Immunohistochemical localization of β₁‐integrins in anterior cruciate and medial collateral ligaments of human and rabbit

Abstract

The integrins are a family of adhesion-mediating cell surface receptors that play critical roles in cell-extracellular matrix interactions and have been shown to be important in the healing response in several tissues. We have studied integrin expression in normal human and rabbit anterior cruciate (ACL) and medial collateral (MCL) ligaments of the knee as a preamble to studies of beta 1-integrin expression in healing ligaments. Histologic sections of human and rabbit ACL and MCL were probed for integrin expression utilizing integrin-specific monoclonal antibodies (mAbs) followed by immunoperoxidase detection. Staining of human specimens with mAbs revealed the presence of beta 1-, alpha 1-, and alpha 5-integrin chains on the tissue fibroblasts of both ACL and MCL, while staining of rabbit specimens with rabbit integrin-reactive monoclonals revealed the presence of beta 1- and alpha 5-integrin on these ligaments. Equivalent amounts of the integrins studied were present on normal ACL and MCL. We conclude that the rabbit is an appropriate model for analyzing the expression and functional role of integrins in ligament wound healing.

Collagen‐platelet rich plasma hydrogel enhances primary repair of the porcine anterior cruciate ligament

“…These results support our hypothesis that an important mechanism for failure of the ACL to heal is a lack of appropriate provisional scaffold. 24,25,38 This is a critical finding as prior research into stimulation of healing in intraarticular tissue defects has focused on overcoming cellular deficiencies, [14][15][16]18,19,26,27,[39][40][41][42][43][44] rather than scaffolding deficiencies. 26 In this study, no cells (except the platelets and white blood cells contained in the collagen-PRP hydrogel) were transplanted, yet a highly cellular repair tissue was seen within the defect after only 4 weeks.…”

“…Proposed mechanisms for the lack of functional healing seen in the ACL after suture repair have previously focused on alterations in the cellular metabolism after injury, 11,12 intrinsic cell deficiencies, [13][14][15][16][17][18][19][20] the complex biomechanics of these tissues, and cell loss within the tissues after injury. 21 However, cell and vessel proliferation, 38 cells with migratory potential, 45 and collagen production 22 have recently been reported within the ACL tissue after rupture.…”

“…[1][2][3][4][5] This is in contrast to rates of nonunion seen in the medial collateral ligament (MCL), where failure of clinical healing is the exception rather than the rule. [6][7][8][9] The lack of healing seen in the ACL and other intra-articular tissues has been attributed to their relative lack of vascularity, the hostile environment of synovial fluid, 10 to alterations in the cellular metabolism after injury, 11,12 intrinsic cell deficiencies [13][14][15][16][17][18][19][20] the complex biomechanics of these tissues, and cell loss within the tissues after injury. 21 However, recent work has reported that human ACL remnants typically contain viable cells and vasculature, 22 yet there is a gap at the rupture site which remains open.…”

Effect of cyclic strain and plating matrix on cell proliferation and integrin expression by ligament fibroblasts

“…24 The presence of specific integrins in ACL and MCL cells have been demonstrated using immunohistochemistry. 25 Integrin subunits are increased in wounded MCL but not in wounded ACL. 26 We have previously reported quantitative differences in integrin expression in ACL and MCL cells 12 and when ligament cells are compared to chondrocytes.…”

Anterior Cruciate Ligament Healing and Repair

“…3,5,35 The impaired healing of the ACL has been attributed to its relative lack of vascularity, 16 intrinsic cell deficiencies, 24,27,28,30,[36][37][38] and cell loss after rupture. 39 These cellular differences, whereas important, are not as striking as the almost complete absence of structure in the injury site of the ruptured ACL.…”