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Given their biomimetic properties that guide cellular organization and enhance cell survival, nanofibrillar
collagen scaffolds have multiple uses in regenerative medicine, ranging from nerve and vascular
regeneration (e.g., neovascularization in ischemic limbs) to bone tissue engineering [20-22] . With regards to
lymphedema, specifically, BioBridge scaffolds mimic native extracellular matrices, enabling endothelial cell
infiltration and remodeling to recreate lymphatic vasculature. Furthermore, the nanofibrillar structure of
these scaffolds guides directional local interstitial flow, which is known to be a factor in stimulating
lymphangiogenesis . The nanofibrillar collagen encourages endothelial cell cytoskeletal reorganization
[23]
[24]
along the direction of the scaffold and provides support to enhance endothelial cell survival . Ultimately,
endothelial cells migrate into the scaffold, attach, and proliferate, leading to the directional development of
mature lymphatic vasculature.

Nanofibrillar collagen scaffolds have been used alone and in combination with other therapies. When
implanted at the time of vascularized lymph node transfer, for instance, nanofibrillar collagen scaffolds have
been shown to accelerate the engraftment of lymphatic tissue by increasing endothelial cell migration and
formation of lymphatic vasculature [25-27] . Lymph node transfer is thought to stimulate lymphangiogenesis in
the surrounding tissue, and the scaffold augments this process by providing soft tissue support for the
directional growth of lymphatic channels, as previously described . However, BioBridge scaffolds have also
[28]
been successfully used alone-the nanofibrillar structure of these scaffolds holds intrinsic capacity to
engender lymphangiogenesis through the aforementioned mechanisms (e.g., stimulating flow of interstitial
fluid, encouraging migration of endothelial cells, and enhancing expression of lymphangiogenetic factors in
the surrounding milieu such as vascular endothelial growth factor) [29,30] . This highlights the immense
potential that biomaterial design and tissue engineering hold for lymphedema treatment, as optimally-
[31]
designed scaffolds can act in a standalone capacity to enhance lymphatic regeneration .

Nanofibrillar collagen scaffolds: preclinical investigations
Preclinical investigations of nanofibrillar collagen scaffolds have spanned both small and large animal
models [Table 1]. In a rat model of acquired lymphedema, implantation of the BioBridge scaffold seeded
with adipose-derived stem cells demonstrated significant positive effects when utilized in a preventative
capacity or as a treatment in animals with established disease . In this study, rodents underwent surgical
[32]
excision of hind limb lymphatics and were assigned into either an untreated control group or one of two
treatment groups - (1) BioBridge placement prior to irradiation (i.e., preventative placement); and (2)
implantation of BioBridge scaffolds seeded with adipose-derived stem cells after lymphedema symptoms
were established (i.e., therapeutic placement). When BioBridge was implanted pre-emptively at the time of
inguinal and popliteal lymph node excision, rats did not develop hind limb lymphedema in the affected
extremity, unlike untreated controls, as determined by computed tomography-based volumetric analysis at
the 1-month postoperative timepoint. Additionally, when BioBridge scaffolds seeded with stem cells were
implanted in rodents with established lymphedema, affected limb volume was significantly reduced
compared to untreated controls at 4 months postoperatively, with enhanced lymphatic regeneration
confirmed by near-infrared fluoroscopy.

Nanofibrillar collagen scaffolds have also demonstrated promising results in large animal models.
Hadamitzky et al. investigated the BioBridge scaffold in a validated porcine model of secondary
lymphedema, which is generated by surgically resecting hindlimb lymphatics and delivering a single dose of
radiotherapy to the groin . In this study, animals were randomized to one of three groups - (1) control (no
[33]
treatment); (2) BioBridge with autologous lymph node fragment transfer; or (3) BioBridge supplemented
with vascular endothelial growth factor-C (VEGF-C), a growth factor known to enhance lymphatic
[34]
sprouting, at a concentration (1.5 micrograms/mL) that optimized VEGF-C loading and release profiles .
Three-month post-treatment outcomes were investigated using bioimpedance ratios and by CT contrast