OBJECTIVE: To induce hematopoietic progenitor/stem cells of umbilical cord blood to differentiate into mature megakaryocytes and platelets in vitro and to investigate the mechanism of production of platelets. METHODS: The CD34+ cells were sorted from umbilical cord blood by magnetic activated cell sorting (MACS) and then cultured in vitro with optimized medium to be differentiated into mature megakaryocytes and platelets. The cultured cells and the platelet-like particles were isolated from the culture and were checked by the fluorescence-activated cell sorter (FACS), immunohistochemistry assays, light microscope,electron microscope and platelet aggregation tests. RESULTS: The cultured megakaryocytes were detected with proplatelets and both the cultured cells and the platelet-sized particles were found to have the same structure with the normal megakaryocytes and platelets by light and electron microscope. The immunohistochemistry assays revealed the cultured cells expressed GP II b III a with a positivity of 95% which was a special antigen for platelets and megakaryocytes. Culture-derived platelet-sized particles aggregated in response to thrombin as the plasma derived-platelets did. The cultured platelets had the same positivity of CD41 as the platelets from platelet rich plasma. CONCLUSION The hematopoietic progenitor/stem cells can be induced to differentiate into purified and mature megakaryocytes and platelets. It provides a practical way to study the mechanism of platelets production.
Antigens, CD34 ; metabolism ; Blood Platelets ; cytology ; Cell Differentiation ; physiology ; Cells, Cultured ; Fetal Blood ; cytology ; metabolism ; Hematopoietic Stem Cells ; cytology ; metabolism ; Humans ; Megakaryocytes ; cytology

This study was aimed to investigate the stability and in vitro function of glycosylated platelets concentrates after long-term refrigeration. The experiments were divided into 4 groups: group preserved at room temperature (RT group), group preserved at 4 degrees C (4T group), group glycosylated and preserved at 4 degrees C (U + 4 group) and group preserved at 4 degrees C and glycosylated (4 + U group). All groups followed for up to 14 days. The binding rate of RCA I lectin and expression of Plt surface markers CD62P, CD42b and Annexin V binding were determined by flow cytometry. pH and mean volume were determined by pH meter and hematotocytometer respectively. Platelet aggregation was detected by aggregometer. The results showed that during storage up to 14 days RCAI binding rate of modified groups was 5 - 6 fold of RT group. The pH of platelets suspension had no significant difference between these two groups (p > 0.05). Mean volumes of both groups (10.6 +/- 1.9 fL and 11.14 +/- 1.1 fL) were also no significant difference (p > 0.05). Furthermore, aggregation responsiveness of modified groups was better than that of RT groups (p < 0.05) although both decreased during the storage. The expression level of CD62P, CD42b and Annexin V binding during 5 days of storage had no significant difference between modified and fresh platelet groups (p > 0.05). While the expression level of CD62P and PS increased and the expression level of CD42b decreased during storage up to 14 days, there was significant difference between modified and fresh platelet groups (p < 0.01). It is concluded that the glycan modification is stable during storage up to 14 days. The glycosylated platelets retain in vitro function better than RT platelets during storage, but it shows activation to varying degrees in vitro after storage for 5 days.
Blood Platelets ; cytology ; metabolism ; Blood Preservation ; Cryopreservation ; methods ; Galactose ; pharmacology ; Glycosylation ; Humans ; Platelet Aggregation ; drug effects

This study was aimed to investigate the aggregation of rehydrated-lyophilized platelets. The aggregation rate of fresh and rehydrated-lyophilized platelets were measured by using thrombin, ristocetin, ADP and collagen as inductors and APACT2 aggregameter; the effects of intra- and extra-cellular trehalose on maximum aggregation rate of rehydrated-lyophilized platelets were detected by using ADP as an inductor. The results showed that the aggregation rate of fresh platelets was all about 100%, while aggregation rate of rehydrated lyophilized platelets was (70.17 +/- 7.36)%, (15.3 +/- 2.81)%, (68.67 +/- 6.86)%, (64.67 +/- 11.6)% respectively, when the concentration of thrombin, ristocetin, ADP and collagen was 1 U/ml, 1.6 mg/ml, 20 micromol/L and 2 microg/ml. The maximum aggregation rates of rehydrated-lyophilized platelets in intra- and extra-cellular trehalose, extracellular trehalose and blank control groups were (66.0 +/- 4.69)%, (25.3 +/- 2.42)% and (11.5 +/- 1.87)% (P < 0.01), meanwhile there was significant difference of rehydrated-lyophilized platelet aggregation rate between intra- and extra-cellular trehalose and extracellular trehalose groups (P < 0.01). It is concluded that the concentrations of thrombin (1 U/ml), ristocetin (1.6 mg/ml), ADP (20 micromol/L) and collagen (2 microg/ml) are optimal for platelets aggregation tests, the internal and extracellular trehalose significantly enhance the aggregation of rehydrated-lyophilized platelets.
Blood Platelets ; cytology ; drug effects ; metabolism ; Blood Preservation ; methods ; Freeze Drying ; methods ; Humans ; Platelet Aggregation ; physiology

Platelet-enriched plasma (PRP) contains high concentration of platelets and abundant growth factors, which is made by centrifuging of blood and separating of blood elements. PRP promotes tendon repair by releasing various cytokines to enhance cell proliferation, tenogenic differentiation, formation and secretion of matrix; meantime, it can reduce pain by inhibiting the expression of pain-associated molecules. A number of clinical studies demonstrated that PRP was effective in treatment of tendinopathy, including patellar tendinopathy, lateral epicondylitis and plantar fasciopathy. However, some studies did not support this conclusion, because of disparity of PRP types, therapeutic courses and injections protocols in clinical application. Based on its safety, PRP can be a choice of treatment for tendinopathy, in case other non-surgical therapies are of no effect.
Blood Platelets ; cytology ; Cytokines ; metabolism ; Humans ; Intercellular Signaling Peptides and Proteins ; metabolism ; Platelet-Rich Plasma ; Tendinopathy ; therapy

Platelet apoptosis elucidated by either physical or chemical compound or platelet storage occurs wildly, which might play important roles in controlling the numbers and functions of circulated platelets, or in the development of some platelet-related diseases. However, up to now, a little is known about the regulatory mechanisms of platelet apoptosis. Protein kinase C (PKC) is highly expressed in platelets and plays central roles in regulating platelet functions. Although there is evidence indicating that PKC is involved in the regulation of apoptosis of nucleated cells, it is still unclear whether PKC plays a role in platelet apoptosis. The aim of this study was to investigate the role of PKC in platelet apoptosis. The effects of PKC on mitochondrial membrane potential (ΔΨm), phosphatidylserine (PS) exposure, and caspase-3 activation of platelets were analyzed by flow cytometry and Western blot. The results showed that the ΔΨm depolarization in platelets was induced by PKC activator in time-dependent manner, and the caspase-3 activation in platelets was induced by PKC in concentration-dependent manner. However, the platelets incubated with PKC inhibitor did not results in ΔΨm depolarization and PS exposure. It is concluded that the PKC activation induces platelet apoptosis through influencing the mitochondrial functions and activating caspase 3. The finds suggest a novel mechanism for PKC in regulating platelet numbers and functions, which has important pathophysiological implications for thrombosis and hemostasis.
Apoptosis ; Blood Platelets ; cytology ; metabolism ; Caspase 3 ; metabolism ; Humans ; Membrane Potential, Mitochondrial ; Phosphatidylserines ; metabolism ; Protein Kinase C ; metabolism

The aim of this research was to study the technology and methods of loading lyoprotectant-trehalose into cytoplasm of human platelets before lyophilization, to optimize experimental conditions of loading trehalose, to investigate the changes of platelets response to agonists and activation after incubation of platelets for 4 hours at 37 degrees C in the presence of lyoprotectant-trehalose, to protract the figures of loading efficiency and intracellular trehalose concentration versus incubation time, temperature and external trehalose concentration, to optimize loading parameters. The response of platelets to different agonists--thrombin, ADP, collagen and ristocetin were measured respectively by APACT2 aggregometer before and after loading trehalose into platelets; the expressions of CD62p and PAC-1 on platelet membranes in the presence and absence of reversible platelets activation inhibitors were measured by flow cytometry respectively before and after loading trehalose into cytoplasm of platelets. The results showed that the loading efficiency was linear to incubation time (2 hours later) and incubation temperature (rang from 30 degrees C to 40 degrees C), respectively. The loading efficiency almost reached 60% when the platelets were incubated at 37 degrees C for 4 hours. The intracellular trehalose concentration was higher with the increase of the extracellular trehalose concentration (< 50 mmol/L). Compared to untreated groups, the values of MPV and aggregation to different agonists in treated groups showed no significant difference, respectively (P > 0.01). After incubation of platelets for 4 hours, the expression of CD62p increased to some extent, however, the expression of CD62p decreased again when the reversible platelets activation inhibitor PGE-1 and adenosine were added to the incubation buffer. It is concluded that 37 degrees C, 4 hours and the extracellular trehalose concentration < 50 mmol/L are the optimal conditions for loading with trehalose. The processing of loading with trehalose before platelet lyophilization has no significant effects on response of platelets to agonists and activation.
Blood Platelets ; cytology ; drug effects ; metabolism ; Blood Preservation ; methods ; Cell Survival ; Cryopreservation ; methods ; Freeze Drying ; Humans ; Trehalose ; blood ; pharmacology

This study was aimed to compare the difference of quality between buffy-coat-collected platelet concentrates (BC-PC) and single-donor plateletpheresis (SDP). 15 packs of BC-PC and 15 units SDP were stored at 20 degrees C - 24 degrees C with agitation. Platelet concentration, platelet volume, residual leukocyte and residual erythrocyte in two groups were examined after preparation for 1 hour. Mean platelet volume, pH value, hypotonic shock response (HSR), CD62p expression and CD62p re-expression of platelet were detected on 0, 1, 2, 3, 4, 5 days of platelet preservation. The results showed that the platelet yields, residual leukocyte and residual erythrocyte in two groups accorded with the national quality standard respectively, but residual leukocyte and residual erythrocyte in BC-PC group were higher than those in SDP group when platelet yields in two groups were equal (p < 0.01). Lactate concentration, CD62p expression of platelet increased with prolongation of preseved time, while pH value decreased gradually. Compared with SDP group, there were significant differences in CD62p expression, CD62p re-expression of platelet preserved for 0 - 5 days (p < 0.01), and in pH value of platelet preserved 2 - 5 days (p < 0.01). There was no changes in HSR of SDP group for 0 - 5 days, while HSR in BC-PC group decreased gradually. There were significant differences in HSR of platelet preserved for 1 - 5 days (p < 0.01). It is concluded that the platelet concentrates prepared by BC-PC are not equal to SDP in quality, the preparation technology of BC-PC should be optimized further in order to reduce residual leukocyte, residual erythrocyte and activated platelet yields, as well as improve the quality of BC-PC.
Blood Platelets ; metabolism ; physiology ; Blood Preservation ; Cell Separation ; methods ; Erythrocytes ; cytology ; Humans ; Lactic Acid ; blood ; Leukocytes ; cytology ; P-Selectin ; blood ; Platelet Count ; Plateletpheresis ; instrumentation ; methods ; Quality Control

The aim of this study was to search a procedure of platelet lyophilization and find a way of long-term storage of human platelets at normal temperature with smaller size and lighter weight, to be convenient to transport at long distance thus to meet the demands in accidents and war time. Human platelets were pretreated by freezing, the first and the second desiccation, and were added with reversible activation-inhibitors of platelets, DMSO and trehalose, then were rehydrated. At the same time, the recovery rate of platelets, platelet maximal aggregation induced by thrombin, coagulation of platelets, CD62p expression and PAC-1 expression were assayed. The results indicated that the recovery rate of the platelets was 56.29%. The platelet maximal aggregation induced by thrombin had no significant difference between lyophilized platelets and the fresh platelet-rich plasma (FPRP), but the aggregation of platelets induced by ADP or propyl gallate was decreased by 49.34% and 26.25%. Coagulation of the lyophilized platelets was not significantly different from FPRP. CD62p expression of the lyophilized platelets (42.36%) was higher than that in FPRP while PAC-1 expression was 2.12%. CD62p re-expression rate induced by thrombin was 50.88% and PAC-1 re-expression was 54.55%. It is concluded that the ability of recovered lyophilized platelets added with reversible activation-inhibitors, DMSO and trehalose to aggregate and coagulate has showed no significant difference as compared with FPRP. The reversible activation-inhibitors can decrease CD62p expression of lyophilized platelets, and may enhance their survival ability and prolongate survival time. Therefore the efficiency of lyophilizing platelets can be improved based on this freeze-drying procedure.
Blood Platelets ; cytology ; drug effects ; metabolism ; Blood Preservation ; methods ; Cell Survival ; Freeze Drying ; methods ; Humans ; Trehalose ; pharmacology

This study was aimed to further optimize trehalose loading technique including loading temperature, loading time, loading solution and loading concentration of trehalose, based on the established parameters. Loading efficiency in plasma was compared with that in buffer at 37 degrees C; the curves of intracellular trehalose concentration versus loading time at 37 degrees C and 16 degrees C were measured; curves of mean platelet volume (MPV) versus loading time and loading concentration were investigated and compared. According to results obtained, the loaing time, loading temperature, loading solution and trehalose concentration were ascertained for high loading efficiency of trehalose into human platelet. The results showed that the loading efficiency in plasma was markedly higher than that in buffer at 37 degrees C, the loading efficiency in plasma at 37 degrees C was significantly higher than that at 16 degrees C and reached 19.51% after loading for 4 hours, but 6.16% at 16 degrees C. MPV at 16 degrees C was increased by 43.2% than that at 37 degrees C, but had no distinct changes with loading time and loading concentration. In loading at 37 degrees C, MPV increased with loading time and loading concentration positively. Loading time and loading concentration displayed synergetic effect on MPV. MPV increased with loading time and concentration while trehalose loading concentration was above 50 mmol/L. It is concluded that the optimization parameters of trehalose loading technique are 37 degrees C (temperature), 4 hours (leading time), plasma (loading solution), 50 mmol/L (feasible trehalose concentration). The trehalose concentration can be adjusted to meet the requirement of lyophilization.
Blood Platelets ; cytology ; drug effects ; metabolism ; Blood Preservation ; methods ; Cryopreservation ; methods ; Cryoprotective Agents ; metabolism ; pharmacology ; Dose-Response Relationship, Drug ; Freeze Drying ; Humans ; Trehalose ; metabolism ; pharmacology

OBJECTIVETo observe the effect of the platelet-rich plasma (PRP) on osteogenesis during bone distraction.

METHODSThe osteoblasts were cultured in vitro. The rabbits were used as the animal model of distraction osteogenesis. The proliferation of osteoblasts was analysed through MTT methods. The osteogenesis was observed by histochemical and histoimmunochemical methods.

RESULTSPRP stimulated the proliferation of osteoblasts and facilitated distraction osteogenesis.

CONCLUSIONSPRP could accelerate the osteogenesis during bone distraction. The application of PRP in clinical practice might shorten the period of distraction osteogenesis.

Animals ; Blood Platelets ; physiology ; Cells, Cultured ; Immunohistochemistry ; Male ; Osteoblasts ; cytology ; metabolism ; Osteogenesis ; physiology ; Osteogenesis, Distraction ; Platelet Count ; Rabbits