The strategy and method in modulating finger regeneration

DLP fabrication of customized porous bioceramics with osteoinduction ability for remote isolation bone regeneration

Currently, various bioceramics have been widely used in bone regeneration. However, it remains a huge challenge to remote isolation bone regeneration, such as severed finger regeneration. The remote isolation bone tissue has a poor regenerative microenvironment that lacks enough blood and nutrition supply. It is very difficult to repair and regenerate. In this study, well-controlled multi-level porous 3D-printed calcium phosphate (CaP) bioceramic scaffolds with precision customized structures were fabricated by high-resolution digital light projection (DLP) printing technology for remote isolation bone regeneration. In vitro results demonstrated that optimizing material processing procedures could achieve multi-level control of 3D-printed CaP bioceramic scaffolds and enhance the osteoinduction ability of bioceramics effectively. In vivo results indicated that 3D-printed CaP bioceramic scaffolds constructed by optimized processing procedure exhibited a promising ability of bone regeneration and osteoinduction in ectopic osteogenesis and in situ caudal vertebrae regeneration in beagles. This study provided a promising strategy based on 3D-printed CaP bioceramic scaffolds constructed by optimized processing procedures for remote isolation bone regeneration, such as severed finger regeneration.

From the Basis of Epimorphic Regeneration to Enhanced Regenerative Therapies

Current cell-based therapies to treat degenerative diseases such as osteoarthritis (OA) fail to offer long-term beneficial effects. The therapeutic effects provided by mesenchymal stem cell (MSC) injection, characterized by reduced pain and an improved functional activity in patients with knee OA, are reported at short-term follow-up since the improved outcomes plateau or, even worse, decline several months after MSC administration. This review tackles the limitations of MSC-based therapy for degenerative diseases and highlights the lessons learned from regenerative species to comprehend the coordination of molecular and cellular events critical for complex regeneration processes. We discuss how MSC injection generates a positive cascade of events resulting in a long-lasting systemic immune regulation with limited beneficial effects on tissue regeneration while in regenerative species fine-tuned inflammation is required for progenitor cell proliferation, differentiation, and regeneration. Finally, we stress the direct or indirect involvement of neural crest derived cells (NCC) in most if not all adult regenerative models studied so far. This review underlines the regenerative potential of NCC and the limitations of MSC-based therapy to open new avenues for the treatment of degenerative diseases such as OA.

Long-Term Outcomes of Atasoy Flap in Children With Distal Finger Trauma

PURPOSE

Distal finger trauma is one of the most frequent emergencies in children and has the potential for functional and cosmetic damage to the hand. The Atasoy flap (AF) is a vascularized, subcutaneous pedicle V-Y advancement flap used to cover a loss of distal finger substance. Our hypothesis was that the AF is a safe, reliable flap that results in few complications and gives satisfactory functional and cosmetic results in children.

METHODS

We retrospectively assessed children with distal finger trauma and AF pulp reconstruction in our pediatric orthopedic department between 2008 and 2017. The lesion zone was classified, and we also evaluated necrosis, infection, the shape of the pulp, pulp sensitivity (Weber test), hyponychial scarring, and the presence of a hook nail deformity. Lastly, we compared patients who developed a hook nail with those who did not.

RESULTS

Thirty children were included (mean age at trauma, 6.4 years [range, 1.3-15.7 years]). In 21 cases, the finger damage was located in Ishikawa subzone II. No cases of necrosis or infection were reported. Epicritical tactile sensitivity was good in 20 patients (67%). A hook nail deformity was observed in 15 children (50%) and hyponychial scarring in 22 patients (73%). The pulp had a normal shape in 13 children (43%). The hook nail group displayed more hyponychial scarring, greater nail dystrophy, and lower pulp sensitivity.

CONCLUSIONS

The AF yielded contrasting results. High reliability, good coverage, and minimal donor-site morbidity were compromised by suboptimal tip length/shape, nail appearance, and sensitivity.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Regeneration and Regrowth Potentials of Digit Tips in Amphibians and Mammals

Tissue regeneration and repair have received much attention in the medical field over the years. The study of amphibians, such as newts and salamanders, has uncovered many of the processes that occur in these animals during full-limb/digit regeneration, a process that is highly limited in mammals. Understanding these processes in amphibians could shed light on how to develop and improve this process in mammals. Amputation injuries in mammals usually result in the formation of scar tissue with limited regrowth of the limb/digit; however, it has been observed that the very tips of digits (fingers and toes) can partially regrow in humans and mice under certain conditions. This review will summarize and compare the processes involved in salamander limb regeneration, mammalian wound healing, and digit regeneration in mice and humans.

PAR2 regulates regeneration, transdifferentiation, and death

Understanding the mechanisms by which cells sense and respond to injury is central to developing therapies to enhance tissue regeneration. Previously, we showed that pancreatic injury consisting of acinar cell damage+β-cell ablation led to islet cell transdifferentiation. Here, we report that the molecular mechanism for this requires activating protease-activated receptor-2 (PAR2), a G-protein-coupled receptor. PAR2 modulation was sufficient to induce islet cell transdifferentiation in the absence of β-cells. Its expression was modulated in an islet cell type-specific manner in murine and human type 1 diabetes (T1D). In addition to transdifferentiation, PAR2 regulated β-cell apoptosis in pancreatitis. PAR2's role in regeneration is broad, as mice lacking PAR2 had marked phenotypes in response to injury in the liver and in digit regeneration following amputation. These studies provide a pharmacologically relevant target to induce tissue regeneration in a number of diseases, including T1D.

In vitro activation of the neuro-transduction mechanism in sensitive organotypic human skin model

Recent advances in tissue engineering have encouraged researchers to endeavor the production of fully functional three-dimensional (3D) thick human tissues in vitro. Here, we report the fabrication of a fully innervated human skin tissue in vitro that recapitulates and replicates skin sensory function. Previous attempts to innervate in vitro 3D skin models did not demonstrate an effective functionality of the nerve network. In our approach, we initially engineer functional human skin tissue based on fibroblast-generated dermis and differentiated epidermis; then, we promote rat dorsal root ganglion (DRG) neurons axon ingrowth in the de-novo developed tissue. Neurofilaments network infiltrates the entire native dermis extracellular matrix (ECM), as demonstrated by immunofluorescence and second harmonic generation (SHG) imaging. To prove sensing functionality of the tissue, we use topical applications of capsaicin, an agonist of transient receptor protein-vanilloid 1 (TRPV1) channel, and quantify calcium currents resulting from variations of Ca⁺⁺ concentration in DRG neurons innervating our model. Calcium currents generation demonstrates functional cross-talking between dermis and epidermis compartments. Moreover, through a computational fluid dynamic (CFD) analysis, we set fluid dynamic conditions for a non-planar skin equivalent growth, as proof of potential application in creating skin grafts tailored on-demand for in vivo wound shape.

Functional differences between neonatal and adult fibroblasts and keratinocytes: Donor age affects epithelial-mesenchymal crosstalk in vitro

Clinical evidence suggests that healing is faster and almost scarless at an early neonatal age in comparison with that in adults. In this study, the phenotypes of neonatal and adult dermal fibroblasts and keratinocytes (nestin, smooth muscle actin, keratin types 8, 14 and 19, and fibronectin) were compared. Furthermore, functional assays (proliferation, migration, scratch wound closure) including mutual epithelial-mesenchymal interactions were also performed to complete the series of experiments. Positivity for nestin and α smooth muscle actin was higher in neonatal fibroblasts (NFs) when compared with their adult counterparts (adult fibroblasts; AFs). Although the proliferation of NFs and AFs was similar, they significantly differed in their migration potential. The keratinocyte experiments revealed small, poorly differentiated cells (positive for keratins 8, 14 and 19) in primary cultures isolated from neonatal tissues. Moreover, the neonatal keratinocytes exhibited significantly faster rates of healing the experimentally induced in vitro defects in comparison with adult cells. Notably, the epithelial/mesenchymal interaction studies showed that NFs in co-culture with adult keratinocytes significantly stimulated the adult epithelial cells to acquire the phenotype of small, non-confluent cells expressing markers of poor differentiation. These results indicate the important differences between neonatal and adult cells that may be associated with improved wound healing during the early neonatal period.

Tissue engineering a human phalanx

A principal purpose of tissue engineering is the augmentation, repair or replacement of diseased or injured human tissue. This study was undertaken to determine whether human biopsies as a cell source could be utilized for successful engineering of human phalanges consisting of both bone and cartilage. This paper reports the use of cadaveric human chondrocytes and periosteum as a model for the development of phalanx constructs. Two factors, osteogenic protein-1 [OP-1/bone morphogenetic protein-7 (BMP7)], alone or combined with insulin-like growth factor (IGF-1), were examined for their potential enhancement of chondrocytes and their secreted extracellular matrices. Design of the study included culture of chondrocytes and periosteum on biodegradable polyglycolic acid (PGA) and poly-l-lactic acid (PLLA)-poly-ε-caprolactone (PCL) scaffolds and subsequent implantation in athymic nu/nu (nude) mice for 5, 20, 40 and 60 weeks. Engineered constructs retrieved from mice were characterized with regard to genotype and phenotype as a function of developmental (implantation) time. Assessments included gross observation, X-ray radiography or microcomputed tomography, histology and gene expression. The resulting data showed that human cell-scaffold constructs could be successfully developed over 60 weeks, despite variability in donor age. Cartilage formation of the distal phalanx models enhanced with both OP-1 and IGF-1 yielded more cells and extracellular matrix (collagen and proteoglycans) than control chondrocytes without added factors. Summary data demonstrated that human distal phalanx models utilizing cadaveric chondrocytes and periosteum were successfully fabricated and OP-1 and OP-1/IGF-1 accelerated construct development and mineralization. The results suggest that similar engineering and transplantation of human autologous tissues in patients are clinically feasible. Copyright © 2016 John Wiley & Sons, Ltd.