| 1. |
- Chau, Michael, et al.
(författare)
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The synovial microenvironment suppresses chondrocyte hypertrophy and promotes articular chondrocyte differentiation
- 2022
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Ingår i: NPJ Regenerative medicine. - : Nature Publishing Group. - 2057-3995. ; 7:1
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Tidskriftsartikel (refereegranskat)abstract
- During the development of the appendicular skeleton, the cartilaginous templates undergo hypertrophic differentiation and remodels into bone, except for the cartilage most adjacent to joint cavities where hypertrophic differentiation and endochondral bone formation are prevented, and chondrocytes instead form articular cartilage. The mechanisms that prevent hypertrophic differentiation and endochondral bone formation of the articular cartilage have not been elucidated. To explore the role of the synovial microenvironment in chondrocyte differentiation, osteochondral allografts consisting of articular cartilage, epiphyseal bone, and growth plate cartilage from distal femoral epiphyses of inbred Lewis rats expressing enhanced green fluorescent protein from a ubiquitous promoter were transplanted either in inverted or original (control) orientation to matching sites in wildtype littermates, thereby allowing for tracing of transplanted cells and their progenies. We found that no hypertrophic differentiation occurred in the growth plate cartilage ectopically placed at the joint surface. Instead, the transplanted growth plate cartilage, with time, remodeled into articular cartilage. This finding suggests that the microenvironment at the articular surface inhibits hypertrophic differentiation and supports articular cartilage formation. To explore this hypothesis, rat chondrocyte pellets were cultured with and without synoviocyte-conditioned media. Consistent with the hypothesis, hypertrophic differentiation was inhibited and expression of the articular surface marker lubricin (Prg4) was dramatically induced when chondrocyte pellets were exposed to synovium- or synoviocyte-conditioned media, but not to chondrocyte- or osteoblast-conditioned media. Taken together, we present evidence for a novel mechanism by which synoviocytes, through the secretion of a factor or factors, act directly on chondrocytes to inhibit hypertrophic differentiation and endochondral bone formation and promote articular cartilage formation. This mechanism may have important implications for articular cartilage development, maintenance, and regeneration.
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| 2. |
- Islam, Mohammad Mirazul, 1984-, et al.
(författare)
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Biomaterials-enabled cornea regeneration in patients at high risk for rejection of donor tissue transplantation
- 2018
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Ingår i: NPJ Regenerative medicine. - : Springer Science and Business Media LLC. - 2057-3995. ; 3
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Tidskriftsartikel (refereegranskat)abstract
- The severe worldwide shortage of donor organs, and severe pathologies placing patients at high risk for rejecting conventional cornea transplantation, have left many corneal blind patients untreated. Following successful pre-clinical evaluation in mini-pigs, we tested a biomaterials-enabled pro-regeneration strategy to restore corneal integrity in an open-label observational study of six patients. Cell-free corneal implants comprising recombinant human collagen and phosphorylcholine were grafted by anterior lamellar keratoplasty into corneas of unilaterally blind patients diagnosed at high-risk for rejecting donor allografts. They were followed-up for a mean of 24 months. Patients with acute disease (ulceration) were relieved of pain and discomfort within 1-2 weeks post-operation. Patients with scarred or ulcerated corneas from severe infection showed better vision improvement, followed by corneas with burns. Corneas with immune or degenerative conditions transplanted for symptom relief only showed no vision improvement overall. However, grafting promoted nerve regeneration as observed by improved touch sensitivity to near normal levels in all patients tested, even for those with little/no sensitivity before treatment. Overall, three out of six patients showed significant vision improvement. Others were sufficiently stabilized to allow follow-on surgery to restore vision. Grafting outcomes in mini-pig corneas were superior to those in human subjects, emphasizing that animal models are only predictive for patients with non-severely pathological corneas; however, for establishing parameters such as stable corneal tissue and nerve regeneration, our pig model is satisfactory. While further testing is merited, we have nevertheless shown that cell-free implants are potentially safe, efficacious options for treating high-risk patients.
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| 3. |
- Padma, Arvind M., et al.
(författare)
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Towards a bioengineered uterus: bioactive sheep uterus scaffolds are effectively recellularized by enzymatic preconditioning
- 2021
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Ingår i: Npj Regenerative Medicine. - : Springer Science and Business Media LLC. - 2057-3995. ; 6:1
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Tidskriftsartikel (refereegranskat)abstract
- Uterine factor infertility was considered incurable until recently when we reported the first successful live birth after uterus transplantation. However, risky donor surgery and immunosuppressive therapy are factors that may be avoided with bioengineering. For example, transplanted recellularized constructs derived from decellularized tissue restored fertility in rodent models and mandate translational studies. In this study, we decellularized whole sheep uterus with three different protocols using 0.5% sodium dodecyl sulfate, 2% sodium deoxycholate (SDC) or 2% SDC, and 1% Triton X-100. Scaffolds were then assessed for bioactivity using the dorsal root ganglion and chorioallantoic membrane assays, and we found that all the uterus scaffolds exhibited growth factor activity that promoted neurogenesis and angiogenesis. Extensive recellularization optimization was conducted using multipotent sheep fetal stem cells and we report results from the following three in vitro conditions; (a) standard cell culturing conditions, (b) constructs cultured in transwells, and (c) scaffolds preconditioned with matrix metalloproteinase 2 and 9. The recellularization efficiency was improved short-term when transwells were used compared with standard culturing conditions. However, the recellularization efficiency in scaffolds preconditioned with matrix metalloproteinases was 200-300% better than the other strategies evaluated herein, independent of decellularization protocol. Hence, a major recellularization hurdle has been overcome with the improved recellularization strategies and in vitro platforms described herein. These results are an important milestone and should facilitate the production of large bioengineered grafts suitable for future in vivo applications in the sheep, which is an essential step before considering these principles in a clinical setting.
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| 4. |
- Togninalli, Matteo, et al.
(författare)
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Machine learning-based classification of dual fluorescence signals reveals muscle stem cell fate transitions in response to regenerative niche factors
- 2023
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Ingår i: NPJ REGENERATIVE MEDICINE. - : Springer Nature. - 2057-3995. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- The proper regulation of muscle stem cell (MuSC) fate by cues from the niche is essential for regeneration of skeletal muscle. How pro-regenerative niche factors control the dynamics of MuSC fate decisions remains unknown due to limitations of population-level endpoint assays. To address this knowledge gap, we developed a dual fluorescence imaging time lapse (Dual-FLIT) microscopy approach that leverages machine learning classification strategies to track single cell fate decisions with high temporal resolution. Using two fluorescent reporters that read out maintenance of stemness and myogenic commitment, we constructed detailed lineage trees for individual MuSCs and their progeny, classifying each division event as symmetric self-renewing, asymmetric, or symmetric committed. Our analysis reveals that treatment with the lipid metabolite, prostaglandin E2 (PGE2), accelerates the rate of MuSC proliferation over time, while biasing division events toward symmetric self-renewal. In contrast, the IL6 family member, Oncostatin M (OSM), decreases the proliferation rate after the first generation, while blocking myogenic commitment. These insights into the dynamics of MuSC regulation by niche cues were uniquely enabled by our Dual-FLIT approach. We anticipate that similar binary live cell readouts derived from Dual-FLIT will markedly expand our understanding of how niche factors control tissue regeneration in real time.
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