The Inflammatory Effect of Leukocyte-poor Versus Leukocyte-rich Platelet-Rich Plasma
+1Dragoo, J L; 1Braun, H J; 1Durham, J L; 1Ridley, B A; 2Arnoczky, S P
+1Stanford University, Palo Alto, CA, 2Michigan State University, East Lansing, MI
[email protected]
INTRODUCTION:
(r=0.659, p<0.05) counts. Tendons treated with LR-PRP also had greater
scores for fiber structure (1.4 vs. 0.5, p=0.006) denoting disrupted
Platelet-rich plasma (PRP) is an injection of blood plasma with
structure, total WBCs (1.1 vs. 0.1, p=0.042), mononuclear cells
enhanced platelet numbers proposed to aid tendon and ligament healing
(macrophages and lymphocytes) (0.8 vs. 0.1, p=0.014), vascularity (1.7
and reduce target inflammation. These injections have been used in
vs. 0.8, p=0.005), and fibrosis (1.0 vs. 0.3, p=0.025). A significant
arthroscopy and sports medicine to treat injuries such as tendinopathy
difference was not observed between PMNs (0.3 vs. 0, p=0.347).
and articular cartilage damage. Despite increasing use, there is a lack of
At 14 days post-injection, there were no significant differences in
consensus as to whether PRP contributes to healing and clinical
semi-quantitative scores between tendons treated with LR-PRP and
improvements. This may be due to the fact that PRP can be created by
those treated with LP-PRP in any of the treatment categories. Compared
repeated centrifugation protocols or through the use of commercially
with LR-PRP, tendons treated with LP-PRP had higher scores for fiber
manufactured kits, which all result in blood plasma with increased
structure (indicating disrupted structure), mononuclear (macrophage and
platelet numbers but are not standardized with regard to other cellular
lymphocyte) cell counts, vascularity, fibrosis, and total tendon score,
constituents. It has recently been shown that concentrations of
however these results were not statistically significant. The total tendon
leukocytes (WBCs) differ depending on the commercial separation
score did not correlate with the WBC (r=-0.028, p=0.927) or platelet
system used to prepare the platelet-rich plasma (PRP). Accordingly, the
(r=0.065, p=0.833) counts. Further analysis using one-way ANOVA and
inflammatory effect of the differing PRP injections is unclear. The
Bonferroni post-hoc comparisons revealed no significant differences
purpose of this study was to examine the inflammatory effect of
between the four treatment conditions: saline, whole blood, LR-PRP,
leukocyte-rich (LR-PRP) versus leukocyte-poor PRP (LP-PRP)
LP-PRP (p’s > 0.05).
injections using a rabbit model.
The average tendon scores for both independent observers were
significantly correlated (r=0.596, p<0.01).
METHODS:
A total of 22 skeletally mature New Zealand White rabbits were
tested. In 8 control rabbits, one patellar tendon was injected with 2cc
autologous whole blood and the other was injected with 2cc sterile
saline. In 14 experimental rabbits, one patellar tendon was injected with
2cc LR-PRP and the other was injected with 2cc LP-PRP. All injections
were administered throughout the patellar tendon with 10 needle passes.
Animals were euthanized at 5 or 14-days post-injection. Tendons were
harvested, formalin-fixed, and paraffin-embedded. Slides were stained
using H&E staining. Two independent, blinded pathologists scored
tendon morphology and cell infiltration using the semi-quantitative
grading scheme outlined in Table 1. Independent samples t-tests were
used to compare the scores from tendons treated with LR-PRP and LPPRP. Correlations of semi-quantitative scores with both leukocyte and
platelet counts was assessed using Pearson correlations. Observer
agreement was also evaluated with Pearson correlations.
Grade
Variable
0
1
Fiber
Structure
Dense
Slight
separation
Total
WBCs
<100
cells/HPF
100-199
PMNs
<50
50-99
cells/HPF
Mononuclear
<50
50-99
cells
cells/HPF
Vascularity Parallel Transverse
vessels
vessles in
tendon
Fibrosis
None
Mild
2
3
Separation Complete loss
and
of structure;
deterioration hyalinization
200-299
>300
100-149
>150
100-149
>150
Moderate
increase in
vessels
Marked
increase in
vessels
(clustering)
Moderate
Severe
Table 1. Semi-quantitative grading scheme used to evaluate structural
and cellular effects of intratendinous injections of leukocyte-poor or
leukocyte-rich platelet-rich plasma.
RESULTS:
At 5 days post-injection, tendons treated with LR-PRP had overall
higher semi-quantitative scores than tendons treated with LP-PRP (6.3
vs. 1.8, p=0.003). Across treatment groups, total tendon scores
significantly correlated with both WBC (r=0.596, p<0.05) and platelet
WBC
(k/uL)
Total
Score
Fiber
Total
WBCs
Mono. Cells
Vasc
Fibr.
LRPRP
19.62
6.3
1.4
1.1
0.8
1.7
1.0
LPPRP
0.5952
1.8
0.5
0.1
0.1
0.8
0.3
Table 2. Significant results at Day 5 for LR-PRP and LP-PRP
experimental groups.
DISCUSSION:
At 5 days post-injection, we observed greater numbers of total
leukocytes and mononuclear cells (macrophages and lymphocytes) in
tendons treated with LR-PRP compared to those treated with LP-PRP.
We also observed increased vascularity, fibrosis, and disrupted fiber
structure in tendons treated with LR-PRP. Together, these results
suggest that LR-PRP causes an early and acute inflammatory response
compared with LP-PRP.
Conversely, at 14 days post-injection, we did not observe significant
differences between tendons treated with LR-PRP and those treated with
LP-PRP or between saline or whole-blood-treated tendons. These
findings suggest that the presence of leukocytes in platelet-rich plasma
causes an early inflammatory reaction that is later resolved. However,
given that scores from tendons treated with LP-PRP trended higher than
those treated with LR-PRP, it is plausible that LP-PRP causes a more
long-term inflammatory response that may be better elucidated with an
increased sample size.
While it is clear that LR-PRP causes a more pronounced
inflammatory effect than LP-PRP at 5 days post-injection, it is unclear
whether this finding is ultimately beneficial or detrimental to the healing
process. On one hand, the acute infiltration and subsequent recruitment
of inflammatory cells after administration of LR-PRP may enable the
healing process to occur more rapidly. On the other hand, an acute
inflammatory response may ultimately prolong the healing phase or
increase pain and symptoms. Future investigations will be necessary to
delineate the effect that these injections have on the healing process.
SIGNIFICANCE:
Due to the wide variety of PRP preparation methods, it is important
to understand the inflammatory effect and subsequent healing and/or
treatment potential of leukocyte-rich versus leukocyte-poor PRP
injections.
Poster No. 1329 • ORS 2012 Annual Meeting