New and Emerging Strategies in Platelet-Rich Plasma Application in Musculoskeletal Regenerative Procedures: General Overview on Still Open Questions and Outlook

Table 3

In vitro studies on musculoskeletal tissue regeneration. The PAW classification has been attributed when possible.

Cell type	PRP formulation	PRP combination	Blood volume (mL)	Centrifugation; (number of spins)	PRP volume; (mL)	Platelet concentration	Activator; (+/−)	Leukocytes; (+/−)	PAW classification	Reference
Alveolar bone hOBs	PRP	PRP	8.5 mL	2	0.6 mL	NS	NS	NS	Not applicable	[9]
Jaw bone; hOBs	PRP	PRP	NS	NS	NS	10^6/mL	Thrombin/Ca-gluconate	NS	P1-x	[10]
Purchased hOB-like cells	PRP	PRP	60 mL	2	NS	0.5–1.0 × 10^6/μL	2% alginate-6% CaCl2	NS	P2-x	[11]
Rabbits ADSCs	PRP	5–10–15% PRP + -microspheres	30 mL	2	NS	NS	500 U bovine thrombin in 1 mL 10% CaCl2	NS	x	[12]
Rat BMSC	PRP	L-M-H PRP + BMSCs	40 mL	2	NS	High: 4358 ± 265 × 10^3; Medium: 1453 ± 88 × 10^3; Low: 48 ± 29 × 10^3; (platelets/μL)	CaCl2/thrombin	NS	P4-x; P4-x; P1-x	[13]
Purchased hMSCs	PRP	PRP	80 mL	Caption device; (no centrifuge)	10 mL	NS	Thrombin/CaCl2	+	x	[14]
Anterior abdominal wall hADSCs	PRP	PRP + OsteoMatrix	NS	2	0.5 mL/cm^2	14 × 10^6/mL	Thrombin/CaCl2	NS	P1-x	[15]
Purchased porcine MSCs	PRP	PRP +; CS-NHS	NS	2	NS	NS	NS	NS	Not applicable	[16]
hBMSCs	PRP	P-PRP; L-PRP	45 mL; 150 mL	1; 2	5 mL; NS	260 ± 37 (83–738); 194 × 10^3/μL; 920 ± 491; (555–1114); 912 × 10^3/μL	10% CaCl2	0.00; 6.4 ± 6.5; (1.8–14.4); 5.7 × 10^3/μL		[17]
Purchased hOBs and tenocytes from semitendinosus and gracilis tendons	PRP	OBs and tenocytes cocultures + PRP	6 mL	2	1 mL	1.005 × 10^12/L	NS	NS	P3	[18]
Human tenocytes from hamstring	PRP	Ciprofloxacin + dexamethasone + 10% PRP	55 mL	1	NS	353000–837000/μL	Bovine thrombin	NS	P2-x	[19]
Human tenocytes from hamstring	-PRCR; -PPCR	10%, 20% PPCR or 10%, 20% PRCR	500 mL	4	NS	PPCR: 6–11 × 10^6/mL; PRCR: 7–19 × 10^6/mL	CaCl2	PPCR and PRCR: 0.10 × 10^6/mL	P1-x-B	[20]
Horse flexor digitorum superficialis tendon	-PRP; -hcPRP; -lrPRP; -clPRP	PRP, hcPRP, lrPRP, or clPRP	PRP, plasma, and hcPRP: 60 mL; lrPRP and clPRP: 90 mL	NS	PRP: 10 mL; hcPRP and clPRP: 5 mL; lrPRP: 8 mL	PRP: 6 × 10^5/uL; hcPRP: 12 × 10^5/uL; lrPRP: 5 × 10^5/uL; clPRP: 6 × 10^5/uL	NS	PRP: 8 × 10^3/uL; hcPRP: 24 × 10^3/uL; lrPRP: 1 × 10^3/uL; clPRP: 28 × 10^3/uL	P2-B; P3-A; P2-B; P2-A	[21]
Human tenocytes from the rotator; cuff	PRP	10% PPP or PRP-Ca, or PRP-Ca-Thr	NS	NS	NS	1400 × 10^3/uL	calcium gluconate ± thrombin	NS	P4-x	[22]
Canine patellar tendon	-PRFMembrane; -PRFMatrix; -BC	PRFMatrix or PRFMembrane or BC eluent	PRFMatrix: 9 mL; PRFMembrane: 18 mL; BC: 4 mL	2	2 mL	NS	PRFMatrix and PRFMembrane: CaCl2	NS	x	[23]
Canine flexor digitorum profundus tendon	PRP	PRP + collagen Patch + MSCs	55 mL	2	1 mL	Mean: 1316 × 103/μL	Bovine thrombin/CaCl2	NS	P4-x	[24]
Immortalized human articular chondrocytes	PRP	PRP + collagen matrix	NS	1	NS	NS	Bovine thrombin	NS	x	[25]
Human chondrocytes from osteoarthritic cartilage	P-PRP; L-PRP; PPP	P-PRP; L-PRP; PPP	45 mL; 150 mL; 150 mL	1; 2; 2	1 mL; NS; NS	Median number: PLT × mm^3 = 929000; PLT × mm^3 = 194000; PLT × mm^3 = 6000	CaCl2; CaCl2; CaCl2	−; +; −	P3-x; P2-x; P1-x	[26]
Porcine and ovine ACL fibroblasts	PRP	Collagen-platelet scaffold	60 mL	1	NS	NS	NS	NS	Not applicable	[27]
Human ACL fibroblasts	PRP	PRP	6 mL	2	NS	3 × that of the whole blood	NS	NS	P1	[28]
Porcine ACL fibroblasts	PPP; PRP	PPP; 1x PRP; 3x PRP; 5x PRP	NS	2; 2; 2; 2	NS	8 × 10^6 PLTs/mL; 129 × 10^6 PLTs/mL; 370 × 10^6 PLTs/mL; 615 × 10^6 PLTs/mL	NS	+	P1; P1; P2; P2	[29]

Not specified (NS), mesenchymal stem cell (MSC), adipose tissue (AT), stromal vascular fraction of AT (SVF AT), bone marrow cells (BMC), low PRP (lPRP), medium PRP (mPRP), high PRP (hPRP), growth factors (GF), CS-NHS (chondroitin sulfate succinimidyl succinate), calcium (Ca), osteoblast (OB), platelet-rich clot releasate (PRCR), platelet-poor clot releasate (PPCR), high-concentration PRP (hcPRP), leukocyte-reduced PRP (lrPRP), concentrated-leukocytes PRP (clPRP), blood clot (BC), mesenchymal stem cells (MSCs), PRP activated with calcium (PRP-Ca), PRP activated with calcium and thrombin (PRP-Ca-Thr), calcium chloride (CaCl₂), white blood cells (WBC), low PRP (P-PRP), high PRP (L-PRP), and platelet-poor plasma (PPP).
PAW classification: P1 (≤baseline), P2 (>baseline-750,000), P3 (>750,000–1,250,000), P4 (>1,250,000), x (exogenous activation), A (above baseline), and B (below baseline).