Particulate cartilage under bioreactor-induced compression and shear

Abstract

Purpose Our aim was to explore the effect of varying in vitro culture conditions on general chondrogenesis of minced cartilage (MC) fragments. Methods Minced, fibrin-associated, bovine articular cartilage fragments were cultured in vitro within polyurethane scaffold rings. Constructs were maintained either free swelling for two or four weeks (control), underwent direct mechanical kneejoint-specific bioreactor-induced dynamic compression and shear, or they were maintained free swelling for two weeks followed by two weeks of bioreactor stimulation. Samples were collected for glycosaminoglycan (GAG)/DNA quantification; collagen type I, collagen type II, aggrecan, cartilage oligomeric matrix protein (COMP), proteoglycan-4 (PRG-4) messenger RNA (mRNA) analysis; histology and immunohistochemistry. Results Cellular outgrowth and neomatrix formation was successfully accomplished among all groups. GAG/DNA and collagen type I mRNA were not different between groups; chondrogenic genes collagen type II, aggrecan and COMP revealed a significant downregulation among free-swelling constructs over time (week two through week four). Mechanical loading was able to maintain chondrogenic expression with significantly stronger expression at long-term time points (four weeks) in comparison with four-week control. Histology and immunohistochemistry revealed that bioreactor culture induced stronger cellular outgrowth than free-swelling constructs. However, weaker collagen type II and aggrecan expression with an increased collagen type I expression was noted among this outgrowth neotissue. Conclusions The method of MC culture is feasible under in vitro free-swelling and dynamic loading conditions, simulating in vivo posttransplantation. Mechanical stimulation significantly provokes cellular outgrowth and long-term chondrogenic maturation at the mRNA level, whereas histology depicts immature neotissue where typical cartilage matrix is expected.

Second-Generation Autologous Minced Cartilage Repair Technique

“…6 The intra-articular environment after surgery might be beneficial to act as an in situ bioreactor to promote outgrowth of the cells and initiate chondrogenesis. 19 The complex and constantly changing cocktail of growth factors and cytokines is unique. Biomechanical stimulation via compression, shear, hydrostatic pressure, and fluid flow is inimitable.…”

Nanofractured autologous matrix induced chondrogenesis (NAMIC©) — Further development of collagen membrane aided chondrogenesis combined with subchondral needling

“…Articular remodeling and chondral maturation may take up to six months so limited weight bearing for a certain amount of time is important. Studies show, however [7,8] that the remodeling of the chondral matrix may actually profit from early mobilization using a combination of compression and shear forces. Since there is sufficient bridging between the drilled holes and the holes are straight there should be no reason for a subchondral impression fracture (Fig.…”

“…Small holes of a defined diameter of one millimeter and a penetration depth of nine millimeters may be placed as subchondral needling or nanofracturing. The postoperative rehab program was adapted to new finds in cartilage development in vitro [7,8]. Cartilage matrix seems to regenerate better and earlier when compression and shear pressure are applied.…”

Management of Knee Cartilage Defects with the Autologous Matrix-Induced Chondrogenesis (AMIC) Technique

“…Since there is sufficient bridging between the drilled holes and the holes are straight there should be no reason for a subchondral impression fracture. Earlier weight-bearing has been suggested after nanofractures [25][26][27].…”