Table 1.
Overview of the studies with scaffolds designed for regeneration of the annulus fibrosus
| Author (year) | Scaffold | In vitro (1)/in vivo (2) | Cells | Anisotropic | Biphasic | Follow-up (days) | Findings | ||
|---|---|---|---|---|---|---|---|---|---|
| Cell attachment, proliferation and differentiattion | ECM expression | Mechanical findings | |||||||
| Shao [107] | Wet-spinned, lyophilized Alginate/chitosan | 1 | Canine AF cells | − | − | 14 | Cell growth in clusters and spread along fibres | Collagen I and II, aggrecan deposition | Scaffolds have unidirectionally aligned fibres |
| No differences cell growth and ECM deposition between alginate and alginate/chitosan scaffolds | |||||||||
| Chang [19] | Porous silk fibroin | 1 | Bovine AF cells | − | − | 56 | 35% cell attachment at 24 h | Tenfold increase in collagen deposition and small increase in proteoglycan content (at day 56) | |
| Significant increase cellularity only at day 56 | RGB decoration results in higher level type II collagen and aggrecan | ||||||||
| RGB decoration has no effect on cell attachment or morphology | |||||||||
| Mizuno [78] | Polyglycolic acid fibres mesh coated with 1.5% w/v polylactid acid solution | 2 | Ovine AF cells | − | − | 102 | DNA content remained constant during first 8 weeks but increased between 12 and 16 weeks in vivo (in AF part) | Amount of hydroxyproline and GAG increased with time with GAG reaching native tissue level at 16 weeks | Compressive modulus increased fivefold during implantation and hydraulic permeability decreased during implantation (at 16 weeks) |
| Nerunkar [84] | Electrospun poly-ε-caprolactone | 1 | Bovine AF cells | + | − | 28 | Elongated cells aligned along the pre dominant fibres direction | sGAG and collagen content increased during culturing | Anistropic and non-linear mechanical behaviour during unaxial tensile testing, comparable to native AF tissue. |
| No cellular differences between fibres angle groups | |||||||||
| Wan [121] | Poly(1,8 octanediol malate) | 1 | Murine AF cells | − | − | 21 | Proliferation of cells with stellate and elongated morphology | Increased gene expression for aggrecan and type II collagen | Tensile strength and degradation time both increased with polymerization time |
| Cell penetration into the scaffold (confirmed by the presence of ECM) | |||||||||
| Helen [47] | PDLLA/Bioglass (0.5 and 30 wt.%) | 1 | Human AF cells | − | − | 28 | More cell cluster attached to the pore walls of PDLLA/30BG and PDLLA/5BG compared to PDLLA/0BG | Deposition of sGAG and collagen highest on the PDLLA/30BG foam | |
| Produced collagen is mainly type I collagen in all cultures | |||||||||
| Wan [122] | Bone matrix gelatin (BMG)/poly (polycapro-lactone triol malate) (PPCLM) | 1 | Rabbit chondrocytes | − | + | 28 | Chondrocytes attached to the scaffold, proliferated and penetrated into the inside (at 4 weeks) | Production of type II collagen and aggrecan could be detected in both parts | Tensile strength and degradation time both increased with polymerization time |
| Incorporation of BMG in PPCLM enhanced compressive strength | |||||||||
| Sato [102] | Type I atelocollagen | 1, 2 | Rabbit AF cells | − | − | 84 | Cells proliferated and retained spherical shape in vitro | Higher increases in type II collagen and GAG content than compared to monolayer content | Significance less disc space narrowing in vivo |
| Accumulation of cartilage like matrix after insertion of cell-containing scaffold in vivo after 12 weeks | |||||||||