Distinct horizontal patterns in the spatial organization of superficial zone chondrocytes of human joints

Abstract

A better understanding of the unique cellular and functional properties of the superficial zone of articular cartilage may aid current strategies in tissue engineering which attempts a layered design for the repair of cartilage lesions to avert or postpone the onset of osteoarthritis. However, data pertaining to the cellular organization of non-degenerated superficial zone of articular cartilage is not available for most human joints. The present study analyzed the arrangement of chondrocytes of non-degenerated human joints (shoulder, elbow, knee, and ankle) by using fluorescence microscopy of the superficial zone in a top-down view. The resulting horizontal chondrocyte arrangements were tested for randomness, homogeneity or a significant grouping via point pattern analysis and were correlated with the joint type in which they occurred. The present study demonstrated that human superficial chondrocytes occurred in four distinct patterns of strings, clusters, pairs or single chondrocytes. Those patterns represented a significant grouping (p<0.0001) with horizontal alignment. Each articular joint surface was dominated by only one of these four patterns (p<0.001). Specific patterns correlated with specific diarthrodial joint types (p<0.001). Further studies need to establish whether these organizational patterns are a consequence of their surrounding environment or whether they are linked to a functional purpose.

Modeling chondrocyte patterns by elliptical cluster processes

“…As published recently in this journal, human CHs of the superficial zone form distinct, almost planar patterns with various types of horizontally oriented clusters such as strings, round or oval clusters, pairs, and single CHs (Rolauffs et al, 2008;Schumacher et al, 2002) (see Figs. 1 and 2).…”

“…We investigated cartilage samples (n = 4) from a standardized location (medial condyle of the distal femur of the knee-joint in full joint extension) where they were taken from the superficial zone of the weightbearing area of the articular surface and were stained with an immunofluorescent reagent as previously described in Rolauffs et al (2008). Based on these four cartilage samples, we recorded eight images of the articular surface for our analysis.…”

“…Moreover, each articular joint surface was shown to be dominated by only one of these four patterns. Their presence within a specific articular surface correlated with the anatomical joint type suggesting a functional role of the organizational structure of superficial CHs (Rolauffs et al, 2008). However, because functional roles of joint-specific CH patterns in the transverse plane have not been shown, alternative hypotheses e.g., that patterns are non-functional consequences of joint-specific developmental processes should also be mentioned.…”

“…The organizational structure of CHs is characterized by highly variable shapes of CH clusters (Rolauffs et al, 2008(Rolauffs et al, , 2011. The coexistence of different shapes such as strings and elliptical clusters in single microscopy images (Fig.…”

Physical mechanisms underlying the strain-rate-dependent mechanical behavior of kangaroo shoulder cartilage

“…However, conclusions of most studies do not consider that the proteoglycan composition and the structural features of the collagen network adapt to external mechanical stimuli, and hence, depend on the local mechanical environment of the tissue. [12][13][14][15][16][17][18] Chondrocytes dynamically synthesize the extracellular matrix (i.e., proteoglycans and collagen) based on the external loading stimuli they receive. [19][20][21] For example, the proteoglycan content of knee cartilages, which bear high compressive loads, is higher than upper limb cartilage tissues which experience less compressive loading.…”