Combined platelet and plasma derivatives enhance proliferation of stem/progenitor cells maintaining their differentiation potential.

BACKGROUND AIMS: Platelet derivatives have been proposed as alternatives to animal sera given that for cell therapy applications, the use of fetal bovine/calf serum (FBS/FCS) is subjected to severe limitations for safety and ethical concerns. We developed a cell culture medium additive obtained by the combination of two blood-derived standardized components. METHODS: A platelet lysate (PL) and a platelet-poor plasma (PPP) were produced in a lyophilized form. Each component was characterized for its growth factor content (platelet-derived growth factor-BB/vascular endothelial growth factor). PL and PPP were used as single components or in combination in different ratio at cumulative 5% final concentration in the culture medium. RESULTS: The single components were less effective than the component combination. In primary cell cultures (bone marrow stromal cells, adipose derived adult stem cells, osteoblasts, chondrocytes, umbilical cord-derived mesenchymal stromal cells, lymphocytes), the PL/PPP supplement promoted an increased cell proliferation in respect to the standard FCS culture in a dose-dependent manner, maintaining the cell functionality, clonogenicity, phenotype and differentiative properties throughout the culture. At a different component ratio, the supplement was also used to support proliferation of a cell line (U-937). CONCLUSIONS: The PL/PPP supplement is an efficient cell culture medium additive that can replace FCS to promote cell proliferation. It can outdo FCS, especially when adopted in primary cultures from tissue biopsies. Moreover, the dual component nature of the supplement allows the researcher to determine the more appropriate ratio of the two components for the nutritional and functional requirements of the cell type of interest.

Biological activity of a standardized freeze-dried platelet derivative to be used as cell culture medium supplement.

Serum of animal origin and in particular fetal bovine serum is the most commonly utilized cell culture medium additive for in vitro cell growth and differentiation. However, several major concerns have been raised by the scientific community regarding the use of animal sera for human cell-based culture applications. Among the possible alternatives to the animal serum, platelet-derived compounds have been proposed since more than 10 years. Nevertheless, the high degree of variability between the different platelet preparations, and the lack of standardized manufacturing and quality control procedures, made difficult to reach a consensus on the applicability of this novel cell culture medium supplement. In this study, we describe the preparation of a standardized platelet-rich plasma (PRP) derivative obtained starting from human-certified buffy coat samples with a defined platelet concentration and following protocols including also freeze-drying, gamma irradiation and biological activity testing prior the product release as cell culture medium additive. Biological activity testing of the different preparations was done by determining the capability of the different PRP preparations to sustain human bone marrow mesenchymal stem cell (MSC) clone formation and proliferation. Taking advantage of a developed MSC in vitro clonogenicity test, we also determined biological activity and stability of the freeze-dried gamma-sterilized PRP preparations after their storage for different times and at different temperatures. The PRP effects on cell proliferation were determined both on primary cell cultures established from different tissues and on a cell line. Results were compared with those obtained in "traditional" parallel control cultures performed in the presence of bovine serum [10% fetal calf serum (FCS)]. Compared to FCS, the PRP addition to the culture medium increased the MSC colony number and average size. In primary cell cultures and in cell line cultures, the PRP promoted cell proliferation also in conditions where the FCS had not a proliferation stimulating effect due to either the nature of the cells and the tissue of origin (such as human articular chondrocytes from elderly patients) or to the critical low density cell seeding (such as for HeLa cells). In summary, the standardized PRP formulation would provide an "off-the-shelf" product to be used for the selection and expansion of several cell types also in critical cell culture conditions.

Osteogenic differentiation of human mesenchymal stromal cells on surface-modified titanium alloys for orthopedic and dental implants.

PURPOSE: Surface properties of titanium alloys, used for orthopedic and dental applications, are known to affect implant interactions with host tissues. Osteointegration, bone growth and remodeling in the area surrounding the implants can be implemented by specific biomimetic treatments; these allow the preparation of micro/nanostructured titanium surfaces with a thickened oxide layer, doped with calcium and phosphorus ions. We have challenged these experimental titanium alloys with primary human bone marrow stromal cells to compare the osteogenic differentiation outcomes of the cells once they are seeded onto the modified surfaces, thus simulating a prosthetic device-biological interface of clinical relevance. METHODS: A specific anodic spark discharge was the biomimetic treatment of choice, providing experimental titanium disks treated with different alkali etching approaches. The disks, checked by electron microscopy and spectroscopy, were subsequently used as substrates for the proliferation and osteogenic differentiation of human cells. Expression of markers of the osteogenic lineage was assessed by means of qualitative and quantitative PCR, by cytochemistry, immunohistochemistry, Western blot and matrix metalloprotease activity analyses. RESULTS: Metal surfaces were initially less permissive for cell growth. Untreated control substrates were less efficient in sustaining mineralized matrix deposition upon osteogenic induction of the cells. Interestingly, bone sialo protein and matrix metalloprotease 2 levels were enhanced on experimental metals compared to control surfaces, particularly for titanium oxide coatings etched with KOH. DISCUSSION: As a whole, the KOH-modification of titanium surfaces seems to allow the best osteogenic differentiation of human mesenchymal stromal cells, representing a possible plus for future clinical prosthetic applications.

DLX5 overexpression impairs osteogenic differentiation of human bone marrow stromal cells.

The transcription factor DLX5 belongs to a family of homeoproteins required for craniofacial morphogenesis and forebrain development. DLX5 is expressed during formation of several skeletal elements such as cartilage, teeth and bone, and its knockout causes severe craniofacial malformations with a delay in the ossification process. Bone marrow contains mesenchymal progenitor cells which may differentiate along multiple pathways, therefore representing an interesting in vitro and in vivo model to study the mesodermal lineage differentiation. Here we report the effect of DLX5 overexpression in ex vivo expanded human bone marrow stromal cells by retroviral infection on the osteogenic lineage differentiation. A reduced mineral deposition was observed in DLX5-transduced cells upon osteogenic induction in culture. When DLX5-transduced cells were implanted in immunodeficient mice, a 60% reduction in bone matrix deposition was observed, whereas the in vitro chondrogenic potential was unaffected. A quantitative gene expression study indicated that DLX5 overexpression does not affect the early osteogenic commitment of bone marrow stromal cells but prevents their terminal differentiation. This block may be mediated by the observed persistent expression of SOX2, a transcription factor known to inhibit osteogenic differentiation.

Platelet-rich plasma-based bioactive membrane as a new advanced wound care tool.

Chronic skin ulcers, consequence of diabetes and other pathological conditions, heavily compromise the patient life quality and represent a high and constantly growing cost for National Health Services. Autologous platelet-rich plasma (PRP), has been proposed to treat these lesions. The absence of guidelines for the PRP production and the need of a fresh preparation for each treatment lead us to develop a protocol for the production of an allogenic PRP-based bioactive membrane (BAM), standardized for platelet concentration and growth factor release. This work compares BAMs obtained starting from two different platelet concentrations. There was no direct correlation between the amount of growth factors released by BAM in vitro and the initial platelet count. However, different release kinetics were noticed for different growth factors, suggesting that they were differently retained by the two BAMs. The angiogenic potential of both BAMs was determined by Luminex Angiogenesis Assay. The biological activity of the factors released by the two BAMs was confirmed by cell proliferation and migration. A diabetic mouse chronic ulcer model was used to define the best PRP therapeutic dose in vivo. Both BAMs induced wound healing by increasing the thickness of the regenerated epidermis and the vessel number. However, a too high platelet concentration resulted in a slowdown of the membrane resorption that interfered with the skin healing. Overall, the results indicate that the BAMs could represent a natural and effective wound healing tool for the treatment of skin ulcers. Copyright © 2016 John Wiley & Sons, Ltd.

Culture Medium Supplements Derived from Human Platelet and Plasma: Cell Commitment and Proliferation Support.

Present cell culture medium supplements, in most cases based on animal sera, are not fully satisfactory especially for the in vitro expansion of cells intended for human cell therapy. This paper refers to (i) an heparin-free human platelet lysate (PL) devoid of serum or plasma components (v-PL) and (ii) an heparin-free human serum derived from plasma devoid of PL components (Pl-s) and to their use as single components or in combination in primary or cell line cultures. Human mesenchymal stem cells (MSC) primary cultures were obtained from adipose tissue, bone marrow, and umbilical cord. Human chondrocytes were obtained from articular cartilage biopsies. In general, MSC expanded in the presence of Pl-s alone showed a low or no proliferation in comparison to cells grown with the combination of Pl-s and v-PL. Confluent, growth-arrested cells, either human MSC or human articular chondrocytes, treated with v-PL resumed proliferation, whereas control cultures, not supplemented with v-PL, remained quiescent and did not proliferate. Interestingly, signal transduction pathways distinctive of proliferation were activated also in cells treated with v-PL in the absence of serum, when cell proliferation did not occur, indicating that v-PL could induce the cell re-entry in the cell cycle (cell commitment), but the presence of serum proteins was an absolute requirement for cell proliferation to happen. Indeed, Pl-s alone supported cell growth in constitutively activated cell lines (U-937, HeLa, HaCaT, and V-79) regardless of the co-presence of v-PL. Plasma- and plasma-derived serum were equally able to sustain cell proliferation although, for cells cultured in adhesion, the Pl-s was more efficient than the plasma from which it was derived. In conclusion, the cells expanded in the presence of the new additives maintained their differentiation potential and did not show alterations in their karyotype.

Bone marrow stromal cells and their use in regenerating bone.

Tissue engineering approaches have recently been devised to repair large bone losses. Tissue engineering takes advantages of the combined use of cultured living cells and 3D scaffolds to deliver vital cells to the damaged site of the patient. Cultured bone marrow stromal cells (BMSCs) can be regarded as a mesenchymal progenitor/precursor cell population derived from adult stem cells. When implanted in immunodeficient mice, BMSCs combined with mineralized 3D scaffolds to form a primary bone tissue that is highly vascularized. We have used autologous BMSC/bioceramic composites to treat full-thickness gaps of tibial diaphysis in sheep. The healing process has been investigated. The sequence of events is as follows: (1) bone formation on the outer surface of the implant; (2) bone formation in the inner cylinder canal; (3) formation of fissures and cracks in the implant body; (4) bone formation in the bioceramic pores. Similar composites whose size and shape reflected each bone defect have been implanted at the lesion sites of three patients. External fixation was used. Patients have been followed for more than three years. The results obtained are very promising and we propose the use of culture-expanded osteoprogenitor cells in conjunction with hydroxyapatite bioceramics as a significant improvement in the repair of critical size long bone defects.

Fluorescence microscopy imaging of bone for automated histomorphometry.

We have developed a computer-based method for the automated quantification of bone tissue in histological sections of decalcified specimens. Bone tissue was generated by ectopic implantation of ceramic-based carriers loaded with human bone marrow stromal cells (BMSCs). The method is based on the acquisition of multimodal images, in order to identify and measure the area covered by bone tissue (using fluorescent light) and the total area of tissue (using transmitted light), thereby excluding the regions corresponding to nonresorbed scaffold. The amount of bone as a percentage of the total area of interest (bone/area) and of the newly formed tissue (bone/tissue) is automatically derived. The computer-based results correlated closely with those obtained by manual identification of bone and tissue areas in the same histological fields (R(2) = 0.997; p < 0.0005), with errors dependent on the magnification used but always lower than 9.4%. The method was used to compare the bone/tissue and bone/area percentages in samples of engineered bone based on human BMSCs expanded in the presence of different biochemical factors and loaded onto different scaffolds. The technique thus represents a valuable tool to quantify reproducibly, accurately, and easily bone formation in a variety of tissue-engineering studies.

Regenerative medicine for the treatment of Teno-desmic injuries of the equine. A series of 150 horses treated with platelet-derived growth factors.

BACKGROUND/AIM: The aim of the present study was to evaluate the safety and the clinical outcome of platelet-rich plasma for the treatment of teno-desmic injures in competition horses. PATIENTS AND METHODS: From January 2009 to December 2011, 150 sport horses suffering from teno-desmic injuries were treated with no-gelled platelet-concentrate. RESULTS: No horse showed any major adverse reaction as a result of the procedure. Full healing was obtained for 81% of the horses. Twelve percent had clinical improvement and only 7% a failure. Eight percent of cases of relapse were observed. No statistically significant correlation existed between clinical outcome and the area of the lesion. A statistically significant correlation existed between the clinical outcome and the age of the horse. CONCLUSION: Treatment with platelet-derived growth factors leads to the formation of a tendon with normal morphology and functionality, which translate in the resumption of the agonistic activity for the horses we treated.

A modified rabbit ulna defect model for evaluating periosteal substitutes in bone engineering: a pilot study.

The present work defines a modified critical size rabbit ulna defect model for bone regeneration in which a non-resorbable barrier membrane was used to separate the radius from the ulna to create a valid model for evaluation of tissue-engineered periosteal substitutes. Eight rabbits divided into two groups were used. Critical defects (15 mm) were made in the ulna completely eliminating periosteum. For group I, defects were filled with a nanohydroxyapatite poly(ester urethane) scaffold soaked in PBS and left as such (group Ia) or wrapped with a tissue-engineered periosteal substitute (group Ib). For group II, an expanded-polytetrafluoroethylene (e-PTFE) (GORE-TEX(®)) membrane was inserted around the radius then the defects received either scaffold alone (group IIa) or scaffold wrapped with periosteal substitute (group IIb). Animals were euthanized after 12-16 weeks, and bone regeneration was evaluated by radiography, computed microtomography (µCT), and histology. In the first group, we observed formation of radio-ulnar synostosis irrespective of the treatment. This was completely eliminated upon placement of the e-PTFE (GORE-TEX(®)) membrane in the second group of animals. In conclusion, modification of the model using a non-resorbable e-PTFE membrane to isolate the ulna from the radius was a valuable addition allowing for objective evaluation of the tissue-engineered periosteal substitute.

A platelet-rich plasma-based membrane as a periosteal substitute with enhanced osteogenic and angiogenic properties: a new concept for bone repair.

The periosteum plays a pivotal role during bone development and repair contributing to bone vascularization and osteoprogenitor cells source. We propose a periosteal substitute engineered using a platelet-rich plasma (PRP) membrane incorporating autologous bone marrow-derived mesenchymal stem cells (PRP/BMSC gel membrane) to be wrapped around an osteoconductive scaffold for regeneration of compromised bone defects. The PRP/BMSC gel membrane was optimized using different compositions for optimal release of vascular endothelial growth factor (VEGF) and platelet derived growth factor-BB (PDGF-BB). Survival and proliferation of cells in the PRP gel membrane with time were confirmed in addition to their osteogenic capacity. Furthermore, to evaluate the possible effects of the PRP/BMSC gel membrane on surrounding progenitor cells in the injury area, we found that the PRP gel membrane products could significantly induce the migration of human endothelial cells in vitro, and increased the expression of bone morphogenetic protein 2 in cultured BMSC. These cells also secreted significant amounts of soluble proangiogenic factors, such as PDGF-BB, VEGF, and interleukin-8 (IL-8). Finally, the functionality of the PRP/BMSC gel membrane periosteal substitute for bone regeneration was tested in vivo both in an ectopic mouse model as well as in a rabbit segmental bone defect model providing evidence of its capacity to biomimic a periosteal response enhancing bone regeneration.

Formation of a chondro-osseous rudiment in micromass cultures of human bone-marrow stromal cells.

Bone-marrow stromal cells can differentiate into multiple mesenchymal lineages including cartilage and bone. When these cells are seeded in high-density 'pellet culture', they undergo chondrogenesis and form a tissue that is morphologically and biochemically defined as cartilage. Here, we show that dual chondro-osteogenic differentiation can be obtained in the same micromass culture of human bone-marrow stromal cells. Human bone-marrow stromal cells were pellet cultured for 4 weeks in chondro-inductive medium. Cartilage 'beads' resulting from the micromass culture were then subcultured for further 1-3 weeks in osteo-inductive medium. This resulted in the formation of a distinct mineralized bony collar around hyaline cartilage. During the chondrogenesis phase, type I collagen and bone sialoprotein were produced in the outer portion of the cartilage bead, which, upon subsequent exposure to beta-glycerophosphate, mineralized and accumulated extracellular bone sialoprotein and osteocalcin. Our modification of the pellet culture system results in the formation of a chondro-osseous 'organoid' structurally reminiscent of pre-invasion endochondral rudiments, in which a bony collar forms around hyaline cartilage. The transition from a cell culture to an organ culture dimension featured by our system provides a suitable model for the dissection of molecular determinants of endochondral bone formation, which unfolds in a precisely defined spatial and temporal frame