Platelet-rich plasma injections for tendinopathy and osteoarthritis

Platelet-rich plasma promotes recruitment of macrophages in the process of tendon healing

INTRODUCTION

Researchers have investigated the use of platelet-rich plasma (PRP) therapy. However, the mechanisms through which PRP affects tissue repair remain unclear. We hypothesize that PRP promotes tissue repair through not only via direct manner on the local cells but also via indirect manner that encourage the recruitment of reparative cells such as macrophages (MPs), and it depends on the quality of PRP including the concentration of leukocytes. The aim of this study is to elucidate the actions of the MPs in the mechanisms of PRP on tissue repair processes.

METHODS

Leukocyte-rich (LR) PRP and leukocyte-poor (LP) PRP were prepared from 12-week-old C57BL6 mice. Full-thickness defects were created in central third of patellar tendons of 12-week-old C57BL/6 mice for histologic analysis (n = 36) and 12-week-old B6.129P-Cx3cr1tm1Litt/J mice for flow cytometry analysis (n = 108). B6.129P-Cx3cr1tm1Litt/J mouse is GFP-positive only in the MP-linage cells thus MPs recruited to the repair tissue can be distinguished whether it had originated from administrated PRP or recruited from host mouse. Mice were treated either with LR-PRP, LP-PRP, or without PRP (control group). Histological analyses were performed to evaluate the tendon healing using Bonar score as semi-quantitative histological scoring system. Flow cytometric analyses were performed to count the number of GFP-positive cells around repaired patellar tendon. In addition, the ratio of pro-inflammatory MPs (M1)/anti-inflammatory MPs (M2) were analyzed in those GFP-positive cells. The statistical analysis was performed using GraphPad Prism ver6. P values < 0.05 were considered statistically significant.

RESULTS

In LR-PRP and LP-PRP groups, all variables in Bonar score such as cell morphology, cellularity, vascularity, and collagen arrangement were significantly improved in comparison with control group, indicating that both PRPs promote tendon hearing. LP-PRP promoted the tendon healing significantly faster than that of LR-PRP on postoperative day 28 (P < 0.001). LR-PRP enhanced angiogenesis (vascularity: P < 0.001), while LP-PRP improved the collagen arrangement on postoperative day 28 (collagen arrangement: P < 0.01). In other variables such as cell morphology and cellularity score, there were no significant differences between LR-PRP and LP-PRP groups in any time points. Flow cytometric findings showed that recruitment of GFP-positive MPs in the LR and LP-PRP groups were significantly increased from postoperative day 4 compared with control group without PRP treatment (P < 0.001). The majority of GFP-positive MPs were M1 at the initiation of tendon healing phase, and M2 were gradually increased from postoperative day 4. The number of M1 was significantly high both in the LP- and LR-PRP groups (day 4 and 7, p < 0.001), but the number of M2 was high only in the LP-PRP group (day 7 and 14, P < 0.05) when it compared with control group. The M1/M2 ratio on postoperative day 7 was significantly lower in the LP-PRP group than those in the control group (P < 0.05).

CONCLUSIONS

This study demonstrated that PRP enhanced the tendon healing and promoted the recruitment of MPs to the injured tissue. The subtypes of MPs were different depends on the types of PRPs, suggesting that leukocytes in PRP influence the effect of PRP therapy.

Analysis of Platelet-Rich Plasma Extraction: Variations in Platelet and Blood Components Between 4 Common Commercial Kits

Background:

Platelet-rich plasma (PRP) has been extensively used as a treatment in tissue healing in tendinopathy, muscle injury, and osteoarthritis. However, there is variation in methods of extraction, and this produces different types of PRP.

Purpose:

To determine the composition of PRP obtained from 4 commercial separation kits, which would allow assessment of current classification systems used in cross-study comparisons.

Study Design:

Controlled laboratory study.

Methods:

Three normal adults each donated 181 mL of whole blood, some of which served as a control and the remainder of which was processed through 4 PRP separation kits: GPS III (Biomet Biologics), Smart-Prep2 (Harvest Terumo), Magellan (Arteriocyte Medical Systems), and ACP (Device Technologies). The resultant PRP was tested for platelet count, red blood cell count, and white blood cell count, including differential in a commercial pathology laboratory. Glucose and pH measurements were obtained from a blood gas autoanalyzer machine.

Results:

Three kits taking samples from the “buffy coat layer” were found to have greater concentrations of platelets (3-6 times baseline), while 1 kit taking samples from plasma was found to have platelet concentrations of only 1.5 times baseline. The same 3 kits produced an increased concentration of white blood cells (3-6 times baseline); these consisted of neutrophils, leukocytes, and monocytes. This represents high concentrations of platelets and white blood cells. A small drop in pH was thought to relate to the citrate used in the sample preparation. Interestingly, an unexpected increase in glucose concentrations, with 3 to 6 times greater than baseline levels, was found in all samples.

Conclusion:

This study reveals the variation of blood components, including platelets, red blood cells, leukocytes, pH, and glucose in PRP extractions. The high concentrations of cells are important, as the white blood cell count in PRP samples has frequently been ignored, being considered insignificant. The lack of standardization of PRP preparation for clinical use has contributed at least in part to the varying clinical efficacy in PRP use.

Clinical Relevance:

The variation of platelet and other blood component concentrations between commercial PRP kits may affect clinical treatment outcomes. There is a need for standardization of PRP for clinical use.

Platelet Rich Plasma Therapy in Non-insertional Achilles Tendinopathy: The Efficacy is Reduced in 60-years Old People Compared to Young and Middle-Age Individuals

Background: Platelet Rich Plasma (PRP) has shown positive and long-lasting effects in patients with tendinopathies. However, information about age-related differences in the clinical outcome is limited. Aim of this retrospective study was to compare the efficacy of PRP therapy in young and elderly subjects suffering for Achilles tendinopathy.

Materials and method: Patients with recalcitrant non-insertional Achilles tendinopathy were enrolled. Clinical (VISA-A) and instrumental (ultrasonography) data were collected at baseline and after 1, 3, 6, and 12 months. PRP injections (once a week for 3 weeks) were performed in sterile conditions and under ultrasound (US) control.

Results: Forty-four subjects (29 young: mean age 39.5 ± 6.9; 15 elderly: mean age 61.5 ± 5.3) were retrospectively evaluated. At baseline, no significant differences were observed in the clinical and US parameters. Throughout the whole length of the study, a significant increase of VISA-A score was seen in both groups (from 50.3 ± 8.8 to 76.1 ± 6.6 in the young group, and from 48.7 ± 7.6 to 61.1 ± 9.4 in the elderly group); however, the infra-groups comparison showed better results in young patients, compared to the aged counterpart.

Conclusion: Our results show that PRP is less effective in aged people. This finding can be ascribed to several biochemical and biomechanical differences documented in tendons of young and elderly subjects (reduced number and functionality of tenocytes and tenoblasts), which becomes more evident in the long-term tissue healing. However, prospective trials, using different PRP preparations and enrolling a larger number of subjects, are needed to draw more sound and definitive conclusions.

Platelet-rich plasma: underlying biology and clinical correlates

Platelet-rich plasma (PRP) has recently become the focus of intensive interest and discussion, in part because of the expanding understanding of platelet function. Anucleate platelets within PRP release a myriad of growth factors and cytokines while contributing to plasma coagulation and fibrin development; the latter acts as vehicle for the local delivery. The biological effects of PRP are largely attributed to the platelet secretome and plasma signaling proteins. Clinical data suggest that PRPs may exploit different regenerative mechanisms under diverse disease conditions, including hemostasis, inflammation, angiogenesis and the synthesis of extracellular matrix. The success of PRP therapies depends on current tissue healing research and the translation of this knowledge into clinical developments.

Platelet-rich plasma (PRP) in chronic epicondylitis: study protocol for a randomized controlled trial

Background

Tendinopathy is a difficult problem to manage and can result in significant patient morbidity. Currently, the clinical use of platelet-rich plasma (PRP) in painful tendons is widespread but its efficacy remains controversial.

Methods/Design

This study is a single-center, randomized double-blind controlled trial. Eighty patients will be allocated to have ultrasound (US)-guided needling combined with a leukocyte-depleted (that is, pure) PRP or lidocaine each alternate week for a total of two interventions. Outcome data will be collected before intervention, and at 6 weeks, 3, 6, and 12 months after intervention. Main outcome measure: Changes in pain and activity levels, as assessed by Disabilities of the Arm, Shoulder and Hand (DASH-E, Spanish version) score, at 6 months. We will compare the percentage of patients in each group that achieve a successful treatment defined as a reduction of at least 25% in the DASH-E score. Secondary outcome measures include changes in DASH-E at 3 and 12 months, changes in pain as assessed by the visual analogue scale (VAS) at the 6-week, 3-, 6-, and 12-month follow-up, changes in sonographic features and neovascularity, and percentage of patients in each group with adverse reactions at 3, 6, and 12 months.

Discussion

The results of this study will provide insights into the effect of pure PRP in tendon and may contribute to identifying the best protocol for PRP application in tendinopathies.

Trial registration

ClinicalTrials.gov: NCT01945528.