Induced Periosteum-Mimicking Membrane with Cell Barrier and Multipotential Stromal Cell (MSC) Homing Functionalities.

The current management of critical size bone defects (CSBDs) remains challenging and requires multiple surgeries. To reduce the number of surgeries, wrapping a biodegradable fibrous membrane around the defect to contain the graft and carry biological stimulants for repair is highly desirable. Poly(ε-caprolactone) (PCL) can be utilised to realise nonwoven fibrous barrier-like structures through free surface electrospinning (FSE). Human periosteum and induced membrane (IM) samples informed the development of an FSE membrane to support platelet lysate (PL) absorption, multipotential stromal cells (MSC) growth, and the prevention of cell migration. Although thinner than IM, periosteum presented a more mature vascular system with a significantly larger blood vessel diameter. The electrospun membrane (PCL3%-E) exhibited randomly configured nanoscale fibres that were successfully customised to introduce pores of increased diameter, without compromising tensile properties. Additional to the PL absorption and release capabilities needed for MSC attraction and growth, PCL3%-E also provided a favourable surface for the proliferation and alignment of periosteum- and bone marrow derived-MSCs, whilst possessing a barrier function to cell migration. These results demonstrate the development of a promising biodegradable barrier membrane enabling PL release and MSC colonisation, two key functionalities needed for the in situ formation of a transitional periosteum-like structure, enabling movement towards single-surgery CSBD reconstruction.

Effect of Combined Intraosseous and Intraarticular Infiltrations of Autologous Platelet-Rich Plasma on Subchondral Bone Marrow Mesenchymal Stromal Cells from Patients with Hip Osteoarthritis.

Osteoarthritis (OA) is a debilitating condition that significantly impacts its patients and is closely associated with advancing age and senescence. Treatment with autologous platelet rich plasma (PRP) is a novel approach that is increasingly being researched for its effects. Subchondral bone mesenchymal stromal cells (MSCs) are key progenitors that form bone and cartilage lineages that are affected in OA. This study investigated the changes in subchondral bone MSCs before and after combined intraosseous (IO) and intraarticular (IA) PRP infiltration. Patient bone marrow aspirates were collected from 12 patients (four male, eight female) aged 40-86 years old (median 59.5). MSCs were expanded in standard media containing human serum to passage 1 and analysed for their colony-forming potential, senescence status, and gene expression. Hip dysfunction and Osteoarthritis Outcome Score (HOOS) at baseline and 6 months post second infiltration were used to assess the clinical outcomes; seven patients were considered responders and five non-responders. The number of colony-forming MSCs did not increase in the post treatment group, however, they demonstrated significantly higher colony areas (14.5% higher compared to Pre) indicative of enhanced proliferative capacity, especially in older donors (28.2% higher). Senescence assays also suggest that older patients and responders had a higher resistance to senescent cell accumulation. Responder and non-responder MSCs tended to differ in the expression of genes associated with bone formation and cartilage turnover including osteoblast markers, matrix metalloproteinases, and their inhibitors. Taken together, our data show that in hip OA patients, combined IO and IA PRP infiltrations enhanced subchondral MSC proliferative and stress-resistance capacities, particularly in older patients. Future investigation of the potential anti-ageing effect of PRP infiltrations and the use of next-generation sequencing would contribute towards better understanding of the molecular mechanisms associated with OA in MSCs.

Colony Formation, Migratory, and Differentiation Characteristics of Multipotential Stromal Cells (MSCs) from "Clinically Accessible" Human Periosteum Compared to Donor-Matched Bone Marrow MSCs.

Periosteum is vital for fracture healing, as a highly vascular and multipotential stromal cell- (MSC-) rich tissue. During surgical bone reconstruction, small fragments of periosteum can be "clinically accessible," yet periosteum is currently not ultilised, unlike autologous bone marrow (BM) aspirate. This study is aimed at comparing human periosteum and donor-matched iliac crest BM MSC content and characterising MSCs in terms of colony formation, growth kinetics, phenotype, cell migration patterns, and trilineage differentiation capacity. "Clinically accessible" periosteum had an intact outer fibrous layer, containing CD271+ candidate MSCs located perivasculary; the inner cambium was rarely present. Following enzymatic release of cells, periosteum formed significantly smaller fibroblastic colonies compared to BM (6.1 mm2 vs. 15.5 mm2, n = 4, P = 0.0006). Periosteal colonies were more homogenous in size (range 2-30 mm2 vs. 2-54 mm2) and on average 2500-fold more frequent (2.0% vs. 0.0008%, n = 10, P = 0.004) relative to total viable cells. When expanded in vitro, similar growth rates up to passage 0 (P0) were seen (1.8 population doublings (PDs) per day (periosteum), 1.6 PDs per day (BM)); however, subsequently BM MSCs proliferated significantly slower by P4 (4.3 PDs per day (periosteum) vs. 9.3 PDs per day (BM), n = 9, P = 0.02). In early culture, periosteum cells were less migratory at slower speeds than BM cells. Both MSC types exhibited MSC phenotype and trilineage differentiation capacity; however, periosteum MSCs showed significantly lower (2.7-fold) adipogenic potential based on Nile red : DAPI ratios with reduced expression of adipogenesis-related transcripts PPAR-γ. Altogether, these data revealed that "clinically accessible" periosteal samples represent a consistently rich source of highly proliferative MSCs compared to donor-matched BM, which importantly show similar osteochondral capacity and lower adipogenic potential. Live cell tracking allowed determination of unique morphological and migration characteristics of periosteal MSCs that can be used for the development of novel bone graft substitutes to be preferentially repopulated by these cells.

Variation of Piezoelectric properties and mechanisms across the relaxor-like/Ferroelectric continuum in BiFeO3- (K0.5Bi0.5)TiO3-PbTiO3 ceramics.

1- x - y)BiFeO3-x(K0.5Bi0.5)TiO3-yPbTiO3 (BFKBT- PT) piezoelectric ceramics were investigated across the compositional space and contrasted against the xBiFeO3- (1-x)(K0.5Bi0.5)TiO3 (BF-KBT) system, whereby a range of relaxor-like/ferroelectric behavior was observed. Structural and piezoelectric properties were closely related to the PbTiO3 concentration; below a critical concentration, relaxor-like behavior was identified. The mechanisms governing the piezoelectric behavior were investigated with structural, electrical, and imaging techniques. X-ray diffraction established that longrange non-centrosymmetric crystallographic order was evident above a critical PbTiO3 concentration, y > 0.1125. Commensurate with the structural analysis, electric-field-induced strain responses showed electrostrictive behavior in the PbTiO3-reduced compositions, with increased piezoelectric switching in PbTiO3-rich compositions. Positive-up-negative-down (PUND) analysis was used to confirm electric-field-induced polarization measurements, elucidating that the addition of PbTiO3 increased the switchable polarization and ferroelectric ordering. Piezoresponse force microscopy (PFM) of the BF-KBT-PT system exhibited typical domain patterns above a critical PbTiO3 threshold, with no ferroelectric domains observed in the BF-KBT system in the pseudocubic region. Doping of BiFeO3-PbTiO3 has been unsuccessful in the search for hightemperature materials that offer satisfactory piezoelectric properties; however, this system demonstrates that the partial substitution of alternative end-members can be an effective method. The partial substitution of PbTiO3 into BF-KBT enables long-range non-centrosymmetric crystallographic order, resulting in increased polar order and TC, compared with the pseudocubic region. The search for novel high-temperature piezoelectric ceramics can therefore exploit the accommodating nature of the perovskite family, which allows significant variance in chemical and physical characters in the exploration of new solid-solutions.