controlling group could be termed as CPC/PLGA composite and pure CPC or fiber-free group, respectively. In this study, we had investigated mechanical properties and microstructures of the CPC/PLGA composite immersed in 0.9% saline solution for different time and its in vivo degradation behaviors after implanting in rabbit muscle and femur bone, respectively. Results showed that the incorporation of the degradable fibers not only greatly increased the initial toughness and flexural strength of the CPC/PLGA composite but also significantly improved its later osteo-conduction as well as degradation rate. The rabbit muscle implant tests showed that the weight loss ratio of the CPC/PLGA composite increased by 41.03% as compared to the pure CPC. And the rabbit femur implant tests showed that the composite exhibits outstanding biocompatibility and bioactivity and more excellent osteoconduction and degradability than the pure CPC.

Physicochemical properties of TTCP/DCPA system cement formed in physiological saline solution and its cytotoxicity.

In this paper, the physicochemical properties and cytotoxicity of calcium phosphate cement (CPC), prepared by mixing cement powders of tetracalcium phosphate (TTCP) and dicalcium phosphate (DCPA) with a cement liquid of physiological saline solution, were investigated. The microstructure evolution of various hardened cement bodies and their hydration crystals as a function of immersion time in similar physiological fluids, physiological saline solution (0.9% NaCl), or simulated body fluids (SBF), were also studied. Results show that the setting time of CPC is in the range of 12-15 min, which meets the clinical application demands. We also found that the mean compressive strength of the CPC samples immersed in SBF for 3 days is 104+/-10 MPa which reaches the transverse compressive strength, 106-133 MPa, of human long bone. The results obtained from both the X-ray powder diffraction analyses (XRD) and scanning electron microscopy (SEM) observations indicated that a reinforcing effect of some remaining TTCP particles in the early stages of immersion is mainly responsible for the increase in the initial strength. Although the CPC failed to keep this high level when immersed for a longer time, the initial reinforcing effect of the remaining TTCP particles provides advantages for clinical applications. This would be effective when the material is loaded at the very beginning of the implantation, especially for the material used as a fixation, which requires a certain initial strength in the early stages of the implantation. The cytotoxicity results showed that the relative growth rate (RGR%) of L929 cells on the CPC samples using physiological saline solution as a cement liquid was slightly superior to that of the samples using the 0.5 mol/L phosphate acid solution as the cement liquid. This was most likely caused by the pH difference between the two CPC samples immersed in a DMEM-BFS medium.

The influence of Sr doses on the in vitro biocompatibility and in vivo degradability of single-phase Sr-incorporated HAP cement.

In previous studies, we developed a new type of Sr-incorporated hydroxyapatite cement (Sr-HAC), which was shown to have many excellent physiochemical properties, by an ionic cement route (Guo et al., Biomaterials 2005;26:4073-4083). As a further study, the main aims of this article were to examine the Sr-HAC's in vitro biocompatibility, including acute toxicity, hemolytic reaction, pyrogen reaction, and cytoxicity, to evaluate its in vivo degradability during intramuscular and femur implantation, and also to investigate the influence of Sr doses on these properties. The in vitro results show that all of the Sr-HAC samples exhibit satisfactory biocompatibility, and the Sr/(Sr+Ca) molar ratio has an important effect on these properties. For example, the Sr-HAC with a Sr/(Sr+Ca) molar ratio of 5% (5% Sr-HAC) has higher biocompatibility than both the one with a Sr/(Sr+Ca) molar ratio of 10% (10% Sr-HAC) and the Sr-free one. The in vivo results of both the rabbit intramuscular and femur implantation experiments show that the Sr-HAC samples exhibit a much faster degradation rate than the Sr-free one, and that this also depends on the Sr/(Sr+Ca) molar ratio. Specifically, the mean degradation rate of the 10% Sr-HAC increases by an amplitude of 73.9 wt % compared with that of the Sr-free HAC. In addition, the optical transmission photographs show that the Sr doses play an important role on the interface between the implants and the new bone. The energy dispersion X-ray spectrum analysis indicates that there exists a gradient distribution of Sr element in the tight and bioactive interface between the implants and new bone, indicating that the Sr element takes a share in the mineralization of the new bone together with Ca element.